Content uploaded by Karen Dyson
Author content
All content in this area was uploaded by Karen Dyson on Mar 13, 2014
Content may be subject to copyright.
Habitat Enhancing Marine Structures:
Creating habitat in urban waters
Karen L. Dyson
A thesis submitted in partial fulfillment of the requirements for the degree of
Master of Marine Affairs
School of Marine Affairs
College of Ocean and Fishery Sciences
University of Washington
2009
c
Copyright 2009
Karen L. Dyson
In loving memory of James ‘Bud’ Olan Low.
ACKNOWLEDGMENTS
I would like to thank those who helped make this thesis possible – Martha Groom, for her
invaluable suggestions and encouragement; Dan Huppert, for his work as thesis chair; Ronald
Alevras, for imparting his knowledge and expertise; Burr Stewart and Jason Toft, for their
open and frank discussion; and finally my family and friends, for their love and support.
Abstract
Habitat Enhancing Marine Structures:
Creating habitat in urban waters
Karen L. Dyson
Maritime cities support a large and increasing portion of the world’s human population. These
concentrated populations cause serious impacts on coastal ecosystems, causing widespread
habitat degradation and fragmentation and the introduction of non native, invasive species.
The potential habitat that urban coastal waters could offer is overlooked, and urban structures
built in the marine environment are not designed or managed for the habitat they provide.
However, the urban waterfront may be capable of supporting a significant proportion of
regional aquatic biodiversity. A wide variety of marine organisms utilize urban marine struc-
tures, and further research and some targeted design modifications could significantly improve
the habitat quality of these human-made structures. Ongoing urban waterfront renovations
present a timely opportunity for ports, cities, and communities to implement habitat improve-
ment projects by incorporating them into existing and future renovation projects
Habitat enhancing marine structures (HEMS) are potentially promising approaches to ad-
dress the impact of cities on marine organisms including habitat fragmentation and habitat
degradation. HEMS are types of habitat improvement projects that are ecologically engineered
to improve the habitat quality of urban marine structures for marine organisms. They are tar-
geted at areas where the urban structures in place cannot be significantly altered or removed.
HEMS projects can contribute to numerous goals including biodiversity enhancement goals,
sustainable development goals, waterfront aesthetic goals, and public environmental educa-
tion goals. The successful addition of habitat to an urban waterfront requires careful planning,
thoughtful design and construction practices, and meaningful management and monitoring
programs. Regional planning incorporating HEMS into the urban landscape can create a mo-
saic of habitat patches supporting regional biodiversity and the economic and social goals of
cities. The success of both local and regional projects will depend on properly selecting the type
of HEMS project to implement given the biological needs of local species, social and economic
concerns, and safety and engineering issues. A toolbox providing examples of different HEMS
modules is provided.
TABLE OF CONTENTS
Page
ListofFigures............................................ iii
ListofTables ............................................ iv
Chapter 1: Habitat Enhancing Marine Structures . . . . . . . . . . . . . . . . . . . . 1
1.1 TheFoundationofHEMS ................................ 2
1.2 Applications of Habitat Enhancing Marine Structures . . . . . . . . . . . . . . . . 4
1.2.1 Biodiversity Enhancement Goals . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2 Sustainable Development and Corporate Sustainability Goals . . . . . . . 8
1.2.3 Governmentally Mandated Goals . . . . . . . . . . . . . . . . . . . . . . . . 10
1.2.4 Recreational and Commercial Harvesting Goals . . . . . . . . . . . . . . . 10
1.2.5 Waterfront Aesthetic Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2.6 Public Environmental Education Goals . . . . . . . . . . . . . . . . . . . . 11
1.2.7 Support Existing Restoration Project Goals . . . . . . . . . . . . . . . . . . 12
1.3 PotentialDrawbacks ................................... 12
1.3.1 Potential to Benefit Non-native Species . . . . . . . . . . . . . . . . . . . . 13
1.3.2 EcologicalSinks.................................. 14
1.3.3 The Attraction-Production Debate . . . . . . . . . . . . . . . . . . . . . . . 14
1.3.4 AttractiveNuisances ............................... 15
1.4 ConcludingThoughts................................... 15
Chapter 2: The value of urban marine structures as habitat for marine organisms . 17
2.1 Overview of Prior Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.1.1 Organisms inhabiting urban waters . . . . . . . . . . . . . . . . . . . . . . 18
2.1.2 Impacts of urban structures on marine organisms . . . . . . . . . . . . . . 20
2.2 Habitat Enhancement of Marine Structures: The Next Step . . . . . . . . . . . . 28
2.3 Concludingthoughts ................................... 30
Chapter 3: Implementing Habitat Enhancing Marine Structures . . . . . . . . . . . 31
3.1 Regional Planning of the Urban Landscape . . . . . . . . . . . . . . . . . . . . . . 31
3.1.1 Regional Planning Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2 TheIssueofScale ..................................... 38
3.3 Implementing a HEMS Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
i
3.3.1 AdaptiveManagement .............................. 40
3.3.2 ProjectPlanning.................................. 42
3.3.3 ProjectDesign................................... 45
3.3.4 Construction and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3.5 Monitoring, maintenance, and management . . . . . . . . . . . . . . . . . 56
3.3.6 Project Outreach and Education . . . . . . . . . . . . . . . . . . . . . . . . 59
3.4 Concluding thoughts and an example . . . . . . . . . . . . . . . . . . . . . . . . . 61
Chapter 4: Designing HEMS Components . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.1 Factors influencing module selection . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.1.1 Phyiscal characteristics of the site . . . . . . . . . . . . . . . . . . . . . . . 65
4.1.2 Biological requirements of local and target species . . . . . . . . . . . . . . 68
4.1.3 Social and economic concerns . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.1.4 Safety and engineering issues . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.1.5 Materials...................................... 73
4.2 ModuleTypes ....................................... 76
4.2.1 Habitat Type 1: HEMS that provide vegetative substrate . . . . . . . . . . 76
4.2.2 Habitat Type 2: HEMS that provide hard substrate . . . . . . . . . . . . . 89
4.2.3 Habitat Type 3: Modules providing other types of substrate . . . . . . . . 101
4.3 ConcludingThoughts................................... 114
Chapter 5: Looking toward the future . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Bibliography............................................. 122
ii
LIST OF FIGURES
Figure Number Page
1.1 Relationships between HEMS goals . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 Photograph of Birds on Rip-Rap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.2 Photograph of a Commercial Dock . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3 Photograph of Waterfront Space with Ferry Dock . . . . . . . . . . . . . . . . . . . 21
2.4 Photograph of the Seattle Seawall . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.1 Diagram of HEMS Installation Process . . . . . . . . . . . . . . . . . . . . . . . . 32
3.2 Cityscape Utilizing Multiple HEMS . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.1 Diagram illustrating the factors influencing HEMS module choice . . . . . . . . . 66
4.2 Illustration of Vertical Garden . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.3 Illustration of Vegetation Basket . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.4 Illustration of Seaweed Reef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
4.5 Illustration of Seagrass Bed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.6 Illustration of Artificial Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
4.7 Illustration of Increased Light Below Docks . . . . . . . . . . . . . . . . . . . . . . 88
4.8 Illustration of Seawall Stairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
4.9 Illustration of Seawall Panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.10 Illustration of Seawall Refuge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
4.11 Illustration of Artificial Reef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
4.12 Illustration of Fish Aggregating Devices (FADs) . . . . . . . . . . . . . . . . . . . 99
4.13 Illustration of Rocky Islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4.14 Illustration of Piling Habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
4.15 Illustration of Habitat Bench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.16 Illustration of Woody Debris on Seawall . . . . . . . . . . . . . . . . . . . . . . . . 106
4.17 Illustration of Habitat Baskets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
4.18 Illustration of a Breakwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.19 Illustration of an Oyster Reef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
4.20 Illustration of Woody Debris on the Seafloor . . . . . . . . . . . . . . . . . . . . . . 112
4.21 Illustration of Sand Filled Fabric Bags . . . . . . . . . . . . . . . . . . . . . . . . . 113
4.22 Illustration of Stationary Netting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
4.23 Illustration of Multiple HEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
iii
LIST OF TABLES
Table Number Page
1.1 HEMSProjectGoals ................................... 5
4.1 HEMS Providing Vegetative Substrate . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.2 HEMS Providing Hard Substrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
4.3 HEMS Providing Other Types of Substrate . . . . . . . . . . . . . . . . . . . . . . 103
iv
1
Chapter 1
HABITAT ENHANCING MARINE STRUCTURES
Maritime cities support a large portion of the world’s human population. There are now 14
megacities (cities with more than 10 million residents) and thousands of major cities located
on the coast worldwide (Tibbers, 2002). By 2015, three more megacities will emerge, and the
coastal population of the United States alone will reach 165 million people (Tibbers, 2002).
These concentrated populations are having a serious impact on coastal ecosystems, causing
widespread habitat degradation and fragmentation and the introduction of non-native, inva-
sive species (Thompson et al., 2002; Tibbers, 2002). As a result, most people believe that urban
waterfronts are ecologically sterile, inhabited only by seagulls and rats, and so overlook the
potential habitat that urban coastal waters1could offer is overlooked. Urban structures built
in the marine environment are not designed or managed for the habitat they provide, and
are built without considering the communities of marine organisms that could colonize them
(Clynick et al., 2008).
However, amidst these challenges lie many opportunities. On land, scientists and city plan-
ners now recognize the ecological value of greenways, including urban parks and tree lined
streets (Fern´
andez-Juricic and Jokim¨
aki, 2001; Hodgkison et al., 2007; Croci et al., 2008). Re-
searchers have identified some key greenway attributes that city planners can use in their
urban greenways to accommodate additional bird and mammal species, including a diversity
of plant species and habitat complexity (Hodgkison et al., 2007; Croci et al., 2008). Over 50%
of regional bird, beetle, and small mammal species were accommodated in well designed urban
greenways (Croci et al., 2008). In the quest to conserve biodiversity, urban landscapes should
not be ignored (Mason et al., 2007).
Although often overlooked, the urban waterfront may also be capable of supporting a sig-
nificant proportion of the regional aquatic biodiversity (see Duffy-Anderson et al., 2003). Sci-
entists have discovered that a diverse array of organisms use urban marine structures, includ-
ing structures such as bulkheads and docks, as habitat (see Connell and Glasby, 1999). The
1For the purposes of this paper, urban coastal waters, or urban waters, include the water and seafloor adjacent to
a large metropolitan area extending approximately 1km offshore. Upper New York Bay in New York City is a good
example of urban coastal waters.
2
suitability of the habitat offered by human-made structures is lower than habitat on natural
substrates (see Connell and Glasby (1999);Chapter 2)). Fortunately, although urban shorelines
will never return to their original condition, scientists think that the habitat quality of these
human-made structures could be significantly improved through further research and some
targeted design modifications (Russell et al., 1983; Goff, 2008).
Habitat Enhancing Marine Structures (or HEMS) are a potentially promising approach to
address the impact of cities on marine organisms including habitat fragmentation and degra-
dation. HEMS are a type of habitat improvement project that are ecologically engineered to
improve the habitat quality of urban marine structures such as bulkheads and docks for marine
organisms. More specifically, HEMS attempt to improve or enhance the physical habitat that
organisms depend on for survival in the inter- and sub-tidal waterfronts of densely populated
areas.
Opportunities to implement HEMS projects abound. Urban waterfronts are undergoing a
period of restoration and rejuvenation (see, for example Heartbeats in the Muck by John Wald-
man). After many years of neglect, water quality improvements have been seen in many cities
setting the stage for incorporating habitat into urban waters (MEC Analytical Systems, Inc.,
2002). In many cities, pier structures, bulkheads, and other urban structures built in the last
century are reaching the end of their life and need to be replaced or rehabilitated (Alevras,
2008). Waterfront revitalization is also transforming industrial waterfronts into community
spaces. These and other projects provide ideal opportunities to incorporate habitat improve-
ments into urban waters (Meyers, 2006). Further, significant financial resources are available
for projects compatible with urban biodiversity protection (Bryant, 2006).
The goal of this thesis is to explore the potential and current uses of Habitat Enhancing
Marine Structures in urban waterfronts. The remainder of this chapter focuses on the goals
that can be fulfilled by HEMS. The next chapter reviews research highlighting the ecology
of traditional urban marine structures and supporting the use of HEMS. The third chapter
investigates how to implement HEMS to best benefit local ecosystems. The fourth and final
chapter is a toolbox that contains an extensive overview of the types of HEMS available for use
in a wide range of ecosystems and with a variety of urban marine structures.
1.1 The Foundation of HEMS
The theory behind HEMS is primarily derived from the fields of conservation management,
structural engineering, and ecology and its subfields including physiological ecology, popula-
3
tion ecology, community ecology, ecosystem ecology, and landscape ecology. Each of these fields
offers important elements to consideration in designing HEMS. Introducing habitat elements
to the environment, especially nesting boxes and burrow refuges, is a well established practice
and important tool in conservation management used to assist bird, mammal and reptile pop-
ulations (Webb and Shine, 2000; Milne et al., 2003; Souter et al., 2003; Goodman et al., 2005).
Attention to structural engineering is especially important when dealing with systems that
bear substantial loads or are subject to large forces to ensure the continued performance of
these structures. Physiological ecology can provide design insight into the habitat preferences
of individuals through the study of the factors controlling growth, reproduction, survival, dis-
tribution. The study of population ecology provides predictions of changes in populations in
response to changes in the environment (including any potential interventions), and can be
used to identify particularly vulnerable or important life stages that could be better supported
through HEMS. Interactions between species, including predation, are studied and modeled
under community ecology. Ecosystem and landscape ecology study large scale processes, in-
cluding primary productivity and trophic interactions, which are important to city and regional
scale planning for HEMS projects.
HEMS projects are targeted at areas where human-made structures cannot be significantly
altered or removed, such as port facilities, bulkheads behind which critical infrastructure and
pipes are located, bulkheads critical to erosion control, and ferry terminals. Thus, the majority
of HEMS projects involve urban structures. Although these techniques also can be used in
less urban or suburban areas, many preferentially pursue restoration or removal, and resort
to HEMS only if removal of the human-made structure is not an option. Further, projects that
include improvements to upland areas (such as wetland restoration projects or creating pocket
beaches) would only include HEMS if the site includes human-made structures that cannot be
removed2. Thus, any discussion of HEMS is confined to cases that involve improvements to
physical structures that are too essential to human livelihoods and safety to be removed.
Although excluded from the discussion of HEMS, upland projects and wetlands restoration
projects can work synergistically with HEMS installations. In some cases, HEMS may support
these projects and increase their habitat value to organisms. Additionally, waterfront revital-
ization can create important opportunities for HEMS projects.
2The Olympic Sculpture Park waterfront habitat project in Seattle is a good example of a project that incorporated
both types of projects (Toft et al., 2008). A section of rip-rap was removed and a portion of the upland area graded in
order to create a pocket beach. In an adjacent area, a type of HEMS called a habitat bench was built in front of an
existing bulkhead that could not be removed.
4
1.2 Applications of Habitat Enhancing Marine Structures
Urban and waterfront planners, corporations, city, local, county and state governments, among
others, are all called upon to fulfill a diverse set of goals regarding urban waterfronts. HEMS
are flexible, modular tools that can accomplish many things, including improving habitat qual-
ity and aesthetics. Depending on how they are designed, HEMS can be tailored to suit many
ecosystems and can be created to benefit particular species. HEMS are also modular, in that
the effects of multiple small HEMS installation projects can be designed to work synergistically
so that different projects completed at different times can strengthen each other.
As a result of these unique characteristics, HEMS can be used to further a diverse set of
goals. Fulfilling biodiversity enhancement goals, including increasing the number of species
supported by urban marine structures, may be the most common reason managers choose to
use HEMS. Corporate sustainability and governmental mandates are procedural goals that
can be fulfilled in part through HEMS. HEMS can also assist cities achieve life quality goals
including recreational and commercial harvest goals, waterfront aesthetics goals, and public
environmental education goals. HEMS projects can also support existing restoration projects.
These goals are summarized in Table 1.1.
1.2.1 Biodiversity Enhancement Goals
An important goal that HEMS can address is enhancing biological diversity, or biodiversity.
Biodiversity3is the ‘quantity, variety, and distribution’ of life on Earth at all scales from genes
to ecosystems (Hiddink et al., 2008). Urban coastal waterfronts historically supported diverse
communities of marine organisms. The impacts of development, including reduced water qual-
ity and physical shoreline changes, have markedly reduced the biodiversity of urban waters.
In many cases, there may only be one representative species in many taxa in urban waters.
Biodiversity enhancement goals often stem from the desire to encourage historically present
species to re-colonize the urban waterfront.
At present, not much is known about how reduced biodiversity specifically impacts urban
marine waters. Generally, higher biodiversity is related to the increased ability of ecosystems
to respond to and recover from disturbances (Chapin et al., 2000; Duarte, 2000; Hiddink et al.,
2008). For example, In many parts of the world, overharvest of sea urchin predators including
as sea otter and Atlantic cod have resulted in increased numbers of sea urchins, which in turn
3There are many papers that discuss biodiversity in great detail, for example, see Hooper et al. (2005). Chapin et al.
(2000) provides a good overview of the consequences of changing biodiversity.
5
Table 1.1: Goals that HEMS projects can address, including example objectives for a HEMS
project and how the HEMS project can further the stated goals.
6
consume vast forests of kelp (Steneck et al., 2002). However, the high diversity of sea urchin
predators has buffered southern California kelp forests from the systematic kelp deforesta-
tion caused by sea urchins (Steneck et al., 2002). Biodiversity may also increase the ability of
ecosystems to resist invasion by non-native species (Steneck et al., 2002). Further, the pres-
ence of specific species is linked to certain ecosystem functioning and ecosystem goods (Chapin
et al., 2000; Duarte, 2000; Hiddink et al., 2008). Biodiversity also has aesthetic, recreational,
cultural, and existence values to humans (Chapin et al., 2000).
The overarching principles for biodiversity enhancement goals can be broken down into
three main groups - increasing the population of a particular species, increasing the number
of species present, and enhancing ecosystem attributes, especially those that benefit humans.
Well designed HEMS can address all three of these guiding principles. Biodiversity enhance-
ment goals are achieved through targeting specific ecological changes with HEMS projects that
would result in increases in biological diversity along one or more of these categories. As biodi-
versity enhancement is a very broad goal, it will be discussed through a number of component
goals that result in distinct types of ecological improvements.
Habitat Area and Quality Goals
Habitat loss and degradation are the primary causes of biodiversity loss (Webb and Shine,
2000; United Nations Environment Programme, 2002; Bryant, 2006). In urban areas, sea-
walls, docks, and other urban structures have replaced natural shoreline. As a result, many
natural habitat elements, including rock pools, and other micro-habitats, have been lost and
replaced with artificial substrates. These artificial substrates are steeper than natural sub-
strates, and reduce the area of the intertidal habitat. Structures such as floating pontoons also
create completely novel habitat. However, these artificial substrates do not provide the same
resources as natural substrates, negatively impacting many native species4.
Adding artificial habitat resources has been suggested as a method for assisting species that
rely on structures that have been lost when urban marine structures replace natural shorelines
(Webb and Shine, 2000). HEMS can assist managers by directly improving and increasing the
available habitat. For example, HEMS projects can be adapted to provide micro habitat such
as crevices that are important to many species (Moreira et al., 2006). Additionally, HEMS have
been used to increase the number of sea turtle eggs laid on slanted seawalls (Isobe, 1998). For
HEMS to be effective, the key habitat components causing species or ecosystem decline that
4Chapter 2 delves more deeply into these impacts.
7
are missing from urban structures must be clearly identified and addressed through the HEMS
(Webb and Shine, 2000).
Habitat Connectivity Goals
Habitat fragmentation occurs alongside habitat loss, and also negatively impacts biodiversity.
Habitat fragmentation isolates small patches of habitat within a previously connected habitat
area and reduces the viability of these patches to support species. Additionally, habitat loss
and fragmentation may cause habitats key to certain life stages to be unavailable to species.
This type of reduction of habitat connectivity can also reduce the ability of species to thrive.
Habitat connectivity is especially important in conserving species with weak dispersal ability
(Croci et al., 2008).
HEMS can assist managers to achieve habitat connectivity goals by creating habitat cor-
ridors to facilitate movement between patches, and by creating ‘stepping stones’ that allow
organisms to utilize additional patches of similar or different habitats (Fern´
andez-Juricic and
Jokim¨
aki, 2001). Landscapes with low connectivity can see great improvements in population
survival if the connectivity between patches can be increased (Vuilleumier et al., 2007). In-
creases in connectivity between urban and less developed waterfronts may also increase the
proportion of local biodiversity found in urban areas and allow cities to be integrated into con-
servation plans (Croci et al., 2008).
Non-native Species Goals
Invasive, non-native species are a severe threat to local species diversity, particularly in port
cities. Although not all non-native species become invasive, those that do can overwhelm an
ecosystem with devastating effects. Although some non-native species may have negligible or
even positive (e.g. by becoming prey) impact on local species, invasive species can negatively
impact native species populations. Possible impacts include competing with native species for
habitat and food or by preying upon native species. However, because it is impossible to tell
which species will become invasive, it may be desirable to limit the influx of all non-native
species.
Non-native species have been found to have an advantage over native species in colonizing
some urban structures, particularly pontoons and pilings, while native species have the ad-
vantage on natural shoreline substrates (Glasby et al., 2007). Native and non-native species
influence each other in complex ways. As local native biodiversity is decreased, the suscepti-
8
bility of ecosystems to non-native species invasions may increase, potentially further reducing
local biodiversity (Manchester and Bullock, 2000). However, the reverse could also be true. In-
creasing the diversity and the abundance of native species may help to reduce the likelihood of
a non-native species introduction, and help control non-native species that are already present.
HEMS can help by increasing biodiversity and providing alternative designs in terms of type
of substratum, complexity, and heterogeneity that could reduce invasion potential of artificial
substrates (Bulleri and Airoldi, 2005).
While biodiversity is an important goal in its own right, biodiversity goals may also in-
fluence a number of other significant goals (Figure 1.1). A corporate sustainability goal, for
example, might be fulfilled by increasing the number of salmon in the near shore area. How-
ever, these other goals are not restricted to, nor defined by, biodiversity goals. While many
of the following goals will be interrelated and include aspects of biodiversity, they may also
include social or economic facets that are equally if not more important. Further, just as biodi-
versity is an important goal in its own right, the following goals are valuable even without ties
to biodiversity.
1.2.2 Sustainable Development and Corporate Sustainability Goals
Sustainable development requires society to conserve ecosystems that currently exist and
also restore those that have been damaged or lost, and ‘good, practical ecosystem restora-
tion promises to play a crucial role in sustainability goals’ (Diefenderfer et al., 2003; Baird,
2005). Modern corporations and local governments now frequently adopt sustainability, cor-
porate responsibility, or triple bottom line5goals (Norman and MacDonald, 2004). In addition
to conserving energy and resources, corporations may also create goals to augment ecosystem
sustainability through habitat enhancement. HEMS can assist in achieving these goals by al-
lowing companies with waterfront property to improve the habitat value of their waterfronts.
Biodiversity and wildlife habitat programs have many benefits. Corporations participat-
ing in programs coordinated by the non-profit Wildlife Habitat Council were surveyed recently
about the impacts that these programs had on their companies. Benefits included improve-
ments in employee morale, relationships with environmental groups, community relations,
relationships with regulators, and annual cost savings (Cardskadden and Lober, 1998).
5The triple bottom line is an expanded framework for measuring corporate (although it could also be societal) suc-
cess that includes ecological and social criteria in addition to the traditional economic criteria. For more information
see Towards the sustainable cooperation: Win-win-win business strategies for sustainable development by Elkington
(1994)
9
Figure 1.1: Illustration of the relationships between HEMS goals. Solid lines indicate strong connections between goals where the
outcome of one goal will significantly impact the other goal. Dashed lines indicate weaker connections where the outcome of one
goal may moderately or weakly impact the other goal.
10
1.2.3 Governmentally Mandated Goals
Companies or government agencies are sometimes legally mandated required to create, en-
hance, or restore habitat as a remediation action. HEMS can help fulfill this goal by creating
and enhancing habitat for many organisms. Although mandated habitat remediation projects
are considered on a case by case basis, HEMS have already been used successfully for this
purpose. In New York City, a ReefBallTM6 installation was used to fulfill habitat provision
requirements for a new park as mandated by the National Oceanic and Atmospheric Adminis-
tration (Alevras, 2008).
1.2.4 Recreational and Commercial Harvesting Goals
Harvesting organisms for consumption, recreational, or cultural reasons is important to urban
residents worldwide. Mussels, fish, and kelp are widely harvested. In the Mediterranean, peo-
ple will walk on bulkheads to harvest the mussels that grow there, despite the practice being
illegal (Airoldi et al., 2005). Fishing from docks is also a favorite pastime in many locations,
and New York City and Los Angeles both have public docks available for this purpose. There
can be risks associated with harvesting organisms, particularly filter feeders, in urban waters.
In areas where water quality is very poor, these organisms can bio-accumulate toxins, which
can cause severe health problems in humans who consume them (for example, see Norstr¨
om
et al. (2009)). Not all urban areas have these toxins present (for example see Russell et al.
(1983)), and some portions of the urban waterfront may be affected where others are not. How-
ever, filter feeders such as mussels are still valuable as water quality enhancers even when
they cannot be consumed.
By providing shelter and habitat to mussels and fish, and providing attachment points for
kelp, HEMS can assist managers to increase the number and availability of important harvest
species. New populations could be created, or existing populations sustained through the use
of HEMS. Similar additions of artificial structure to lakes, ponds, and reservoirs have been
successful (Bolding et al., 2004). Care must be taken to avoid overharvesting of these resources
(Airoldi et al., 2005). This is especially important for certain harvested fish species which
respond to HEMS through aggregation (see also the Production Attraction debate described in
the Potential Drawbacks section later in this chapter).
6ReefBallTM’s are hollow, domed concrete structures with multiple openings of different sizes that provide habitat
for many species associated with hard substrate. More information can be found at http://www.reefball.org.
11
1.2.5 Waterfront Aesthetic Goals
Urban waterfronts sometimes mar an otherwise beautiful marine landscape. Improving the
aesthetics of the urban waterfront may help tourism, improve public opinion, and citizen con-
nection and appreciation of nature. Enhanced waterfront aesthetics may also help with urban
renewal or waterfront revitalization projects by increasing the attractiveness of the waterfront,
which can in turn increase property values.
Certain types of HEMS can help managers reach waterfront aesthetic goals. Increasing
overwater vegetation by using a vertical seawall planting can add greenery to an otherwise
concrete dominated structure, in addition to providing terrestrial plant and insect input into
the marine ecosystem (Toft and Cordell, 2006). A habitat bench that supports aquatic plants
would provide similar aesthetic appeal. However, HEMS which are not visible above the wa-
terline, while important habitat, will not fulfill this goal.
1.2.6 Public Environmental Education Goals
Urban residents may be disconnected from their natural surroundings and uninformed about
the organisms with which they share their city. This may be especially true for marine or-
ganisms, which are largely unseen by the public. Critically, environmental education for the
general public is thought to be linked to increasing support for conservation measures both
locally and abroad, and to increased sensitivity to environmental issues (Savard et al., 2000;
Bryant, 2006).
A HEMS project can increase public support for restoration by creating a local example
of a habitat enhancement project in a visible location and bringing people into contact with
nature. Urban greenways on land can both stimulate the preservation and restoration of urban
habitats and educate visitors about the conserved ecosystem (Bryant, 2006). It is likely that
HEMS will be able to accomplish similar objectives in marine systems.
Environmental education can have many important benefits specifically for students, in-
cluding: improved school and science grades; improved understanding of complex scientific
systems; improvements in integrated learning; improved reading and thinking skills; and im-
proved behavior (Coyle, 2005). Due to their multidisciplinary nature, HEMS could provide
a good way to teach a combination of concepts including biological, engineering, and physics.
HEMS could also help with environmental education goals by providing nearby and accessi-
ble examples of the marine environment. A recent report on environmental education found
that the best environmental education involved lab or field experience. Learning outside of the
12
classroom created ‘more powerful, focused, and memorable learning experiences’ (Coyle, 2005).
These experiences may be more probable in urban areas where HEMS projects are installed,
as they allow shorter, cheaper school excursions.
1.2.7 Support Existing Restoration Project Goals
HEMS can also support the goals of existing restoration projects and increase the effective-
ness of these existing projects. This may be through increased public support and funding, or
through supporting the ecological goals of existing restoration projects. However, these areas
are still separated from each other and from the ocean by the urban waterfront. Improv-
ing habitat in urban waterfronts may facilitate the movement of organisms, connecting these
projects with each other and the ocean. As an example, urban waterfronts are hostile land-
scapes for juvenile salmon migrating from restored urban watersheds to the ocean (Toft and
Cordell, 2006). HEMS could increase the food and shelter available to juvenile salmon while
passing through the urban waterfront, and potentially increase their survival. A HEMS project
like this will relate strongly to the habitat area and quality goals of the existing restoration
project.
Habitat Enhancing Marine Structures can help managers address many different goals.
Habitat enhancement and biodiversity goals will likely play a key role in the decision to use
HEMS. However, many of the above goals can be fulfilled even without significant increases in
biodiversity by satisfying important social or economic objectives. The flexibility and diversity
of purposes for which HEMS can be used highlights the potential for HEMS as important
management tools.
1.3 Potential Drawbacks
Although HEMS can be used to successfully address many goals, there are a few potential
drawbacks associated with their use. HEMS will be more effective in some situations than
others. Understanding the situational advantages and disadvantages of HEMS will help man-
agers utilize HEMS properly and avoid wasting time and resources. There are a number of
situations where another solution may be a better option than HEMS. First, HEMS should
not be used in situations where habitat limitation is not a consideration. In areas with very
poor water quality due to pollutants or other contaminants, it is likely that there will be no
organisms for which HEMS can provide habitat. In these situations, water quality problems
should be addressed first, while HEMS projects are considered for future implementation once
13
water quality has improved. HEMS should also not be used where physical or biological fac-
tors not related to habitat are the limiting factors for a species’ population growth. Finally,
techniques to avoid or reduce urban aquatic structures should be used wherever possible, par-
ticularly in suburban or rural areas. These techniques will likely provide better quality habitat
than HEMS and thus HEMS discussed here should be used where urban marine structures are
necessary.
Four of the key concerns that a successful HEMS project needs to address are the potential
for (1) enhancement of non-native species, (2) creation of ecological sinks, (3) attraction of
organisms in such a way that they can cause public harm, and (4) attraction of organisms away
from other locations, rather than encouraging new production that expands local populations.
1.3.1 Potential to Benefit Non-native Species
Recent research has shown that human-made substrates can facilitate populations of non-
native species, especially in areas that are susceptible to invasion such as ports (Bulleri and
Airoldi, 2005). Fiberglass and concrete pontoons and pilings in Australia were found to support
many more non-native species when compared to nearby rocky reefs (Connell and Glasby, 1999;
Glasby et al., 2007). While both native and non-native species successfully colonized these ar-
eas, it is thought that differences in the physical properties of the substrates led to differences
in post-settlement processes, including growth rates and competition, and the observed pattern
of abundance7.
The main concern is that HEMS projects will inadvertently encourage non-native species
in areas where they are damaging or unwanted. This concern can be alleviated through care-
ful design and selection of construction materials. Pontoons and pilings, both structures with
no natural counterpart, consistently supported different communities and more non-native
species (Connell and Glasby, 1999; Connell, 2000; Neves et al., 2007; Perkol-Finkel et al., 2008).
Therefore, reducing the number of floating surfaces and vertical poles should reduce the ad-
vantage for non-native species. Additionally, seawalls constructed of sandstone were found to
support similar communities as the natural sandstone shores (Connell and Glasby, 1999). As
a result, using local materials may also help to reduce non-native species (Tyrell and Byers,
2007). There is also concern that connecting habitat patches will facilitate the spread of dis-
ease or non-native species. However, these organisms can likely spread between patches even
without corridors present (Bryant, 2006). A good scientific knowledge of the system will make
7More evidence to support these ideas is provided in Chapter 2.
14
implementing HEMS safer and more worthwhile.
1.3.2 Ecological Sinks
When attempting to connect a landscape of habitat fragments, managers must plan carefully
to avoid creating ecological sinks. Ecological sinks are habitat patches that seem to provide
acceptable habitat for organisms, but do not provide sufficient resources to allow the organ-
isms to thrive and/or reproduce. The poor quality habitat may become an ecological sink, as
organisms from the good quality habitat consistently colonize the poorer habitat and fail to
survive or reproduce (Pullman, 1988). As a result, the population in the patch is sustained by
immigration from a source population. Ecological sinks can occur when poor quality habitats
are connected to high quality habitats.
When HEMS are being used to connect two existing habitat fragments, managers should
avoid connecting a poor quality habitat to a higher quality habitat. Managers might consider
improving the quality of the poor quality habitat before corridors are created, and if there
is still doubt, consider not connecting the two habitats. However, in ecosystems where there
is already connectivity between good and poor habitats, HEMS could be used to improve the
habitat in the ecological sink.
1.3.3 The Attraction-Production Debate
The fundamental question in the attraction-production debate is whether human-made habi-
tats contribute to the new production of organisms, or if they simply attract organisms from the
surrounding environment (Brickhill et al., 2005). While similar to the ecological sink question,
the attraction-production debate has focused more on the ability of human made structures to
produce new biomass and organisms that would not have existed if not for the structure.
Although the debate has raged for at least two decades, it is likely that the true answer de-
pends on the species and ecosystem being considered8. The chances of human-made habitats
contributing to new biomass is related to a species’ habitat limitation, territoriality, and for ar-
tificial reefs if the species is an obligate reef species (Pickering and Whitmarsh, 1997). Species
that are not habitat limited, but recruitment limited, are highly mobile or pelagic, and are not
reef-dependent are likely to follow the attraction hypothesis (Pickering and Whitmarsh, 1997).
However, these species may still benefit if the biomass of key food sources is increased due to a
8The Pickering and Whitmarsh paper presents a comprehensive overview of the attraction-production debate and
provides insight into the artificial reef design and construction parameters that are critical for increasing production.
15
HEMS project, or if only one life stage is habitat limited (Buckley, 1982).
Many species in urban waters are likely to be habitat limited because of the scale of habitat
destruction in these areas (Powers et al., 2003). Research to determine the best design and
construction parameters of man-made habitats for species is also crucial, and greater surface
area may help reefs be more productive (Pickering and Whitmarsh, 1997; Osenberg et al., 2002;
Figley, 2003; Brickhill et al., 2005). Breakwaters in urban areas have been found to contribute
generously to local reef fish larval pools (Stephens and Pondella, 2002). Additionally, protecting
HEMS projects from harvest can serve to eliminate uncertainty and avoid further depletion of
the species (Pitcher and Seaman, 2000; Powers et al., 2003). When harvest of organisms is also
a management goal, managers can use strategies such as situating the HEMS so that only part
of the installment is accessible for fishing.
1.3.4 Attractive Nuisances
An attractive nuisance is ‘an area, habitat, or feature that is attractive to wildlife (or humans)
and has, or has the potential to have, waste or contaminants left on the site that are harmful to
plants or animals (or humans) after a completed remediation action’ (Environmental Protection
Agency, 2007). For example, oysters growing on HEMS may accumulate toxins from the water
column, presenting a danger to wildlife or residents who try to consume them. There are also
liability concerns when the public is involved.
Attractive nuisances are a concern only when HEMS are being installed in a contaminated
environment. The Environmental Protection Agency (EPA) recommends that managers be
aware of and manage the exposure pathways and way that wildlife or humans can alter ex-
posure pathways (Environmental Protection Agency, 2007). While it may be difficult to pre-
dict all of the potential consequences of a HEMS installation project, the EPA suggests that
attractive nuisances are not likely to be a problem if: ‘the site is remediated in a way that
appropriately considers attractive nuisance issues; initial studies consider potential attractive
nuisance issues; sampling and monitoring data is used to assess potential risk; and any risks
are recognized and eliminated or properly managed’ (Environmental Protection Agency, 2007).
1.4 Concluding Thoughts
The technical development of HEMS projects that mimic natural substrates is a promising
technique to ‘assist in the restoration of the ecological quality’ of urban waterfronts (Isobe,
1998; Tanaka et al., 2000). Habitat Enhancing Marine Structures are a flexible tool that man-
16
agers can use now to fulfill a broad range of goals. While biological diversity is the fundamen-
tal goal that HEMS can tackle, many other important goals including corporate responsibility
goals, aesthetic goals, and public environmental education goals can also be addressed through
HEMS projects. However, HEMS are not a one size fits all solution. Care and thought must go
into the design of each project to ensure that it is properly tailored to fit the application. There
are also some concerns regarding HEMS and other man-made habitats, including non-native
species, ecosystem sinks, attractive nuisance, and the production-attraction debate. These
concerns do not threaten the viability of HEMS projects, but simply highlight the need for
attentive and thoughtful design.
Now that HEMS projects have been defined and the reasons behind their use explained, it
is appropriate to present the research supporting these projects. The next chapter will explore
research examining the relationship between marine organisms and urban marine structures,
and present the support that has been expressed for engineering solutions, like HEMS, to
address the differences that researchers have found between communities on natural and man-
made substrates.
17
Chapter 2
THE VALUE OF URBAN MARINE STRUCTURES AS HABITAT FOR
MARINE ORGANISMS
Urban marine structures, including docks, bulkheads, and breakwaters, provide a large
proportion of the habitat available to marine organisms living in urban waterways. Further,
experts expect the number of urban marine structures in the marine environment to increase in
response to population growth in urban areas and sea level rise. Although obvious differences
exist where urban marine structures introduce hard substrate into areas with soft substrate,
it was assumed that urban marine structures simply added or replaced habitat in areas with
rocky or hard shores (Airoldi et al., 2005). Only recently have researchers challenged this
assumption and examined urban and natural substrates in greater detail.
In the past decade, researchers have found evidence of declines in community composi-
tion, ecosystem functioning, and non-native species abundances between assemblages on ur-
ban marine structures and natural rocky shores. Further, these biological differences seem to
be caused, at least in some cases, by underlying physical differences between the two types
of habitat. Understanding the characteristics of urban marine structures that affect the link
between habitat structure and the observed biological differences may lead to enhancing the
conservation value of urban marine structures (Connell, 2000).
There are both biological and cultural motivations for improving the quality of habitat of
urban marine structures for native marine organisms. Biologically, improving habitat qual-
ity may result in higher ecosystem function and more diverse communities, which are more
similar to natural rocky shores. The advantage and abundance of non-native species may also
be reduced, diminishing the potential for future non-native species invasions. Further, people
who live in cities value marine organisms for aesthetic and recreational uses. Fishing, bivalve,
and algae collection are some of these uses. Although a number of approaches could facilitate
improvement in the biological resources, a number of researchers have suggested engineer-
ing urban marine structures to create habitat more similar to natural rocky shores on urban
marine structures. HEMS projects are one way of accomplishing this aim.
The following sections will explore recent research examining the community differences
between urban marine structures and natural surfaces, as well as the underlying physical and
18
biological mechanisms that are thought to cause the community differences. Finally, the key
links between this background research and employing engineering solutions such as HEMS
projects to address the underlying physical differences between urban marine structures and
natural surfaces will be made.
2.1 Overview of Prior Research
The literature1examining ecological differences between urban marine structures and natural
substrates has developed in the past two decades, primarily by groups of researchers in Aus-
tralia and Italy. In addition to identifying a wide range of organisms inhabiting urban waters,
researchers have discovered a number of differences in the communities of organisms living on
and near docks, bulkheads, breakwaters, and other urban marine structures. Most research
has been focused on differences in the abundance and species present between types of urban
structures and rocky shores. A smaller subset of studies has also identified important differ-
ences in the ecosystem functions and non-native species abundances among urban structures,
and between urban structures and natural habitats. This research has also attempted to iden-
tify the root differences between urban marine structures and natural substrates that have
lead to the observed biological differences.
2.1.1 Organisms inhabiting urban waters
A diverse collection of organisms live in association with urban marine structures. Benthic
plant communities in urban waters are comprised largely of algae, including kelp and encrust-
ing algae, and seagrasses, such as eelgrass (MEC Analytical Systems, Inc., 2002). Hundreds
of species of invertebrates are often present in urban waters, including barnacles, mussels,
oysters, whelks, crabs, sea urchins, anemones, and starfish (Connell and Glasby, 1999; MEC
Analytical Systems, Inc., 2002; Toft et al., 2004). Additionally, many species of fish associate
closely with urban marine structures, including juvenile halibut, anchovies, and salmon (MEC
Analytical Systems, Inc., 2002; Toft et al., 2004; Toft and Cordell, 2006). Various marine mam-
mals and birds, including gulls, little penguins (Eudypyula minor), and sea lions have also
been found in urban waters (Figure 2.1; see MEC Analytical Systems, Inc., 2002; Preston et al.,
2008).
1There may be biases in what research is published (only results showing a difference may be submitted for publi-
cation), which locations are represented(almost all work on seawalls has been done by the same group of researchers
in Australia and Italy), analysis methods, and other details affecting the general trend seen with these studies.
However, this summary represents the current state of the research completed on these topics.
19
Figure 2.1: Photograph of seabirds perching and nesting on a rip-rap breakwater near Redondo
Beach, Los Angeles, California.
20
2.1.2 Impacts of urban structures on marine organisms
Docks and overwater structures
The addition of docks and overwater structures to the urban shoreline has directly impacted
marine organisms. These structures include ferry slips, piers, pontoons, wharfs, and buildings
or portions of buildings that are built over the water (see Figures 2.2 and 2.3). This chapter is
concerned only with large docks associated with present or historical commercial activity and
large overwater. However, some important research has only looked at smaller recreational
docks, and therefore these studies are also mentioned. Installing docks and overwater struc-
tures causes a number of physical changes along the urban shoreline. These structures create
shade, introduce novel habitat, and can change water flow patterns by introducing structure to
the water column. A number of differences related to these physical changes have been noted
between the communities associated with docks and adjacent communities.
Shading reduces the amount of light available for plants to use in photosynthesis. Work
with small docks indicated that low light conditions result in reduced plant density under small
docks by reducing photosynthesis and increasing plant mortality (Sanger et al., 2004; Castellan
and Kelty, 2005). As a result, communities of aquatic vegetation valued as nursery habitat
for fish, crabs, and shrimp are depressed under and around docks and overwater structures
(Sanger et al., 2004; Castellan and Kelty, 2005).
Although young-of-year fish are prevalent in the lower Hudson River estuary in New York
City, they were rare under large commercial piers (Able et al., 1998). In adjacent areas, young-
of-year fish were abundant, which suggests that large docks do not provide adequate habitat
for these fish (Able et al., 1998). Further research by Duffy-Anderson et al. (2003) corroborated
these results. It is thought that low light conditions from shading is the root difference result-
ing in the changes in fish behavior under docks and overwater structures, however the exact
biological mechanism has not been identified (Toft et al., 2004). Increased predation risk and
difficulty finding food may be two explanations for fish avoidance of low light conditions Toft
et al. (2004).
Hard structures associated with docks, including fiberglass and concrete pontoons and pil-
ings, support different species abundances than natural rocky shores (Connell and Glasby,
1999; Perkol-Finkel et al., 2006). More filter feeders (Israel) and non-native species (Aus-
tralia) were found on these substrates (Perkol-Finkel et al., 2008; Glasby et al., 2007). The
size, surface complexity, construction material, position in the water column, movement of the
substrate, altered light levels, water movement, orientation, and age of the surfaces exam-
21
Figure 2.2: Photograph of the Port of Tacoma commercial docks in Tacoma, Washington.
Figure 2.3: Photograph of ferry terminal docks in Sydney, Australia. A waterfront public space
bordered by a seawall can be seen in the background.
22
ined have been suggested as possible causes of the observed assemblage differences (Connell
and Glasby, 1999; Connell, 2000, 2001; Glasby and Connell, 2001; Perkol-Finkel et al., 2006,
2008). However, support for these factors is mixed and sometimes conflicting (Connell and
Glasby, 1999; Connell, 2000, 2001; Glasby and Connell, 2001; Holloway and Connell, 2002;
Perkol-Finkel et al., 2008). Further research is necessary, and localized research is especially
important as the relative importance of these factors may vary by location.
Dock pilings also alter water flow patterns. Dense pilings located in New York have been
observed to cause changes in the water velocities resulting in accumulations of soft substrate
(Alevras, 2008). This area historically was primarily wetland and rocky intertidal areas. Ac-
cumulations of up to 30 ft of anoxic sediments support many polychete worms, but few other
organisms (Alevras, 2008; Alevras and Zappala, 2008). Reduced biodiversity in these areas is
likely due to the loss of hard substrate and the low oxygen content of the sediments that few
organisms can survive.
Bulkhead and Seawall faces
Urban marine environments also are extensively modified through the addition of seawalls
and bulkheads. In general, these structures are made of solid concrete, wood, metal, or stone
and are designed to protect the shoreline from wave energy, erosion, and flooding in order to
stabilize the shoreline (see Figure 2.4). Profound changes have been noted when seawalls are
installed in areas with previously soft substrate (Airoldi et al., 2005). These changes include
reduced area of soft bottom habitat, reduced soft-bottom species richness, with corresponding
increases in hard-bottom substrate and species richness (Airoldi et al., 2005). These results
are also supported by Peterson et al. (2000). However, the ecological changes that arise when
seawalls are installed in areas with hard substrate are more nuanced.
Unlike docks and overwater structures that are quite different than structures normally
found in most coastal regions, sea walls and bulkheads are superficially more similar to natural
rocky coasts. In fact, Connell and Glasby (1999) found that assemblages on natural sandstone
reefs and sandstone seawalls were not different, although they did differ from other surfaces
such as pilings and pontoons. Further research found similar assemblages at the low-shore
level, but differences at the mid- and high- shore levels (0.6-1.1m above low water spring tides)
for unknown reasons (Chapman and Bulleri, 2003; Bulleri et al., 2005). Assemblages of en-
crusting, foliose, and filamentous algae as well as sessile animals on seawalls and rocky shores
were similar (Chapman and Bulleri, 2003).
23
Figure 2.4: Photograph of the Seattle Seawall, a vertical poured concrete seawall in Seattle,
Washington. Image courtesy of the United States Army Corps of Engineers
24
Despite these similarities, a number of differences in community structure have been found
between seawalls and natural rocky shores. The number of mobile animal species found on
rocky shores was almost twice as large as the number found on seawalls (Chapman and Bul-
leri, 2003). Species found only on rocky shores included starfish, limpets, chitons, snails, and
predatory whelks (Chapman, 2003). Further research found that while seawalls may provide
acceptable habitat for common mollusks, species including coiled snails and those restricted to
specialist microhabitats could not persist on seawalls (Chapman, 2006). These findings were in
part supported by research in Italy which showed that the encrusting communities on seawalls
contained fewer taxa than bulkheads and natural rock walls due to consistent differences in
rare species (Bulleri et al., 2004). However, more research in other areas is needed to determine
the generalizablity of these results for other invertebrates.
In urban freshwater, fewer fish were found near seawalls than other habitat types in Oregon
(Friesen et al., 2003), and in Washington, the Lake Washington juvenile Chinook were found
in disproportionately low numbers near bulkheads and rip rap (Tabor and Piaskowski, 2002).
Similarly, species richness was lower near bulkheads than near rip rap or natural sites in
Wisconsin (Jennings et al., 1999). However, areas with rip-rap2had similar fish assemblages
as natural shorelines, and were important habitat for adult fish in both fresh and salt water
(Barwick and Kwak, 2004; U.S. Army Corps of Engineers, 2008). Rip-rap shorelines on the
urban marine shore in Seattle had greater taxa richness than nearby seawalls, and in Italy
only small inconsistent differences in communities were found (Toft et al., 2004; Bulleri et al.,
2004).
The reduced surface complexity of seawalls when compared with natural rocky shores may
be partially responsible for these observed differences. Reduced surface complexity of artificial
substrates has been linked to reduced species diversity on artificial substrates in Spain, Italy,
and other areas (Bulleri et al., 2004; Gacia et al., 2007). Many species found only on rocky
shores live in rock-pools3, however seawalls do not have rock-pools and cannot support these
species. This suggests that the lack of micro-habitat in seawalls affects the species — especially
rare species — found there (Chapman, 2003). Crevices in seawalls also provide important
micro-habitat to chitons by providing protection against predators and physical stress and
increasing survival and recruitment (Moreira et al., 2006). The availability of these micro-
habitats may have wider ecosystem influences as chitons influence the distribution of algae
2Rip-rap structures are composed of rock or concrete pieces mounded along the shoreline or in the water around a
harbor or beach for protection.
3Rock pools are small depressions in the rock that hold water.
25
and other organisms (Moreira et al., 2006). Conversely, rip-rap supports a wide range of species
as it creates habitat complexity by providing a variety of sizes of holes for marine organisms
to inhabit. At the landscape scale, however, increasing amounts of rip-rap reduced habitat
diversity (Jennings et al., 1999). Additionally, urban marine structures which occur in close
proximity may modify the communities found at each site (Blockley, 2007).
Unlike dock and overwater shading, the factors influencing community structure on sea-
walls are diverse. Other physical differences between substrates may cause many of the ob-
served biological differences. The orientation of the urban marine structure — vertical ver-
sus horizontal – could be important in determining assemblages (Glasby and Connell, 2001).
Substrate depth may also be important, perhaps due to differences in larval availability at
different depths4(Holloway and Connell, 2002; Perkol-Finkel et al., 2008). Shallow substrates
receive more light for photosynthesis, but are subject to higher wave energy than deeper sub-
strates. Other physical factors, including size, shape, arrangement, and age have also been
suggested as possible causes of the observed assemblage differences, but the evidence support-
ing these conclusions is mixed (Connell and Glasby, 1999; Connell, 2000, 2001; Perkol-Finkel
et al., 2008).
The distance between the natural and man-made substrates may also be important. In
areas with naturally soft substrate, hard man-made substrates may act as corridors that can
alter communities on natural substrate through genetic mixing and non-native species intro-
ductions (Gacia et al., 2007). In areas with naturally hard substrate, urban marine structures
closer to the natural substrate develop communities that are more similar to those found on
the natural substrate (Gacia et al., 2007).
Wave energy may also play a role in determining species composition between exposed
breakwaters and natural reefs and sheltered breakwaters (Clynick, 2006). For urban marine
structures such as pontoons, differences in assemblages may be due to their floating nature.
Floating creates specific physical differences between pontoons and natural substrate, includ-
ing increased light levels and changes in water movement (Connell, 2001; Glasby and Connell,
2001; Perkol-Finkel et al., 2008).
4For example, barnacle larvae tend to be found near the surface, and settle on shallow substrate (Perkol-Finkel
et al., 2008).
26
In addition, reduced shoreline vegetation along urban waterfronts impacts marine species
through alteration of food availability. Reduced shoreline vegetation was associated with lower
abundances of insects available to juvenile salmon in Seattle, altering feeding behavior (Toft
et al., 2004; Toft and Cordell, 2006).
Comparison of ecosystem functions
Urban marine structures and natural substrates differ in more complex biological ways as
well. Decreased recruitment rates were found on seawalls compared to rocky shores in Aus-
tralia (Bulleri, 2005a). The ability to support reproduction also differed between natural and
man-made substrates. Shorelines with rip-rap had similar species assemblages as natural
shorelines, but these structures did not provide habitat for spawning bluegill (Barwick and
Kwak, 2004). On seawalls the reproductive capacity of limpets was greatly reduced as the
limpets on seawalls were smaller and therefore laid smaller and fewer egg-ribbons (Moreira
et al., 2007). Differences in which species were recruiting to seawalls versus natural rocky
shores were also found (Bulleri, 2005a).
These differences were due mostly to the percentage of bare rock at seawall sites, which may
perhaps result in limited supply or slower settlement of larvae, or greater mortality of larvae
on seawalls (Bulleri, 2005a). Recruitment differences could not be attributed solely to the
material properties of the substrate as identical settling panels attached to seawalls and rocky
shores developed different assemblages (Bulleri, 2005a). Differences in predation, topography,
and other physical and ecological processes at multiple scales likely interact in complex ways
to produce the observed patterns of recruitment (Bulleri, 2005a). Further research is needed
to determine exactly what factors influenced the observed differences (Bulleri, 2005a).
Biodiversity and community composition are each integrally tied to ecosystem functioning
(Hooper et al., 2005). The abundance and diversity of species present influences organismal
traits and species interactions, which in turn influence ecosystem processes (Chapin et al.,
2000). As differences in biodiversity and community composition have been found between ur-
ban marine structures and natural substrates, one might expect that differences in ecosystem
functioning would also be found. Early research has shown that this is true. Differences in
key species abundance may exert a strong influence on communities through ecosystem engi-
neering, predation, and other mechanisms. For example, oysters are ecosystem engineers and
create habitat for a number of other species, including whelk (Jackson et al., 2008). Jackson
et al. (2008) hypothesize that if seawalls vary in their capacity to support oysters from rocky
27
reefs, other species including whelks will be detrimentally affected.
Differences in non-native species
Non-native, or introduced species5are often found in association with urban marine structures,
including docks and bulkheads. There is concern that urban marine structures, particularly
those in and around port cities, could facilitate invasion by those introduced species in areas
where these species are a concern. Although some introduced species may not be harmful,
and may even be beneficial, other introduced species can cause significant environmental and
economic harm (see Pimentel et al., 2000; Manchester and Bullock, 2000; Eno et al., 1997; Ruiz
et al., 1997). Introduced species are a ‘significant force of change in marine’ and estuarine
environments and some may threaten commercially important species (Ruiz et al., 1997).
Natural and man-made structures have been found to differentially influence native and
non-native species populations. Pontoons and pilings supported about twice as many non-
native species as nearby rocky reefs in Australia (Glasby et al., 2007). However, this is not
true for all urban marine structures, as more native than non-native species were found on
sandstone seawalls (Glasby et al., 2007).
There is legitimate concern that man-made structures may increase the ability of non na-
tive species to establish by creating additional favorable habitat (Connell, 2001; Glasby et al.,
2007). For example, adding more favorable habitat has increased the invasion potential of
many bryozoans and colonial ascidians, which are limited by their small natural dispersal
ranges (Connell, 2001; Bulleri and Airoldi, 2005; Glasby et al., 2007). Floating test panels
located approximately 5 m from shore were found to be colonized more readily by non-native
species than natives (Glasby et al., 2007). These panels mimic floating docks or pontoons, and
increasing the number of these urban structures may make it more likely for viable populations
to establish and increase the likelihood of a successful invasion (Glasby et al., 2007).
Researchers have devoted significant time to determining why non-native species are so
abundant on urban marine structures. Differences in community development, but not re-
cruitment, were noted between native and non-native species on urban marine structures and
natural shorelines (Glasby et al., 2007; Tyrell and Byers, 2007). In Maine, natural and man-
made substrates recruited similar numbers of native and non-native species, suggesting that
both groups of species are capable of settling on a wide range of substrates (Tyrell and Byers,
2007). However, on urban marine structures non-native abundances rose quickly, while native
5Non-native species are not indigenous to the ecosystem of interest, but arrived there due to human activity.
28
abundances declined (Tyrell and Byers, 2007).
It is thought that post-settlement processes, including relative adhesion strength, growth
rates, and competition, contribute to this pattern (Tyrell and Byers, 2007). Differences in
the physical properties of the substrates likely lead to these observed changes. Urban marine
structures represent novel habitat for both native and non-native species, and as a result native
species may lose the competitive evolutionary advantage they possess on natural substrate on
urban marine structures (Tyrell and Byers, 2007). However, the exact physical mechanisms
are yet unknown.
2.2 Habitat Enhancement of Marine Structures: The Next Step
The implication for shoreline management of these studies is that there is a clear need to
seriously consider how urban marine structures are designed and how this impacts marine
species. Where preserving and encouraging local biodiversity is deemed important, society
must consider how to actively design urban marine structures to the benefit of local species. A
number of the researchers whose work is discussed above have come to the same conclusion.
While there are many aspects of habitat design that differ between urban marine structures
and natural shorelines, two in particular are mentioned in the literature. The first is the slope
or orientation of the substrate. As previously mentioned, many urban marine structures, and
particularly seawalls, are much steeper than natural shorelines. Additionally, seawalls and
pilings are strictly vertical, while natural shorelines contain both vertical and horizontal faces.
This results in physical differences in habitat and reduced habitat area. In response, Chapman
(2003) suggests that seawalls could be designed to incorporate a gentler slope or a combination
of horizontal and vertical surfaces.
Researchers also emphasize the need to incorporate microhabitat into urban marine struc-
tures. Features such as crevices, which provide important refugia for many organisms, are
largely absent in man-made structures. Support for including microhabitat in urban marine
structure design is wide. Chapman (2003) recommended that micro habitat cavities designed
to retain water during low tide should be integrated into the design of seawalls. This sugges-
tion was echoed by Moreira et al. (2006) as they suggest that seawalls be designed to include
crevices and other analogous features in order to maintain chitons and other similar species.
They maintain that these simple design changes would improve the quality of seawalls as habi-
tat and greatly help sustain populations of chitons and other species that rely on crevices to
survive in an area (Moreira et al., 2006).
29
More generally, there is broad support for mitigating the habitat changes when urban ma-
rine structures are built in place of natural shorelines (Bulleri, 2005a). However, researchers
also emphasize the need to understand the needs of fish and other organisms to best accom-
modate species’ habitat requirements in re-designing urban marine structures (Bulleri, 2005a;
Gacia et al., 2007; Moreira et al., 2006; Moreau et al., 2008). In one of the only tests of this idea,
an experiment manipulating artificial substrate to increase the number of micro-crevices, frac-
tures, and rockpools resulted in increasing the number of species present and the biodiversity
present on the artificial substrate (Moschella et al., 2005).
Initiatives to improve the habitat quality of urban marine structures are especially relevant
given the expected increases in urban marine structures. Both increasing human population
and sea level rise are anticipated to contribute to this trend. Moreira et al. (2006) note that “in
an increasingly urbanized world, understanding how to improve the value as habitat of man-
made structures will be essential for conserving biodiversity.” A statement from Chapman
(2003) provides a good summary; “With the increasing conversion of natural shores to artificial
habitats, understanding how to build such structures to maximize their ability to maintain
natural biodiversity in urban environments must take priority, whilst simultaneously main-
taining engineering and safety standards.”
A significant amount of research is necessary to support any initiative to improve the habi-
tat quality offered by urban marine structures. Understanding which species or taxa are af-
fected by replacing natural shores with urban structures is an important first step. Studies
similar to those conducted by Moreira et al. (2006) may illuminate key physiological differ-
ences in species between natural shores and urban structures. These studies will likely point
to possible causes of the observed differences between natural shores and urban structures.
Understanding what characteristics of urban structures affect key species will therefore be
an important next step. Valuable comparisons might include provision of micro-habitat, tex-
ture/material of the substrate, and environmental characteristics including water temperature,
wave energy, and water movement. Experiments examining whether the HEMS designs affect
these variables or ask how they function in areas with different physical conditions would also
be valuable. These tests will help to differentiate between situations where HEMS might be
able to help and those that are limited by environmental factors that HEMS cannot address,
as well as to help tailor HEMS to specific conditions to get the best results.
Further avenues of research should explore locations that have not been previously studied,
locations where new urban structures or HEMS are being considered, and examine changes at
30
small and large scales. The scale of the research will largely depend on the ecological scale
being addressed in the research. Studies examining the effects of habitat characteristics on a
species may be conducted on replicates on the scale of centimeters (20 x 20cm plots were used in
Moschella et al., 2005) with meters between replicates. Studies that address more basin wide
effects, such as changes in the invasion potential of non-native species due to urban structures,
may require replicates at the scale of meters with hundreds of meters between replicates.
This research will be crucial to the proper design of HEMS. Studies testing how differences
in urban structure design impact marine species can be integrated into the pilot phases of
HEMS projects. The study conducted by Moschella et al. (2005) is a particularly valuable
resource, as they both compared the diversity on coastal defense structures and natural rocky
shores and the effects of various design features on assemblages. Although general studies like
this are valuable, other studies should be conducted within an estuary instead of in different
countries in order to provide targeted advice for HEMS projects.
Additionally, there is also a need to address the differences between urban benthic habi-
tats, and more natural benthic habitats. Multiple habitat types, including rocky areas and
seagrass/kelp beds are largely absent from urban areas. While structures such as artificial
reefs built to support marine protected areas and fisheries have been widely studied in non-
urban waters, their use in an urban environment has not been systematically studied.
2.3 Concluding thoughts
Research on urban marine structures has revealed some important differences in community
composition, ecosystem functioning, and non-native success between urban marine structures
and their natural counterparts. Engineering approaches to improving habitat in urban waters
draw upon this research to identify potential areas where urban marine structures could be
altered to improve their habitat value. Although this research is still quite preliminary, many
scientists researching urban marine structures have voiced support for habitat improvement
projects. Research opportunities in this area are even more urgent given anticipated increases
in human pressures on urban waters due to growing coastal populations and sea level rise.
31
Chapter 3
IMPLEMENTING HABITAT ENHANCING MARINE STRUCTURES
Successful addition of habitat to an urban waterfront requires careful planning, thought-
ful design and construction practices, and meaningful management and monitoring programs.
The installation of Habitat Enhancing Marine Structures (HEMS) is no exception to these gen-
eral standards Unfortunately, no guidance on how to successfully implement HEMS projects
has been published to date. To begin filling that gap, this thesis will draw upon a significant
body of literature concerning the implementation of artificial reefs, terrestrial habitat improve-
ment projects, and wetland restoration. While HEMS projects are unique in how they address
improving the habitat value of urban waterfronts, these other fields provide important lessons
that can be applied to HEMS projects. This chapter draws on the experience gained in these
other fields to discuss the implementation of HEMS projects. Regional planning of the ur-
ban landscape is considered first, as these planning efforts support individual HEMS projects.
Second, the planning, design, construction, management and monitoring, and education and
outreach components of an individual HEMS project are considered, with references to more
in-depth authorities where appropriate. Figure 3.1 summarizes this implementation process.
3.1 Regional Planning of the Urban Landscape
The use of HEMS can help create an aesthetically pleasing urban waterfront that fulfills the
economic and social goals of cities and the habitat needs of marine organisms (Figure 3.2).
A waterfront designed to take advantage of HEMS could support a mosaic of habitat patches
tailored to the needs of regional biodiversity. Each individual HEMS project would contribute
a specific habitat patch to the larger urban landscape. Viewed broadly, this waterfront would
emulate a naturally patchy landscape composed of common habitat types found in the region.
A number of researchers have encouraged the adoption of landscape scale restoration and
planning over traditional site-by-site restoration (see eg. Weinstein, 2007). Characteristics of
the surrounding landscape impacts the abundance and species richness of a smaller patch
restoration project (Hodgkison et al., 2007). As a result, integrating the management of in-
dividual HEMS projects with the management of the surrounding landscape can improve the
32
Figure 3.1: Diagram of HEMS installation process.
33
Figure 3.2: Multiple HEMS projects installed along an urban waterfront, showing how multiple HEMS can be used in conjunction
with each other to create a mosaic of different habitats.
34
success of HEMS projects and further the overall landscape level habitat goals (Hodgkison
et al., 2007). Improving habitat within a localized patch without addressing landscape level
concerns may only result in cosmetic changes (Hodgkison et al., 2007). The performance of
rehabilitation programs is also dependent on strategic planning at the landscape scale, and
the ability for each subsequent project to learn from existing projects (Simenstad et al., 2004).
Support for all stages in the lifecycle of non-migratory regional marine organisms could be ad-
dressed through these habitat patches. Some life stages of migratory species (e.g. salmon) may
also be supported.
These landscape scale habitat improvements cannot be implemented quickly. Staffing, tech-
nical, and practical considerations limit the number of HEMS that can be installed concur-
rently. Additionally, while HEMS projects are cost-competitive, budgets are often very limited,
especially in difficult economic times. Therefore, regional planning tools must be used to work
towards the long term vision of the urban waterfront.
3.1.1 Regional Planning Tools
Fortunately, existing planning tools can guide the implementation of many individual HEMS
projects over time to form, like pieces in a puzzle, the larger urban habitat landscape. This is
the ideal ecological result from the construction of HEMS projects. Further, the goals identified
in the first chapter for a single HEMS project can be reinforced across multiple HEMS installa-
tions. For example, informational signs for multiple habitat types (each a HEMS project) could
be linked together to form an ‘urban habitat informative trail,’ creating a diverse and informa-
tive opportunity for public education. With landscape scale planning, specific areas can also be
reserved for commercial activities, such as keeping a shipping lane clear of any potential navi-
gational hazards, or designating certain areas as ports. These reservations will allow planners
to choose HEMS projects that suit the area; no HEMS projects may be compatible with the
strict navigational requirements of shipping lanes, however many different HEMS could be
integrated into port facilities.
A number of different planning approaches are available at each level of government. Gen-
erally, goal and priority setting should precede selection of specific management tools, such as
zoning. Partnerships and, in the United States, the Coastal Zone Management Act may be
useful in formalizing these planning approaches. There are many other methods than those
mentioned here, and they will vary by country, state, and local regulations. Which specific
approach is used is highly situational, and may depend on who has jurisdiction over the water
35
column and ocean bottom.
Goal and priority setting
Setting goals and priorities for a region involves defining the issues of import at a regional
scale. These may include disparate goals such as improving water quality, improving marine
ecosystems, or increasing port capacity. Multiple, competing goals such as these are involved
in shoreline management, and placing additional emphasis on habitat or installing HEMS
may come at the expense of another objective. Potential tradeoffs as well as opportunities for
action should be recognized and anticipated in a coherent plan. Community and stakeholder
participation is valuable in setting landscape scale goals and priorities that are in line with
(Restore America’s Estuaries, 2002).
Evaluating the degree to which these goals and priorities have been met requires monitor-
ing of both individual HEMS projects and the overall landscape. Baseline conditions should be
gathered so that future progress can be evaluated (Restore America’s Estuaries, 2002).
Restore America’s Estuaries (2002) found that when a habitat restoration project was part
of a larger planning project that set goals and priorities at the landscape scale, it was more
effective. They suggest that landscape planning that sets goals and priorities, including habitat
quality and quantity goals, should be completed for all areas of the United States (Restore
America’s Estuaries, 2002). These efforts can help direct limited resources to the most critical
needs, ‘allow benefits to be accrued over a larger scale, and enhance the overall effectiveness’
of projects, including HEMS (Restore America’s Estuaries, 2002).
Zoning
Zoning is a planning tool that allows managers to dictate the acceptable uses of land or wa-
ter. While zoning is most frequently used on land, the technique can be successfully used in
marine environments, most notably in the multi-use Great Barrier Reef Marine Park1. The
Zoning Plans created for the Reef describe which activities can occur in each part of the reef.
Regulated activities include aquaculture, boating, diving, photography, fishing, research, ship-
ping, tourism, and trawling. The zones allow a range of these activities. The least permissive
is the ‘Preservation Zone’ where all activities except for permitted research are prohibited. The
most permissive is ‘General Use Zones,’ where all activities are allowed, although harvesting
1http://www.gbrmpa.gov.au/corp_site/management/zoning
36
and tourism activities require permits. These zones have successfully allowed competing uses
to co-exist and minimized conflict.
A similar approach could be used in the urban waterfront. Different zones, including those
where habitat or commercial activities are the priority, could be created. The documentation for
each zone should contain a list of acceptable/non-acceptable uses, use priorities, and objectives
for the area. Permits may be required for some uses in each area. Extensive information
regarding the zoning techniques and implementation used in the Great Barrier Reef Marine
Park have been published by the Australian Government, and these may be of interest to
planners and managers2.
Habitat Networks
Habitat networks consist of patches of habitat (nodes) connected by corridors, which are ei-
ther explicit habitat corridors or a stream of organisms traveling between two nodes (Opdam,
2002). Habitat networks “emphasize the functioning of landscapes and may be used by plan-
ners and landscape architects to facilitate or inhibit flows and movements across land mosaics”
(Dramstad et al., 1996).
Habitat backbones are a conceptual offshoot of habitat networks developed in the Nether-
lands to manage permanent and transient habitat patches in the dynamic urban environment.
A habitat backbone is a “planning and design approach aimed to create a network consisting
of stable (key) patches surrounded by patches of a more temporary nature” (Snep and Ottburg,
2008). Species with low or medium dispersal abilities that are found in dynamic habitats are
the primary beneficiaries of habitat backbones (Snep and Ottburg, 2008). Habitat backbones
take advantage of opportunities for biodiversity conservation in urban areas with high land
turnover (Snep and Ottburg, 2008). Port areas are good candidates for habitat backbones as
they are constantly being upgraded and rebuilt.
There are five criteria for a habitat backbone strategy: (1) the backbone layout, which is
“a continuous or well-connected structure of habitat patches;” (2) the backbone destination,
or the stability of the permanent habitat patches; (3) the backbone management, taking into
account the requirements of the target species; (4) the size of the backbone, which should
accommodate enough individuals of the target species to ensure the persistence of the species
among at least three key patches; and (5) the backbone location and temporary habitats, as the
2They can be found on-line at http://www.gbrmpa.gov.au/corp_site/management/zoning/planners_
info
37
current and future temporary habitats must be accessible from the habitat backbone (Snep and
Ottburg, 2008). A habitat backbone project was installed in The Port of Antwerp, Belgium to
benefit natterjack toads (for further information, see Snep and Ottburg, 2008). Although this
implementation benefited a land based species, the habitat backbone philosophy along with
broader habitat networking concepts should be applied to urban waterfronts.
Planning Partnerships
Planning partnerships between cities, counties, states, or some combination can create plans
that set goals and implement projects at a broader scale. Partnerships may also occur between
non-governmental organizations, private organizations, and government bodies. A partnership
may form to pursue a specific goal, such as water quality or a habitat improvement project, or
to coordinate multiple goals or create a zoning plan that is cohesive over multiple jurisdictions.
Additionally, planning partnerships can involve the private landowners who own the land near
HEMS projects. The management actions of these landowners can have profound effects on the
HEMS site, and thus forming partnerships can increase the success of HEMS projects (Mason
et al., 2007).
Restore America’s Estuaries (2002) explains that partnerships are essential to the success
of restoration projects. While planning partnerships refer to partnerships whose main goal is to
produce landscape scale plans, these groups may overlap in whole or in part with partnerships
to implement HEMS projects, as discussed later in this chapter.
A number of planning partnerships for habitat restoration and enhancement have already
been formed. The Chesapeake Bay Program created the Chesapeake 2000 Agreement, which
is meant to guide restoration and protection projects in the bay during this decade (Borde
et al., 2004). The Comprehensive Everglades Restoration Plan, approved in 2000, will guide
the restoration, protection, and preservation of the Everglades over the next 30 years (Borde
et al., 2004).
Coastal Zone Management Act or Other Legislation
The Coastal Zone Management Act (CZMA) of 1972 encourages states to create coastal zone
management plans ‘to preserve, protect, develop, and where possible, restore or enhance, the
resources of the Nation’s coastal zone for this and succeeding generations’ (16 U.S.C. §1452(1)
(1996)). Many different approaches to the coastal zone management programs (CZMPs) are
allowed under the CZMA, although the requirements for federal approval of the state plan is
38
detailed in 16 U.S.C. §1455-6.
Every coastal state, save for Illinois, has implemented their own CZMP. As dictated by the
statute, each program includes procedures for public participation, administrative coordina-
tion, and prioritizing uses of the coastal zone. Both goal and priority setting and zoning, along
with other planning methods, can be employed in CZMPs. If these methods are written into
CZMPs as ‘enforceable policies,’ any future federal actions that are likely to affect land or water
in a state’s coastal zone will be required to meet the consistency requirements of the CZMA.
Other legislation at the federal, state, or local levels can also create regional plans. In
Louisiana, the Coastal Wetlands Planning, Protection and Restoration Act is a federal law
enacted to develop a restoration plan for the state’s coastal wetlands. The program has coordi-
nated and integrated restoration efforts through 141 authorized projects. Funding is supplied
jointly by the federal and state governments (Borde et al., 2004; Louisiana Coastal Wetlands
Conservation and Restoration Task Force, 2006).
Advanced planning should ensure a cohesive landscape as multiple HEMS projects are im-
plemented over time. Broad planning can help to make more efficient use of available funding
or implementation opportunities as they arise. Regardless of the regional planning tool used,
good records and well documented plans are essential to long-term success. These documents
will provide consistency though staff turnover and elections.
3.2 The Issue of Scale
In the course of implementing HEMS projects, the issue of integrating multiple ecological
scales, be it temporal, spatial, or otherwise, will undoubtedly arise. The issues of pattern
and scale are central to ecology (Levin, 1992), and their importance is no less when considering
HEMS. There are two components and four dimensions of scale in ecology. The components are
the resolution, or how finely the study space is divided, and the extent of the study area. The
dimensions of scale include space, time, taxonomic resolution, and organizational level — from
individual organisms to entire communities. Although all of these factors are important to the
research and implementation of HEMS in urban waters, the dimension of space is particularly
important.
Spatial scales affect nearly every aspect of urban marine structure research and habitat im-
provement project design and implementation, including HEMS projects. Most urban marine
structure research, particularly concerning community composition and ecosystem functioning
studies, is conducted at scales of meters to tens of meters. Many HEMS projects will be de-
39
signed for these scales as well. However, although research and design have focused on the
important processes at these small scales, many scales are or will be impacted. Changes in
habitat heterogeneity — for example adding rock-pools to a seawall — will not only change the
relative abundance of rare species on the portion of the seawall that has been modified, but
may also impact local species patterns at scales of tens to hundreds of meters. Smaller scale
patterns such as food chain dynamics and relative species abundances at scales of less than a
meter may also be impacted by the novel presence of the rock-pool dependent species.
The research conducted by Jennings et al. (1999) shows the importance of spatial scales in
installing urban marine structures. Short rip-rap installations (25 m to 100 m) in Wisconsin
lakes were found to support relatively high species richness. Looking at these patches (small
extent and fine resolution) individually showed that rip-rap was correlated with increased fish
and habitat diversity compared to sites with seawalls and those with no structure . However, at
the landscape spatial scale (large extent and coarser resolution) increasing amounts of rip-rap
in lake in fact reduced habitat diversity because rip-rap replaces other habitat types.
The rip-rap example demonstrates a key consideration in planning and designing HEMS
projects. At the small spatial scale of an individual project, increasing habitat heterogeneity
by, for example, adding texture, rock pools, or a range of orientations to seawall panels may
provide habitat for habitat-specific rare species and result in communities and ecosystem func-
tioning on urban marine structures that is similar to natural substrate. However, while these
projects individually may be very beneficial, using the same seawall panels everywhere in an
urban waterfront may risk reducing landscape scale habitat heterogeneity. This would defeat
the purpose of implementing HEMS projects, which are designed to combat the homogeneous
habitat offered by seawalls and docks in urban waters. Striking a balance is therefore impor-
tant to increasing habitat diversity and avoiding habitat homogeneity at both small and large
spatial scales.
3.3 Implementing a HEMS Project
Regional planning at the landscape scale is ideally the first step to planning HEMS projects.
However, further steps are necessary to properly implement an individual HEMS project as
part of the larger landscape. Although no one has directly addressed the best practices to
implement a HEMS project, ample literature has discussed methods for implementing other
habitat enhancement projects. Among these papers, which address coastal habitat restoration,
estuarine restoration, the installation of artificial habitat for fisheries enhancement, and ter-
40
restrial habitat enhancement, there are five reoccurring themes. These are project planning,
project design, construction and installation, management and monitoring, and education and
outreach. While these concepts are taken from other fields, they are informative to HEMS
projects as these fields share much of the same theoretical base. For example, an excellent set
of detailed steps for implementing an ecological restoration project are available through the
Society for Ecological Restoration International3(Clewell et al., 2005).
3.3.1 Adaptive Management
Adaptive management is a resource management technique developed by C.S. Holling and C.J.
Walters. It is ‘a systematic approach for improving resource management by learning from
management outcomes,’ or more specifically;
Adaptive management [is a decision process that] promotes flexible decision mak-
ing that can be adjusted in the face of uncertainties as outcomes from management
actions and other events become better understood. Careful monitoring of these
outcomes both advances scientific understanding and helps adjust policies or opera-
tions as part of an iterative learning process. Adaptive management also recognizes
the importance of natural variability in contributing to ecological resilience and pro-
ductivity. It is not a ’trial and error’ process, but rather emphasizes learning while
doing. Adaptive management does not represent an end in itself, but rather a means
to more effective decisions and enhanced benefits. Its true measure is in how well
it helps meet environmental, social, and economic goals, increases scientific knowl-
edge, and reduces tensions among stakeholders. (National Research Council, in
Williams et al., 2007)
Importantly, adaptive management allows managers to acknowledge the uncertainty about the
functioning of urban ecosystems and how management actions affect them, improves the un-
derstanding of how the urban ecosystem functions in order to achieve management objectives,
and uses management interventions and monitoring to increase understanding and improve
future management decisions (Williams et al., 2007).
Many, but not all, HEMS projects are good candidates for adaptive management. HEMS
projects where there is a management choice to be made, for example techniques with vary-
3This is also available online at http://www.ser.org/content/guidelines_ecological_restoration.
asp.
41
ing feasibilities, costs, or degrees of public acceptance, may benefit from using adaptive man-
agement. When solutions are pre-determined, trying to use adaptive management may be
detrimental. There should also be opportunities to apply the learning gleaned from adaptive
management. In urban waterfronts where each HEMS project will inform subsequent projects,
or where a HEMS project may be revised in the future, adaptive management should be used
(Williams et al., 2007). Additionally, adaptive management can be used to guide the man-
agement of harvest, recreational, or commercial impacts on HEMS projects. The latter use of
adaptive management is beyond the scope of this review, but may be helpful to note should a
project involve these management goals.
Project managers considering utilizing adaptive management should consider the qualities
of their HEMS project as well as the future monitoring and management of the project. For
example, suppose a management team is going to incorporate small depressions and fissures
into a seawall rebuild. If the managers have a number of techniques at their disposal, for
example building the texture into the concrete molds or cutting them with a grinder after the
concrete has set, then adaptive management should be considered. Similarly, if the managers
want to apply the lessons learned from this HEMS project to other seawall rebuilds, for future
modification of this seawall, or as information for seawall projects elsewhere in the world,
the managers should consider using adaptive management. However, if managers are going to
install chiton habitat on seawalls and do not want to consider improving the design or alternate
techniques, adaptive management will be a poor fit.
According to Williams et al. (2007), the five key elements in using adaptive management
are stakeholder involvement, management objectives, management alternatives, predictions
of the effects of potential management actions, and monitoring protocols and plans. Once these
key elements are in place, an iterative process begins. First, a management action from the
set of alternatives is identified and implemented. Then, follow up monitoring is used to follow
changes in the system as they occur, and baseline data may be collected before the manage-
ment action if it is deemed necessary. Assessment of the monitoring data and comparisons
of the actual data to predicted outcomes is the next step. This assessment offers greater un-
derstanding of management impacts, assists in selecting management actions, and is used to
evaluate management effectiveness. The final step is iteration, where improvements in under-
standing from monitoring and assessment steps are used to select the management action to
be used at the next decision point (Williams et al., 2007).
42
This is a very brief summary of the adaptive management process. An excellent source for
further information about adaptive management is the U.S. Department of the Interior’s Adap-
tive Management Technical Guide.4The guidebook Systematic Approach to Coastal Ecosystem
Restoration by Diefenderfer et al. (2003) also contains a good section on adaptive management.
While these guidebooks are focused more on habitat restoration than enhancement, they con-
tain much valuable information for HEMS projects.
3.3.2 Project Planning
Many different project planning systems for habitat enhancement or restoration have been
developed. The HEMS project planning method presented here combines many of the ele-
ments from project planning methods created for restoration projects. As HEMS projects are
implemented in urban areas and are designed to enhance urban marine structures, meth-
ods described for planning restoration projects have been modified here for application to
HEMS projects. Further customization based on the needs of the local ecosystem and the
social/economic environment where a HEMS project is being installed will be necessary. How-
ever, these localizations are outside the scope of this overview.
The key steps for planning a HEMS project include: stakeholder participation and creating
project partnerships, and identification of project objectives and goals. Other closely related
steps including location selection and module design will be considered in the next section cov-
ering project design. These steps correspond to the ‘stakeholder involvement’ and ‘management
objectives’ steps identified in the adaptive management framework discussed above.
Stakeholder involvement
Stakeholder involvement from the earliest planning stages for HEMS projects will increase
the chances of success. This is particularly important for urban habitat enhancement (Borde
et al., 2004). Stakeholders are persons or groups which have an interest in the HEMS project
because they can be directly or indirectly affected by the HEMS project. Stakeholders for a
HEMS project may include members of the public, commercial or recreational harvesters, port
officials, city planners, and other commercial or recreational users of the urban waterfront.
Productive stakeholder involvement requires early involvement by stakeholders during the
planning process and through construction to management phases. Stakeholders are educated
and informed by their involvement and the project plans should be adjusted to accommodate
4Available on-line at http://www.doi.gov/initiatives/AdaptiveManagement/documents.html.
43
stakeholder concerns during the process. While this does not guarantee that every stakeholder
will support the plan, stakeholder involvement allows stakeholders to understand the project
planning and design process and outcome, and they will have been able to express their views
and present suggestions. These actions can greatly reduce the level of conflict concerning a
project.
Each area where HEMS projects are implemented will be different, however it is impor-
tant to identify all stakeholders, perhaps through public meetings, in the earliest stages of
project planning and work with these stakeholders to assure public acceptance of the project.
Incorporating stakeholder input will also allow planners to identify possible drawbacks to or
opportunities for HEMS projects. When there are a number of distinct stakeholder groups, the
control of information dissemination becomes important. (Sayer and Wilding, 2002)
A more formal form of stakeholder participation is a project partnership. Creating project
partnerships is linked to successful habitat enhancement and restoration projects. Project
partnerships can occur between any combination of non-governmental organizations, citizen
groups, schools, local land owners, corporations, universities, and federal, state, and local gov-
ernments. According to Borde et al. (2004), successful partnerships have three key features:
collective involvement, a shared vision, and measureable goals Many successful partnerships
have been documented, including a partnership to improve the Bahia Grande in Texas and
a partnership organized by the S’Klallam Tribe in Washington to restore the Jimmy-Come-
Lately estuary (Borde et al., 2004)).
Project partnerships provide a number of benefits to HEMS implementation, including con-
flict resolution, securing funds, and providing multi-disciplinary expertise. Increasing dialogue
and providing a forum for conflict resolution is especially important for projects where interests
or project goals are at odds. Partnerships in which different viewpoints are represented can
be important in these cases (Borde et al., 2004). Partnerships can also help to secure funding
resources for HEMS projects though matching grants, monetary and material donations, and
volunteering efforts. By forming alliances, groups can pool resources and leverage additional
funds that would not be available if the parties were working separately. Project partnerships
are ideally multidisciplinary. Such teams have been found to be extremely effective through the
planning process and through to other project phases (Lamberti and Zanuttigh, 2005). When
people or groups with different areas of expertise are brought together, they can improve prob-
lem solving and effectively manage more aspects of a HEMS project. Useful areas of expertise
include biologists, ecologists, physical oceanographers, education and outreach specialists, and
44
project managers, among others.
Define project goals and objectives
Perhaps the most essential task for any HEMS project is to identify the goals and objectives
of the project. A project’s objectives and goals guide all stages of project implementation, but
they are particularly important for project design and making future management decisions
(Gilbert and Anderson, 1998). Many goals and objectives can be created for a HEMS project,
including those mentioned in the first chapter. The most common goals will likely be ecological,
and the best goals create a strong link to habitat enhancement (Restore America’s Estuaries,
2002). Important social goals include issues of safety and access, environmental education,
and aesthetic. Stakeholder participation in defining project goals and objectives is especially
important to the success of the HEMS project (Restore America’s Estuaries, 2002).
Goals and objectives should be explicitly worded so that they can meaningfully guide project
design are able to be quantified to assist project monitoring and management (Seaman and
Miller, 2004). Instead of general goals such as “increase oyster numbers,” more specific goals
such as “increase, by 2010, native oyster populations in the Chesapeake Bay to ten times the
1994 population levels” should be used (Restore America’s Estuaries, 2002). Spatial and tem-
poral scales should be included where they are applicable (Restore America’s Estuaries, 2002).
This will facilitate future management and monitoring efforts by providing a standard with
which to measure future progress. Precise goals and objectives are especially important when
adaptive management is being used. However, project goals should not reference any means
that will be used to implement them (Restore America’s Estuaries, 2002). Project goals and
objectives will also need to be prioritized in order to address possible conflicts. Stakeholder in-
volvement and project partnerships can provide valuable feedback to the prioritization process
so that public support stays high and stakeholder groups are satisfied.
When formulating goals and objectives for use in urban areas, it is important to realize
that the presence of humans is an inherent issue. As a result, HEMS project goals and ob-
jectives need to be aligned with this reality. For example, managers should strive for habitat
enhancement, and not habitat restoration to a human-free state. Weinstein and Reed (2005)
recommend that a ‘conscious baseline shift’ occur to explicitly include humans in the landscape.
Many different tools for creating project goals and objectives exist. A number of techniques tar-
geted specifically at coastal habitat restoration can be found, for example, in Goal Setting and
Success Criteria for Coastal Habitat Restoration, by Wilber et al. (2000).
45
At the completion of the project planning stage, a number of significant events crucial to
the success of the HEMS project will have taken place. Stakeholders, including members of the
public and special interest groups, will have been identified and invited to participate in the
planning process. A project partnership will have been forged that will aid conflict resolution,
securing funds, and providing multi-disciplinary expertise for the project. Finally, a set of
goals and objectives for the HEMS project will have been created by the project partnership
with public input that will guide the project at all future steps.
3.3.3 Project Design
With the foundations for a HEMS project established in project planning, design decisions can
be made. The design considerations for HEMS projects include site selection, the type of habi-
tat to be built, the HEMS module type and construction material(s) to be used, the predictive
model to be used, the monitoring methods to be used, the legal considerations for the project,
and finally securing project funding. These correspond to the management alternatives, pre-
dictions of the effects of potential management actions, and designing monitoring protocols and
plans steps of adaptive management as discussed previously. While these design steps are rec-
ommended based on what is currently known, they are likely to change in the future as more
information is gathered and better HEMS techniques are devised.
Additionally, it is important that stakeholders are engaged before the design phase because
success is less likely if the public is shown a designed project. The public needs to feel ‘own-
ership’ through contributing to goals and design in a meaningful way in order to ensure good
support for project and make project more likely to be implemented.
Site selection
Site selection for HEMS projects may be pre-determined based on opportunities that arise
for HEMS installations. Examples include waterfront revitalization projects, dock and pier
refurbishment, and seawall rebuilds or improvements. For example, in anticipation of the
rebuilding of the Seattle seawall, test panels with different textures have been installed to
evaluate their relative effectiveness in providing habitat (Goff, 2008). The integration of HEMS
projects into urban structure projects from an early phase is essential. Early integration will
allow time for test projects to ensure an effective HEMS is installed, to adequately involve
stakeholders, and to encourage effective integration between projects.
If the HEMS project site has not been pre-determined, there are many methods available to
46
help managers choose a project site. Correct siting is important as many habitat enhancement
projects have failed due to incorrect siting (Claro and Garc´
ıa-Arteaga, 1999; Kennish et al.,
2002). One method that has been used successfully in an urban environment is the use of
constraint mapping and prioritization techniques (Kennish et al., 2002). Officials in Hong
Kong successfully used this technique to site an artificial reef (Kennish et al., 2002).
Constraint mapping and prioritization first uses a Geographical Information System (GIS)
to integrate environmental, economic, and social considerations using constraint mapping,
which has a long history of use (Kennish et al., 2002). A constraint map is created first by iden-
tifying all of the constraints to siting in the area and then creating colored layers to represent
each of these constraint types. These layers are then overlaid and the remaining unconstrained
areas are identified. The unconstrained areas are available for HEMS project implementation.
As HEMS projects are installed in busy urban waters, constraint mapping is a good tool for
avoiding conflicts and/or project failure due to poor site selection. Possible constraints include
safety concerns, shipping lanes, areas near outfalls or other areas with unusually poor water
quality, and areas restricted by the military (Buckley, 1982). Further considerations include
depth, slope, light penetration, currents, substrate type, rate of sedimentation, topography, and
turbidity (Claro and Garc´
ıa-Arteaga, 1999; Bolding et al., 2004). A list of potentially important
geophysical attributes for site selection can be found in (Gordon, 1994).
If more than one area is identified, prioritization techniques can be used to choose between
candidate locations. There are also many methods for ranking sites. In the Hong Kong exam-
ple, the criteria for prioritization included environmental criteria, socio-economic criteria, and
efficiency criteria (Kennish et al., 2002). A rigs-to-reefs project in Norway ranked potential
sites using an unweighted list of impacts for which each site was given a positive or a nega-
tive score (Cripps and Aabel, 2002). The prioritization technique used must be tailored to the
specific location and goals of the HEMS project.
Type of habitat
Different types of habitat can be created or enhanced using HEMS projects. These include
rocky shores, natural reefs, shallow intertidal areas, seagrass meadows, and kelp forests. The
habitat types that can be addressed through HEMS projects will be described in greater de-
tail in the next chapter (Chapter 4). The habitat type decision should be based on historical
habitat coverage, and scientific input, along with the project goals and objectives. While the
project goals and objectives should reflect stakeholder interests, further stakeholder involve-
47
ment should be solicited throughout the design process.
The type of habitat that a HEMS project attempts to enhance is strongly influenced by
site selection. While there is some debate about whether the project site or the project design
should be decided first, choosing the project site first is recommended here for several reasons.
First and foremost, if the site is selected first the design of the habitat can be tailored to
the precise environmental conditions and ecological requirements of the site. Sites may also
become available opportunistically, requiring the design to be completed second, and there is
some efficiency value in using the same process for each HEMS project installation.
HEMS module and material selection
Once the target habitat type and location have been identified, the HEMS module type and
construction material must be selected. A HEMS module is the smallest discrete building block
of a HEMS project. Examples include as single seawall habitat panel or a single artificial reef
ReefBallTM, which is a hollow concrete dome designed to support marine organisms. Multiple
HEMS modules may be installed in a single HEMS project. Different methods for arranging
multiple HEMS modules in relation to each other exist, especially for benthic artificial reef
type modules. These methods will be discussed in more detail in the next chapter (Chapter 4).
There are many HEMS module types described in the next chapter, and many more that
have not yet been described. The choice of HEMS modules is sensitive to the habitat require-
ments of the target organisms, local environment, project goals and objectives, availability of
funding, and ease of installation, among other factors. The ecology of the organisms has been
used to successfully design artificial reef structures (Seaman and Miller, 2004; Seaman, 2007).
Similar techniques should be used to design HEMS modules. The size and number of inter-
stitial spaces in HEMS rocky reef modules will determine which species or size classes will
utilize the HEMS, and therefore these elements should be considered in design (Buckley, 1982;
Bolding et al., 2004). Differences in orientation should also be considered during the design
phase, as these have been tied to differences in the development of communities (Knott et al.,
2004). The design of HEMS modules should also consider concerns about non-native species
(Bulleri and Airoldi, 2005).
One critical physical factor to consider is the impact of storms on the HEMS modules, as
incorrectly designed HEMS could break or move on the sea floor in storm surge ( Joint Arti-
ficial Reef Technical Committee , 1998). The materials used to construct HEMS modules is
dependent on the type of module, in addition to project goals and objectives, physical stresses
48
in the local environment, funding, and ease of installation. These factors will also be discussed
in greater detail in the next chapter.
Pilot studies to compare the effectiveness of different modules or variations of a module are
highly recommended (Seaman, 2007). These studies can assist managers in selecting the most
suitable HEMS module for their location without the expense of a full-scale installation. Pilot
studies can also identify appropriate materials and module arrangements, if applicable.
Model selection
Models are representations of the real world. They can be simple verbal or rigorous mathemat-
ical descriptions of system dynamics (Williams et al., 2007). For example, a verbal model could
be “increasing surface rugosity on this seawall will increase biodiversity” while a mathematical
model could use population dynamics to predict changes in species populations in relation to
changes in surface rugosity. While models are recommended for all HEMS projects, they are
especially important when adaptive management is used.
Many different types of models exist. Managers of a HEMS project can choose from an ex-
isting model or create their own model to describe their system. Multiple competing models
can and should be used to describe a HEMS project system, especially where adaptive man-
agement is being used. Each competing model should predict different outcomes based on the
same management decision. Williams et al. (2007) recommend the following attributes for a
biological model under adaptive management, although their suggestions are also valid for
HEMS projects not using adaptive management:
•The biological system is characterized by key components of interest including population
size, biomass, and biodiversity. These are the focus of ecological management and are
monitored.
•The biological system changes through time and changes are described in terms of pro-
cesses (reproduction, movement, mortality) that are thought to be influenced by HEMS
management.
•Fluctuations in environmental conditions (e.g. temperature, salinity) are included in the
model to account for environmental influences on the biological system.
•The implications of management decisions are described in relevant terms or processes;
for example, increase biodiversity, reduce costs.
•Models are calibrated with available data and knowledge to ensure compatibility with
current understanding.
49
Models for predicting social effects of HEMS can also use this framework, using social system
characterizations (e.g. visitor usage of the site, economic impacts, public education regarding
coastal ecosystems), processes (information dissemination, cost savings), terms, and processes
instead of their biological counterparts. Each model acts as a hypothesis or prediction that
managers can evaluate with monitoring and management methods. For very small or simple
projects, the models may be very simple and crude visual pictures or verbal explanations. For
larger projects, more effort should be invested in the creation of more complete and realistic
models of the biological and social processes impacted by the project.
Monitoring and management considerations
A monitoring program ‘organizes, controls, and adapts a set of operations ranging from col-
lection of field data to data processing for impact assessment’ (Claudet and Pelletier, 2004).
Although monitoring may not occur until after construction is complete, project monitoring
methods should be designed before construction begins. Early consideration of these methods
allows for the collection of baseline data, provides feedback that project goals and objectives can
be adequately measured, and ensures that the appropriate types of data are collected for the
HEMS project models (Borde et al., 2004). Baseline data collection can determine the existing
functions and assess the potential for contaminant release (Borde et al., 2004).
Appropriate monitoring methods should be designed based on the goals and objectives de-
fined in the planning section, and the habitat type and models chosen. Environmental, ecologi-
cal, social, and economic variables can all be monitored. Standard monitoring protocols should
be designed, especially when many observers or volunteers will be used to conduct monitoring
(Borde et al., 2004). There are many possible monitoring regimes, which differ by sampling
design, sampling methods, and sample handling and processing (Seaman and Sprague, 1991;
Diefenderfer et al., 2003). Monitoring methods also need to consider the timing, frequency,
and duration of the monitoring effort, and which statistical methods - if any - should be used
(Seaman and Sprague, 1991; Diefenderfer et al., 2003). Standardizing data collection within a
region can facilitate the exchange of monitoring data (Seaman, 2004).
Examples of monitoring methods and parameters can be found in Diefenderfer et al. (2003).
An excellent source of information as well as a detailed list of potential monitoring variables
can be found in Artificial Habitat for Marine and Freshwater Fisheries, edited by Seaman and
Sprague (1991). Experts in the relevant fields should be consulted or partnered with to ensure
that sound monitoring techniques are used. Other resources include Benedetti-Cecchi and Osio
50
(2007), Ault and Johnson (1998), Tanaka et al. (2003), Shyue and Yang (2002), Recasens et al.
(2006), Relini et al. (2002), Wilding and Sayer (2002a), Danovaro et al. (2002), Steimle et al.
(2002), Burton et al. (2002), and Toft (2005, 2007).
Secure Project Funding
Funding from a HEMS project can come from a number of sources. These include federal,
state, or local grants, private investment, and donations. As mentioned previously, project
partnerships can ensure successful project funding. Many federal funding projects exist for
wetlands and coastal restoration programs (Borde et al., 2004). Unfortunately, it is not known
if these grant programs will fund HEMS projects. Existing HEMS installations have been
funded by research grants and state environmental departments.
Projects may also want to consider innovative ways of defraying the costs associated with
HEMS. For example, a ship sunk for habitat enhancement and tourism, the Spiegel Grove, sells
commemorative medallions as an extra source of revenue to help with debt (Williams, 2006).
Other types of souvenirs could also be used. Naming rights and guided tours might also help
defray costs.
Project funding must be sufficient to cover the anticipated planning, construction, and man-
agement costs. Some of these costs include:
•Hiring personnel for planning and design, administration, and construction,
•Renting or building facilities for administrative offices, warehousing and assembly areas,
and docking,
•Pre-construction costs, including site surveys,
•Materials acquisition and preparation,
•Transportation of materials to assembly areas and the deployment site,
•Management, and maintenance costs, including repairs,
•Monitoring costs, including assessments of effectiveness,
•Any necessary insurance for liability coverage,
•Possible external costs, such as damage to a donor site,
•And if necessary, dismantling and removal costs (Baqueiro and Mendez, 1994; Seaman
and Sprague, 1991; Spurgeon, 2001).
To assure efficient use of project funding, some form of cost-benefit analysis may be suggested
either to justify a HEMS project or choose between candidate HEMS projects (Spurgeon, 2001).
51
However, caution is urged when using cost-benefit type analysis to determine the ‘value’ of
a HEMS project. While it is relatively straight forward to estimate the ‘costs’ of installing a
HEMS project, the economic methods for determining the ‘benefit’ of habitat projects, including
HEMS, are more complex as they are not traded in the market (Seaman and Sprague, 1991;
Spurgeon, 2001).
Since it is difficult for economists to estimate the monetary value of the enhanced habitat,
these valuation methods may tend to underestimate the benefits of a habitat enhancement
project. Some benefits may also be impossible to convert into monetary terms. Additionally,
cheap methods may look good on paper but fail to provide appropriate habitat for marine or-
ganisms, defeating the purpose of HEMS installation. While the relative costs of different mod-
ules or materials should be considered, in the end, the decision to carry out a HEMS project or
choose between candidate HEMS projects may be better informed by the ecological and social,
rather than economic, virtues of the HEMS project.
Legal considerations
HEMS projects should always be implemented and managed in full compliance with all appli-
cable federal, state, and local laws. Which laws are important will change depending on the
specific location of the HEMS project and the agency or group implementing the project. The
law may require projects to obtain permits, review environmental impacts, or hold public meet-
ings. A legal expert on the project implementation area should always be consulted during the
planning stages to assure that the potential project complies with all applicable laws and will
not be unduly delayed due to legal concerns.
In the United States, the applicable laws and permits required are in part determined by
the agency responsible for creating and implementing the HEMS project, and in part deter-
mined by where the HEMS is being installed. Some of the laws and permits pertinent to
HEMS projects include:
•Laws and regulations applying to all HEMS installers :
State and Local Laws
The states have jurisdiction over internal waters, including some bays. Additionally,
under the Submerged Lands Act (43 U.S.C.A. §§1301-1315), states have title to the
territorial sea and its resources. Based on this authority, various state and local laws
govern the use of urban waterfronts nationwide.
52
Rivers and Harbors Act of 1899 (33 U.S.C. §403)
Section 10 of the Rivers and Harbors Act of 1899 require authorization from the
United States Army Corps of Engineers to build structures, excavate, or fill in the
navigable waters of the United States.
United States Coast Guard Regulations
The USCG is charged with promulgating and enforcing regulations related to marine
safety. The local USCG office should be consulted with to ensure compliance with
these regulations.
Ocean Dumping Act (33 U.S.C. §§1401–1445)
The first two titles of the Marine Protection, Research, and Sanctuaries Act, com-
monly known as the Ocean Dumping Act, regulates the dumping of all types of ma-
terials into ocean waters. This act does not apply to materials placed to increase
fisheries resources or for purposes for other than disposal. However, projects that
re-use waste materials may need to prove that disposal is not the primary objective.
Clean Water Act (33 U.S.C.A. 1344)
Section 404 of the Clean Water Act governs the discharge of dredged or fill material.
A permit may be needed for some HEMS projects depending on the method used.
Marine Mammal Protection Act (16 U.S.C.A. §§1361 – 1421) and
the Endangered Species Act (16 U.S.C.A. §§1531-1544)
These Acts are designed to protect marine mammals and threatened and endan-
gered marine organisms. The MMPA prohibits harassing, hunting, capturing, or
killing protected marine mammals. The ESA prohibits harassing, harming, pursu-
ing, hunting, shooting, wounding, killing, trapping, capturing, or collecting threat-
ened or endangered marine species. Additionally, significant habitat modifications
that actually injure threatened or endangered marine species by altering essential
behavior patterns are also prohibited. HEMS projects need to be mindful of these
restrictions.
The National Fishing Enhancement Act
(16 U.S.C. §1220 and 33 U.S.C. §2101 – 2106)
The Act was enacted to ensure the responsible development of artificial reefs. It con-
tains guidelines on the siting, construction, monitoring, and management of artificial
reefs. The Act focuses on enhancing fisheries resources and making them available
to recreational and commercial fisherman. While the Act may not be applicable to all
53
HEMS projects, those using artificial reefs, especially those with fish harvest goals,
should consult the Act ( Joint Artificial Reef Technical Committee , 1998).
•Laws and regulations pertaining to some HEMS installers :
Coastal Zone Management Act (16 U.S.C.A. §§1451-1464)
The Coastal Zone Management Act enables states to create Coastal Zone Manage-
ment Plans (CZMP) to effectively manage their coastal waters. States with approved
plans are entitled to the federal consistency requirement, which requires federal ac-
tions and activates ‘directly affecting5the coastal zone’ must be carried out ‘in a
manner which is, to the maximum extent practicable, consistent with the [enforce-
able policies of] approved state management programs’ (§1456(c)(3)). Federal agency
activities6or projects7are required to make a consistency determination. The federal
agency will determine if the action affects the coastal zone, and if so, if it is consis-
tent ‘to the maximum extent practicable’ with the enforceable policies of the state’s
Coastal Management Plan. States may object to the determination, and there are
steps set up for mediation. Any HEMS project that meets the requirements for being
a federal agency activity or project must make a consistency determination. A con-
sistency certification is required for applicants for federal licenses, including USCG
permits, CWA permits, and others. The state must concur with the certification be-
fore the federal licenses or permits can be issued. Any HEMS project that requires
a federal permit will need to complete a consistency certification. However, HEMS
projects implemented by the state may not be subject to the CZMA requirements.
National Environmental Policy Act (42 U.S.C.A. §§4321-4347)
Federal agencies that play a role in the encouragement, promotion, or implementa-
tion of HEMS projects will need to adhere to NEPA requirements. An Environmental
Assessment (EA) and/or an Environmental Impact Statement (EIS) will need to be
prepared for HEMS projects that are being implemented by federal agencies.
5The effects can be direct and indirect, and can be later in time or farther removed in distance, as long as they are
reasonably foreseeable.
6Any functions performed by or on behalf of a federal agency in the exercise of its statutory responsibilities. This
encompasses a wide range of federal agency activities which initiate an event or series of events where coastal effects
are reasonably foreseeable; e.g., rulemaking, planning physical alteration, exclusion of uses.
7A federal agency activity involving the planning, construction, modification, or removal of public works, facilities,
or other structures, and includes the acquisition, use, or disposal of any coastal use or resource.
54
Other countries will have their own laws and regulations to which HEMS projects will
need to adhere. For example, three permits and licenses are required in the United Kingdom:
navigational consent, seabed lease and a small works license, and a marine construction license
(Sayer and Wilding, 2002). In Canada, multiple permits are required from both the Federal
government and local municipal authorities (Fisheries and Oceans Canada, 2002a,b). Local
legal experts should always be consulted early in project design to determine which options are
legally available.
Planning and design are important steps, but at some point a decision must be made. Of
the management options generated during the planning and design phases, one must be chosen
based on the project goals and objectives and current understanding. Many decision making
frameworks exist to assist managers in choosing between design alternatives. An example
project can be found in Zanuttigh et al. (2005). For HEMS projects utilizing adaptive manage-
ment, this is the ‘decision making’ phase (Williams et al., 2007).
3.3.4 Construction and Installation
While the planning and design phases of a HEMS project are important, the ultimate success of
the project will be determined by the ability of the managers to execute the on-site installation
of the designed HEMS ( Joint Artificial Reef Technical Committee , 1998). Ideally, managers
should at this stage have all of the necessary permits and design documents, and should also
have pre-site surveys or monitoring complete. This section will contain some general advice
from experienced practitioners, and some points on the use of volunteers, site preparation and
selecting plant stock and organisms for relocation, which may or may not be applicable to a
given HEMS project.
The Joint Artificial Reef Technical Committee (JARTC) , whose members have installed
numerous artificial reefs, have the following advice to offer that is also applicable to HEMS
projects ( Joint Artificial Reef Technical Committee , 1998):
•Acquire an adequate environmental and biological data base,
•Select safe weather and water conditions appropriate to the type of transportation and
construction technique,
•Employ reputable and competent personnel,
•Coordinate with any biologists, oceanographers, or engineers studying the HEMS project,
•Coordinate with USCG or local marine police,
•Assure that all equipment is tested, sufficient for the task to be performed,
55
•Obtain liability insurance, if needed, to protect all involved,
•Assure that all pre-surveyed sites can be successfully relocated and are clearly marked
by project coordinators prior to arrival of materials,
•Maintain staging area to be compatible with surrounding neighborhood and to avoid po-
tential conflicts at the staging area,
•Stage and deploy primary or emergency navigational aids, as required,
•Manage the flow of raw materials to the staging area and the movement of completed
units to the project site,
•Assess daylight and other operational constraints,
•Supervise any required clean-up after installing materials on the site,
•Be prepared to cancel operations if necessary to ensure the safety of participants and the
proper placement of materials, and
•Secure funding and other support to complete construction.
JARTC also highlights the importance of choosing a staging area. The staging area should
allow ‘safe and efficient construction, storing, and loading of materials’ ( Joint Artificial Reef
Technical Committee , 1998). The equipment and personnel needed for the installation should
be available at the staging area so that construction can proceed without delay ( Joint Artificial
Reef Technical Committee , 1998).
If the HEMS project is using volunteers, project personnel will need to be on hand to train
and coordinate volunteer efforts. While liability issues limit the use of volunteers in many
HEMS projects, they can be useful in planting efforts, and later for education and outreach
programs. There may also be opportunities for volunteers to assist with monitoring efforts.
Site preparation efforts begin with the demolition, removal, and disposal of unwanted struc-
tures, trash removal, and other cleanup efforts. Sufficient site supervision is required to assure
that no trash or materials that could harm people or machinery is left at the site (Gilbert and
Anderson, 1998). If planting is going to occur, proper preparation of the benthic substrate is
necessary (Gilbert and Anderson, 1998). Similarly, if a HEMS module is going to be attached
to an existing structure, surface preparation of the structure is necessary.
When plants, including seagrass and kelp, are going to be planted or relocated to the HEMS
site, choosing the right plants is critical. Managers should consider first the species that they
want to plant (Gilbert and Anderson, 1998). This choice may be based on the design documents,
or on model ecosystems nearby. Species should be capable of competing and surviving given
the substrate characteristics and physical environment at the HEMS project site (Gilbert and
56
Anderson, 1998). It is also recommended that where possible, plants be taken or propagated
using local genetic stock (Gilbert and Anderson, 1998). These guidelines are equally applicable
to other organisms, including mobile and sessile invertebrates and potentially even fish species.
Obtaining local species can be difficult. Transplantation may be an option where abundant
local sources exist. It may also be possible to propagate local species by collecting seeds or
propagules from the wild (Gilbert and Anderson, 1998). This also provides an opportunity for
local environmental groups and schools to volunteer and be responsible for growing and prop-
agating species for planting (Gilbert and Anderson, 1998). A project in Tampa Bay, Florida,
created a program called ‘Sea Grasses in Classes’ that used Tampa Bay high schools to suc-
cessfully grow salt-marsh grasses to provide a source of plants for many large-scale Tampa
Bay restoration projects (Borde et al., 2004). However, there can be negative impacts from col-
lection for transplantation or propagation, including trampling other organisms, or depletion
of the target species from the donor location. Therefore, collections should be carefully consid-
ered to make sure that the benefits outweigh the risks. If collection is pursued, experienced
professionals should be hired in order to minimize any disturbance to the donor location.
The brevity of this section belies the complexity of the HEMS construction process. The im-
portance of the construction step cannot be understated, and the success of the HEMS project
is in large part dependent on the ability of the managers involved in overseeing the installa-
tion. They will need to work closely with many groups to ensure that the project is completed
on time and without going over budget. After physical construction is complete, they will need
to wrap up the construction process by informing the necessary authorities that the project
is installed. Then, the HEMS project can be handed over to the team in charge of long term
monitoring, maintenance, and management.
3.3.5 Monitoring, maintenance, and management
A HEMS project does not end with construction. Continued involvement with the project is
necessary to ensure long term success. This section will look at the monitoring, management,
and maintenance aspects of a HEMS project that continue after construction is complete8. The
primary purpose of monitoring, maintenance, and management is to determine if the project
goals and objectives were successfully achieved and to correct where necessary (Seaman and
8Both the ecological and socio-economic aspects of the HEMS project should be considered under long-term mon-
itoring and management. Many habitat restoration or enhancement programs to date have considered only the
environmental aspects, however these fields could learn from artificial reef management, which also includes user
satisfaction, economic success, and other socio-economic analyses (see for example Seaman and Sprague 1991 and
Joint Artificial Reef Technical Committee 1998)
57
Sprague, 1991). Where adaptive management is used, these steps correspond to the follow-up
monitoring, assessment, and iteration steps.
Monitoring programs should be carried out over a sufficiently long time period to capture
relevant trends and establish the status of HEMS projects. For example, the Coastal Wet-
lands Planning, Protection and Restoration Act in Louisiana mandates 20 years of funding for
each approved project (Borde et al., 2004). Computer databases and coordinating information
collection between projects would also be useful (Seaman and Sprague, 1991). However, moni-
toring data collected at one site may not necessarily be extrapolated to another site (Sherman
et al., 2001). Additionally, monitoring one design at one site has limited use in furthering our
knowledge of effective HEMS design (Sherman et al., 2001).
There are multiple types of monitoring programs that can be used for HEMS projects. Mon-
itoring may be required for adaptive management, to assure compliance with conditions re-
quired by permits or other laws, and/or to assess the performance of HEMS projects ( Joint
Artificial Reef Technical Committee , 1998). Monitoring plans for HEMS do not need to be
complex to be effective (Diefenderfer et al., 2003). As Diefenderfer et al. (2003) note, ‘a well-
designed, systematic program that targets key parameters tied to goals, objectives, and per-
formance criteria should be sufficient to produce concise and informative results.’ However, a
control area or baseline data may be necessary for rigorous hypothesis testing (Claudet and
Pelletier, 2004).
Engineering studies evaluate the effectiveness of HEMS modules and materials. Monitor-
ing the durability, effectiveness, and safety of the surfaces provided for the ecological commu-
nities is critical to determining the success of the HEMS project (Seaman and Sprague, 1991;
Joint Artificial Reef Technical Committee , 1998). This information should be carefully doc-
umented along with the relevant environmental conditions so that future HEMS projects can
learn from past experience ( Joint Artificial Reef Technical Committee , 1998).
Biological studies address the most common goals of HEMS projects — benefiting the local
ecology. A detailed biological study should be conducted to determine if the project has met its
biological goals or if there have been any negative drawbacks ( Joint Artificial Reef Technical
Committee , 1998). These studies can also provide valuable information about the succession
of organisms colonizing HEMS projects ( Joint Artificial Reef Technical Committee , 1998).
Additional studies that could be conducted include: ‘an accounting of development of sessile
invertebrate communities on different types of structures, the importance and degree of in-
teraction between fish communities and invertebrate communities associated with the project,
58
and the association of key fish species with certain HEMS designs or locations and long-term
changes, which may take place in community structures as they age’ ( Joint Artificial Reef
Technical Committee , 1998). Many methodological approaches to biological reef assessments
are available for HEMS managers (Lucy and Barr, 1994; Buckley et al., 1994; Blau and Byers-
dorfer, 1994; Thorne, 1994; Halusky et al., 1994; Uchida et al., 1995; Lindeman et al., 2001;
Wood and Pullin, 2002; Benedetti-Cecchi and Osio, 2007).
Socio-economic studies are also a key element to measuring the success of a HEMS project (
Joint Artificial Reef Technical Committee , 1998). While biological goals may be more common,
HEMS projects may serve primarily social functions (Seaman and Sprague, 1991). According
to Seaman and Sprague (1991), three main types of information should be gathered: ‘infor-
mation that can be duplicated by different investigators, information on testable hypotheses
on the net outcomes of the project, and information on the economic efficiency of the project’.
Studies should take place at the state, county, or municipal level, and can document the overall
success of the reef and provide a basic measurement for cost/benefit analysis ( Joint Artificial
Reef Technical Committee , 1998). Socio-economic monitoring may include direct and indirect
economic benefits, lessened or increased user conflicts, usage studies, quantifying economic im-
pacts, and public opinion and attitudes toward the project (Seaman and Sprague, 1991; Joint
Artificial Reef Technical Committee , 1998).
Compliance monitoring is required by law, regulations, or as a condition for permit approval
( Joint Artificial Reef Technical Committee , 1998). It may include documenting the structural
integrity and material stability of a HEMS project, and may use hull mounted depth recorders,
side-scan sonar, or visual checks by SCUBA divers or cable-controlled cameras ( Joint Artificial
Reef Technical Committee , 1998). Performance monitoring includes on-going assessments of
HEMS projects to determine if they are meeting project goals and objectives, having any nega-
tive consequences, identify research priorities, and provide feedback for future HEMS projects
( Joint Artificial Reef Technical Committee , 1998). More detail and examples of monitoring
regimes can be found in Seaman and Sprague (1991), Joint Artificial Reef Technical Com-
mittee (1998), and Diefenderfer et al. (2003). All three are excellent resources for managers
considering or implementing HEMS projects.
Long term management includes analyzing the monitoring results, comparing them with
the model predictions that were made, and making the appropriate management decisions.
This process is especially important for HEMS projects utilizing adaptive management. Other
important function of long term management include ‘public or administrative awareness
59
about the effectiveness of HEMS projects, assurance of adequate long-term funding for the
program, encouragement of research on HEMS projects, and documentation of HEMS develop-
ment and effects’ ( Joint Artificial Reef Technical Committee , 1998).
Analysis of the monitoring results may include parameter estimation, comparative assess-
ments, or other statistical analyses (Williams et al., 2007). The monitoring data should be
compared with model predictions, if any were made, in order to update the understanding of
management impacts (Williams et al., 2007). Comparisons can improve confidence in those
models that were able to predict the changes, whereas confidence is decreased for inaccurate
models (Williams et al., 2007). Comparisons between anticipated and actual results of the
HEMS installation process can be used to assess the effectiveness of HEMS planning, design,
and construction (Williams et al., 2007).
Another important part of long-term management is continued maintenance. Depending on
the project design, maintenance may have been planned. Examples of planned maintenance
include periodic plantings, non-native species removal, or sand and soil replacement. However,
monitoring can also expose the need for unexpected maintenance. Regular monitoring can
reveal broken habitat elements, unexpected species interactions, or other issues that need to
be addressed through maintenance. Planned or unplanned maintenance may be necessary to
comply with permit requirements, including painting, repair, or replacement of buoys ( Joint
Artificial Reef Technical Committee , 1998). Maintenance may also be necessary to maintain
reef effectiveness, for example if HEMS material has subsided into the substrate, or to improve
the attractiveness of HEMS to target species ( Joint Artificial Reef Technical Committee , 1998).
Long term monitoring, management, and maintenance are especially important to HEMS
projects as they are largely untested. Maintaining documentation on the project’s development
is important to determining the effectiveness and long-term costs of the HEMS project ( Joint
Artificial Reef Technical Committee , 1998). Relevant information should be recorded and
shared with other parties interested in or building HEMS projects.
3.3.6 Project Outreach and Education
The main goal of project outreach and education is to provide information to other parties,
including professionals and the public, so that they can learn about the HEMS project. Dis-
seminating information to other researchers, planners, and managers allows for the collective
learning from past experiences, and is imperative to improving the success of future projects
(Borde et al., 2004). Even when public education is not a goal, informing stakeholders and the
60
public about HEMS projects is an effective method of gaining public acceptance and support
(Diefenderfer et al., 2003; Borde et al., 2004). HEMS projects may also affect stakeholders,
and it is important that they be informed of the outcomes (Diefenderfer et al., 2003). When
there are multiple stakeholder groups, it is important to carefully control the release of infor-
mation, as the premature or haphazard dispersal of information can lead to misinterpretation
or disenchantment (Sayer and Wilding, 2002). Stakeholders should also be informed of new
developments in a HEMS project before the media (Sayer and Wilding, 2002).
There are four key considerations with regard to disseminating information: purpose, audi-
ence, timing, and venues (Diefenderfer et al., 2003). The purpose of disseminating information
is as described above. Potential audiences include project developers and managers, scientists,
planners, fishermen, amateur naturalists, recreationists, engineers, government environmen-
tal managers, permitting agencies, and politicians, among others (Diefenderfer et al., 2003).
Each of these groups will have specific questions, and it is critical to understand each audience
as well as their needs (Diefenderfer et al., 2003). To this end, it may be useful to compile a list
of interested parties based on attendance during project planning meetings (Diefenderfer et al.,
2003). In addition, the general public is often interested to learn of local habitat enhancement
efforts (Diefenderfer et al., 2003).
There are numerous venues that project managers can use to disseminate information
about their HEMS project. Each venue will reach a slightly different audience, so multiple
venues should be utilized. The internet has proven to be a useful tool for information dissem-
ination both to the professional community and the public. Websites describing and providing
downloadable documents about habitat enhancement projects have been used successfully to
communicate with the public (Borde et al., 2004). Online databases are a good method of dis-
tributing project data. NOAA and the EPA have set up collective restoration databases, which
may or may not be appropriate for HEMS projects (Diefenderfer et al., 2003; Borde et al.,
2004). However, a separate HEMS database could be developed. Individual project databases
have also been created for restoration projects, and HEMS projects could use a similar tactic
(Diefenderfer et al., 2003; Borde et al., 2004).
There are also venues that specifically target the professional community. Technical reports
can be circulated to scientists as well as regulators (Diefenderfer et al., 2003). Publication in
peer reviewed journals and presentations at professional conferences attended by managers,
scientists, and planners are also good venues for communicating with, and getting feedback
from, professionals in the field (Diefenderfer et al., 2003).
61
Community outreach can be accomplished through other venues. Shorter, non-technical
project reports can be released as news reports to the local media or as website updates
(Diefenderfer et al., 2003). Special programs run on local or cable channels detailing a HEMS
project could reach a wide audience (Borde et al., 2004). Videos distributed on DVDs or as
downloadable content can be used to distribute information and provide training to volunteers
(Borde et al., 2004). Presentations and tours of a HEMS project can be offered to interested
stakeholders or parties (Borde et al., 2004). Schools can also be invited to visit and learn about
the HEMS project through field trips (Borde et al., 2004).
These are only some of the numerous outreach and education techniques that are available
to HEMS project managers. Successfully employing these techniques to inform others of the
HEMS project can benefit both current and future HEMS projects. Although current HEMS
projects may benefit from increased public acceptance and support, it is perhaps future HEMS
projects that will benefit the most. Disseminating information about current HEMS projects
to researchers, planners, and managers allows for collective learning that can improve the
planning, design, construction, and management of future HEMS projects. Further, if the
public and stakeholders accept and support current HEMS projects, they are more likely to
support, and even request, future HEMS projects.
3.4 Concluding thoughts and an example
Careful planning and design, attentive construction practices, meaningful management and
monitoring programs, and project outreach and education are all necessary components to
the successful addition of a HEMS project to the urban waterfront. The techniques detailed
above are drawn from successful artificial reef, wetland restoration, and terrestrial restora-
tion projects. While no similarly comprehensive documents were found on implementation of
HEMS, there is at least one installed HEMS project that provides valuable lessons for future
HEMS projects
The New York Economic Development Corporation (EDC) recently completed a HEMS
project on the West Harlem waterfront in New York City (Alevras, 2008). The EDC originally
planned to turn a parking lot into a one-acre park with a fishing pier. However, upon further
review of the plans, the National Oceanic and Atmospheric Administration and the New York
Department of Environmental Conservation requested that fish habitat be added to the design.
While it was too late in the design process to incorporate habitat into the design of the dock,
it was decided that some sort of benthic habitat should be installed. A pile field, or a group of
62
vertical wooden piles spaced closely together was first proposed, but this was not satisfactory
to the community. ReefBallsTM were another suggested alternative, and which was accepted
by the community and NOAA. However, no further goals and objectives other than to provide
fish habitat and fishing opportunities were identified.
Multiple factors were considered during the design phase. ReefBallsTM were initially sug-
gested based on historical habitat type data around Manhattan. Although presently soft sub-
strate is the dominant habitat type, before development there was abundant rocky habitat
around the island. Additionally, while many juvenile fish inhabit the West Harlem waterfront,
there are very few adults due mostly to missing structure. Three foot by five foot ReefBallTM
units weighing 2.5 tons each were chosen as the best fit to target these fish. Pebbles were added
to the concrete in order to give the outside of the units more texture. Other biological design
considerations included the light regime and the surface, area, and volume, of the ReefBallsTM.
The soft sediment that currently dominates the urban waters of NYC provided multiple
obstacles to using the concrete ReefBallsTM. If they were placed on top of the soft sediment,
they would likely sink and become un-useable as habitat within a short period of time. There-
fore, the ReefBallsTM were designed to be supported by piles approximately one foot above the
riverbed. The rate of sedimentation was another concern. If placed too closely together, the
ReefBallsTM might reduce the current velocity and increase the rate of sedimentation. There-
fore, the ReefBallsTM were spaced far enough apart so that the current would not be overly im-
peded. Other environmental design considerations included wave energy, depth, and topology.
There were also hazards posed by buried infrastructure, as a gas pipeline had to be avoided.
The final design called for a group of ReefBallsTM to be installed in a grid pattern within fishing
distance of the new dock.
The project was reviewed under the City Environmental Quality Review, the State Envi-
ronmental Quality Review, and also completed NEPA requirements. Permits were obtained
through the Department of Environmental Protection and the New York State Department
of Environmental Conservation, among others. Construction of the reef took five days. The
ReefBallTM units, which cost approximately US$25,000 for all 40 units including delivery to
the site, were assembled with their pilings on a barge and then pushed into the soft sediment.
Subsequent monitoring efforts have revealed that while there appears to be some ice damage to
a ReefBallTM module, the reef installation has been successful and is being used by many fish
and fishers. Additionally, a number of community groups have been informed about the West
Harlem project, although no other groups contemplating the creation of parks has stepped
63
forward to request a HEMS project.
In West Harlem, there is now a park not just for people, but also for fish. This example
underlines the relevance of the lessons learned through experience in implementing artificial
reefs, wetland restorations, and terrestrial habitat improvement projects. At the landscape
planning scale, opportunities to implement HEMS projects as part of other initiatives need to
be identified early. Having a set of landscape scale goals and objectives can help to identify
opportunities for HEMS projects early enough so that HEMS can be effectively integrated
into these other initiatives. It is possible that the West Harlem project could have integrated
additional fish habitat into other structures such as pier pilings if the opportunity had been
identified earlier.
In the planning of a HEMS project, stakeholder participation, creating project partner-
ships, and identification of project objectives and goals are all important. For example, in the
West Harlem project speaking with stakeholders allowed project planners to identify that us-
ing ReefBallsTM was preferable to installing a piling field. Site selection, the type of habitat to
be built, the HEMS module type and construction material(s) to be used, the predictive model
to be used, the monitoring methods to be used, the legal considerations for the project, and
securing project funding are integral in HEMS project design. By giving adequate considera-
tion to the biological and physical environmental design concerns, project designers were able
to design a reef that supported a good population of fish and has not subsided into the soft
substrate.
The construction of the West Harlem project also paralleled many of the professional sug-
gestions offered by artificial reef installers. For example, partnering with reputable and compe-
tent personnel allowed the successful and timely completion of the reef installation. The long-
term monitoring, management, and maintenance of the project, was not very complex. How-
ever, it effectively addressed the question of whether fish were using the reef structure, which
was the original intention as requested by NOAA and the DEC. Finally, information about the
project has been presented at professional conferences and to interested citizen groups.
From examples taken from other fields, it is thought that successful implementation of an
individual HEMS project involves planning, design, construction, long term monitoring and
management, and education and outreach. While currently there are few examples of HEMS
projects from which to draw experience, each subsequent project will reveal new lessons for
planners, managers, scientists, and stakeholders
64
Chapter 4
DESIGNING HEMS COMPONENTS
An important part of the project design phase for a Habitat Enhancing Marine Structure
(HEMS) project is choosing the physical attributes of the HEMS components. There are many
different structures available for project managers to use in HEMS projects. Although to date
few modules have been designed specifically for use as HEMS, many techniques from related
fields can be easily adapted for habitat enhancement in urban environments. There are many
factors influencing which specific module (or modules) a project manager will choose. As dis-
cussed in Chapters 1 and 3, the choice will be guided by both regional and project goals and
objectives. Importantly, the biological needs of local species, social and economic concerns, and
safety and engineering issues will also factor into the choice of and design of the modules used
in the HEMS projects.
This chapter contains practical information about designing physical HEMS components.
Some of the biological, socio-economic, and engineering factors that may influence the will be
discussed first. While these factors will certainly vary by project, it is important that project
managers keep these factors in mind while considering potential HEMS modules. An exten-
sive, but far from comprehensive, list of potential HEMS modules will be presented second.
This “toolbox” provides examples of different HEMS modules that can be used to create differ-
ent habitat types on or near urban structures.
4.1 Factors influencing module selection
HEMS module selection will be dependent on previous project decisions and conditions. Re-
gional and project goals and objectives will determine the desired end result. This will guide
the general requirements for module selection. For example, if the project goals include provid-
ing harvest opportunities to fishermen, the general requirements for the module might include
providing fish habitat appropriate for the target fish species in an accessible location. How-
ever, there will likely be many different modules that could fulfill the general requirements
outlined by the regional and project goals and objectives. Continuing the example, managers
for this project would still need to decide which type of fish habitat is most appropriate for
65
their site. Additionally, they would need to consider if fishermen would prefer habitat incorpo-
rated into pier pilings or habitat placed on the seafloor, as each of these locations would provide
different fishing experiences.
These specific considerations are interrelated and will differ for each project. Project man-
agers must consider the conditions specific to their HEMS installation. HEMS units that are
successful in one location may fail in another (Bayle-Sempere et al., 1994). In general the
considerations may include the physical characteristics of the project site, the biological re-
quirements of local species and target species, social and economic concerns, and safety and
engineering issues (Figure 4.1). Additionally, managers will need to consider the suitability of
different materials for use in their projects.
4.1.1 Phyiscal characteristics of the site
The project site selected during earlier phases of the planning process will impose physical con-
straints on the HEMS module. A number of these factors have been described in the literature
and include storm exposure, current velocity, the type of substrate at the site, water depth and
the amount of light penetration. These factors will also affect the types of species that will be
attracted to the site as well as safety and engineering issues, and in some cases may increase
the cost of construction. Additionally, if the site chosen for the HEMS project is incompatible
with the goals and objectives of the project based on the physical characteristics of the site, the
selection should be reconsidered.
One critical physical factor to consider is the impact of storms on the HEMS modules, as
incorrectly designed HEMS could break or move on the sea floor in storm surge ( Joint Artificial
Reef Technical Committee , 1998). This is especially important for urban areas that experience
hurricanes and other strong storms. Sheltered harbors will need to consider wind driven wave
energy and boat wash. Water velocity can also influence the type and spacing of HEMS modules
that can be installed. In urban areas that are prone to siltation, benthic HEMS modules will
need to be spaced far enough apart to avoid excessive siltation and the burying of the HEMS
modules (Alevras, 2008).
Substrate type will also have important consequences for HEMS design. Soft substrate may
prevent the use of, or require modifications to, seafloor reef-type modules as they may subside
into the substrate. Rods or pilings can be driven through reef units or the units can be mounted
on articulated mats to increase the stability of bottom units (Harris, 2004). The properties
of the bottom substrate are also important if plantings are part of the habitat improvement
66
Figure 4.1: Diagram illustrating the factors influencing HEMS module choice. The combination physical site characteristics, bi-
ological requirements of local species, socio-economic concerns, and engineering concerns specific to each site will guide the final
choice of HEMS modules during the project design phase.
67
project. Nutrients such as phosphorous and nitrogen are critical to plant growth. Thenutrient
richness of the substrate will dictate the species of plants that can thrive in that area. Nutrient
richness also has implications for species diversity. Soils that have high concentrations of
these nutrients may quickly be dominated by single species stands of aggressive plants. Less
nutrient rich soils may support greater biodiversity (Gilbert and Anderson, 1998).
The substrate or habitat types that surround the HEMS site will influence the types of
organisms that will colonize HEMS. On land, the surrounding landscape matrix was found to
be an important predictor of species living in greenways in part due to edge effects (Mason
et al., 2007). Recruits to HEMS will also come from the surrounding substrates (Moreno,
2002). Local habitat, such as rocky reefs and seagrass beds, can act as sources for larvae and
adults in some species (Moreno, 2002). If the HEMS project goal is to provide habitat for local
organisms, then project managers will need to select the HEMS module that will provide the
most necessary habitat for the site. Similarly, the types of habitat historically present near
the project site should influence HEMS design. Project managers should consider installing
habitat that is similar to what was historically available to organisms. The New York City
case study presented in Chapter 3 chose to use ReefBallTM modules in part because they were
the most useful habitat for the fish that were present in the area. ReefBallsTM were also used
because they mimicked the rocky shores present when the city was first settled.
Light penetration is another important site characteristic. This is especially important
when dealing with docks or seawall/bulkhead projects adjacent to docks. Salmonids and cer-
tain other species of fish rarely cross the light/shade boundary created in the water by docks.
Research suggests that their eyes may not adjust well to sudden light changes (Toft et al.,
2004). Predatory species are also known to hide near pilings and avoiding docks may be a tac-
tic in predator avoidance. Additionally, shading created by docks reduces the light available for
photosynthesis. Although some species are more shade tolerant than others, below a certain
level photosynthesis cannot occur. Some target species require significantly more light than
others.
The water depth at a site can also influence the type of HEMS modules that will be appropri-
ate, particularly for benthic modules. In shallow areas, seafloor units might not be appropriate
as modules that protrude from the seafloor in these areas may reduce the draft and prevent
boats from entering the area. Additionally, the depth of water at a site may determine which
species will be present. For example, copper rockfish are sensitive to water depth while brown
rockfish are not (Casselle et al., 2002).
68
The water quality in the project area needs to be consistently within acceptable levels for
the target organisms. The dissolved oxygen content must also consistently be above the bio-
logical requirement of the organisms that will colonize the introduced habitat. If these water
quality requirements are not met for the target organisms, the organisms may experience high
mortality rates or fail to colonize the habitat improvement project. Project managers may want
to consider monitoring these and other water quality parameters for an appropriate length of
time before proceeding with a habitat improvement project. If water quality parameters do
not meet the appropriate local requirements, efforts should focus on improving water quality
before habitat improvement projects are considered.
Project managers should enlist the help of experts, including engineers and biologists, to
determine how site selection might influence the projects goals and objectives. There are a
number of methods available for this purpose. Structural marine engineers can use hydrody-
namic models to test the ability of HEMS modules to withstand wave energy and storm surge.
Models can also be used to predict siltation due to changes in water velocity under different
module configuration scenarios. The impacts of substrate on HEMS modules can also be mod-
eled or determined from previous experience. Additional experiments concerning water depth
and light intensity should be conducted in coordination with studies designed to determine
the biological requirements of local and target species. Biological surveys are also useful to
determine the effects of water depth on species. Additionally, the light requirements for many
species are known. These values can be compared to measurements of light intensity at a site
to determine which species will be able to survive at the site.
4.1.2 Biological requirements of local and target species
Project managers must also consider the biological requirements of local and target species
when designing HEMS components. Most importantly, these biological requirements will dic-
tate the characteristics of the installed HEMS substrate. The biological requirements will also
determine what species will be able to colonize a HEMS project given the physical character-
istics of the project site, including the characteristics of the surrounding habitat, water depth,
and light intensity. As the freedom of project managers to tailor HEMS modules to their tar-
get organisms is necessarily constrained by these physical characteristics of the project site,
project managers must carefully choose a site that is favorable to their target organisms.
Project managers need to choose a HEMS module and module arrangement that fulfills the
habitat requirements of the species of concern. An excellent example of the types of variables
69
to consider and studies to conduct is found in Deysher et al. (2002). These researchers derived
a set of design specifications to try to ensure persistent populations of giant kelp in northern
San Diego County, California1(Deysher et al., 2002). Potential types, sizes, and arrangements
for the substrate were considered in order to create guidelines for a pilot reef (Deysher et al.,
2002). These guidelines indicated the relief, proportion of hard substrate to sand, and the type
and size of the hard substrate to be used (Deysher et al., 2002).
Two distinct surveys were used to estimate these parameters. First, Deysher et al. (2002)
compiled the available information, which consisted of quantitative evaluations of the physical
and biological characteristics as well as non-quantitative observations of relative kelp abun-
dances for six existing artificial reefs (Deysher et al., 2002). Next, they compared the substrate
characteristics of natural kelp beds with either high or low persistence of kelp populations
(Deysher et al., 2002). They used a Geographic Information System (GIS) database containing
maps of annual kelp canopy surveys and aerial surveys of kelp to determine where the areas
of high and low persistence were located (Deysher et al., 2002). SCUBA divers surveyed each
of the areas of high persistence as well as a nearby area of low persistence and noted depth
change, substrate composition, and kelp density (Deysher et al., 2002). Additionally, previous
studies examined the survival rate of kelp plants on differently sized substrate (Deysher et al.,
2002).
Deysher et al. (2002) found that solid rock substrate with moderately low relief and mod-
erate coverage by sand supported the most persistent beds of kelp. Less persistent kelp popu-
lations were associated with very low reefs with an abundance of sand (Deysher et al., 2002).
These results agree with Patton et al. (1994), who also noted that kelp-fouling organisms and
kelp eating fish were more common on high relief structures, as well as Dean et al. (1995),
Jahn et al. (1995), and Patton et al. (1995). However, further study was needed to determine
the best material and percent coverage for the hard substrate. From their results, a pilot reef
was designed with multiple configurations of quarry rock and recycled concrete.
The approach used by Deysher et al. (2002), is a good example of a study that examines
the biological needs of the target organism. Similar approaches could be used for other target
organisms including eelgrass or fish associated with rocky reefs. Another very good study was
conducted by Hasegawa et al. (1995), who looked at site selection, season for construction, as
well as the design of an artificial reef for kelp. In some cases, previous research examining the
mechanisms for differences between urban structures and natural surfaces could also be used
1For more information about this project, see Mitigating effects on a kelp forest community by Ambrose, 1994.
70
to determine what types of substrate would be beneficial to target organisms. For example,
research in Australia has found that seawalls with cracks support more chitons than seawalls
without cracks (Moreira et al., 2006). Cracks and other surface roughness could be incorporated
into HEMS modules in order to accommodate these species.
A number of other studies have highlighted the importance of properly designed shelter.
Grouper were consistently found in artificial reef holes that matched their body size (Beets
and Hixon, 1994). In the Mediterranean, slipper lobsters inhabiting artificial reefs much lower
mortality due to reduced predation (Barshaw and Spanier, 1994). Structurally complex ar-
tificial reefs and seagrass beds also reduce predation on juvenile fish (Kakimoto et al., 1995).
These results highlight the importance role of the artificial reefs and how effective sheltering is
as a protection strategy (Barshaw and Spanier, 1994). Properly designed shelter is also impor-
tant, as some species may prefer protective rock ledges leading to open habitat, holes between
rocks, or under rock ledges (Andrews and Anderson, 2004). Project managers should consider
shelter configuration, direction and size, number of openings, and opening size and location
when designing structures to serve as shelter for species (Spanier, 1995).
The complexity of a HEMS module is related to species richness, and therefore is an im-
portant biological consideration for HEMS project design. Both complexity of the habitat and
the amount of shelter provided by the habitat is significantly and positively related to species
richness (Casselle et al., 2002). This pattern held true for a wide range of species, and is
supported by other studies (Casselle et al., 2002; Sherman et al., 2002). Project managers con-
sidering HEMS projects that aim to increase species richness may want to consider the degree
of complexity of HEMS modules.
The timing of construction of the project will influence what species initially colonize the
HEMS project. For example, the installation date influences the ‘initial rates of colonization by
macrobenthic algae’ (Reimers and Branden, 1994). Two factors influenced this, specifically the
timing of algal spawning and the rough conditions during part of the year that spread algal
spores more effectively (Reimers and Branden, 1994). This agrees with results from Noda et al.
(1995). These initial recruits can have profound impacts on the later community, so project
managers may want to consider researching when deployment of the HEMS units would be
most successful.
Other important factors include the slope or orientation of substrates and the vertical pro-
file, or height, for seafloor projects (see, e.g. Andrews and Anderson (2004); Knott et al. (2004);
Moura et al. (2008)). Some local organisms may prefer horizontal rather than vertically sloped
71
surfaces, although studies suggest that the number of species is maximized when the surface
is neither horizontal nor vertical (Falace and Bressan, 2002). If a project manager wishes to
encourage species that prefer horizontal surfaces, he may choose a HEMS module that rests
on the seafloor or a module that creates horizontal surfaces on a vertical seawall. Similarly,
HEMS modules that are installed on the sea floor can be designed to have more or less vertical
relief. Surveys, such as those used by Deysher et al. (2002), can be used to determine the most
appropriate substrate for the target species. Additionally, test substrates with a slope of 0, 45,
and 90 degrees could be installed at the project site as part of pilot studies. Biological surveys,
including visual or photographic census, can then be used to examine the communities that
colonize each substrate. Design decisions can be made based on these results and the desired
outcome of the HEMS project.
4.1.3 Social and economic concerns
The design of HEMS components will also need to incorporate social and economic concerns.
While these concerns may not have as visible an impact as the biological requirements, they
can still be very influential in approving or rejecting the design of a HEMS module. The two
main concerns include the cost of the module and the installation, and public acceptance.
Cost is always an issue for HEMS project planning. Costs specific to HEMS modules include
the cost of fabrication and the cost of installation. These costs can vary drastically depending
on the materials used, the intricacy of the module design, the difficulty and location of the
installation, and the equipment and personnel required. Cost benefit analysis can be used
to determine the relative cost effectiveness of different HEMS modules. For more complex
cases, Montefalcone et al. (2007) used an ecological measure called the ‘phase shift index’ to
determine if seagrass restoration would be economically viable; similar methods could be used
to determine if HEMS habitat enhancement projects are viable. However, there are many
options for HEMS modules that are very cost effective. The ReefBallsTM for the New York
City project (see previous chapter) cost US$500 each, including fabrication and delivery to the
project site (Alevras, 2008).
Public acceptance may sometimes be crucial to the choice of HEMS module. Some possible
designs may be strongly disliked by the general public. This may be due to real or perceived
aesthetic or pollution concerns. For example, the project in New York City was considering
using a piling field to provide fish habitat. However, the community objected to this plan
partially on aesthetic grounds. As a result, ReefBallsTM were proposed as an alternate module
72
type and were used instead.
4.1.4 Safety and engineering issues
Project managers must consider all relevant safety and engineering issues in the design of
HEMS modules. If not addressed, these issues can delay or prevent the installation of the
HEMS project. Many of the safety and engineering concerns stem from the conditions at the
site, navigation issues, and permitting concerns. Additionally, as mentioned above, the wave
energy that the HEMS modules will need to be engineered to withstand is largely determined
by the site conditions and the water depth will in part determine the engineering techniques
used to install the HEMS modules.
If a HEMS project is being implemented as part of a bulkhead renewal or rebuild, the new
structure can be designed with the habitat improvement project in mind. However, the physical
conditions of the urban structures at the project site are critically important if the HEMS
modules are going to be retrofitted to existing structures. The HEMS modules installed may
not exceed the load bearing capacity of the existing structure (Alevras, 2008). This affects both
the total weight of the HEMS module along with its position. Projects mounted close to the wall
will be less stressful on the existing structure than cantilevered projects. These concerns are
especially relevant to existing bulkheads or seawalls. In these situations, the project managers’
choice of HEMS modules will necessarily be constrained by the physical limitations of the
existing structure. Habitat improvement projects that are too heavy or project more than a
certain distance cannot be used. HEMS modules can often be altered to be lighter without
major redesign or significant additional cost (Alevras, 2008). It may be possible to have the
modules sit on the bottom and only be anchored by the shoreline structure (Alevras, 2008).
Sediment contamination is another important safety consideration that is dependent on site
conditions. If the sediments at the project site are contaminated, which is common in urban
areas, project managers will need to carefully evaluate their choice of HEMS modules. If the
HEMS module will disturb contaminated sediments, the sediments may need to be contained
or cleaned in conjunction with HEMS installation. Because this can significantly increase the
cost of a project, project managers may want to consider habitat improvement projects that do
not disturb sediment in these areas.
Navigational concerns are particularly important where ships will be in proximity to HEMS
modules. HEMS projects that want to create habitat on the seafloor will need to consider
how these projects will interact with ships’ draft. If very low profile HEMS modules will still
73
interfere with ship passage, project managers will need to examine other options. Navigation
issues can also arise when HEMS projects create major changes in currents. Cross currents in
particular are undesirable for berthing ships (Alevras, 2008). Project managers need to ensure
that HEMS projects will not interfere with the thresholds for safe navigation (Alevras, 2008).
Adequate access to the proposed site is important for construction and monitoring. The
distance from the nearest road to the site, the existing land use and topography of this area,
and the property rights associated with this land are all important. For some projects, man-
agers may need to obtain permits or written permission from the landowner. Other sites may
only be accessible from the water because buildings or steep slopes limit waterfront access to
construction machinery. These projects may need to be installed from a barge, which increases
costs. For larger projects, a staging area may also need to be set up. This requires enough open
land for materials and equipment storage, as well as adequate access to the site.
Regular inspections of piers and shoreline structures are also necessary (Alevras, 2008).
HEMS modules cannot block diver access to these important structures, thus structure should
not be added over critical support elements, for example, by cladding pier pilings to provide
texture (Alevras, 2008). Project managers will need to consider other types of HEMS modules2.
4.1.5 Materials
There are many different materials that are available for project managers to use to fabricate
HEMS modules. The choice of material is largely defined by the type of HEMS module, the
design considerations discussed in the previous sections, and species preference. The following
materials have been used to build artificial reefs and other marine structures, and can be
adapted for use in a wide variety of HEMS modules. For more in depth discussion about these
materials, an excellent resource is Guidelines for Marine Artificial Reef Materials (Lukens and
Selberg, 2004).
Concrete products include both traditional marine concrete mixtures and more recent mix-
tures. Traditional concrete is comprised of Portland cement, a mineral aggregate and sufficient
water to cause the materials to bind (Lukens and Selberg, 2004). Uncured cement (also called
‘green’ cement) may have a surface pH of 10 to 11, which is significantly more basic than sea-
water and may cause the surface to be toxic to organisms for 3-12 months (Lukens and Selberg,
2004). Project managers may want to consider adding pozzalanic materials (including pulver-
2Alternatively, managers can limit this sort of habitat project to fender piles and fender clusters, which are sacrifi-
cial elements that do not support above water structures (Alevras, 2008).
74
ized fly ash) to neutralize the pH or curing the concrete fully before installation (Lukens and
Selberg, 2004). Additionally, ferrous sulfate sheets embedded in the surface of the concrete
structure during casting will prevent this leaching, provide iron, a required trace nutrient, to
organisms, and offer a rugged surface for seaweed adhesion (Hotta et al., 1995).
More recent concrete mixtures also incorporate pulverized fly ash (PVA, a byproduct of
coal combustion), shredded tire pieces, flue gas desulfurization gypsum and slurry, quarry by-
products, and stabilized harbor mud (Gilliam et al., 1995; Relini et al., 1995; Suzuki, 1995;
Collins et al., 1994; Relini et al., 1995; Kress et al., 2002; Lukens and Selberg, 2004; Wilding
and Sayer, 2002b). Although these materials can be hazardous on their own, the setting pro-
cess of concrete seems to stabilize them. In general, concrete blocks made with fly ash retain
their strength in seawater, leech only small amounts of heavy metals (ppb), and result in little
or no bioaccumulation of heavy metals (Collins et al., 1995, 1994; Leung et al., 1995; Sampaolo
and Relini, 1994; Shieh and Duedall, 1994; Kress et al., 2002). Additionally, marine organisms
colonize fly ash blocks just as well if not better as traditional concrete blocks (Sampaolo and
Relini, 1994; Nelson et al., 1994). Including micro-silica in concrete mixtures has increased
their expected life to 500 years or more (Reef Innovations Inc., 2008). Overall, concrete is very
durable and stable in the marine environment.
Natural materials including wood, shells, and rocks could also be used to fabricate HEMS
modules. Wood has been used to create artificial reefs and fish aggregation devices in many
parts of the world. Wooden reefs provide complex habitat structure and large amounts of food
as they break down (Lukens and Selberg, 2004). However, because they are rapidly broken
down by boring and microbial organisms, wooden reefs do not last long in the marine environ-
ment (Lukens and Selberg, 2004). Wood structures must also be strongly secured as they are
very light (Lukens and Selberg, 2004). Pressure treated wood should not be used for HEMS
projects, as it contains toxic compounds (Lukens and Selberg, 2004).
Shells are most commonly used to create or replenish oyster reefs, although they have also
been linked to increases in some other species (Lukens and Selberg, 2004). Shell reefs have
a low profile in the water column, which reduces conflicts with navigation, but shell material
may be difficult to obtain and the lightweight shells have a tenancy to shift in high wave energy
areas (Lukens and Selberg, 2004). Alternate methods of using shells include impregnating
them in poured concrete modules (Reef Ball Foundation, Inc., 2007).
Quarry rock is considered a good reef material as it is inexpensive, easy to handle, extremely
long lasting, and experiences reduced scouring and sedimentation compared with other mate-
75
rials (Lukens and Selberg, 2004). The best type of rock to use depends on the local species.
Kelp, which secrete mucus and require minute wrinkles to firmly attach to a surface prefer
rocks with complex small scale irregularities such as andesite (Ohgai et al., 1995). Like shells,
smaller pieces of rock can be cemented to the surface of modules to create a more varied surface
(Lukens and Selberg, 2004).
Other materials, including steel, fiberglass, fiber-reinforced plastic, polyvinyl chloride, ce-
ramic, and composite materials have been used to create designed reef structures in Japan,
Singapore, and the United States (Angel and Spanier, 2002; Lukens and Selberg, 2004; Loh
et al., 2006). Carbonated slag blocks, a byproduct of steel making, also shows promise as a
reef substrate (Isoo et al., 2000). Although infrequently used, these materials may be useful in
HEMS module fabrication as they can be configured to a number of designs. Further research
is necessary to determine the efficacy and environmental safety of these materials.
Electrodeposition is a potentially useful technique that uses an electric current to accrete
calcium and magnesium salts on a cathode (Schuhmacher and Schillak, 1994; Lukens and Sel-
berg, 2004). Commonly, wire mesh is used as the cathode, iron rods are used as anodes, and
an electric current is created using solar or wind energy (Schuhmacher and Schillak, 1994;
Lukens and Selberg, 2004). The result is a wire mesh structure that is coated in a material
that mimics coral reefs (see Schuhmacher and Schillak, 1994). Many marine organisms colo-
nize the electrochemical deposits, including sponges, scleractinians, bryozoans and ascidians
(Schuhmacher and Schillak, 1994). These structures are light and highly configurable, and
may be useful for installing hard substrate in an area where concrete or rock may subside
(Lukens and Selberg, 2004). The substrate created by electro-deposition was also preferred
over concrete (Schuhmacher and Schillak, 1994). However, they are still somewhat experimen-
tal and in one case may have been associated with a chlorine gas mediated fish kill (Lukens
and Selberg, 2004).
Rubber tires, often ballasted by concrete, have also been used to create artificial reefs
(Lukens and Selberg, 2004). Un-ballasted tires are not very durable and move easily, dam-
aging reefs and other natural habitat (Lukens and Selberg, 2004). Tires in general have been
found to support few species, although more stable tire reefs support more species (Lukens and
Selberg, 2004). During storms, tires can flex and shed organisms, which may lead to the ob-
served pattern of low species (Collins et al., 2002). Tires also leech compounds that have been
found to be toxic to certain species, most notably rainbow trout and black sea bass (Lukens
and Selberg, 2004). Due to these and other concerns, many states now ban the use of tires as
76
artificial reefs.
Although decommissioned boats, aircraft, military hardware, and oil and gas platforms
have been used to create artificial reefs, they are also not recommended for HEMS use. HEMS
are installed in an urban environment and often must be specially designed to fit a specific
space, and decommissioned structures often are not compatible with these needs. Although
metal boats remain structurally sound, fiberglass boats and car bodies may also quickly dete-
riorate in the marine environment (Branden et al., 1994; Szedlmayer and Shipp, 1994; Lukens
and Selberg, 2004). Additionally, the costs of cleaning the vehicles of oil and other residue may
be prohibitively expensive, especially when compared with relatively cheap solutions such as
poured concrete ReefBallsTM (Lukens and Selberg, 2004).
4.2 Module Types
This section highlights some of the many types of HEMS modules available for use. The mod-
ules described here are organized first by the target ecosystem substrate type - vegetation,
hard substrate, and other substrates - and then by where the HEMS would be installed, in-
cluding the seawall, seafloor, pier, and water column. The modules described here are some-
what skewed towards modules that can be installed on the seafloor because of the work that
has been done on artificial reefs. Where available and relevant, examples of the modules and
the ecological principles the tools are based on are also mentioned. The design considerations
detailed in the previous section should be considered while looking through these modules.
4.2.1 Habitat Type 1: HEMS that provide vegetative substrate
Aquatic vegetation, while important in itself, is valued for the habitat and food it provides for
many other organisms. Seagrasses and algae are especially valued for the habitat they provide
to marine organisms. For example, the dense blades in a seagrass bed create protection for
juvenile fish by making it harder for predators to find and catch the juveniles (Kakimoto et al.,
1995). There are two main ways to create vegetative substrate. The first is to provide the
appropriate conditions and encourage the vegetation to grow. The second is to install artificial
vegetation substitutes where live vegetation would not survive. Although some of the modules
discussed here could be classified under hard or other substrates, they are included here be-
cause their primary goal is to provide suitable substrate for vegetation. These techniques are
summarized in Table 4.1.
77
Table 4.1: Table summarizing different techniques to introduce vegetative substrate to the urban waterfront. A short description of
each technique, when to use or not use each technique, and key resources for learning more about each technique are given.
78
Vegetation: Seawall and Bulkhead Faces
VERTICAL GARDEN S: Vertical gardens are vertical structures that allow plants to be grown
without soil on a surface (Figure 4.2). The structure is composed of a metal frame, a PVC layer,
and a layer of felt. The metal frame is hung on the wall, and a 1cm thick PVC sheet is riveted
to the frame to provide rigidity and waterproofing (Blanc, 2009). A polyamide felt, which is rot
proof and has high capillarity, is then stapled to the PVC and provides a surface for the roots to
grow (Blanc, 2009). Plants are then planted on the felt as seeds, cuttings, or pre-grown plants.
While vertical gardens have traditionally been used as architectural accents, these modules
show promise as a method to introduce vegetation to the urban waterfront. For example, verti-
cal gardens could be installed on seawalls above the high-tide line in order to provide shading
and a food source for intertidal organisms. A project like this would also work synergistically
with other projects installed on seawalls designed to provide habitat for fish and other marine
organisms. Although it may require some modification, vertical gardens could also be installed
in the intertidal area on seawalls and planted with intertidal algae.
Vertical gardens are reasonably light weight, weighing only 30kg per square meter, and can
therefore be retrofit to existing seawalls more easily (Blanc, 2009). Vertical gardens are also
very beautiful, and could add aesthetic value to the urban waterfront. While the raw materials
are inexpensive, the design is copyright of Patrick Blanc, and royalties of 10% to 50% must be
paid, depending on the scale of the project.
VEGETATION BASKETS: Vegetation baskets are containers that hold growing medium for
aquatic plants that are attached to or hang off of seawalls (Figure 4.3). These baskets can
be designed for vegetation that is only partially submerged, is periodically submerged by the
tide, or is completely submerged. Depending on the type of aquatic plants used, vegetation bas-
kets can provide food, shelter, or reproductive sites for marine organisms. Vegetation that is
visible from docks and walkways along seawalls can provide aesthetic and educational benefits
as well.
Cuyahoga Habitat Underwater Baskets (CHUB) are a patented vegetation basket that was
specifically designed for the Cuyahoga River. CHUBs are molded rubber baskets that hold
mesh bags filled with custom-blended soils and native plants that hang on a chain/brindle sys-
tem within the recesses of corrugated bulkheads (see Figure 4.3; Cuyahoga River Community
Planning Organization, 2008). The baskets are designed to hold 75-100 lb of planting medium
and plants, and they are designed to withstand extreme conditions (Cuyahoga River Commu-
nity Planning Organization, 2008). Additionally, because they fit within the recesses of the
79
Figure 4.2: Vertical gardens mounted to the seawall to allow vegetation to grow along the seawall and provide vegetative habitat
for marine organisms in the urban waterfront.
80
Figure 4.3: Vegetation baskets mounted to the seawall to allow vegetation to grow along the seawall and provide vegetative habitat
for marine organisms in the urban waterfront. Vegetation baskets can be designed to fit into corrugated seawalls or along flat
seawalls.
81
bulkheads, they are out of the way of ship traffic (Cuyahoga River Community Planning Or-
ganization, 2008). The baskets could also be mounted to straight seawalls that are protected
from boat strikes.
Around 400 CHUBs have been installed in the Cuyahoga River for the benefit of some 70
species of fish in 2008 (Scott, 2008). The CHUBs are expected to make it easier for fish to feed
and find shelter along the river, enabling them to make the upriver swim to the Cuyahoga’s
tributaries (Scott, 2008). Results of these test baskets should be forthcoming.
HABITAT BENCHES: Habitat benches are areas of shallow water created adjacent to seawalls
that can create habitat for seaweeds. This technique will be detailed further in the ‘other
substrate’ section.
HABITAT STEPS: Habitat steps, or habitat skirts, resemble concrete bleachers, and can be
installed on seawalls and buildings to create habitat for seaweeds. This technique will be
detailed further in the ‘hard substrate’ section.
SEAWA LL TEXTURING: There are many methods of creating relief on seawalls that could in-
crease the availability of habitat for seaweeds. These techniques will be detailed further in the
‘hard substrate’ section.
Vegetation: Seafloor
SEAW EED REEF S: A number of different types of artificial reefs have been designed especially
to encourage seaweed growth, including kelps. In general, these structures have relatively low
relief, are made from rock or concrete, are slightly elevated above the seafloor, and sometimes
provide points of attachment for kelp holdfasts. Kelp holdfasts resemble a cluster of roots, and
while they do not take up nutrients, they anchor the kelp in place and prevent it from washing
away in storms. Much of the research on artificial reefs targeted at kelp growth has occurred
in Japan and southern California.
Seaweed bed creation became a common technique in urban areas in Japan in the 1990s
(Isobe, 1998; Terawaki et al., 2001). Many coastal development projects, including commer-
cial and fishing port construction and construction of breakwaters for coastal defenses, have
adopted the use of seaweed habitat creation (Terawaki et al., 2001). Artificial seaweed reefs
have also been used to mitigate for habitat loss due to land reclamation (Yokouchi et al., 1991).
Multiple modules suitable for use in HEMS projects have been described in the literature
(Figure 4.4). Granite blocks, large greenschist (a type of rock) boulders, and small greenschist
rocks contained by a vinyl net created communities that approximated natural seaweed reefs
82
Figure 4.4: Seaweed reefs installed on the seafloor in order to provide hard substrate for marine organisms in the urban waterfront.
A few types of seaweed substrates are shown, including quarry rock, rocks in vinyl netting, and a boulder field. SEASUP concrete
blocks can be installed on top of boulder fields to provide additional habitat.
83
after 2-3 years (Yokouchi et al., 1991). Andesite, a rock with many minute surface irregulari-
ties, also provided very good substrate for kelp attatchement (Ohgai et al., 1995). Mounds of
cobble substrate have also created giant kelp populations (Zabloudil et al., 1995). Reefs used
for enhancing abalone numbers and spiny lobster populations have also been used successfully
to recruit seaweed and kelp (Choi et al., 2002). The ‘SEASUP’ concrete block is a modular ‘T’
shaped cast concrete product is also creates effective kelp reefs when kelp knobs are used (see
Terawaki et al., 2001, figure). The kelp knobs function as places for kelp holdfasts to attach
(Terawaki et al., 2001). Kelp holdfasts successfully adhered to these knobs and a kelp bed was
formed on the blocks in three years (Terawaki et al., 2001).
Intensive research in California has been focused on the artificial reef designed to mitigate
for losses caused by the operation of the San Onofre Nuclear Generating Station (Deysher et al.,
2002). Pilot reefs consisting of quarry rock and recycled concrete were constructed in 1999, and
following the success of these sites, a 170 acre kelp reef was constructed in the summer of 2008
(Southern California Edison, 2009). The reef was created out of a 125,000 tons of volcanic
rock carefully placed in a single layer in areas with the correct water and sand depth, and was
estimated to cost US$40 million (Rosenblatt, 2008). Projects of smaller sizes would be vastly
cheaper. Publications on the project are forthcoming.
Researchers have found that by reproducing as closely as possible the environmental con-
ditions of natural seaweed beds, artificial seaweed beds can be relatively ‘maintenance free’
(Terawaki et al., 2001). These factors include creating shallow and gentle sloping bottom sub-
strata, as the water depth and sediment characteristics of the substrata are especially impor-
tant (Terawaki et al., 2001). Techniques including seeding the area with zoospores and waiting
for natural colonization have been used to colonize the reefs (Terawaki et al., 2001; Falace
et al., 2006). Transplantation, including using polyurethane foam, non-toxic adhesives, and
resins, has also been used successfully (Falace et al., 2006; North, 1970, 1973). However, each
species responds differently and tests, such as those found in Falace et al. (2006) are recom-
mended. In some areas, maintenance ‘disturbance’ may be needed to help maintain the desired
community (Patton et al., 1995). Nets over seaweed reefs may help reduce grazing (Falace and
Bressan, 1995). Additionally, the slope should be carefully chosen, as communities of seaweeds
differed between substrates installed at 0, 45, and 90 degrees, likely due to incident light and
differences in water movement over the panels surface (Somsueb et al., 2001).
SEAGRASS BEDS: Techniques for restoring seagrasses, including eelgrass, have also been ex-
plored by researchers. Like seaweeds, these plants provide habitat structure for an ecosys-
84
Figure 4.5: A seagrass bed planted in the seafloor in order to increase the population of seagrass and provide vegetative habitat for
marine organisms.
85
tem, refuges from predation, and form the basis of the food web supporting juvenile salmon
and other species (see Figure 4.5; Levings, 1991). However, it is important to note that some
seagrasses are more sensitive to disturbance and enhancement of seagrass beds in highly dis-
turbed areas may be difficult. Project managers should also consider the next technique, arti-
ficial vegetation, in these situations.
Seagrasses grow in soft substrate within the photic zone. The most common method for
creating or enhancing seagrass beds is transplantation. Plant material for transplantations
comes from donor areas and can be directly planted or taken and propagated to produce many
more plants. Innovative programs that use schools as nurseries to provide material for trans-
plantation have been used successfully (Maryland Department of Natural Resources, 2009).
One study transplanted Zostera marina, a species of eelgrass, to a mitigation location in
San Diego Bay where it quickly developed into a thriving meadow that persisted through the
5 year study (Pondella et al., 2006). The mitigation location was located on the shore of the
North Island Naval Air Station, near vessel traffic lanes but not in a port. This project was
installed in conjunction with rocky reef modules, and the resulting habitat was successful.
ARTIFICIA L VEGETATIO N: Artificial beds of algae and seagrasses have been used successfully
in a number of ecological studies (e.g., see Figure 4.6; Levin et al. (1997); Jenkins et al. (1998);
Godoy and Coutinho (2002). Researchers are increasingly examining if these research sub-
strates could be used for habitat enhancement (e.g., Godoy and Coutinho (see 2002). Artificial
vegetation may be useful when a HEMS project site is subject to repeated disturbance, such as
prop scouring from boats. The artificial vegetation can provide food, shelter, and reproductive
support, as well as erosion control and possibly even nutrient or toxic removal from the water
(McNeil, 2000).
There are many methods of creating artificial vegetation. One study used 2200 plastic
aquarium plants 30cm in length (Godoy and Coutinho, 2002). The plastic plants, which resem-
bled Sargassum furcatum were tied onto an iron structure with a 25cm mesh at a density of
65 plants per square meter (Godoy and Coutinho, 2002). The artificial vegetation successfully
supported a very similar community to nearby natural vegetation, and it was concluded that
they may be an effective tool to sustain fish populations (Godoy and Coutinho, 2002). More
advanced designs include layered ribbons where one layer is a buoyant layer made of polyethy-
lene or another closed cell foam, surrounded by a layer designed to promote biological growth
(McNeil, 2000). Nutrients can also be added to the surface of these ribbons to enhance algal or
bacterial growth (McNeil, 2000).
86
Figure 4.6: Various types of artificial vegetation installed on the seafloor of the urban waterfront to provide vegetative substrate
for marine organisms. Three types of artificial vegetation are depicted here, including plastic aquarium plants, streamers, and
patented artificial “ribbon” vegetation
87
BREAKWATE RS: Wave breaks that create calm waters and allow soft sediment to accumulate
can provide good habitat for marine vegetation. These structures will be considered in the
‘Other Substrate’ section.
Vegetation: Docks and Pilings
INCREASED LIGHT BELOW DOCKS: Over-water structures such as ferry terminal docks shade
the seafloor, and may cause ecological consequences including loss of submerged aquatic veg-
etation (Blanton et al., 2002). Shading by over-water structures can also affect fish by reduc-
ing the food and shelter provided by aquatic vegetation as well as by creating a sharp shade
boundary that impedes fish movement (Blanton et al., 2002; Toft et al., 2004). Maintaining sub-
merged vegetation requires significantly more light than allowing for fish passage and feeding
(Blanton et al., 2002). Mathematical models exist to predict dock shading and allow project
managers to design docks, including the dimensions and the number and spacing of piles, that
will reduce the impact on submerged vegetation and fish.
A number of commercially available modules are available to increase the amount of light
underneath docks for submerged vegetation (see e.g. Figure 4.7). An excellent summary of
these modules can be found in Evaluation of Methods to Increase Light Under Ferry Terminals
(Blanton et al., 2002). Deck prisms and glass blocks were found to be aesthetically pleasing
cost effective ways at passing some light through a ferry dock (Blanton et al., 2002). However,
glass blocks could not be installed where weight is a concern and prisms become ineffective at
providing light for submerged vegetation when the dock is more than 10 feet from the seafloor
(Blanton et al., 2002). Sun TunnelsTM produced much more light and would be better option
where possible; however there were concerns about cost and where to locate the tunnels on the
dock (Blanton et al., 2002). Reflective panels provide a small amount of supplemental light and
can be easily attached to the undersides of docks (Blanton et al., 2002).
Metal or fiberglass grating is another option that passes a lot of light, although it can be
expensive and does not provide adequate structural strength for vehicle traffic (Blanton et al.,
2002). In tests, it was found to transmit between 52% and 61% of the natural light and allowed
for the persistence of seagrass (Shafer and Robinson, 2001). However, it was suggested that
grating could be used on the margins of docks for pedestrian walkways to create a more gradual
sun to shade transition or in other locations where structural integrity and surface runoff
would not be a problem (Blanton et al., 2002).
Overall, Blanton et al. (2002) recommend that a band of grating or SunTunnels be installed
88
Figure 4.7: A dock with devices installed to increase the amount of light that reaches the water under the dock in order to encourage
aquatic vegetation growth and fish survival. Grating, glass blocks, and deck prisms are among the products that can be used.
89
in nearshore areas over submerged aquatic vegetation where possible. Tighter clusters of light
products are recommended where the dock is more than 10 feet from the seafloor (Blanton
et al., 2002). Where fish are the focus for enhancement, fewer light products would be needed
(Blanton et al., 2002). However, in this case efforts should be made to dissipate dark shad-
ows and create a more gradual light-dark transition through the use of grating or glass blocks
(Blanton et al., 2002). This advice was recently employed in the rebuilding of a Port Townsend,
WA dock (Diefenderfer, 2003). The dock utlizied grating in strategic locations and highly re-
flective panels, as they were the options most suited to the uses of the dock and the desired
aesthetics (Diefenderfer, 2003). The grating should reduce the light/dark transition for fish,
while the reflective panels should be able to provide enough light for eelgrass to survive, al-
though further results will determine if this holds true (Diefenderfer, 2003).
4.2.2 Habitat Type 2: HEMS that provide hard substrate
Natural hard shorelines include cliffs, rocky shores, boulder beaches, and other shorelines
where solid rock is the predominant substrate feature. There are many similarities between
natural hard shorelines and urban waterfronts; for example, cliffs resemble seawalls in that
they have a vertical face and are resistant to erosion (Johnson, 1991). However, seawalls lack
the fissures, crevices, and other micro-habitats that characterize natural rock cliffs and are
important to marine organisms (Johnson, 1991). Due to these similarities, however, it is rel-
atively straightforward to manipulate the urban waterfront to more closely resemble natural
hard shorelines. Techniques for adding hard substrate habitat to the urban waterfront are
summarized in Table 4.2. While cobble and pebble shorelines are also made of rock, they are
subject to wave disturbance and will therefore be considered in the next section covering other
substrates.
Rocky Substrate: Seawalls and Bulkhead Faces
SEAWA LL STAIRS: A seawall stair is ‘a bioengineered structure with a series of permanent,
stepped, pre-cast, concrete benches that are comprised of rough surface features attached to
and extending out from the perimeter’ of a seawall, building, or docks (see Curtiss et al., 2006,
Figure 4.8). The steps resemble a set of bleachers when installed, and are designed to provide
intertidal habitat for organisms including seaweed (Thompson, 2008). The concrete benches
can incorporate undulating patterns of exposed aggregate and depressions designed to mimic
tide-pools (EBA Engineering Consultants Ltd., 2008). Additional habitat complexity could be
90
Table 4.2: Table summarizing different techniques to introduce hard substrate to the urban
waterfront. A short description of each technique, when to use or not use each technique, and
key resources for learning more about each technique are given.
91
Figure 4.8: Seawall stairs mounted on the seawall in order to provide hard substrate for marine organisms in the urban waterfront.
Each stair can be textured to provide micro-habitat and can also incorporate depressions which can act as tide pools.
92
added by creating holes in the steps or through other methods (Curtiss et al., 2006). These
features provide a variety of micro-habitats and micro-elevations that encourage colonization
and long-term utilization (EBA Engineering Consultants Ltd., 2008). In addition to providing
habitat and enhancing food production, seawall stairs have the potential to improve migration
corridors for organisms such as juvenile salmon (Curtiss et al., 2006).
The largest known installation of seawall stairs is at the Vancouver Convention Center,
and was constructed as mitigation for an expansion project (EBA Engineering Consultants
Ltd., 2008). This project was expected to be completed in 2009. It will also serve as an educa-
tional installation for local schoolchildren (EBA Engineering Consultants Ltd., 2008). Further
projects could be adapted from this design to local intertidal heights and seaweed species.
Project managers will need to consider the weight of the stairs when retrofitting an existing
or designing a new seawall. However, by using a stair step design with stringers, much of the
weight could rest on the seafloor.
SEAWA LL TEXTURING: There are many methods of creating relief on seawalls that could in-
crease the availability of habitat for marine organisms. The underlying premise of seawall tex-
turing is to create microhabitats that support marine organisms. These micro-habitats include
crevices, shallow pools, ledges, and angled or horizontal surfaces. Texture can be incorporated
into seawalls either in the design phase for seawall replacement projects, or retrofit onto ex-
isting structures. These techniques have been used with good results in Tokyo Bay (Tanaka
et al., 2000).
The planning phase for seawall replacement projects is an excellent opportunity to consider
adding texture to the seawalls. At this time, any engineering concerns can be addressed so
that the texturing does not create a safety hazard or compromise the strength of the struc-
ture. Additionally, test panels can be installed to determine the most appropriate texturing
approach to use in the final project. For example, Seattle is currently in the planning phases
of a major seawall replacement project, and is currently testing six different designs for inclu-
sion in the final replacement project (Goff, 2008). When test panels are used, field sampling,
including sessile invertebrate and algae assemblage sampling, epibenthic sampling, and fish
observations, should be completed so that the most appropriate panel type is used in the final
replacement project (Goff, 2008).
Some of the types of texturing that could be incorporated into seawalls are shown in Figure
4.9 (see Johnson, 1991; Saeki et al., 1995; Curtiss et al., 2006; Goff, 2008). These designs could
be incorporated into the casting of a new concrete seawall, stamped into a newly poured wall,
93
Figure 4.9: Seawall panels mounted to or integrated into the seawall to provide hard substrate habitat for marine organisms.
94
or attached after construction or as a retrofit to completed seawalls. In addition to concrete
or rock, texturing could be fabricated using the electro-deposition technique. Hollow domes,
steps, or other shapes could also be attached to a seawall using epoxy (see Curtiss et al., 2006,
and Figure 4.9).
In addition to these practical designs, seawall texture could also be more artistic or aesthet-
ically oriented. Buildings use textured facades as architectural design elements, and similar
approaches could be used for seawalls. For example, stone veneers, used for attractive build-
ing facades, could also be used to make seawalls more aesthetically pleasing and appear more
‘natural.’ Granite and other stone can also be carved by sculptors into beautiful pieces of public
art that also provide habitat for marine organisms.
SEAWA LL REFUGES: Seawalls that use caissons3can incorporate openings into the caissons to
provide refuges for fish and other marine organisms. This technique was successfully used in
the Port of Vancouver, who created the openings at the foot of the caissons (Desjardin et al.,
1995). While these refuges were not available to juvenile salmon, they were appropriate for
Giant Pacific Octopus and other marine organisms (Desjardin et al., 1995). Additionally, the
Port connected the caisson refuges to create more connected habitat (Desjardin et al., 1995).
Seawalls built without using caissons could be cast with depressions in the surface to create
small shelters for fish and other marine organisms (see Figure 4.10).
Hard Substrate: Seafloor
ARTIFICIA L REEF MODULES: Artificial reefs are used worldwide to “improve habitat, increase
resources, and manipulate assemblages of organisms in ways that benefit human kind” (Sea-
man and Sprague, 1991). Although there are still unresolved questions in the attraction-
production debate for fish populations, as discussed in the first chapter, researchers believe
that designs appropriate for the fish species and region in question are more likely to increase
production (Pickering and Whitmarsh, 1997). These reefs have also been installed under docks,
and used to plant massive corals with good results (see Figure 4.11; Iversen and Bannerot,
1984; Ortiz-Prosper et al., 2001).
A large number of artificial reef units4have been developed in the past decades. These mod-
3Caissons are “a chamber, usually of steel but sometimes of wood or reinforced concrete, used in the construction of
foundations or piers in or near a body of water” (The Columbia Electronic Encyclopedia, 2007).
4This follows the Japanese literature conventions in artificial reef terminology. A single module is called a ‘reef
unit,’ an aggregation of reef units is a ‘reef set,’ and a collection of reef sets and sometimes reef units is a ‘reef group.’
Multiple reef groups are referred to as a ‘reef complex.’ See Artificial Habitats for Marine and Freshwater Fisheries
(Seaman and Sprague, 1991).
95
Figure 4.10: : Seawall refuges installed in the seawall to provide habitat for marine organisms. Refuges can be drilled into the
seawall face when seawalls are built with caissons, or can be hollow cylinders incorporated into new seawalls.
96
Figure 4.11: Artificial reef units installed on the seafloor of the urban waterfront to provide hard substrate habitat for marine
organisms. The artificial reef units depicted here are ReefBallTM units.
97
ules were developed to provide shelter for mobile marine organisms and substrate for algae and
sessile invertebrates. Of particular interest are units that have been designed to achieve spe-
cific biological or use goals. Reef Ball Foundation, Inc. has created a specific technology and
process to allow project managers to create modules optimal for their site (Reef Ball Foun-
dation, Inc., 2007). These ReefBallsTM have been used successfully in thousands of projects,
including the West Harlem project in New York City highlighted in Chapter 3.
While concrete is the most common material used to fabricate artificial reef units, there is
also room for research and experimentation with other materials, such as pulverized fly ash,
and other techniques, including electro-deposition. Further information concerning artificial
reef modules, including a wide range of designs, can be found in the vast artificial reef liter-
ature (e.g., see Jordan et al., 2005; Foster et al., 1995; Grove et al., 1994; Jara and C´
espedes,
1994; Lozano-Alverez et al., 1994; Moreno et al., 1994; McCormick et al., 1994; Foster et al.,
1994; Kim et al., 1994; Pamintuan et al., 1994; Falace and Bressan, 1994; G ´
omez-Buckley
and Haroun, 1994; Omar et al., 1994; Lin and Su, 1994; Antsulevich, 1994; L¨
ok et al., 2002;
Thanner et al., 2006; Yano et al., 1995; Hasegawa and Shimizu, 1995; Takaki et al., 1995;
Hasegawa et al., 1995; Lapchine, 1995; Steimle et al., 1995; Yabe, 1995; Kakimoto et al., 1995).
Project managers considering artificial reef type modules should consider investigating this lit-
erature and consulting with artificial reef experts. Project managers will also need to consider
the safety of installing artificial reef modules near shipping lanes or where vessel navigation
is an issue.
An important biological consideration for artificial reef type HEMS is the spacing and size
of reef units and sets within a reef group. A number of researchers have studied the effects of
these factors. One such study was conducted by Jordan et al. (2005), who installed concrete
reefs on the seafloor in Florida. The reefs were designed to systematically test the effects of
different distances between reef group components and different number of reef units per set
(Jordan et al., 2005). SCUBA divers conducted a visual census of the experimental reefs every
other month for two years (Jordan et al., 2005).
Despite the brevity of this study, Jordan et al. (2005) found that, in general, the total num-
ber of fish and species richness increased with the distance between the reef group components,
up to the maximum tested distance of 25m. However, two abundant species did not follow this
pattern, and had the highest number of fish present at 5m and 15m respectively (Jordan et al.,
2005). These results agree with other studies, including Frazer and Lindberg (1994), who
found that crabs preferred widely spaced reef units to closely spaced reef units, Bohnsack et al.
98
(1994) who found more biomass on multiple small reefs than one large reef of equal material,
and Figley (2003) who also noted the importance of intermediate sand habitat for foraging. Ad-
ditionally, increasing the number of reef units in the reef set also increased the total number of
fish and the species richness (Jordan et al., 2005). This agrees with Seaman et al. (1995) who
suggested that this may be due to increased physical mass of the reef structure and complexity
of microhabitats, and Jan et al. (2003), who found that the most efficient size was 4-10 reef
units, and Charbonnel et al. (2002). Calculating the fractal dimension of the surface is also a
useful tool to evaluate complexity (Abelson and Shlesinger, 2002; Lan and Hsui, 2006). Project
managers should consider the spacing and size of artificial reef type HEMs projects and how
they affect both the target species and general biodiversity.
REEF ATTRACTANTS: Fish aggregating devices (FADs) have a long history of use worldwide.
FADs were originally used to attract target fish to a location for easy harvest. However, re-
searchers have also attempted to use mid-water FADs to focus the recruitment of juvenile fish
to artificial reef modules (Brock and Kam, 1994). It is thought that the mid-water FADs will
increase the vertical profile of the reef and act as a signal that attracts more passing juvenile
fish to settle on the artificial reef (Brock and Kam, 1994).
To support this, greater fish settlement has been observed over reefs with mid-water FADs
than reefs without mid-water FADS in a number of studies (Brock and Kam (1994); Beets, 1989
in Brock and Kam (1994)). Beets (1989) also found that a reef outfitted with a mid-water FAD
developed a greater fish community than reefs deployed without FADS or the FADs alone (in
Brock and Kam (1994)). However, a single streamer was not sufficient to attract fish to reefs,
indicating that the FADs must be suitably complex (Sherman et al., 2002). Light attractants
may also attract fish to a reef (Sherman et al., 2002). Designs for some FAD devices that have
successfully helped with juvenile recruitment are shown in Figure 4.12.
If FADs are used to target juvenile fish settlement onto reef modules, the reef modules
must be designed to provide adequate shelter for the small fish (Brock and Kam, 1994). Small
shelters inaccessible to predators, or ReefBallsTM with predator exclusion devices in use should
be used to prevent excessive mortality of juvenile fish due to predation. Additionally, the reefs
fitted with FADs should be small in size to avoid colonization by piscivores (Brock and Kam,
1994).
ROCKY ISLANDS: Rocky islands are piles of rocks designed to imitate the small islands or rocky
outcrops that commonly occur with rocky shores (see Johnson, 1991, Figure 4.13). These small
islands could provide ‘shallow areas of slower water in mid-stream to attract fish;’ seabirds
99
Figure 4.12: A mid-water fish attraction device (FAD) installed on an artificial reef. FADs may help increase the number of fish and
other organisms settling on artificial reefs
100
Figure 4.13: A rocky island installed on the seafloor to provide hard substrate for marine organisms in the urban waterfront.
101
and ducks a place to nest without disturbance; and people with ‘an opportunity to see tidal
pools’ (Johnson, 1991). In some areas, small islands could also create habitat for marine mam-
mals such as sea lions. Project managers need to choose their materials carefully to create an
aesthetically pleasing island instead of a dumping site. Additionally, small islands cannot be
created where they would create a safety hazard for boat traffic (Johnson, 1991).
Hard Substrate: Dock and Pilings
PILING HABI TAT: Habitat can be created on pilings by creating more surface area for algae,
barnacles, and other organisms to grow. Fish and mobile invertebrates can then exploit these
food resources. Additionally, benthic habitat can be added around the bases of pier pilings in
order to provide shelter for fish and other marine organisms. This will allow pilings to provide
both shelter and food.
It may not be feasible to retrofit pilings that support docks and relieving platforms to in-
clude habitat as it may interfere with required safety inspections (Alevras, 2008). Piling habi-
tat will need to be incorporated in the design phase for load bearing structures. Some potential
designs for integrated piling habitat are shown in Figure 4.14. However, non-load bearing pil-
ings, such as the sacrificial pilings used to protect docks from accidental ship strike, can be
retrofit and clad with habitat.
4.2.3 Habitat Type 3: Modules providing other types of substrate
Numerous types of habitats can be installed using HEMS in urban waterfronts other than
vegetative and hard substrate habitat. These include relatively coarse substrates including
cobble and pebble shorelines, fine substrates including sand and silt, and woody substrate.
However, very few projects have utilized these alternate substrates. As a result, there are
ample opportunities for new research and design. Table 4.3 summarizes these techniques for
adding these habitats to the urban waterfront.
Other Substrate: Seawall and Bulkhead Faces
HABITAT BENCHES: Habitat benches are areas of shallow water created adjacent to seawalls
using coarse rocky substrate (Figure 4.15). The substrate is intermediate between rigid sea-
walls or cliffs and soft shores like marshes, and is often found naturally at the foot of cliffs
(Johnson, 1991). This type of project, which could also be called a cobble or gravel beach,
provides complex habitat in an area of the water column where photosynthesis can occur. The
102
Figure 4.14: Structural pilings built to incorporate hard substrate habitat. The cross section of the piling resembles a multi-pointed
star that increases surface area.
103
Table 4.3: Table summarizing different techniques to introduce other substrates to the urban waterfront. A short description of
each technique, when to use or not use each technique, and key resources for learning more about each technique are given.
104
Figure 4.15: A habitat bench installed on the seawall to provide shallow habitat for marine organisms. Large rocks are used at the
base of the habitat bench to prevent the smaller substrate of the habitat bench from shifting.
105
complicated, porous texture of the substrate provides habitat for many kinds of algae, seaweed,
fish, and invertebrates (Johnson, 1991; Curtiss et al., 2006).
A habitat bench installed in Seattle used 50,000 tons of rock to create a 15 to 20 foot wide
strip that mimics the tidelands historically found in the area (Cornwall, 2007). The taxa rich-
ness of epibenthic samples at the completed habitat bench was higher than adjacent riprap or
unaltered seawall sites (Toft et al., 2008). Juvenile salmon were observed feeding more often
than at nearby rip-rap and significantly more than at the previous unaltered seawall site (Toft
et al., 2008). A similar habitat bench installed at Pier 94 at the Port of Vancouver also provided
habitat for many organisms, including kelps and other algae (Desjardin et al., 1995).
Habitat benches should be constructed out of materials that will not wash away. Alter-
natively, larger rocks or ReefBallsTM could support the seaward side of the habitat bench to
prevent the substrate from washing away (Curtiss et al., 2006). Extensive monitoring in Seat-
tle found that the coarse, angular, well-packed sediment used to create the habitat bench was
resistant to transport, in part because it was rarely exposed by the tide (Toft et al., 2008). How-
ever, the habitat bench was vulnerable to failure of the riprap buttress of the sea wall, which
covered part of the relatively narrow habitat bench (Toft et al., 2008). Monitoring similar to
what Toft et al. (2008) conducted is recommended for habitat benches and other projects using
rocks that may be susceptible to movement.
WOODY DEBRIS: Woody debris is an important component of near shore habitats that is miss-
ing in urban waterfronts (Curtiss et al., 2006). Woody debris is ‘organic detritus,’ material
that is ‘the principle energy source for the food webs of estuarine and shallow, marine ben-
thic portions of the ecosystem’ (Brennan and Culverwell, 2004 in Curtiss et al. (2006)). Woody
debris provides substrate for detrivores including bacteria and fungi to grow, as well as more
structurally complex algae and larger marine vegetation (Curtiss et al., 2006). Sessile inver-
tebrates often settle on woody debris, and mobile invertebrates graze on the algae, bacteria,
fungi, and sessile invertebrates (Curtiss et al., 2006). Woody debris creates habitat complexity
that benefits juvenile and adult fish, providing an area for them to forage, find refuge, and
spawn (Curtiss et al., 2006). Small fish also spawn near woody debris, providing forage for
piscivorous fish (Curtiss et al., 2006).
One way that woody debris can be added to the urban waterfront is by attaching it to the
seawall. Logs or branches could be arranged on the seawall face in an attractive design (see
Micklam et al., 2000, Figure 4.16). The horizontal ledges created by the timbers would provide
spaces for algae and other marine plants could grow (Micklam et al., 2000). Such a project could
106
Figure 4.16: Wood installations on seawalls to provide woody debris and habitat for marine organisms in the urban waterfront. A
basket containing cut branches and various configurations of logs mounted to the seawall are shown.
107
be completed at an acceptable cost and could be aesthetically pleasing (Micklam et al., 2000).
Maintenance will be required as timbers deteriorate in the marine environment, although the
timing of this maintenance will depend on the size, type, and porosity of the wood and the
availability of oxygen (Curtiss et al., 2006).
HABITAT BASKETS: Baskets containing different substrates including gravel, cobbles, sand,
or no substrate could be hung from or mounted to the seawall face. Researchers in Japan cre-
ated hanging gravel baskets that were used for fish spawning near dams (see Ishikawa and
Iwamizu, 1995, Figure 4.17). These baskets were used for spawning by schools of small fish
(Ishikawa and Iwamizu, 1995). Salmon also dug nests in the gravel and spawned success-
fully (Ishikawa and Iwamizu, 1995). Ishikawa and Iwamizu (1995) also suggested that these
spawning baskets could be used in concert with baskets for aquatic plants.
In Seattle, three experimental troughs were hung from the seawall (see Arnesen, 2008,
Figure 4.17). Three different substrates were used to fill the troughs, including cobble, gravel,
and one as a tide pool (Arnesen, 2008). The experimental trough functioning as a tide pool was
originally filled with sand, however the sand quickly eroded (Toft, 2008). Sand does not seem
to be a good material for habitat baskets as it washes away quickly, however further results
are forthcoming.
Other Subtrate: Seafloor
BREAKWATE RS: Soft sediment in some urban areas is quickly scoured away by wave action
and wakes from large ships. Creating breakwaters in front of seawalls can create a section of
soft, shallow bottom can create sheltered habitat for algae, small invertebrates and juvenile
fish (see Johnson, 1991, Figure 4.18). In addition, wave intake works can be integrated into
these designs to improve port water quality (Yamamoto et al., 1995).
In Japan, a submerged wave dissipater was used in front of a breakwater to protect existing
kelp beds, create new kelp beds, and create a calm area for sea urchin, small fish, and other ma-
rine organisms while still preserving the function of the breakwater (Hasegawa and Shimizu,
1995; Akeda et al., 1995; Takaki et al., 1995; Yano et al., 1995). Kelp beds successfully grew
on the rear step of this structure, and the ecosystem approached that of natural reefs after
ten years (Akeda et al., 1995; Yano et al., 1995). For the best results, Hasegawa and Shimizu
(1995) recommend that the wave dissipater should be one wave length away from the breakwa-
ter. Additionally, these structures were originally proposed as a way to save construction time
(Hasegawa and Shimizu, 1995). Rows of ReefBallTM units have also been used as breakwaters,
108
Figure 4.17: Habitat baskets installed on a seawall to provide habitat along the seawall. A habitat basket containing cobble and
small boulders is shown.
109
Figure 4.18: A breakwater installed in front of the seawall. The breakwater forces waves to break, which creates a calm area
between the breakwater and the seawall.
110
and they also increased soft sediment habitat (Harris, 2004).
OYSTER REEF S: Natural oyster reefs are common in the southern United States. These reefs
are built through the reproduction and settling of oyster larvae onto existing reef structure
(Hill, 2002). Over time, these oyster reefs create very complex three dimensional habitats that
provide many micro-habitats for other species. Sponges, other mollusks, and many species of
fish and invertebrates are closely associated with oyster reefs; one study found 303 different
species inhabiting oyster reefs in North Carolina (Hill, 2002). Oyster reefs also provide food
to a variety of organisms that consume both the oysters and the small organisms that inhabit
them, and contribute to improved water quality (Hill, 2002).
Oyster reefs could be incorporated into the urban waterfront in a number of ways. Mounds
of oyster shells placed on the seafloor will quickly become colonized by oysters and other marine
organisms (see North Carolina Division of Marine Fisheries, 2009, Figure 4.19). These mounds
would need to be placed in relatively shallow water. However, oyster shells can sometimes be
hard to obtain, as they are also desired for other uses. Alternate designs include impregnating
oyster shells into artificial reef modules, such as ReefBallsTM.
WOODY DEBRIS: Pieces of large woody debris can also be installed at the foot of seawalls and
in other shallow areas (see Curtiss et al., 2006, Figure 4.20). Like woody debris attached to
seawalls, woody debris placed on the seafloor can help replace the benefits of natural woody
debris including food production and shelter and increase fish populations (Yabe, 1995; Curtiss
et al., 2006). Project managers could consider constructing mesh baskets on the seafloor that
can hold woody debris (see Yabe, 1995, Figure 4.20). These baskets could be replenished with
woody debris through routine maintenance. Log cribs, half-logs, stumps, and brush piles have
been used successfully in eastern lakes (Bassett, 1994). Appropriate woody debris must not be
treated lumber, but could for example include cuttings from city trees and donated Christmas
trees.
SAND FILLED FABRIC BAGS: Bags constructed from geotextiles and filled with sand could be
piled at the base of seawalls or in other shallow areas of the seafloor to create habitat (see Cur-
tiss et al., 2006, Figure 4.21). Geotextiles are permeable fabrics made from polymers (Curtiss
et al., 2006). Although typically used for shoreline protection structures, marine organisms
have been observed successfully using geotextile bags as habitat (Curtiss et al., 2006). One
researcher in Australia compared different types of geotextiles to quantify the quality of the
habitat provided, and found that reinforced non-woven geotextiles supported the most diverse
communities (Edwards, n.d. in Curtiss et al. (2006)). After only 16 days, non-woven geotex-
111
Figure 4.19: Piles of oyster shells arranged on the seafloor in order to provide habitat for marine organisms in the urban waterfront
including oysters.
112
Figure 4.20: Woody debris installed on the seafloor to provide habitat for marine organisms in the urban waterfront. A basket
containing cut branches and a log pile are shown.
113
Figure 4.21: Geotextile bags filled with sand placed on the seafloor in order to provide habitat for marine organisms in the urban
waterfront.
114
tiles supported more than 1,500 organisms and woven geotextiles supported more than 800
organisms (Edwards, n.d. in Curtiss et al. (2006)). Other studies have shown that seaweed
quickly covered geotextile bags within months of deployment (Restal et al., n.d. in Curtiss
et al. (2006)).
However, no researchers have evaluated the habitat value of geotextile bags compared to
more traditional artificial reef modules including ReefBallsTM. Additionally, geotextile bags
must be installed carefully to avoid tearing the seams, and boat anchors may damage the bags
(Curtiss et al., 2006). As they are traditionally used for reducing shoreline wave energy and
minimizing erosion, any geotextile bags installed for habitat would also provide these benefits
(Curtiss et al., 2006).
Other Substrate: Docks and Pilings
Unfortunately, no modules have been developed for pilings.
Other Substrate: Water Column
STATIONARY NETTING: Permanent swimming nets installed in Sydney Harbor to keep sharks
out of swimming enclosures are being used extensively by marine organisms including sea-
horses (Clynick, 2008). For seahorses, these nets replicated seagrass and mangrove habitat by
providing a surface that the seahorses can grasp (Clynick, 2008). Densities of seahorses on the
nets was very high, and other organisms including macroalgae and sponges also colonized the
nets (Clynick, 2008). Most seahorses were found within 1 meter of the seafloor, indicating that
nets in the water column may only need to extend a few meters above the seafloor (Clynick,
2008). Similar nets designed with seahorses and other marine organisms in mind could im-
prove the availability of habitat in urban waters for organisms such as seahorses which have
limited mobility, restricted home ranges, and slow rates of colonization (see Figure 4.22 Clyn-
ick, 2008). Managers should not install these nets where they might interfere with navigation.
4.3 Concluding Thoughts
Selecting the appropriate Habitat Enhancing Marine Structure (HEMS) module is a critical
step in the HEMS implementation process. The HEMS module must be appropriately chosen to
fulfill both regional and project goals and objectives, and be appropriate for the biological needs
of local species, satisfy social and economic concerns, and comply with safety and engineering
115
Figure 4.22: Netting installed on the seafloor to provide habitat for marine organisms. Many species including seahorses have
benefited from permanent swimming nets installed in Australia.
116
requirements. When properly designed and installed, each of the modules covered in this
chapter will provide habitat for marine organisms.
There are many opportunities for future development and research. New HEMS modules
must continue to be developed. Basic research comparing the effectiveness of different HEMS
modules is almost completely lacking. Additionally, monitoring results from installed HEMS
projects has either never been collected or not been published for public or professional access.
Existing HEMS modules will need to be tested, revised, and improved based on the information
gathered from monitoring installed projects. Further, little, if any, information is available on
combinations of HEMS modules. Researchers will need to examine how modules interact, how
organisms utilize multiple modules placed together, and other important ecological aspects
of utilizing multiple HEMS modules. Social and economic studies, including public opinion
surveys to gauge public acceptance of and attitudes towards HEMS projects are also needed.
These research needs are in addition to the basic research needs examining the interaction of
urban structures and marine organisms discussed in Chapter 2.
Functioning ecosystems are quite complex, and multiple habitat types may exist in close
proximity and interact in important ways. For example, Lindquist et al. (1994) found that
some reef species rely upon sandy substrate as well as reefs. They recommended that reef
units be placed in proximity to appropriate sandy substrate so that these reef fish would be
able to forage on sand infauna (Lindquist et al., 1994). In urban waterfronts where appropriate
sandy substrate is not present, project managers should consider installing HEMS units that
encourage sandy substrate, such as wave breaks, along with rocky reefs to accommodate these
species.
As a result, project managers may want to consider utilizing multiple HEMS modules at a
location to layer different components of an ecosystem and realize greater improvements to the
urban waterfront. Using combinations of different HEMS modules will be more effective than
any one module by itself (Curtiss et al., 2006). Diverse habitats at the small scale will also
contribute to regional urban waterfront habitat goals and habitat backbones. Suites of HEMS
projects should also be chosen and designed with attention to the regional and project goals and
objectives, and should address the same considerations as single HEMS projects. Additionally,
managers will need to consider how the different modules will work together.
Figure 4.23 illustrates an example of using multiple HEMS projects concurrently in the ur-
ban waterfront. A rebuilt dock has been outfitted with habitat integrated into the dock pilings,
including fluting along the piling and artificial reef units placed at the base. A nearby break-
117
Figure 4.23: Multiple HEMS projects can be installed in close proximity within the urban waterfront. Here, habitat integrated into
dock pilings, a breakwater, and habitat baskets work together to provide habitat for marine organisms in the urban waterfront.
118
water has created a calm area and some valuable soft sediment habitat. Reef fish occupying
the artificial reef units at the base of the pilings can forage on the sand infauna, and juvenile
fish and other organisms can find shelter in the area of calm water created by the breakwa-
ter. Additionally, vegetation baskets mounted on the seawall can provide additional vegetative
habitat as well as a source of food for the juvenile fish using the calm area behind the break-
water. This is only one of many possible combinations of HEMS projects that can be tailored to
the specific regional and project goals and objectives.
119
Chapter 5
LOOKING TOWARD THE FUTURE
Among the challenges the future holds, there are many opportunities to improve our ur-
ban waterfronts. How we choose to seize these opportunities will decide the future of urban
waterfronts and the people and marine organisms that live alongside them.
Currently, maritime cities support a large portion of the world’s human population, There
are now 14 megacities and thousands of major cities located on the coast (Tibbers, 2002). How-
ever, people who live and work along the waterfront generally don’t notice the other species
with which they share the waterfront (Johnson, 1991). Similarly, urban marine structures in-
cluding docks and seawalls provide a large portion of the habitat available to marine organisms
living in urban waterways. Researchers have found differences in habitats found in urban wa-
terfronts and less disturbed shorelines. These differences have important ramifications for the
marine organisms that inhabit urban waterfronts.
In the future, more maritime cities will emerge and even more urban structures will be
installed in the water. By 2015, three more megacities are projected to emerge, and the coastal
population of the United States alone will reach 165 million people (Tibbers, 2002). Further,
experts expect the number of urban marine structures in the marine environment to increase
in response to population growth in urban areas and global climate change. These changes
may have profound implications for the marine organisms that share the urban waterfront.
There is also currently a desire to reconnect cities to their urban waterfronts. Urban water-
fronts are being rediscovered and transformed from industrial areas into areas where urban
residents can live, shop, and recreate. Piers, seawalls, and other urban marine structures in the
working waterfront built during the previous century are reaching the end of their useful life.
Necessary restorations include the Alaskan Way Seawall in Seattle. Built between 1916 and
1936, the seawall is facing severe deterioration and is currently being examined by the Army
Corps of Engineers for replacement. Redevelopment projects in the urban waterfronts, such as
the West Harlem Park project in New York City, also offer opportunities to install HEMS. More
companies, ports, and cities are also looking for opportunities for ‘green’ action, and the urban
public is becoming increasingly environmentally aware. Projects will incrementally redesign
120
and reconstruct the urban waterfront.
However, even when projects transform waterfront land, the aesthetic and habitat benefits
currently end at the water’s edge. Companies, ports, and cities have started green initiatives,
but they have mainly focused on improving air and water quality and providing habitat away
from the urban waterfront. While important, these actions ignore the marine organisms that
share our cities. Luckily, there are new environmentally aware methods of advancing function-
ality and aesthetic appeal to the waterfront that were unavailable in the last century.
The Habitat Enhancing Marine Structures (HEMS) described in this document are tools
that can truly reconnect cities to their urban waterfronts both now and into the future. HEMS
provide people with the ability to work within the conditions and constraints imposed by the
current urban waterfront to improve habitat for marine organisms. Opportunities to imple-
ment HEMS projects are numerous. Any waterfront project including restoring old industrial
waterfronts can easily harness the ability of HEMS to provide urban waterfront habitat for
marine organisms. Projects that choose to utilize well designed HEMS can achieve a wide
range of goals and objectives including:
•HEMS can enhance biodiversity through increasing the area and
quality of urban waterfront habitat available to marine organisms,
connect isolated patches of habitat, and potentially reduce the im-
pact of non-native species, if necessary.
•Corporate sustainability can be achieved using HEMS projects to
provide biodiversity and wildlife habitat programs.
•Companies and government agencies can use HEMS projects to sat-
isfy legally mandated requirements.
•HEMS projects can improve waterfront aesthetics and improve pub-
lic environmental education.
Many different HEMS units to accomplish these goals are currently available for implementa-
tion. Additionally, new HEMS solutions are continuously being designed.
The successful addition of habitat to an urban waterfront will require careful planning,
thoughtful design and construction practices, and meaningful management and monitoring
programs. All HEMS projects will need to be tailored to the meet the biological needs of lo-
cal species, address social and economic concerns, and comply with safety and engineering
requirements. These concerns will factor into the choice of and design of the modules used in
the HEMS projects.
121
Therefore, there are two futures laid out for the urban waterfront. The current path will
provide us with a rebuilt waterfront designed for its human users. There will be parks and
recreational areas available, new apartments where industrial warehouses once stood, and a
refurbished working waterfront ready to serve future generations. This path is easy, familiar,
and will satisfy many of the demands we place on the urban waterfront.
With HEMS projects we can provide both humans and marine organisms with high quality
spaces to use. The utilization of properly executed HEMS can help create an aesthetically
pleasing urban waterfront that fulfills the economic and social goals of cities while providing
the habitat needs of marine organisms. A waterfront designed to take advantage of HEMS
can support a mosaic of habitats tailored to the needs of regional biodiversity. Each individual
HEMS project will contribute a specific habitat to the larger urban landscape. Viewed broadly,
this waterfront will emulate a naturally variable landscape composed of common habitat types
found in the region. Support for all stages in the lifecycle of regional marine organisms will be
addressed through these varied habitats.
While county, state, or federal level multi-disciplinary groups can be convened to make
recommendations, the path taken must ultimately be decided by stakeholders of each urban
waterfront. Continuing with business as usual will be easier, but urban areas will forgo many
potential benefits. Adding habitat for the marine organisms that share our waters can enhance
the urban waterfront for both people and marine organisms. With the use of HEMS urban
residents and planners will come to see the urban waterfront both as a commercially useful
area and as habitat for marine organisms.
122
BIBLIOGRAPHY
Joint Artificial Reef Technical Committee (1998, December). Coastal Artificial Reef Plan-
ning Guide. Technical report, Atlantic and Gulf States Marine Fisheries Commissions.
Abelson, A. and Y. Shlesinger (2002). Comparison of the development of coral and fish com-
munities on rock-aggregated artificial reefs in Eilat, Red Sea. ICES Journal of Marine Sci-
ence 59, S122–S126.
Able, K. W., J. P. Manderson, and A. L. Studholme (1998, December). The Distribution of
Shallow Water Juvenile Fishes in an Urban Estuary. Estuaries 21(4), 731–744.
Airoldi, L., M. Abbiati, M. Beck, S. Hawkins, P. Jonsson, D. Martin, P. Moschella, A. Sun-
del´
of, R. Thompson, and P. ˚
Aberg (2005). An ecological perspective on the deployment and
design of low-crested and other hard coastal defence structures. Coastal Engineering 52,
1073–1087.
Airoldi, L., F. Bacchiocchi, C. Cagliola, F. Bulleri, and Abbiati (2005). Impact of recreational
harvesting on assemblages in artificial rocky habitats. Marine Ecology Progress Series 299,
55–66.
Akeda, S., K. Yano, A. Nagano, and I. Nakauchi (1995). Improvement Works of Fishing Port
Taken with Care to Artificial Formation of Seaweed Beds. In Proceedings of the International
Conference of Ecological System Enhancements Technology for Aquatic Enviroments, Tokyo,
Japan, pp. 394–399.
Alevras, R. and S. Zappala (2008, 1 July). Incorporating Aquatic Habitat Values in Working
Waterfronts. In Coastal Footprints: Minimizing Human Impacts, Maximizing Stewardship,
pp. 21. The Coastal Society.
Alevras, R. A. (2008, July 28). Personal Communication.
Ambrose, R. F. (1994). Mitigating the EFfects of a Coastal Power Plant on a Kelp Forest
Community: Rationale and Requirements for an Artificial Reef. Bulletin of Marine Sci-
ence 55(2–3), 694–708.
Andrews, K. S. and T. W. Anderson (2004). Habitat-dependent recruitment of two temperate
reef fishes at multiple spatial scales. Marine Ecology Progress Series 277, 231–244.
Angel, D. L. and E. Spanier (2002). An application of artificial reefs to reduce roganic en-
richment caused by net-cage fish farming: preliminary results. ICES Journal of Marine
Science 59, S324–S329.
123
Antsulevich, A. E. (1994). Artificial Reefs Project for Improvement of Water Quality and En-
vironmental Enhancement of Neva Bay (St.-Petersburg County Region. Bulletin of Marine
Science 55(2–3), 1189–1192.
Arnesen, J. (2008, September 9). City of Seattle Habitat Test Panels and Troughs Study.
Published online. http://www.sustainabilitypro.com/uwr_speaker.php .
Ault, T. and C. Johnson (1998). Relationships between habitat and recruitment of three
species of damselfish (Pomacentridae) at Heron Reef, Great Barrier Reef. Journal of Exper-
imental Marine Biology and Ecology 223, 145–166.
Baird, R. C. (2005, March). On Sustainability, Estuaries, and Ecosystem Restoration: The
Art of the Practical. Restoration Ecology 13(1), 154–158.
Baqueiro, E. C. and R. L. Mendez (1994). Artificial Reefs: An Alternative to Enhance Mexi-
can Littoral Commercial Fisheries. Bulletin of Marine Science 55(2-3), 1014–1020.
Barshaw, D. E. and E. Spanier (1994). Anti-Predator Behaviors of the Mediterranean Slipper
Lobster, Scyllarides latus.Bulletin of Marine Science 55(2–3), 375–382.
Barwick, R. D. and T. J. Kwak (2004). Fish Populations Associated with Habitat-Modified
Piers and Natural Woody Debris in Piedmont Carolina Reservoirs. North American Journal
of Fisheries Management 24, 1120–1133.
Bassett, C. E. (1994). Use and Evaluation of Fish Habitat Structure in Lakes of the Eastern
United States by the USDA Forest Service. Bulletin of Marine Science 55(2-3), 1137–1148.
Bayle-Sempere, J. T., A. A. Ramos-Espl´
a, and J. A. G. Charton (1994). Intra-Annual Vari-
ability of an Artificial Reef Fish Assemblage in the Marine Reserve of Tabarca (Alicante,
Spain, SW Mediterranean. Bulletin of Marine Science 55(2–3), 824–835.
Beets, J. and M. A. Hixon (1994). Distribution, Persistence, and Growth of Groupers
(Pisces:Serranidae) on Artificial and Natural Patch Reefs in the Virgin Islands. Bulletin
of Marine Science 55(2–3), 470–483.
Benedetti-Cecchi, L. and G. C. Osio (2007). Replication and mitigation of effects of con-
founding variables in environmental impact assessment: effect of marinas on rocky-shore
assemblages. Marine Ecology Progress Series 334, 21–35.
Bishop, M. J. (2004). A posteriori Evaluation of Strategies of Management: The Effective-
ness of No-wash Zones in Minimizing the Impacts of Boat-Wash on Macrobenthic Infauna.
Environmental Management 34(1), 140–149.
Blanc, P. (2009). Vertical Garden. Online resource for those looking to create vertical garden
structures. See website at http://www.verticalgardenpatrickblanc.com/mainen.php .
Blanton, S., R. Thom, A. Borde, H. Diefenderfer, and J. Southard (2002, January). Evalua-
tion of Methods to Increase Light Under Ferry Terminals. Technical Report PNNL-13714,
Pacific Northwest National Laboratory, Sequim, Washington.
124
Blau, S. F. and S. C. Byersdorfer (1994). Sausage-Shaped Artificial Collector Developed in
Alaska to Study Young-of-Year Red King Crabs. Bulletin of Marine Science 55(2-3), 878–886.
Blockey, D. J. (2007). Effect of wharves on intertidal assemblages on seawalls in Sydney
Harbour, Australia. Marine Environmental Research 63, 409–427.
Blockley, D. and M. Chapman (2008). Exposure of seawalls to waves within and urban
estuary: effects on intertidal assemblages. Austral Ecology 33, 168–183.
Blockley, D. J. (2007). Effect of wharves on intertidal assemblages on seawalls in Sydney
Harbour, Australia. Marine Environmental Research 63, 409–427.
Bohnsack, J. A., D. E. Harper, D. B. McClellan, and M. Hulsbeck (1994). Effects of Reef Size
on Colonization and Assemblage Structure of Fishes at Artificial Reefs Off Southeastern
Florida, U.S.A. Bulletin of Marine Science 55(2–3), 796–823.
Bolding, B., S. Bonar, and M. Divens (2004). Use of Artificial Structure to Enhance An-
gler Benefits in Lakes, Ponds, and Reservoirs: A Literature Review. Reviews in Fisheries
Science 12, 75–96.
Borde, A. B., L. O’Rourke, R. Thom, and G. Williams (2004, January). National Review of
Innovative and Successful Coastal Habitat Restoration. Technical report, Battelle Marine
Sciences Laboratory, Sequim, Washington. Prepared for National Oceanic and Atmospheric
Administration.
Branden, K. L., D. A. Pollard, and H. A. Reimers (1994). A Review of Recent Artificial Reef
Developments in Australia. Bulletin of Marine Science 55(2-3), 982–994.
Brickhill, M. J., S. Y. Lee, and R. M. Connolly (2005). Fishes associated with artificial reefs:
attributing changes to attraction or production using novel approaches. Journal of Fish
Biology 65 Supplement B, 53–71.
Brock, R. E. and A. K. H. Kam (1994). Focusing the Recruitment of Juvenile Fishes on Coral
Reefs. Bulletin of Marine Science 55(2–3), 623–630.
Bryant, M. M. (2006). Urban landscape conservation and the role of ecological greenways at
local and metropolitan scales. Landscape and Urban Planning 76(1–4), 23–44.
Buckley, R. M. (1982, June-July). Marine Habitat Enhancement and Urban Recreational
Fishing in Washington. Marine Fisheries Review 44(6–7), 28–37.
Buckley, R. M., J. E. West, and D. C. Doty (1994). Internal Micro-Tag Systems for Marking
Juvenile Reef Fishes. Bulletin of Marine Science 55(2–3), 848–857.
Bulleri, F. (2005a). Experimental evaluation of early patterns of colonisation of space on
rocky shores and seawalls. Marine Environmental Research 60, 355–374.
125
Bulleri, F. (2005b, February 18). Role of recruitment in causing differences between inter-
tidal assemblages on seawalls and rocky shores. Marine Ecology Progress Series 287, 53–65.
Bulleri, F. and L. Airoldi (2005). Artificial marine structures facilitate the spread of a non-
indigenous green alga, Codium fragile ssp. tomentosoides in the north Adriatic Sea. Journal
of Applied Ecology 42, 1063–1072.
Bulleri, F., M. Chapman, and A. Underwood (2004). Patterns of movement in of the limpet
Cellana tramoserica on rocky shores and retaining seawalls. Marine Ecology Progress Se-
ries 281, 121–129.
Bulleri, F., M. Chapman, and A. Underwood (2005). Intertidal assemblages on seawalls and
vertical rocky shores in Sydney Harbour, Australia. Austral Ecology 30, 655667.
Burton, W., J. Farrar, F. Steimle, and B. Conlin (2002). Assessment of out-of-kind mitiga-
tion success of an artificial reef deployed in Delaware Bay, USA. ICES Journal of Marine
Science 59, S106–S110.
Cardskadden, H. and D. J. Lober (1998). Environmental stakeholder management as busi-
ness strategy: the case of the corporate wildlife habitat enhancement programme. Journal
of Environmental Management 52, 183–202.
Casselle, J., M. Love, C. Fusaro, and D. Schroeder (2002). Trash or habitat? Fish assem-
blages on offshore oilfield seafloor debris in the Santa Barbara Channel, California. ICES
Journal of Marine Science 59, S258–S265.
Castellan, A. and R. Kelty (2005, May). Small Dock and Pier Management Workshop Work-
book. National Oceanic and Atmospheric Administration.
Chapin, III, F. S., E. S. Zavaleta, V. T. Eviner, R. L. Naylor, P. M. Vitousek, H. L. Reynolds,
D. U. Hooper, S. Lavorel, O. E. Sala, S. E. Hobbie, M. C. Mack, and S. D´
ıaz (2000, 11 May).
Consequences of changing biodiversity. Nature 405.
Chapman, M. (2003, December 15). Paucity of mobile species on constructed seawalls: effects
of urbanization on biodiversity. Marine Ecology Progress Series 264, 21–29.
Chapman, M. (2006). Intertidal Seawalls as Habitats for Molluscs. Journal of Molluscan
Studies 72, 247–257.
Chapman, M. and F. Bulleri (2003). Intertidal seawalls — new features of landscape in
intertidal environments. Landscape and Urban Planning 62, 159–172.
Chapman, M. and F. Bulleri (2004). Intertidal assemblages on artificial and natural habitats
in marinas on the north–west coast of Italy. Marine Biology 145, 381391.
Chapman, M., J. People, and D. Blockley (2005). Intertidal assemblages associated with
natural corallina turf and invasive mussel beds. Biodiversity and Conservation 14, 1761–
1776.
126
Charbonnel, E., C. Serre, S. Ruitton, J.-G. Harmelin, and A. Jensen (2002). Effects of in-
creased habitat complexity on fish assemblages associated with large artificial reef units
(French Mediterranean coast). ICES Journal of Marine Science 59, S208–S213.
Choi, C. G., Y. Takeuchi, T. Terawaki, Y. Serisawa, M. Ohno, and C. H. Sohn (2002). Ecology
of seaweed beds on two types of artificial reef. Journal of Applied Phycology 14, 343–349.
Claro, R. and J. P. Garc´
ıa-Arteaga (1999, May). Perspectives on an Artificial Habitat Pro-
gram for Fishes of the Cuban Shelf. Technical report, Institute of Oceanology, Havana,
Cuba.
Claudet, J. and D. Pelletier (2004). Marine protected areas and artificial reefs: A review of
the interactions between management and scientific studies. Aquating Living Resources 17,
129–138.
Clewell, A., J. Rieger, and J. Munro (2005, December). Guidelines for Developing and Man-
aging Ecological Restoration Projects. Technical report, Society for Ecological Restoration
International.
Clynick, B. (2008). Harbour swimming nets: a novel habitat for seahorses. Aquatic Conser-
vation: Marine and Freshwater Ecosystems 18, 483–492.
Clynick, B., M. Chapman, and A. Underwood (2008). Fish assemblages associated with
urban structures and natural reefs in Sydney, Australia. Austral Ecology 33, 140–150.
Clynick, B. G. (2006). Assemblages of fish associated with coastal marinas in north-western
Italy. Journal of the Marine Biological Association of the United Kingdom 86, 847–852.
Collins, K., A. Jensen, A. Lockwood, and S. Lockwood (1994). Evaluation of Stabilized Coal-
Fired Power Station Waste for Artificial Reef Construction. Bulletin of Marine Science 55(2-
3), 1251–1262.
Collins, K., A. Jensen, and J. Mallinson (1995). Biological development of a stabilized coal
ash artificial reef, Poole Bay, U.K. In Proceedings of the International Conference of Ecologi-
cal System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 119–124.
Collins, K., A. Jensen, J. Mallinson, V. Roenelle, and I. Smith (2002). Environmental impact
assessment of a scrap tyre artificial reef. ICES Journal of Marine Science 59, S243–249.
Connell, S. D. (2000). Floating pontoons create novel habitats for subtidal epibiota. Journal
of Experimental Marine Biology and Ecology 247, 183–194.
Connell, S. D. (2001). Urban structures as marine habitats: an experimental comparison
of the composition and abundance of subtidal epibiota among pilings, pontoons and rocky
reefs. Marine Environmental Research 52, 115–125.
Connell, S. D. and T. Glasby (1999). Do urban structures influence local abundance and
diversity of subtidal epibiota? A case study from Sydney Harbour, Australia. Marine Envi-
ronmental Research 47, 373–387.
127
Cornwall, W. (2007, 17 January). Seattle trying to woo salmon back downtown with park’s
seawall makeover. The Seattle Times.http://seattletimes.nwsource.com/html/
sculpturepark/2003528358_waterfront17m.html.
Coyle, K. (2005, September). Environmental Literacy in America. Technical report, The
National Environmental Education & Training Foundation.
Cripps, S. and J. Aabel (2002). Environmental and socio-economic impact assessment of
Ekoreef, a multiple platform rigs-to-reef development. ICES Journal of Marine Science 59,
S300–S308.
Croci, S., A. Butlet, A. Georges, R. Aguejdad, and P. Clergeau (2008, December). Small urban
woodlands as biodiversity conservation hot-spot: a multi-taxon approach . Biomedical and
Lifesteam Sciences 23(10), 1171–1186.
Curtiss, H., M. Wilson, S. Peterson, M. Kuharic, Y. Huang, S. Goldberg, and G. Hund (2006,
June). Rethinking the Urban Marine Edge: Ecological Opportunities along a Seawall In-
terface, Seattle’s Central Waterfront. Technical report, Prepared for Keystone Project, En-
vironmental Management Certificate Program, Program on the Environment, University of
Washington, Seattle, WA.
Cuyahoga River Community Planning Organization (2008). Cleertec Green Bulkhead High
Peformance Shoreline Edge System (HPSES). Available as an online resource at http://www.
cuyahogariverrap.org/GREENBULKHEAD.html .
Danovaro, R., C. Gambi, A. Mazzola, and S. Mirto (2002). Influence of artificial reefs on the
surrounding infauna: analysis of meiofauna. ICES Journal of Marine Science 59, S356–362.
Dean, T. A., A. E. Jahn, L. E. Deysher, and R. S. Grove (1995). Design of an Artificial Reef as
Habitat for Giant Kelp. In Proceedings of the International Conference of Ecological System
Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 263–265.
Desjardin, D. J., J. Baumann, and A. J. Jordan (1995). Mitigation and Enhancement of
Marine Habitat through Development Projects in Vancouver, Harbour, British Columbia. In
Proceedings of the International Conference of Ecological System Enhancements Technology
for Aquatic Enviroments, Tokyo, Japan, pp. 569–574.
Deysher, L. E., T. A. Dean, R. Grove, and A. Jahn (2002). Design considerations for an
artficial reef to grow giant kelp (Macrocystis pyrifera) in Southern California. ICES Journal
of Marine Science 59, S201–S207.
Diefenderfer, H. (2003, July 17). Port Townsend dock promotes fish habitat: Diverse team re-
designs dock to encourage eelgrass growth. DJC.com Environmental Outlook 2003: Special
Section. Retrieved from http://www.djc.com/news/en/11146937.html on July 21, 2003.
Diefenderfer, H., R. Thom, and J. Adkins (2003, September). Systematic Approach to Coastal
Ecosystem Restoration. Technical report, Battelle Marine Sciences Laboratory, Sequim,
Washington.
128
Dramstad, W. E., J. D. Olson, and R. T. Forman (1996). Landscape Ecology Principles in
Landscape Architecture and Land-Use Planning. Harvard University Graduate School of
Design.
Duarte, C. M. (2000). Marine biodiversity and ecosystem services: an elusive link . Journal
of Experimental Marine Biology and Ecology 250(1–2), 117–131.
Duffy-Anderson, J. T., J. P. Manderson, and K. W. Able (2003). A Characterization of Juve-
nile Fish Assemblages Around Man-made Structures in the New York-New Jersey Harbor
Estuary, U.S.A. Bulletin of Marine Science 72(3), 877–889.
EBA Engineering Consultants Ltd. (2008, February 20). VCCEP Habitat Project Largest of
Its Kind. Online article at http://www.eba.ca/news.asp?a=261 .
Edmunds, S. (2007, July 22 to 26, 2007). Planning for Portland’s Working Waterfront. In
Proceedings of Coastal Zone 07, Portland, Oregon.
Elkington, J. (1994). Towards the sustainable corporation: Win-win-win business strategies
for sustainable development. California Management Review 36(2), 90–100.
Eno, N. C., R. A. Clark, and W. G. Sanderson (1997). Non-native marine species in British
waters: a review and directory. Technical report, Joint Nature Conservation Committee,
Monkstone House, City Road, Peterborough, PE1 1JY, UK. http://www.jncc.gov.uk/pdf/
pub02_nonnativereviewdirectory.pdf .
Environmental Protection Agency (2007, June). Ecological Revitalization and Attractive
Nuisance Issues. Technical Report EPA 542-F-06-003, Office of Superfund Remediation and
Technology Innovation, U.S. Environmental Protection Agency.
Fabry, V., C. Langdon, W. Balch, A. Dickson, R. Feely, D. Hales, B. Hutchins, K. J.A., and
C. Sabine (2008). Present and Future Impacts of Ocean Acidification on Marine Ecosys-
tems and Biogeochemical Cycles, report of the Ocean Carbon and Biogeochemistry Scoping
Workshop on Ocean Acidification Research held 9–11 October 2007, La Jolla, CA, XX pp.
Falace, A. and G. Bressan (1994). Some Observations on Periphyton Colonization of Artificial
Substrata in the Gulf of Trieste. Bulletin of Marine Science 55(2–3), 924–931.
Falace, A. and G. Bressan (1995). Adapting an Artificial Reef to Biological Requirements. In
Proceedings of the International Conference of Ecological System Enhancements Technology
for Aquatic Enviroments, Tokyo, Japan, pp. 634–639.
Falace, A. and G. Bressan (2002). Evaluation of the influence of inclination of substrate
panels on seasonal changes in a macrophytobenthic community. ICES Journal of Marine
Science 59, S116–S121.
Falace, A., E. Zanelli, and G. Bressan (2006). Algal Transplantation as a Potential Tool for
Artificial Reef Management and Environmental Mitigation. Bulletin of Marine Science 78(1),
161–166.
129
Fern´
andez-Juricic, E. and J. Jokim¨
aki (2001). A habitat island approach to conserving birds
in urban landscapes: case studies from southern and northern Europe. Biodiversity and
Conservation 10, 2023–2041.
Figley, B. (2003, January). Marine Life Colonization of Experimental Reef Habitat in Tem-
perate Ocean Waters in New Jersey. Technical report, New Jersey Department of Environ-
mental Protection.
Fisheries and Oceans Canada (2002a, February). Working Around Water? Factsheet Series
(Saskatchewan Edition): What You Should Know About Fish Habitat and Building Materi-
als.
Fisheries and Oceans Canada (2002b, February). Working Around Water? Factsheet Series
(Saskatchewan Edition): What You Should Know About Fish Habitat and Docks, Boathouses
and Boat Launches.
Foster, K., R. Kropp, F. Steimle, W. Muir, and B. Conlin (1995). Fish Community and Feeding
Habitats at a Pre-Fabricated Concrete Artificial Reef in Delaware Bay, U.S.A. In Proceedings
of the International Conference of Ecological System Enhancements Technology for Aquatic
Enviroments, Tokyo, Japan, pp. 266–271.
Foster, K. L., F. W. Steimle, W. C. Muir, and R. K. Kropp (1994). Mitigation Potential of
Habitat Replacement: Concrete Artificial Reef in Delaware Bay — Preliminary Results.
Bulletin of Marine Science 55(2–3), 783–795.
Frazer, T. K. and W. J. Lindberg (1994). Refuge Spacing Similarly Affects Reef-Associated
Species from Three Phyla. Bulletin of Marine Science 55(2–3), 344–400.
Fresh, K. L., D. Rothaus, K. W. Mueller, and C. Waldbillig (2003). Habitat Utilization by
Smallmouth Bass in the Littoral Zones of Lake Washington and Lake Union/Ship Canal. In
Greater Lake Washington Chinook Workshop, pp. 1–2.
Friesen, T. A., H. K. Takata, J. S. Vile, J. C. Graham, R. A. Farr, M. J. Reesman, and C. B.
S. (2003, February). Relationships Between Bank Treatment / Nearshore Development and
Anadromous / Resident Fish in the Lower Willamette River. Technical report, Oregon De-
partment of Fish and Wildlife, Columbia River Investigations Program, 17330 SE Evelyn
Street, Clackamas, Oregon.
Gacia, E., M. S. Paola, and D. Martin (2007, June). Low crested coastal defence structures on
the Catalan coast of the Mediterranean Sea: how they compare with natural rocky shores.
Scientia Marina 71(2), 259–267.
Garrison, P. J., D. W. Marshall, L. Stremick-Thompson, P. L. Cicero, and P. D. Dearlove
(2005, March). Effects of Pier Shading on Littoral Zone Habitat and Communities in Lakes
Ripley and Rock, Jefferson County, Wisconsin. Technical Report PUB-SS-1006 2005, Wis-
consin Department of Natural Resources, Jefferson County Land and Water Conservation
Department, and Lake Ripley Management District.
130
Gilbert, O. L. and P. Anderson (1998). Habitat Creation and Repair. Oxford University
Press.
Gilliam, D. S., K. Banks, and R. E. Spieler (1995). Evaluation of a Novel Material for Artifi-
cial Reef Construction. In Proceedings of the International Conference of Ecological System
Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 345–350.
Glasby, T. and S. D. Connell (2001, April). Orientation and position of substrata have large
effects on epibiotic assemblages. Marine Ecology Progress Series 214, 127–135.
Glasby, T. M., S. D. Connell, M. G. Holloway, and C. L. Hewitt (2007). Nonindigenous biota
on articifical structures: could habitat creation facilitate biological invasions? Marine Biol-
ogy 151, 887–895.
Godoy, E. A. S. and R. Coutinho (2002). Can artificial beds of plastic mimics compensate
for seasonal absence of natural beds of Sargassum furcatum?ICES Journal of Marine
Science 59, S111–S115.
Goff, M. (2008, September 28). Effect of Habitat Enhancement on Urban Seawall Ecology.
Technical report, University of Washington, School of Aquatic and Fishery Sciences: Wetland
Ecosystem Team.
G´
omez-Buckley, M. C. and R. J. Haroun (1994). Artificial Reefs in the Spanish Coastal Zone.
Bulletin of Marine Science 55(2–3), 1021–1028.
Goodman, R. M., F. J. Burton, and A. C. Echternacht (2005). Habitat use of the endangered
iguana Cyclura lewisi in a human-modified landscape on Grand Cayman. Animal Conserva-
tion 8(4), 397–405.
Goodsell, P., M. Chapman, and A. Underwood (2007). Difference between biota in anthro-
pogenically fragmented habitats and in naturally patchy habitats. Marine Ecology Progress
Series 351, 15–23.
Gordon, Jr., W. R. (1994). A Role for Comprehensive Planning, Geographical Information
System (GIS) Technologies and Program Evaluation in Aquatic Habitat Development. Bul-
letin of Marine Science 55(2-3), 995–1013.
Great Barrier Reef Marine Park Authority (2009a). Marine Park Zoning. Downloaded on
May 15, 2009 from http://www.gbrmpa.gov.au/corp_site/management/zoning .
Great Barrier Reef Marine Park Authority (2009b). Marine Park Zoning: Information of
interest to Planners and Managers. Downloaded on May 15, 2009 from http://www.gbrmpa.
gov.au/corp_site/management/zoning/planners_info .
Grove, R. S., M. Nakamura, K. Hiroshi, and C. J. Sonu (1994). Aquatic Habitat Technology
Innovation in Japan. Bulletin of Marine Science 55(2–3), 276–294.
131
Halusky, J. G., W. Seaman, Jr., and E. W. Strawbridge (1994). Effectiveness of Trained Vol-
unteer Divers in Scientific Documentation of Artificial Aquatic Habitats. Bulletin of Marine
Science 55(2-3), 939–959.
Harris, L. E. (2004). Combined recreational amenities and coastal erosion protection us-
ing submerged breakwaters for shoreline stabilization. In National Conference on Beach
Preservation Technology. Florida Shore & Beach Preservation Organization.
Hasegawa, H., Y. Kawasaki, and T. Terawaki (1995). Study on New Method for Kelp Foun-
dation Creation. In Proceedings of the International Conference of Ecological System En-
hancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 481–486.
Hasegawa, H. and T. Shimizu (1995). New Concept of Breakwater Structure More Suitable
to Fishery Resource Propagation. In Proceedings of the International Conference of Ecologi-
cal System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 412–417.
Hiddink, J., B. MacKenzie, A. Rijndorp, N. Dulvy, E. Nielson, D. Bekkevold, M. Heino, P. Lo-
rance, and H. Ojaveer (2008). Importance of fish biodiversity for the management of fisheries
and ecosystems. Fisheries Research 90, 6–8.
Hill, K. (2002, June 23). Oyster Reef Habitats. Online resource found at http://www.sms.si.
edu/IRLspec/Oyster_reef.htm .
Hodgkison, S., J.-M. Hero, and J. Warnken (2007). The efficacy of small-scale conservation
efforts, as assessed on Australian golf courses. Biological Conservation 136, 576–586.
Holloway, M. and S. D. Connell (2002, June 19). Why do floating structures create novel
habitats for subtidal epibiota? Marine Ecology Progress Series 235, 43–52.
Hooper, D. U., F. S. Chapin, III, J. J. Ewel, A. Hector, P. Inchausti, S. Lavorel, J. H. Lawton,
D. M. Lodge, M. Loreau, S. Naeem, B. Schmid, H. Set´
’al´
’a, A. J. Symstad, J. Vandermeer,
and D. A. Wardle (2005, February). Effects of Biodiversity on Ecosystem Functioning: A
Consensus of Current Knowledge. Ecological Monographs 75(1), 3–35.
Hotta, K., T. Suzuki, and M. Ohno (1995). Technology for Creating an Artificial Seaweed
Community Using Ferrous Sulfate. In Proceedings of the International Conference of Ecolog-
ical System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 487–494.
Ishikawa, S. and M. Iwamizu (1995). Preliminary Test of Man-made Spawning Beds for
Fishes Dwelling in a Dam Reservoir. In Proceedings of the International Conference of Eco-
logical System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 351–
355.
Isobe, M. (1998, 11–12 June). Toward Integrated Coastal Zone Management in Japan. In
ESENA Workshop: Energy-Related Marine Issues in the Sea of Japan, Tokyo, Japan.
Isoo, T., T. Takahashi, and M. Okada (2000, July). Evaluation of carbonated solids as sea-
weed bed substratum. Nippon Suisan Gakkaishi 66(4), 647–650.
132
Iversen, E. S. and S. P. Bannerot (1984). Artificial Reefs Under Marina Docks in Southern
Florida. North American Journal of Fisheries Management 4, 294–299.
Jackson, A. C., M. G. Chapman, and A. J. Underwood (2008). Ecological interactions int he
provision of habitat by urban development: whelks and engineering by oysters on artificial
seawalls. Austral Ecology 33, 307–316.
Jahn, A. E., L. E. Deysher, T. A. Dean, and R. S. Grove (1995). Siting Study for a Kelp Ar-
tificial Reef Mitigation Project. In Proceedings of the International Conference of Ecological
System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 575–580.
Jan, R.-Q., Y.-H. Liu, C.-Y. Chen, M.-C. Wang, G.-S. Song, H.-C. Lin, and K.-T. Shao (2003).
Effects of pile size of artificial reefs on the standing stocks of fishes. Fisheries Research 63,
327–337.
Jara, F. and R. C´
espedes (1994). An Experimental Evaluation of Habitat Enhancement on
Homogenous Marine Bottoms in Southern Chile. Bulletin of Marine Science 55(2–3), 295–
307.
Jenkins, G., M. Keough, and P. Hamer (1998). The contributions of habitat structure and
larval supply to broad-scale recruitment variability in a temperate zone. Journal of Experi-
mental Marine Biology and Ecology 226, 259–278.
Jennings, M. J., M. A. Bozek, G. R. Hatzenbeler, E. E. Emmons, and M. D. Staggs (1999).
Cumulative Effects of Incremental Shoreline Habitat Modification on Fish Assemblages in
North Temperate Lakes. North American Journal of Fisheries Management 19, 1827.
Johnson, M. (1991). Life on the Edge: Urban Waterfront Edges with Aquatic Habitats. Pre-
pared as part of a phd dissertation in city and regional planning, University of Pennsylvania.
Jordan, L. K., D. S. Gilliam, and R. E. Spieler (2005). Reef fish assemblage structure affected
by small-scale spacing and size variations of artifical patch reefs. Journal of Experimental
Marine Biology and Ecology 326, 170–186.
Kakimoto, H., M. Ohgai, K. Tsumura, and M. Noda (1995). The Effect of Artificial Reef
and seaweed bed on Survival of Prey Fish. In Proceedings of the International Conference
of Ecological System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp.
227–232.
Kautsky, H., S. Qvarfordt, and T. Malm (2006). Development of fouling communities on
vertical structures in the Baltic Sea. Estuarine, Coastal and Shelf Science 67, 618–628.
Kennish, R., K. D. Wilson, J. Lo, S. C. Clarke, and S. Laister (2002). Selecting sites for large-
scale deployment of artificial reefs in Hong Kong: constraint mapping and prioritization
techniques. ICES Journal of Marine Science 59, S164–170.
Khalaf, M. and M. Kochzius (2002). Changes in trophic community structure of shore fishes
at an industrial site in the Gulf of Aqaba, Red Sea. Marine Ecology Progress Series 239,
287–299.
133
Kim, C. G., J. W. Lee, and J. S. Park (1994). Artificial Reef Designs for Korean Coastal
Waters. Bulletin of Marine Science 55(2–3), 858–866.
Knott, N., A. Underwood, M. Chapman, and T. Glasby (2004). Epibiota on vertical and
on horizontal surfaces on natural reefs and on artificial structures. Journal of the Marine
Biological Association of the United Kingdom 84, 1117–130.
Kress, N., M. Tom, and E. Spanier (2002). The use of coal fly ash in concrete for marine
artificial reefs in the southeastern Mediterranean: compressive strength, sessile biota, and
chemical composition. ICES Journal of Marine Science 59, S231–S237.
Lamberti, A. and B. Zanuttigh (2005). An integrated approach to beach management in Lido
di Dante, Italy. Estuarine, Coastal and Shelf Science 62, 441–451.
Lan, C.-H. and C.-Y. Hsui (2006). Insight from Complexity: A new Approach to Designing
the Deployment of Artificial Reef Communities. Bulletin of Marine Science 78(1), 21–28.
Lapchine, O. M. (1995). The Integrity of Artificial Reefs and Underwater Fish Cages: The
Ecologically Balanced Fisheries. In Proceedings of the International Conference of Ecological
System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 558–568.
Leung, A., K. Leung, K. Lam, and B. Morton (1995). The deployment of an experimental
artificial reef in Hong Kong: objectives and initial results. In Proceedings of the International
Conference of Ecological System Enhancements Technology for Aquatic Enviroments, Tokyo,
Japan, pp. 131–140.
Levin, P., R. Petrik, and J. Malone (1997). Interactive Effects of Habitat Selection, Food
Supply and Predation on Recruitment of an Estuarine Fish. Oecologia 112(1), 55–63.
Levin, S. A. (1992, December). The Problem of Pattern and Scale in Ecology: The Robert H.
MacArthur Award Lecture. Ecology 73(6), 1943–1967.
Levings, C. D. (1991). Strategies for Restoring and Developing Fish Habitats in the Strait
of Georgia-Puget Sound Inland Sea, Northeast Pacific Ocean. Marine Pollution Bulletin 23,
417–422.
Lin, J.-C. and W.-C. Su (1994). Early Phase of Fish Habitation Around a New Artificial Reef
off Southwestern Taiwan. Bulletin of Marine Science 55(2–3), 1112–1121.
Lindeman, K. C., P. A. Kramer, and J. S. Ault (2001). Comparative Approaches to Reef
Monitoring and Assessment: An Overview. Bulletin of Marine Science 69(2), 335–337.
Lindquist, D., L. Cahoon, I. Clavijo, M. Posey, S. Bolden, L. Pike, S. Burk, and P. Cardullo
(1994). Reef Fish Stomach Contents and Prey Abundance on Reef and Sand Substrata As-
sociated with with Adjacent Artifical and Natural Reefs in Onslow Bay, North Carolina.
Bulletin of Marine Science 55(2–3), 308–318.
134
Loh, T.-L., J. Tanzil, and L. Choi (2006). Preliminary study of community development
and scleractinian recruitment on fibreglass artificial reef units in the sedimented waters of
Singapore. Aquatic Conservation: Marine and Freshwater Ecosystems 16, 61–76.
L¨
ok, A., C. Metin, A. Ulas¸ , F. O. D ¨
uzbastilar, and A. Tokac¸ (2002). Artificial reefs in Turkey.
ICES Journal of Marine Science.
Louisiana Coastal Wetlands Conservation and Restoration Task Force (2006, 17 April).
Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA): A Response to
Louisiana’s Land Loss. Technical report, Louisiana Coastal Wetlands Conservation and
Restoration Task Force.
Lozano-Alverez, E., P. Briones-Fourz´
an, and F. Negrete-Soto (1994). An Evaluation of Con-
crete Block Structures as Shelter for Juvenile Caribbean Spiny Lobsters, Panulirus argus.
Bulletin of Marine Science 55(2–3), 351–362.
Lucy, J. A. and C. G. Barr (1994). Experimental monitoring of Virginia artificial reefs using
fishermen’s catch data. Bulletin of Marine Science 55(2–3), 527–537.
Lukens, R. R. and C. Selberg (2004, January). Guidelines for Marine Artificial Reef Materials
(Second ed.). Artificial Reef Subcommittes of the Atlantic and Gulf States Marine Fisheries
Commissions.
Manchester, S. J. and J. M. Bullock (2000, October). The Impacts of Non-Native Species on
UK Biodiversity and the Effectiveness of Control. Journal of Applied Biology 37(5), 845–864.
Maryland Department of Natural Resources (2009). Bay Grasses in Classes: An Interactive
Program that Allows Students to Participate in Restoring the Chesapeake Bay. Online
resource found at http://www.dnr.state.md.us/bay/sav/bgic/ .
Mason, J., C. Moorman, G. Hess, and K. Sinclair (2007). Designing suburban greenways to
provide habitat for forest-breeding birds. Landscape and Urban Planning 80, 153–164.
McCormick, T., K. Herbinson, T. Mill, and J. Altick (1994). A Review of Abalone Seeding,
Possible Significance and a New Seeding Device. Bulletin of Marine Science 55(2–3), 680–
693.
McNeil, R. J. (2000, May 9). United States Patent Number 606153. Retrieved from http:
//www.wikipatents.com/6060153.html on April 5, 2009.
MEC Analytical Systems, Inc. (2002, June). Ports of Long Beach and Los Angeles Year 2000
Biological Baseline Study of San Pedro Bay. Technical report, MEC Analytical Systems, Inc.,
2433 Impala Drive, Carlsbad, California, 92008.
Meyers, J. (2006, May). Culvert replacement can yield untapped resources and unplanned
benefits. Public Works Magazine.
Micklam, A., J. Gibbins, S. Proctor, and A. Braham (2000, May). Riverside renewal at Green-
wich peninsula. In Proceedings of ICE - Civil Engineering, Volume 138, pp. 36–41.
135
Milne, T., M. C. Bull, and M. N. Hutchinson (2003). Fitness of the Endangered Pygmy Blue
Tongue Lizard Tiliqua adelaidensis in Artificial Burrows. Journal of Herpetology 37(4), 762–
765.
Montefalcone, M., G. Albertelli, C. Morri, and C. N. Bianchi (2007). Urban seagrass: Status
of Posidonia oceanica facing the Genoa city waterfront (Italy) and implications for manage-
ment. Marine Pollution Bulletin 54, 206–213.
Moreau, S., C. P´
eron, K. Pitt, R. Connolly, S. Lee, and T. Meziane (2008). Opportunistic
predation by small fishes on epibiota of jetty pilings in urban waterways. Journal of Fish
Biology 72, 205–217.
Moreira, J., M. Chapman, and A. Underwood (2006). Seawalls do not sustain viable popula-
tions of limpets. Marine Ecology Progress Series 322, 179–188.
Moreira, J., M. Chapman, and A. Underwood (2007). Maintenance of chitons on seawalls
using crevices on sandstone blocks as habitat in Sydney Harbour, Australia. Journal of
Experimental Biology and Ecology 347, 134–143.
Moreno, I. (2002). Effects of substrate on the artificial reef fish assemblage in Santa Eulalia
Bay (Ibiza, western Mediterranean). ICES Journal of Marine Science 59, S144–S149.
Moreno, I., I. Roca, O. Re˜
nones, J. Coll, and M. Salamanca (1994). Artifical Reef Program in
Balearic Waters (Western Mediterranean). Bulletin of Marine Science 55(2–3), 667–671.
Moschella, P., M. Abbiati, P. ˚
Aberg, L. Airoldi, J. Anderson, F. Bacchiocchi, F. Bulleri, G. Di-
nesen, M. Frost, E. Gacia, L. Granhag, P. Jonsson, M. Satta, A. Sundel¨
of, R. Thompson, and
S. Hawkins (2005). Low-creted coastal defence structures as artificial habitats for marine
life: Using ecological criteria in design. Coastal Engineering 52, 1053–1071.
Moura, A., L. Cancela Da Fonseca, J. C´
urdia, S. Carvalho, D. Boaventura, M. Cerqueira,
F. Leit ˜
ao, M. Santos, and C. Monteiro (2008, September). Is surface orientation a determi-
nant for colonisation patterns of vagile and sessile macrobenthos on artificial reefs. Biofoul-
ing 24(5), 381–391.
Nelson, W., D. Savercool, T. Neth, and J. Rodda (1994). A Comparison of the Fouling Commu-
nity Development on Stabilized Oil-Ash and Concrete Reefs. Bulletin of Marine Science 55(2-
3), 1303–13–15.
Neves, C. S., R. M. Rocha, F. B. Pitombo, and J. J. Roper (2007). Use of artificial substrata
by introduced and cryptogenic marines specias in Paranagu´
a Bay, southern Brazil. Biofoul-
ing 23(5), 319–330.
Noda, M., M. Ohgai, H. Kakimoto, and A. Yamashita (1995). The relationship between algal
vegetation found on concrete blocks and the month when those substrata were installed in
the sea. In Proceedings of the International Conference of Ecological System Enhancements
Technology for Aquatic Enviroments, Tokyo, Japan, pp. 476–480.
136
Norling, K., R. Rosenburg, S. Hulth, A. Gr´
emare, and E. Bonsdorff (2007). Importance of
functional biodiversity and species-specific traits of benthic fauna for ecosystem functions in
marine sediment. Marine Ecology Progress Series 332, 11–23.
Norman, W. and C. MacDonald (2004, April). Getting to the bottom of “Triple Bottom Line”.
Business Ethics Quarterly.
Norstr¨
om, K., G. Czub, M. S. McLachlan, D. Hu, P. S. Thorne, and K. C. Hornbuckle (2009).
External exposure and bioaccumulation of PCBs in humans living in a contaminated urban
environment. Article in Press, Corrected Proof. Available on http://www.sciencedirect.
com .
North, W. J. (1970, 30 June). Kelp Habitat Improvement Project. Technical report, W.M.
Keck Laboratory of Environmental Health Engineering, California Institute of Technology.
North, W. J. (1973, 30 June). Kelp Habitat Improvement Project. Technical report, W.M.
Keck Laboratory of Environmental Health Engineering, California Institute of Technology.
North Carolina Division of Marine Fisheries (2009). Oyster Shell Recycling - Trash to Trea-
sure. Online resource found at http://www.ncfisheries.net/shellfish/recycle1.htm .
Ohgai, M., N. Murase, H. Kakimoto, and M. Noda (1995). The growth and survival of Sar-
gassum patens on andesite and granite substrata used in the formation of seaweed beds. In
Proceedings of the International Conference of Ecological System Enhancements Technology
for Aquatic Enviroments, Tokyo, Japan, pp. 470–475.
Omar, R. M. N. R., C. E. Kean, S. Wagiman, A. M. M. Massan, M. Hussein, R. B. R. Hassan,
and C. O. M. Hussin (1994). Design and Construction of Artificial Reefs in Malaysia. Bulletin
of Marine Science 55(2–3), 1050–1061.
Opdam, P. (2002). Assessing the Conservation Potential of Habitat Networks (Illustrated
ed.)., Chapter 21, pp. 381–404. Springer.
Ortiz-Prosper, A. L., A. Bowden-Kerby, H. Ruiz, O. Tirado, A. Cab´
an, G. Sanchez, and J. C.
Crespo (2001). Planting Small Massive Corals on Small Artificial Concrete Reefs or Dead
Coral Heads. Bulletin of Marine Science 69(2), 1047–1051.
Osenberg, C. W., C. M. St. Mary, J. A. Wilson, and W. J. Lindberg (2002). A quantitative
framework to evaluate the attraction-production controversy. ICES Journal of Marine Sci-
ence 59, S214–S221.
Pamintuan, I. S., P. M. Ali ˜
no, D. Gomez, Edgardo, and R. N. Rollon (1994). Early Succes-
sional Patterns of Invertebrates in Artifical Reefs Established at Clear and Silty Areas in
Bolinao, Pangasinan, North Phillippines. Bulletin of Marine Science 55(2–3), 867–877.
Patton, M., R. Grove, and L. Honma (1995). Substrate Disturbance, Competition from Sea
Fans (Muricea sp.) and the design of an Artificial Reef for Giant Kelp (Macrocystis sp.). In
Proceedings of the International Conference of Ecological System Enhancements Technology
for Aquatic Enviroments, Tokyo, Japan, pp. 272–276.
137
Patton, M., C. Valle, and R. Grove (1994). Effects of Bottom Relief and Fish Grazing on the
Density of the Giant Kelp, Macrocystis.Bulletin of Marine Science 55(2–3), 631–644.
Perkol-Finkel, S., G. Zilman, I. Sella, T. Miloh, and Y. Benayahu (2006). Floating and fixed
artificial habitats: effects of substratum motion on benthic communities in a coral reef envi-
ronment. Marine Ecology Progress Series 317, 9–20.
Perkol-Finkel, S., G. Zilman, I. Sella, T. Miloh, and Y. Benayahu (2008). Floating and fixed
artificial habitats: Spatial and temporal patterns of benthic communities in a coral reef
environment. Estuarine, Coastal and Shelf Science 77, 491–500.
Peterson, M. S., B. H. Comyns, J. R. Hendon, P. J. Bond, and G. A. Duff (2000, June). Habi-
tat use by early life-history stages of fishes and crustaceans along a changing estuarine
landscape: difference between natural and altered shoreline sites. Wetlands Ecology and
Management 8, 209–219.
Pickering, H. and D. Whitmarsh (1997). Artificial reefs and fisheries exploitation: a review
of the ‘attraction versus production’ debate, the influence of design and its significance for
policy. Fisheries Research 31, 39–59.
Pimentel, D., L. Lach, R. Zuniga, and D. Morrison (2000, January). Environmental and
Economic Costs of Nonindigenous Species in the United States. BioScience 50(1), 53–65.
Pitcher, T. J. and W. Seaman, Jr. (2000). Petrarch’s Principle: how protected human-made
reefs can help the reconstruction of fisheries and marine ecosystems. Fish and Fisheries 1,
73–81.
Pondella, II, D. J., L. G. Allen, M. T. Craig, and B. Gintert (2006). Evaluation of Eelgrass
Mitigation and Fishery Enhancement Structures in San Diego Bay, California. Bulletin of
Marine Science 78(1), 115–131.
Powers, S. P., J. H. Grabowski, C. H. Peterson, and W. J. Lindberg (2003). Estimating en-
hancement of fish production by offshore artificial reefs: uncertainty exhibited by divergent
scenarios. Marine Ecology Progress Series 264, 265–277.
Preston, T. J., Y. Ropert-Coudert, A. Kato, A. Chiaradia, R. Kirkwood, P. Dann, and R. D.
Reina (2008). Foraging behaviour of little penguins Eudyptula minor in and artificially
modified environment. Endangered Species Research 4, 95–103.
Pullman, R. H. (1988). Sources, Sinks, and Population Regulation. The American Natural-
ist 132, 652.
Recasens, L., A. Lombarte, and P. S ´
anchez (2006). Teleostean Fish Assemblages in an Ar-
tificial Reef and a Natural ROcky Area in Catalonia (Northwestern Mediterranean): an
Ecomorphological Approach. Bulletin of Marine Science 78(1), 71–82.
Reed, D. C., S. C. Schroeter, D. Huang, T. W. Anderson, and R. F. Ambrose (2006). Quan-
titative Assessment of Different Artificial Reef Designs in Mitigating Losses to Kelp Forest
Fishes. Bulletin of Marine Science 78(1), 133–150.
138
Reef Ball Foundation, Inc. (2007, October 19). Styles of Reef Balls-From Layer Cakes to
Lobster Balls... . Online resource found at http://www.reefball.org/reef_ball_styles.htm .
Reef Innovations Inc. (2008). Reef Ball Brochure.
Reimers, H. and K. Branden (1994). Algal Colonization of a Tire Reef - Influence of Place-
ment Date. Bulletin of Marine Science 55(2–3), 460–469.
Reise, K., T. J. Bouma, S. Olenin, and T. Ysebaert (2009). Coastal habitat engineers and the
biodiversity in marine sediments. Helgol Marine Research 63, 1–2.
Relini, G., M. Relini, G. Torchia, and G. Palandri (2002). Ten years of censuses of fish fauna
on the Loano artificial reef. ICES Journal of Marine Science 59, S132–S137.
Relini, G., M. Relini, G. Torchia, F. Tixi, and C. Nigri (1995). Coal Ash Tests in Loano Artifi-
cial Reef. In Proceedings of the International Conference of Ecological System Enhancements
Technology for Aquatic Enviroments, Tokyo, Japan, pp. 107–113.
Relini, G., N. Trentalance, M. Relini, G. Torchia, and F. Tixi (1995). Stabilized Harbour
Muds for Artificial Reef Blocks. pp. 114–118.
Restore America’s Estuaries (2002, April). A National Strategy to Restore Coastal and Es-
tuarine Habitat. Technical report, National Oceanic and Atmospheric Administration, 3801
N. Fairfax Drive, Suite 53, Arlington, VA, 22203.
Rosenblatt, S. (2008, June 12). Off San Clemente, an artificial reef is going up, er, down. Los
Angeles Times.
Ruiz, G. M., J. T. Carlton, E. D. Grosholz, and A. H. Hines (1997). Global Invasions of
Marine and Estuarine Habitats by Non-Indigenous Species: Mechanisms, Extent, and Con-
sequences. American Zoologist 37, 621–632.
Russell, G., S. J. Hawkins, L. C. Evans, H. D. Jones, and G. D. Holmes (1983). Restoration
of a Disused Dock Basin as a Habitat for Marine Benthos and Fish. Journal of Applied
Ecology 20, 43–58.
Saeki, N., T. Itakura, N. Wada, H. Tokushige, and T. Natori (1995). Ecological Works Meth-
ods of Block Revetment in Small River. In Proceedings of the International Conference of
Ecological System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp.
525–530.
Sampaolo, A. and G. Relini (1994). Coal Ash for Artifical Habitats in Italy. Bulletin of Marine
Science 55(2-3), 1277–1294.
Sanger, D. M. and A. F. Holland (2002). Evaluation of the Impacts of Dock Structures on
South Carolina Estuarine Environments. Technical Report 99, Marine Resources Research
Institute, Marine Resources Division, South Carolina Department of Natural Resources,
P.O. Box 12559, Charleston, South Carolina, 29422-2559.
139
Sanger, D. M., F. A. Holland, and C. Gainey (2004). Cumulative Impacts of Dock Shading
on Spartina alterniflora in South Carolina Estuaries. Environmental Management 33(5),
741–748.
Sargeant, S. L., M. C. Miller, C. W. May, and R. M. Thom (2004, June). Phase II-Conceptual
Model Development for Bank Stabilization in Freshwater Systems. Technical Report PNNL-
14436, Pacific Northwest National Laboratory.
Savard, J.-P. L., P. Clergeau, and G. Mennechez (2000). Biodiversity concepts and urban
ecosystems. Landscape and Urban Planning 48, 131–142.
Sayer, M. D. J. and T. A. Wilding (2002). Planning, licensing, and stakeholder consultation in
an artificial reef development: the Loch Linnhe reef, a case study. ICES Journal of Marine
Science 59, S178–S185.
Schuhmacher, H. and L. Schillak (1994). Integrated Electrochemical and Biogenic Depo-
sition of Hard Material—A Nature-Like Colonization Substrate. Bulletin of Marine Sci-
ence 55(2–3), 672–679.
Scott, M. (2008, August 18). How goes the project to make the lower end of the Cuyahoga
River more fish-friendly? Cleveland Plain Dealer.
Seaman, W. (2004, April). Artificial Reef Monitoring in Florida Coastal Counties. Technical
Report SGEB-58, Florida Sea Grant College Program, PO Box 110400, University of Florida,
Gainesville, FL 32611-0400.
Seaman, W. (2007). Artificial habitats and the restoration of degraded marine ecosystems
and fisheries. Hydrobiologia 580, 143–155.
Seaman, W., W. J. Lindberg, T. K. Frazer, and K. M. Portier (1995). Fish Abundance and
Diversity in Response to Variable Dispersion of ARtificial Reef Units. In Proceedings of the
International Conference of Ecological System Enhancements Technology for Aquatic Envi-
roments, Tokyo, Japan, pp. 12–17.
Seaman, W. and M. Miller (2004). Fisheries Conservation and Habitat Improvement in
Marine Ecosystems. Technical report, University of Florida: Department of Fisheries and
Aquatic Sciences and NOAA Southeast Fisheries Science Center.
Seaman, Jr., W. and L. M. Sprague (1991). Artificial Habitats for Marine and Freshwater
Fisheries. Academic Press, Inc.
Shafer, D. and J. Robinson (2001). An evaluation of the use of grid platforms to minimize
shading impacts to seagrasses. In WRAP Technical Notes Collection. (ERDC TN-WRAP-01-
02), U.S. Army Engine Research and Development Center, Vicksburg, MS www.wes.army.
mil/el/wrap.
Sherman, R., D. Gilliam, and R. Spieler (2002). Artificial reef design: void space, complexity,
and attractants. ICES Journal of Marine Science 59, S196–S200.
140
Sherman, R. L., D. S. Gilliam, and R. E. Spieler (2001). Site-Dependant Differences in Artifi-
cial Reef Function: Implications for Coral Reef Restoration. Bulletin of Marine Science 69(2),
1053–1056.
Shieh, C.-S. and I. W. Duedall (1994). Chemical Behavior of Stabilized Oil Ash Artificial Reef
at Sea. Bulletin of Marine Science 55(2-3), 1295–1302.
Shyue, S.-w. and K.-c. Yang (2002). Investigating the terrain changes around artificial reefs
by using a multi-beam echosounder. ICES Journal of Marine Science.
Simenstad, C., C. Tanner, C. Crandell, J. White, and J. Cordell (2004). Challenges of Habitat
Restoration in a Heavily Urbanized Estuary: Evaluating the Investment. Journal of Coastal
Research 40, 6–23.
Snep, R. P. and F. G. Ottburg (2008). The ‘habitat backbone’ as strategy to conserve pioneer
species in dynamic port habitats: lessons from the natterjack toad (Bufo calamita) in the
Port of Antwerp. Landscape Ecology 23, 1277–1289.
Somsueb, S., M. Ohno, and H. Kimura (2001). Development of seaweed communities on
suspended substrata with three slop angles. Journal of Applied Phycology 13, 109–115.
Souter, N. J., M. C. Bull, and M. N. Hutchinson (2003, April). Adding burrows to enhance
a population of the endangered pygmy blue tongue lizard, Tiliqua adelaidensis.Biological
Conservation 116(3), 403–408.
Southern California Edison (2009). Power Generation - Marine Mitigation. Online resource
detailing the creation of an Experimental Kelp Reef offshore of San Clemente, CA. Re-
source website http://www.sce.com/PowerandEnvironment/PowerGeneration/MarineMitigation/
kelp-reef- dedication.htm .
Spanier, E. (1995). Do We Need Special Artificial Habitats for Lobsters. In Proceedings
of the International Conference of Ecological System Enhancements Technology for Aquatic
Enviroments, Tokyo, Japan, pp. 548–553.
Spurgeon, J. P. (2001). Improving the Economic Effectiveness of Coral Reef Restoration.
Bulletin of Marine Science 69(2), 1031–1045.
Steimle, F., K. Foster, R. Kropp, and B. Conlin (2002). Benthic macrofauna productivity
enhancement by an artificial reef in Delaware Bay, USA. ICES Journal of Marine Science 59,
S100–S105.
Steimle, F., W. Muir, K. Foster, R. Kropp, and B. Conlin (1995). Benthic community en-
hancement by a prefabricated concrete artificial reef in lower Delaware Bay. In Proceedings
of the International Conference of Ecological System Enhancements Technology for Aquatic
Enviroments, Tokyo, Japan, pp. 581–586.
Steneck, R. S., M. H. Graham, B. J. Bourque, D. Corbett, J. M. Erlandson, J. A. Estes, and
M. J. Tegner (2002). Kelp forest ecosystems: biodiversity, stability, resilience, and future.
Environmental Conservation 29(4), 436–459.
141
Stephens, Jr., J. and D. Pondella, II (2002). Larval productivity of a mature artificial reef: the
ichthyoplankton of King Harbor, California, 1974–1997. ICES Journal of Marine Science 59,
S51–S58.
Suzuki, T. (1995). Application of High-Volume Fly Ash Concrete to Marine Structure. In
Proceedings of the International Conference of Ecological System Enhancements Technology
for Aquatic Enviroments, Tokyo, Japan, pp. 141–144.
Szedlmayer, S. T. and R. L. Shipp (1994). Movement and Growth of Red Snapper, Lutjanus
campechanus, from an Artificial Reef Area in the Northeastern Gulf of Mexico. Bulletin of
Marine Science 55(2-3), 887–896.
Tabor, R. A. and R. M. Piaskowski (2002, February). Nearshore Habitat Use by Juvenile
Chinook Salmon in Lentic Systems of the Lake Washington Basin, Annual Report, 2001.
Technical report, U.S Fish and Wildlife Serve, Western Washington Office, Division of Fish-
eries and Watershed Assessment, Lacey, Washington.
Takaki, N., H. Kida, and M. Fukuya (1995). Planning of Fishing Port Facility Considering
Ecological Environment. In Proceedings of the International Conference of Ecological System
Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 418–423.
Tanaka, M., Y. Shimbo, and B. K. Lim (2003). Habitat Evaluation Method for Coastal Wet-
land. In Workshop on Hydro Environmental Impacts of Large Coastal Developments.
Tanaka, Y., H. Suzuki, and H. Nakata (2000). Habitat creation using seawalls: A seawall
construction project in Tokyo Bay (Yokosuka Port). In Techno-Ocean 2000. Nippon Founda-
tion.
Terawaki, T., H. Hasegawa, S. Arai, and M. Ohno (2001). Management-free techniques for
restoration of Eisenia and Ecklonia beds along the central Pacific coast. Journal of Applied
Phycology 13, 13–17.
Terawaki, T., K. Yoshikawa, G. Yoshida, M. Uchimura, and K. Iseki (2003). Ecology and
restoration techniques for Sargassum beds in the Seto Inland Sea, Japan. Marine Pollution
Bulletin 47, 198–201.
Thanner, S. E., T. L. McIntosh, and S. M. Blair (2006). Devlopement of Benthic and Fish
Assemblages on Artificial Reef Materials Compared to Adjacent Natural Reef Assemblages
in Miami-Dade County, Florida. Bulletin of Marine Science 78(1), 57–70.
The Columbia Electronic Encyclopedia (2007). Caissons. Columbia University Press.
The Vancouver Convention Centre Expansion Project (2006). Project Implementation Plan:
Volume 1 — Project Definition . Published online. http://www.vccep.bc.ca/theproject/
governance.html .
Thompson, R., T. Crowe, and S. Hawkins (2002). Rocky intertidal communities: past en-
vironmental changes, present status and predictions for the next 25 years. Environmental
Conservation 29(2), 168–191.
142
Thorne, R. E. (1994). Hydroacoustic Remote Sensing for Artificial Habitats. Bulletin of
Marine Science 55(2-3), 897–901.
Tibbers, J. (2002, November). Coastal Cities Living on the Edge. Environmental Health
Perspectives 110(11), A674–A681.
Toft, J. (2005, February). Benthic Macroinvertibrate Monitoring at Seahurst Park 2004, Pre-
Construction of Seawall Removal. Technical Report SAFS-UW-0502, University of Washing-
ton: Wetland Ecosystem Team. Prepared for City of Burien.
Toft, J. (2007, March). Benthic Macroinvertibrate Monitoring at Seahurst Park 2006, Post-
Construction of Seawall Removal. Technical Report SAFS-UW-0702, University of Washing-
ton: Wetland Ecosystem Team. Prepared for City of Burien.
Toft, J. (2008, November 17). Personal Communication with Karen L. Dyson.
Toft, J. and J. Cordell (2006, April). Olympic Sculpture Park: Results from Pre-construction
Biological Monitoring of Shoreline Habitats. Technical Report SAFS-UW-0601, University
of Washington: Wetland Ecosystem Team. Prepared for Seattle Public Utilities.
Toft, J., J. Cordell, S. Heerhartz, E. Armbrust, A. Ogston, and E. Flemer (2008, July).
Olympic Sculpture Park: Results from Year 1 Post-construction Monitoring of Shoreline
Habitats. Technical Report SAFS-UW-0801, University of Washington: School of Aquatic &
Fishery Sciences. Prepared for Seattle Public Utilities.
Toft, J., C. Simenstad, J. Cordell, and L. Stamatiou (2004, March). Fish Distribtuion, Abun-
dance, and Behavior at Nearshore Habitats along City of Seattle Marine Shorelines, with
an Emphasis on Juvenile Salmonids. Technical Report SAFS-UW-0401, University of Wash-
ington: Wetland Ecosystem Team. Prepared for Seattle Public Utilities.
Turpin, R. K. and S. A. Bortone (2002). Pre- and post-hurricane assessment of artificial
reefs: evidence for potential use as refugia in a fishery management strategy. ICES Journal
of Marine Science 59, S74–S82.
Tyrell, M. C. and J. E. Byers (2007). Do artificial substrates favor nonindigenous fouling
species over native species? Journal of Experimental Marine Biology and Ecology 342, 54–
60.
Uchida, K., H. Maeda, K. Tabuchi, A. Hamano, and K. Kubota (1995). Distribution of Fish
Assembling Around 54-Large-Scaled Artificial Reef Clusters Settled in an Area. In Pro-
ceedings of the International Conference of Ecological System Enhancements Technology for
Aquatic Enviroments, Tokyo, Japan, pp. 18–23.
United Nations Environment Programme (2002). Global Environment Outlook 3, Chapter
Chapter 2: State of the Environment and Policy Retrospective: 19722002, Biodiversity, pp.
120–149. United Nations Environment Programme.
143
U.S. Army Corps of Engineers (2008). Port of Los Angeles Channel Deepening Project Draft
Supplemental Environmental Impact Statement/Draft Subsequent Environmental Impact
Report. Technical report, Los Angeles Harbor Department.
U.S. Department of the Interior (2007, May 24). Adaptive Management Overview & Ori-
entation. Published online. http://www.doi.gov/initiatives/AdaptiveManagement/documents/
AMtraininghandout.pdf .
Vuilleumier, S., C. Wilcox, B. J. Cairns, and H. P. Possingham (2007, 77-85). How patch
configuration affects the impact of disturbances on metapopulation persistence. Theoretical
Population Biology 72(1).
Webb, J. K. and R. Shine (2000). Paving the way for habitat restoration: can artificial rocks
restore degraded habitat of endangered reptiles? Biological Conservation 92, 93–99.
Weinstein, M. P. (2007, April). Perspectives in Estuarine and Coastal Science. Estuaries and
Coasts 30(2), 365–370.
Weinstein, M. P. and D. J. Reed (2005, March). Sustainable Coastal Development: The Dual
Mandate and a Recommendation for “Commerce Managed Areas”. Restoration Ecology 13(1),
174–182.
Wilber, P., G. Thayer, M. Croom, and G. Mayer (2000). Goal setting and success criteria for
coastal habitat restoration. Ecological Engineering.
Wilding, T. A. and M. D. J. Sayer (2002a). Evaluating artificial reef performance: approaches
to pre- and post-deployment research. ICES Journal of Marine Science 59, S222–S230.
Wilding, T. A. and M. D. J. Sayer (2002b). The physical and chemical performance of artificial
reef blocks made using quarry by-products. ICES Journal of Marine Science 59, S250–S257.
Williams, B., R. Szaro, and C. Shapiro (2007). Adaptive Management: The U.S. Department
of the Interior Technical Guide. Washington, D.C.: Adapative Management Working Group,
U.S. Department of the Interior.
Williams, T. W. (2006, August 1). Sinking Poor Decision Making with Best Practices. Phd
dissertation, Virginia Commonwealth University.
Wood, B. C. and A. S. Pullin (2002). Persistence of species in a fragmented urban land-
scape: the importance of dispersal ability and habitat availability for grassland butterflies.
Biodiversity and Conservation 11, 1451–1468.
Yabe, K. (1995). Wooden Artificial Reef. In Proceedings of the International Conference of
Ecological System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp.
708–713.
144
Yamamoto, J., T. Takeuchi, and A. Nakayama (1995). Water-Intake Works for Improving
Environmental Conditions of Habitat in Fishing Ports. In Proceedings of the International
Conference of Ecological System Enhancements Technology for Aquatic Enviroments, Tokyo,
Japan, pp. 622–627.
Yano, K., S. Akeda, Y. Miyamoto, and A. Nagano (1995). Toward Ports and Harbors That
Coexist with Nature. In Proceedings of the International Conference of Ecological System
Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 400–405.
Yokouchi, H., R. Yamamoto, and Y. Ishizaki (1991). Construction of Artificial Seaweeds Beds
Accompanied with the Reclamation of Unit No. 3 of Ikata Power Station. Marine Pollution
Bulletin 23, 719–722.
Zabloudil, K. F., R. S. Grove, and L. E. Deysher (1995). A Kelp Artificial Reef Adjacent to
a Nuclear Generating Station. In Proceedings of the International Conference of Ecological
System Enhancements Technology for Aquatic Enviroments, Tokyo, Japan, pp. 464–469.
Zanuttigh, B., L. Martinelli, L. Lamberti, A. Lamberti, P. Moschella, S. Hawkins, S. Marzetti,
and V. U. Ceccherelli (2005). Environmental design of coastal defence in Libo di Dante, Italy.
Coastal Engineering 52, 1089–1125.
