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Journal of Coastal Conservation
Planning and Management
ISSN 1400-0350
J Coast Conserv
DOI 10.1007/s11852-017-0554-0
Wildlife corridors under water: an
approach to preserve marine biodiversity in
heavily modified water bodies
Peter Krost, Matthias Goerres & Verena
Sandow
1 23
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Wildlife corridors under water: an approach to preserve marine
biodiversity in heavily modified water bodies
Peter Krost
1
&Matthias Goerres
1,2
&Vere n a S a n d ow
1
Received: 27 September 2016 /Revised: 11 July 2017 / Accepted: 22 August 2017
#Springer Science+Business Media B.V. 2017
Abstract Coastal areas commonly consist of an environment
of intense economic uses and are thus exposed to conflicts
between anthropogenic activities and biodiversity. While sev-
eral approaches of nature protection have been applied to the
terrestrial domain, aquatic biotopes frequently still lack a good
ecological state as required by EU policies (WFD and MSFD).
For numerous years, the underwater world has been consid-
ered as one sphere and was neglected in the development of
distinctive concepts of conservation for its variety of biotopes.
This paper’s objective is the enhancement of ecological con-
nectivity within the study area through the design of benthic
wildlife corridors and a consequent sublittoral biotope net-
work. A step-by-step approach is presented for the optimiza-
tion of ecological potential in heavily modified coastal water
bodies, using Kiel Fjord (Western Baltic Sea) as a case study.
The procedure for the development of wildlife corridors in-
cludes defining and mapping of existing biotope types, the
identification of key species for each biotope type and delin-
eating their mobility range, the reconstruction of near-natural /
pre-industrial conditions and deriving the protection priorities
by comparing past with current / modified conditions. By
harmonizing these scientific insights with the local land use
of human society, proposals for biotope restoration and im-
provements can be made. In Kiel Fjord, compensation mea-
sures, obligatory for human interventions, such as construc-
tion work in the marine environment in this case, have been
implemented and present an opportunity to enhance the con-
nectivity of biotopes, thus creating wildlife corridors for their
inhabitants. The composition of benthic wildlife corridors,
forming a sublittoral biotope network in accordance with the
present anthropogenic uses, holds potential for implementa-
tion in comparably altered coastal water bodies and integra-
tion into national and international frameworks, in anticipa-
tion of its functionality.
Keywords Sublittoral .Wildlife corridor .Biotope network .
Ecological connectivity
Introduction
The concept of wildlife corridors is a logical consequence of
applying island biogeography (MacArthur 1965)tourbanized
areas, where biotopes are often fragmented by buildings and
traffic routes, leadingto isolated and genetically impoverished
populations (Tewksbury et al. 2002).
Although wildlife corridors have been a well-established
concept in terrestrial ecology since the early 1990ies (Jedicke
1990) and have become an integral part in environmental gov-
ernance fromcommunity to European Union(EU) level in the
subsequent years (Jongman and Kamphorst 2002), sublittoral
wildlife corridors applied to marine ecology have –to our
knowledge –not yet been realized.
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s11852-017-0554-0) contains supplementary
material, which is available to authorized users.
*Matthias Goerres
m.goerres@tu-bs.de
Peter Krost
peter.krost@crm-online.de
1
Coastal Research & Management (CRM), Tiessenkai 12,
D-24159 Kiel, Germany
2
Working Group for Environmental Systems Analysis and Landscape
Ecology, Institute of Geoecology, Technical University
Braunschweig, Langer Kamp 19c,
D-38106 Braunschweig, Germany
J Coast Conserv
DOI 10.1007/s11852-017-0554-0
Author's personal copy
A reason for this asymmetry might be found in the limited
accessibility of underwater environments to humans, giving rise
to the perception that the underwater world is merely ‘one bio-
tope’, and consequently does not require any corridors to facil-
itate connectivity among species populations. However, increas-
ing the visualization of the sublittoral realm by modern instru-
mentation and diving has revealed the diversity of sublittoral
habitats and biotopes –their fragility and vulnerability –to a
broader public, including political and administrative officials.
In this paper, the term ‘biotope’is used in the most recent
definition linking the physical environment (habitat) and its
distinctive species community (or biocenosis), as a progres-
sive interpretation of the concepts by Kiel’s marine biologists
Karl Möbius (1877) and Friedrich Dahl (1908). The term
‘habitat’, which is often employed synonymously to biotope
in English speaking countries, is here applied according to
geographical location, physiographic features, physical and
chemical environment (Olenin and Ducrotoy 2006).
Benthic biotope types have been described in several
concepts of marine and coastal biotope and habitat clas-
sifications on multiple institutional scales. We used six
schemesasabasisofourownadaptedtypologyforthe
specific area of this study. BIn an underwater biotope
classification system, communities of organisms associ-
ated with specific environmental parameters are grouped
and organized based on how similar or different they
are from each other. A classification can be used both
to depict similarities and differences between biotopes
and to delineate and identify biotopes based on environ-
mental gradients^(HELCOM 1998). It ought to be
based on coherent and specific criteria in order to cate-
gorize all functional biotopes.
The EUNIS classification is a hierarchical system for hab-
itat identification and description and covers all types of hab-
itat from natural to artificial, from terrestrial to freshwater and
marine (Dauvin et al. 2008a). EUNIS habitats are arranged in
a hierarchy, of three levels for terrestrial and freshwater, and
four levels of marine habitats. It defines a habitat as Baplace
where plants or animals normally live, characterized primarily
by its physical features (topography, plant or animal physiog-
nomy, soil characteristics, climate, water quality, etc.) and sec-
ondarily by the species of plants and animals that live there^.
Most but not all EUNIS habitats are in effect ‘biotopes’, which
are defined to be Bareas with particular environmental condi-
tions that are sufficiently uniform to support a characteristic
assemblage of organisms^(European Commission 2013).
The Red List of endangered biotope types is a document pro-
vided by the Federal Agency for Nature Conservation (BfN).
It classifies the defined biotope types according to their con-
servation status. Benthic biotopesof the Red List are primarily
defined according to their abiotic substrate (Riecken et al.
2009). The EU Habitats Directive (FFH) ensures the conser-
vation of a wide range of rare, threatened or endemic animal
and plant species. In addition to species, approx. 200 rare and
characteristic habitat types are also targeted for conservation.
Together with the Birds Directive, FFH forms the EU wide
Natura 2000 network of protected areas. Annex I lists 233
European natural habitat types, including 71 priorities (i.e.
habitat types in danger of disappearance and whose natural
range mainly falls within the territory of the European Union)
(European Commission 2013). HELCOM (Baltic Marine
Environment Protection Commission / Helsinki
Commission) is the governing body of the Convention on
the Protection of the Marine Environment of the Baltic Sea
Area, known as the Helsinki Convention. It is aiming at a
healthy Baltic Sea environment with diverse biological com-
ponents functioning in balance, resulting in a good ecological
status and supporting a wide range of sustainable economic
and social activities. In its 2013 published Technical Report
(HELCOM 2013) on the HELCOM Underwater Biotope and
habitat classification (HELCOM HUB) following a previous
document on a Red List of marine and Coastal Biotopes
(HELCOM 1998), 328 biotope types are defined in ten bio-
tope complexes based on six hierarchy levels. It was designed
comparable to the existing marine EUNIS system, in which
habitats are coarsely divided according to substrate (Wikström
et al. 2010). The biotope protection directive of the German
federal state of Schleswig-Holstein covers most, but not all, of
the FFH habitats, which are represented in Schleswig-Holstein
(LLUR 2016). The Federal Nature Conservation Act of
Germany (Bundesnaturschutzgesetz (BNatSchG)) lists ten
marine habitats, which are protected according to §30.
BNatSchG states that these protected habitats shall be part of
a wildlife connectivity system (‘Biotopverbund’), if this con-
tributes to a permanent protection of wild animal and plant
populations including their habitats, biotopes and biocenosis
and the protection, restoration and development of functional
ecological interactions (§21 BNatSchG).
As recommended by the environmental authorities in
Europe, the concept of a biotope network as an inter-
connected system of habitats guaranteeing the mobility /
dispersal of species and exchange among several popu-
lations has been implemented as a primarily terrestrial
framework, yet with limited quantitative proofs on its
actual benefits. As a matter of fact, due to the complex-
ity of the issue, there is –even in the terrestrial ecology
–little evidence worldwide (Tewksbury et al. 2002). A
pioneering study showed that habitat patches connected
by corridors retained more native plant species than iso-
lated patches and that local diversity can be increased
by corridors (Damschen et al. 2006; Damschen and
Brudvig 2012). Tewksbury et al. (2002) state that
Bcorridors not only increase the exchange of animals
between patches, but also facilitate two key plant–ani-
mal interactions: pollination and seed dispersal. Our re-
sults show that the beneficial effects of corridors extend
P. Krost et al.
Author's personal copy
beyond the area they add, and suggest that increased
plant and animal movement through corridors will have
positive impacts on plant populations and community
inter-actions in fragmented landscapes^.
A legal foundation for the implementation in coastal and
marine areas is presented by the Water Framework Directive
(WFD) as well as the Marine Strategic Framework Directive
(MSFD) of the European Union (EU). Both directives aim at
reaching a good ecological state for all European fresh and
marine water bodies (by 2015 and 2020 respectively), with the
exception of ‘altered water bodies’. There are two types of
altered water bodies: ‘Artificial Water Bodies’(AWB) and
‘Heavily Modified Water Bodies’(HMWB). HMWB are bod-
ies of water which, as a result of physical alterations by human
activity (e.g. by irrigation, drinking water supply, power gen-
eration and navigation) are substantially changed in character
and thus cannot meet a ‘good ecological state’(GES). The
WFD recognizes that in some cases the benefits of such uses
need to be retained. However, both WFD and MSFD demand
that within the given limitations a good –or better the maxi-
mum! –ecological potential shall be realized applying Bthe
ecosystem approach to the management of human activities
[that have] an impact on the marine environment, integrating
the conceptsof environmental protectionand sustainable use^
(European Commission 2003,2008).
The German law for environmental protection (§15
BNatSchG) demands compensations for inevitable interventions
into nature (BNatSchG 2009), which are obviously prevalent in
HMWB. These compensations should be used as the financial
base for sustainable biotope restorations and improvements. With
this paper we aim at optimizing the efficiency of these efforts in
order to yield the ‘maximum nature protection per Euro’.
The establishment of nature conservation measures –and
particularly the development of wildlife corridors, requiring
physical constructions –depends on available financial re-
sources. As a chronic malnutrition prevails in environmental
funds, we focus on investing money provided for compensa-
tion measures, which are required in licensing procedures for
construction works in Germany and Europe (e.g. Target 2 of
EU Biodiversity Strategy and part of Environmental Impact
Assessments 2011). Indeed, a number of compensation mea-
sures, mostly in the form of artificial stone reefs, have so far
been established in Kiel Fjord, the Northern German case study
location of the Southwestern Baltic Sea featured in this paper.
In this paper we would like to propose the idea and
first approaches towards an integrated plan to connect
present and future compensation measures in an ecologi-
cally effective way, in order to progress towards the max-
imum ecological potential, as demanded by the EU WFD
and MSFD. We will present a methodological framework
to optimize the ecological potential of a heavily modified
coastal and marine water body (HMWB) by creating a
sublittoral biotope network.
Material and methods
In this section the developed approach for the establish-
ment of sublittoral wildlife corridors is explained step-
by-step after briefly introducing the characteristics of
the study area Kiel Fjord.
Study area
The study area, the Inner Kiel Fjord, is one of the most
intensely and diversely used marine areas in Germany
(Fig. 1). Uses include shipping, shipbuilding, navy ac-
tivities, aquaculture, beaches and all sorts of water
sports. It should be noted that at the same time Kiel
Fjord has been a hotspot of marine science with a cu-
mulated knowledge about species, hydrography and
ecology for more than 100 years.
Fig. 1 Overview of study area Kiel Fjord at the German Baltic Sea (in
red on the overview map, source of satellite image: Bing 2016)
Wildlife corridors under water: an approach to preserve marine biodiversity in heavily modified water bodies
Author's personal copy
Coastal structure
Inner Kiel Fjord is separated from the outer Kiel Fjord by the
bottleneck near Friedrichsort (marked in orange, Fig. 1); the
Inner Fjord is approx. 9.5 km long with a width of between
140 and 2600 m. The coastal structure is an important factor
for the ecological situation and potential of a water body, this
being particularly true for the shallowest areas. The total
length of coastline of the Inner Kiel Fjord sums up to more
than 30 km, of which less than 10% have retained a natural
character. Table 1shows the coastal structures which are
found in the Inner Kiel Fjord. Two thirds of the total coastline
are quay walls, even more at the western shore (>80%) than
along the eastern shore.
Morphological changes altered the waterside area which
was urbanized (waterfront development) and sealed (seawalls
and sheet piling instead of natural shorelines), continuously
growing into the Fjord area, which decreased the marine area
significantly (see supplementary material Fig. A2). These
changes were propelled by the decision to turn Kiel into a
Bwar harbor^in 1865, which went along with harbor construc-
tions, development of ship yards and a rapid increase in pop-
ulation from 17,541 in 1860 to 211,627 in 1910.
In conclusion, we witness the following physio-
morphological changes over the past 150 years:
&Total area of the Inner Fjord decreased,
&A significant part of shallow areas disappeared,
&Bottom topography changed (steeper slopes),
&Hard substrate might have disappeared due to stone exca-
vation (Steinfischerei),
&Waterfront was paved and sealed.
Further changes, such as eutrophication and pollution,
suspended sediment and turbidity, temperature, salinity, noise,
etc., are not taken into account here.
In the past two decades, a considerable number of habitat
reconstructions have been put into place, compensating for
dredging and harbor construction, and as Kiel’s port and ship-
ping activities are still growing it can reasonably be assumed
that more compensation measures will be implemented in the
future.
Methods
The following methodological steps were performed sequen-
tially and/or in parallel:
1. Defining biotope types in Kiel Fjord
The relevant biotopes types need to be defined in order
develop a biotope network. The aim was to identify a
number of biotope types a) high enough to sufficiently
cover the variety of existing biotopes on Kiel Fjord, and
b) realistic for potential biotope connection. As a base for
our classification system we used six established and pub-
lished classification schemes which refer to Kiel Fjord:
–Habitat types of the European Nature Information
System (EUNIS), published by the European
Environmental Agency (EEA) in 2015, here abbre-
viated as ‘EUNIS’;
–Biotope classification based on the Flora Fauna
Habitat (FFH) directive of the European
Commission from 1992, as documented in the
Interpretation Manual of European Union Habitats
2013, here abbreviated as ‘FFH’;
–Underwater biotope and habitat classification pub-
lished by HELCOM in 2013 as Technical Report
139 of the Baltic Sea Environment Proceedings,
here abbreviated as ‘HELCOM’;
–Federal Law for Nature Protection of Germany
(Gesetz über Naturschutz und Landschaftspflege,
Bundesnaturschutzgesetz) issued by Federal
Ministry of Nature Protection in 2009, here abbre-
viated as ‘BNatSchG‘;
Tabl e 1 Coastal structures of Inner Kiel Fjord. Data from Daschkeit et al. (2007), obtained using Google Earth and validated by own observations
Inner Kiel Fjord West coast East coast
Length [m] % Length [m] % Length [m] %
Natural beach 2778 8.98 908 6 1870 11.27
Maintained beach 298 0.96 0 0 298 1.80
Coastline fortified by rocks 2708 9 1138 8 1570 9.46
Brick quay walls 20,608 66.61 11,578 80.76 9030 54.40
Metal quay walls 880 2.84 0 0 880 5.30
Natural coastline 2077 6.71 0 0 2077 12.51
Others 1587 5.1 712 5 875 5.30
Total 30,936 100 14,336 46.34 16,600 53.66
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–Red List of Threatened Habitat Types, published by
Riecken et al. in Riecken et al. 2009 for BfN,
Federal Agency for Nature Conservation (2009),
here abbreviated as ‘Red List’;
–Biotope types of Schleswig-Holstein, published by
LLUR, State Agency for Agriculture, Environment
and Rural Areas of Schleswig-Holstein (2016), here
abbreviated as ‘B-SH’.
Multiple definitions ofbiotope types inthe Baltic
Sea area were collated and summed up in a com-
plete list of biotope types of the Kiel Fjord (cf.
Costello 2009).
2. Mapping biotope types and compensation measures
a) Data Acquisition
For the mapping of prevailing abiotic conditions as
well as ecological characteristics, several data sources
were used: Baseline shapefiles of Kiel Fjord were
gathered from the Environmental Protection Agency
and Urban Planning Agency (‘Rahmenplan Kieler
Förde’) of the municipality. Information on the water
depths was obtained from the Institute of Geography at
the Christian-Albrechts-University of Kiel, based on
measurements of the German Bundesamt für
Seeschifffahrt und Hydrographie (BSH). For silty
areas, biotopes and sediment types coincide. We used
published sediment data (Kögler and Ulrich 1985;
Schwarzer and Themann 2003) to map these biotopes.
For shallower areas with more diverse biotope patterns
the main data source were diving protocols, of which
approx. 50 were available from various impact assess-
ments carried out in Kiel Fjord over the past 19 years
(CRM 1998–2016, unpublished and listed in the sup-
plementary material A3; Schwarzer pers. comm.).
b) GIS processing and analysis
After the geo-referencing of the sediment data
with geographic extent and current uses of Kiel
Fjord, the multiple biotope types, as portrayed in
numerous studies, assessments and investigations
and associated with distinct environmental condi-
tions, were mapped by means of Quantum GIS 2.8.
This step also included the digitalization of
existing compensation measures with Google
Earth. Since direct diver and UW-camera observa-
tions cover only a small part of the shallow areas
of Kiel Fjord, we transferred this empirical data to
unexplored sites by assuming the same biotope
type if 1) divers’information was available at
two sites with the same water depth and a similar
sediment type, 2) validated biotopes were not fur-
ther than 200 m apart, and 3) there were no known
inconsistencies in between these sites. In case of
the diving protocols, mapping was performed by
buffering the dive track with the distance of the
underwater visibility and assigning the ascertained
biotope types accordingly. Determining optimal
locations for effective corridors among the imple-
mented compensation/restoration measures as well
as their future realization was performed depend-
ing on depths and uses.
3. Defining key species for each biotope type
Typical, characteristic and –if possible –endemic key
species for the respective biotope types were identified
and a comprehensive list –yet evolving with scientific
state of the art –was compiled. An emphasis was laid
upon ‘umbrella species’, i.e. species, whose habitat and
protection requirements coincide with those of other, less
prominent species.
4. Dispersal range of key species
The ability of species to disperse and to recolonize
territories is the decisive factor for the arrangement of
biotope reconstruction in a wildlife corridor system. The
dispersal potential and mobility of key species - for adults
as well as for larval stages - was assessed on literature
base.
5. Reconstructing pre-industrial biotope conditions
Sublittoral biotope types of pre-industrial times
were reconstructed to the best of our knowledge.
Historical maps and literature (Daschkeit et al. 2007)
were used as a foundation. According to a historical
bathymetric map (Kiel 1853) we can differentiate bio-
tope distribution according to water depth. This infor-
mation, however, is not sufficient to distinguish be-
tween different shallow water habitats, which are thus
generically referred to as Bshallow water habitats^and
include all habitat types except for silt and deeper
sand areas.
The seafloor of Kiel Bay suffered a significant loss
of hard substrates due to stone excavation (in
Northern Germany known as Steinfischerei)inthe
19th and twentieth century, which was performed in
order to recover material for coastal protection and
construction works (Karez and Schories 2005;and
literature therein). Despite the fact that there is no data
on stone excavation in Kiel Fjord specifically, we find
it plausible that it was also performed in this area to
some extent and we thus assume a –yet unquantified
–loss of hard substrate in Inner Kiel Fjord.
6. Mapping of land use (conflicts) in the Kiel Fjord
Suitable compensation measures for elements of a
wildlife corridor have to be harmonized with the uses of
Kiel Fjord. A cartographic assessment regarding the com-
patibility of compensation measures was conducted as
background material and transferred to a compatibility
matrix (cf. Salomidi et al. 2012).
Wildlife corridors under water: an approach to preserve marine biodiversity in heavily modified water bodies
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7. Prioritization of protection
The protection demand was derived by comparing pre-
industrial with present biotope types (steps 2 vs. 5), de-
pending on the areal loss of the respective biotope types.
Furthermore, the ‘value’and prioritization for restoration
activities was assigned based on a consideration of the
conservation status of biotope types and (key) species in
the area as well as for the Baltic Sea.
8. Proposals for biotope reconstruction
In conclusion of tasks 2, 6 and 7, suitable locations
for the realization of biotope reconstructions were de-
termined in order to acquire a sublittoral biotope net-
work. In connection to the prioritization (step 7), an
action plan with the order for implementation of par-
ticular measures was elaborated. An exemplary area
was implemented (visible in Fig. 5) along the Eastern
shore of the Inner Kiel Fjord (approximately 640 m).
9. Design of benthic wildlife corridors and sublittoral
biotope network
After the potential for biotope connectivity in the
Inner Kiel Fjord was evaluated by means of the
above mentioned methodological steps, the develop-
ment of the respective benthic wildlife corridors was
carried out taking into account the six-step-checklist
for corridor design and evaluation of Beier and Loe
(1992), according to whom the critical functions are
the migration potential of animals, the propagation
potential of plants, the possibilities for genetic inter-
change, movement of populations and recolonization
of habitats through individuals. Restoration and
management efforts are hereby equally important as
the future evaluation of the successful (re-)establish-
ment of ecological connectivity (Bond 2003).
Depending on the species of interest, linear patches
may serve as corridors yet do not necessarily guar-
antee the targeted connectivity (Rosenberg et al.
1997). Thus, a diverse set of measures suits as an
experimental approach to reach the aspired connec-
tivity among the biotopes within the wildlife
corridors.
Results
The afore explained step-by-step approach led to a variety
of results for the case study area of Kiel Fjord. With
reference to established classifications of habitat and bio-
tope types on multiple scales, eleven applicable categories
for Kiel Fjord are outlined. Relevant key species are
interlinked with their respective mobility range and distri-
bution potential and set into context with the water depths
of the biotopes in which they occur. Maps of the entire
Kiel Fjord - with focus on the inner part - as well as a
partially restored section at the Eastern shore near
Mönkeberg exhibit the distribution of biotopes. In com-
parison with pre-industrial / near-natural conditions, the
human alterations of the coastal environment are made
evident. Restricted by the current uses of the Fjord and
its shorelines, priorities for conservation are evaluated and
potential sublittoral wildlife corridors designed.
Biotope types in Kiel Fjord
Table 2lists the distinguishable biotope types in Inner
Kiel Fjord. The here presented classification scheme dif-
fers from that of the other schemes to some extent: It
differentiates more biotope types than e.g. BNatSchG
andB-SH,whichlistonlyfiveresp.sixtypes,anddo
not differentiate algae stocks in different water depths
(such as bladder wrack, kelp and red algae); but is less
sophisticated than the HELCOM scheme, which identifies
37 biotope types for Kiel Fjord –a number we find too
high in the light of the limited area of Inner Kiel Fjord,
and impractical for the purpose of biotope connection.
Some of the established systems (BNatSchG, Red List,
B-SH) focus mainly on endangered or protected biotope
types, others (EUNIS, Red List) predominantly on sedi-
ment types. Table 2relates the biotope types to other
classification schemes.
Mapping of biotope types
Based on the sediment types and water depths in the Inner
Kiel Fjord (Schwarzer and Themann 2003)inadditiontothe
above mentioned sources (cf. Table 2), maps were created
representing the biotope types in Fig. 2. As visible by the
darker shades, the southern tip of the Fjord (Hörn) is domi-
nated by muddy sediment without recognizable biota (type 1),
which is also present in the center of the basin along the main
waterways for ferries and cargo transit. The largest area of
Kiel Fjord is covered by fine sediments mud, and fine to
medium sand, and exhibits a comparatively low biodiversity.
The majority of this areais settled by endofauna and epibiota
(type 2), within this area can be occasional patches of hard
substrates and macrophytes (type 3). Along the shallower
shores at the eastern and western coast of the Fjord, sublittoral
sands with seagrass beds, algae and rich endofauna popula-
tions are abundant (Fig. 2).
Due to the large scale of the Kiel Fjord map, stone reefs are
primarily and exemplary visible in the section of restored hard
substrate habitats off Mönkeberg (Fig. 4)amidstlargerzones
of sublittoral sands with rich endofauna and occurring
seagrass.
P. Krost et al.
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Tabl e 2 Biotope types with reference to classifications according to biotope type codes in parentheses (Red List: Riecken et al. 2009; EUNIS: EEA
and EUNIS 2015; FFH: European Commission 1992;HELCOM2013; BNatSchG: Bundesministerium für Naturschutz 2009; B-SH: Ministerium für
Landwirtschaft, Umwelt und Ländliche Räume in Schleswig-Holstein 2009)
# Biotope Type Classified in context of conservation status as
1 Mud without recognizable epibiota
(BHafenschlick^)
EUNIS Organically-enriched or anoxic sublittoral habitats (A5.72)
HELCOM AA.H4U
2 Sublittoral mud, fine and medium
grained
sand with endofauna and epibiota
EUNIS Sublittoral mud (A5.3)
FFH Large shallow inlets and bays (1160)
Shallow waters and seagrass meadows (1160 Kfbs)
HELCOM AA.H1K, AA.H1V, AA.H3L, AA.H3M
BNatSchG Muddy areas with drilling megafauna
Red List Fine substrate habitats in Baltic Sea internal waters (04.02.08)
3 Mud with occasional occurrence of
hard substrate and macrophytes
EUNIS Sublittoral mud (A5.3) in low or reduced salinity (A5.32)
FFH Large shallow inlets and bays (1160)
HELCOM AA.H1K, AA.H1Q, AA.H1V, AA.H3L, AA.H3M, AA.M1 J
BNatSchG Muddy areas with drilling megafauna
4 Bare sandbank HELCOM AA.L
Red List Sandbank in Baltic Sea internal waters (04.02.07)
5 Sublittoral sandbank of the Baltic
Sea
EUNIS A5.2 Sublittoral sand
FFH Sandbanks which are slightly covered by sea water all the time (1110)
HELCOM AA.L
BNatSchG Sublittoral sands (sublitorale Sandbänke)
Red List Shallow sand habitats in Baltic Sea internal waters (04.02.06)
6 Sublittoral sand with red algae and
rich endofauna
EUNIS Sublittoral mixed sediment (A5.4) in low or reduced salinity (A5.41)
FFH Large shallow inlets and bays (1160)
HELCOM AA.A1C, AA.I1C, AA.J1 V, AA.J3 M4
BNatSchG Gravel, sand and shell detritus areas with high species diversity
(artenreiche Kies-, Grobsand- und Schillgründe im Meeres- und Küstenbereich)
Red List Shallow sand habitats in Baltic Sea internal waters (04.02.06)
B-SH Gravel, sand and shell detritus sublittoral areas with high species diversity
(artenreicher Kies, Grobsand bzw Schill im Sublitoral (1.2.8 KFa))
7 Sublittoral sand with occasionally
occurring seagrass, algae and rich
endofauna
EUNIS Sublittoral sand (A5.2)
FFH Large shallow inlets and bays (1160)
HELCOM AA.I1C, AA.I1S, AA.I1V, AA.I2W, AA.I2T, AA.I3M, AA.J1S2, AA.J1 V, AA.J3 M2,
AA.J3 N3, AA.M1S, AA.M1 V, AA.M2 W, AA.M2 T
BNatSchG Gravel, sand and shell detritus areas with high species diversity
(artenreiche Kies-, Grobsand- und Schillgründe im Meeres- und Küstenbereich)
Red List Shallow sand habitats in Baltic Sea internal waters (04.02.06)
B-SH Gravel, sand and shell detritus sublittoral areas with high species diversity
(artenreicher Kies, Grobsand bzw Schill im Sublitoral (1.2.8 KFa))
8 Sublittoral seagrass meadows EUNIS Sublittoral seagrass beds (A5.53)
FFH Large shallow inlets and bays (1160)
HELCOM AA.I1B7, AA.J1B7, AA.M1B7,
BNatSchG Seagrass meadows and other macrophyte stocks (Seegraswiesen und
sonstige marine Makrophytenbestände)
B-SH Sublittoral seagrass meadow (Sublitorale Seegraswiese (1.2.9 KFg))
9 Sublittoral mussel beds EUNIS Sublittoral biogenic reefs (A5.5)
Sublittoral mussel beds on sediment (A5.62)
FFH Reefs (1170)
HELCOM AA.A1E1, AA.E1E, AA.H1E, AA.I1E, AA.J1E1, AA.M1E1
Red List Biogenic reefs in Baltic Sea internal waters (04.02.03)
10 Kelp and seaweed communities on
sublittoral sediment
EUNIS Kelp and seaweed communities on sublittoral sediment (A5.52)
FFH Large shallow inlets and bays (1160)
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Defining key species for each biotope type
Species typical for the biotope types are listed among the
respective water depths in Table 3. Relevant mobility resp.
dispersal ranges are discussed in the next chapter.
Dispersal potential and mobility of key species
As mentioned in before the ability of organisms for mobility
and dispersal is important for the arrangement of biotope re-
construction elements, by defining the maximum distances in
between. As a biotope often comprises of multiple key spe-
cies, their combined (minimum) dispersal range has to be
taken into account when biotope reconstruction is considered.
We refer to mobility and dispersal data which was available
(see literature), but new information on species behavior
might result in modifications of derived biotope distribution
patterns.
Zostera marina:In the Baltic, the eelgrass Zostera marina
represents an extremely valuable, but also very vulnerable
coastal biotope (Waycott et al. 2009). Zostera marina grows
and spreads mainly vegetatively, i.e. by rhizomal growth, the
horizontal spreading rate does not exceed 0.2 m/a (Worm and
Reusch 2000). Since the vertical distribution of eelgrass is
limited by light availability, water depths of more than 10 m
impose an impenetrable barrier for lateral spreading. As point-
ed out by Boström et al. (2014), the Bsignificant declines in
eelgrass depth limits and areal cover [over the past decades
and] particularly in regions experiencing high human
pressure^suggest that the failure of a proper re-
establishment without human restoration efforts is due to
Bcomplex recovery trajectories and calls for much greater con-
servation effort to protect existing meadows^.
Fucus vesiculosus:This important and habitat building
shallow water species is characterized by oogony, i.e. it repro-
duces through large eggs with limited floatation. The
fertilization takes place in the water. The gametes have a max-
imum viability of two hours and thus can only spread in a very
limited range (2 to 10 m) into their surroundings per genera-
tion (Pehlke et al. 2008). Fucus requires relatively large rocks
as attachment substrate, which can also be a solid subsoil in
exposed areas.
Syngnathus typhle and Entelurus aequoreus:These two
indigenous species of the seahorse family, the broadnosed
pipefish (Syngnathus typhle) and the snake pipefish
(Entelurus aequoreus) have their natural habitat in shallow
water seagrass meadows and algae stands. The eggs of both
species are transferred into the brood pouch of the male where
they are fertilized and remain until hatching. Due to insuffi-
cient knowledge about these species, we assume a range of
movement of no more than 50 m from the edge of the macro-
phyte stand.
Nereis pelagica, a polychaete worm, is an omnivore spe-
cies which can be found in empty worm pipes between
Mytilus banks, in the vegetation cover of posts and sea buoys
in the euphotic zone, between Fucus, kelp and red algae. It is
assumed that it does not appear in pelagic life stages in the Bay
of Kiel (Hartmann-Schröder 1996). It seems to avoid silt and
thus deeper, siltier layers act as a barrier of distribution. Due to
the suspected missing of pelagic stages we assume a range of
movement of not more than 50 m for this species as well.
Delesseria sanguinea: The sea beech settles on hard sub-
strate, Kiel Fjord in in water depth of 4–10 m (Sandow, pers.
Comm.). It produces large, in the carpogonium deposited
eggs, which are fertilized by relatively short lived sperm.
Similar to the Fucus-example, we assume a lateral distribution
of only a few meters per generation. Other than Fucus,how-
ever, fertilized eggs that produce carposporophytes and
tetrasporophytes (the latter being more resistant against light
than the adult plant), have a higher chance to be transported
with detached and drifting plant material and might thus have
a higher chance to (re)settle and disperse.
Tabl e 2 (continued)
# Biotope Type Classified in context of conservation status as
HELCOM AA.A1C, AA.M1C
BNatSchG Seagrass meadows and other macrophyte stocks (Seegraswiesen
und sonstige marine Makrophytenbestände)
Red List Shallow natural hard substrate habitats in Baltic Sea
internal waters (04.02.01)
B-SH Other sublittoral macrophyte stocks (Sonstiger sublitoraler
Makrophytenbestand (1.2.10 KFv))
11 Stone reef (3D hard
substrate structure)
FFH Reefs (1170)
HELCOM AA.A1I, AA.A1J, AA.A1R, AA.K, AA.M1 J
BNatSchG Reefs (Riffe)
Red List Hard substrate reefs in Baltic Sea internal waters (04.02.02)
B-SH Stone reef in shallow water, rich in macrophytes (Makrophytenreiches
Hartsubstratriff im Flachwasser (1.2.2 KFb))
P. Krost et al.
Author's personal copy
Fig. 2 Map of the biotope types of Inner Kiel Fjord (cartography: Matthias Goerres, Lotta Maack, Solveig Blöcher 2016; coordinate system: Gauß-
Krüger zone 3, EPSG 31467)
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Reconstructing pre-industrial biotope conditions
In order to assess the extent of historically prevalent con-
ditions of benthic biotopes in Kiel Fjord, we compared a
historical map of Kiel Fjord from 1853 with the present
situation. Central and deeper parts of the Inner Fjord
could be characterized as muddy and thus similar to the
current extent. The main changes were visible regarding
the distribution of shallow water areas and availability of
hard substrates.
Shallow water areas
In 1853, Kiel Fjord was almost void of anthropogenic influ-
ence (cf. supplementary material Fig. A2). From that time on,
and in connection with Kiel’sriseasharborandnavalcity,
shallow water areas have suffered a tremendous loss due to
construction and dredging activities. Shallow water areas,
which give room for habitat types 5 to 10, including macro-
phytes and seagrass meadows were almost entirely lost. The
southernmost part of Kiel Fjord which was throughout
shallower than 6 m was completely drained and overbuilt.
Only marginal rests of shallow water biotopes remained in
the urbanized part of Inner Kiel Fjord at the western coast.
At the eastern coast, practically the entire shallow area has
disappeared.
Hard substrates (stone reefs)
Between 1850 and 1970 stone excavation (BSteinfischerei^,
stone fishery) was an important source of income for the local
fishery and industry. Large stones were craned with assistance
from divers and used for port and road construction. At least
3.5 million tons of stones were extracted in ecologically sen-
sitive areas along the Baltic coast of Schleswig-Holstein.
Karez and Schories (2005) conclude that about 5.6 km
2
hard
bottom surface has been removed in the area of Kiel Bight
within an area of a water depth less than 20 m (approx.
1700 km
2
). There is no direct evidence for stone excavation
in Kiel Fjord, but we assume a probable hard substrate remov-
al of lower intensity. The prevailing sediment distribution of
silt and sand (Schwarzer and Themann 2003)allowacom-
pensation for losses of hard substrates.
Mapping of human uses in Kiel Fjord
Table 4considers the intense and diverse use of KielFjord and
its shorelines. As visible, activities like research or surfing
bear a relatively positive compatibility with most biotope
types. Remarkably, this also applies to the proximity of aqua-
culture, industrial facilities and military restricted areas.
Heavily used port facilities and fairways as well as dredging
activities and partially beaches are in conflict with biotope
restoration and ecological connectivity.
Tabl e 3 Key species of the biotope types in Kiel Fjord. Species with limited mobility range in boldface (see 3.4)
# Water Depth [m] Key species
from to
1
Mud without rec. Biota
14 23 Halicryptus spinulosus
2
Mud with endo- and epibiota
215Nereis pelagica,Tea l ia f e l ina ,Elysia viridis
3
Mud with occ. Macrophytes
410Nereis pelagica,Tea l ia f e l ina ,Saccharina latissima
4
Sandbank
~0 ~0 Phoca vitulina
5
Sublittoral sandbank
04Arenicola marina,Cerastoderma edule,Zostera marina
6
Sand with red algae
412Delesseria sanguinea,Halichondria panicea,Metridium senile
7
Sand with algae and seagrass
05Fucus spp.,Mytilus edulis,Littorina littorea,Zostera marina
8
Seagrass meadows
25Zostera marina,Syngnathus typhle,Entelurus aequoreus,Spinachia spinachia
9
Mussel beds
17Mytilus edulis, Callithamnion corymbosum,Asterias rubens
10
Kelp
410Saccharina latissima,Mytilus edulis
11
Stone Reef
07Fucus spp.,Ctenolabrus rupestris,Anguilla anguilla,Ciona intestinalis,
Halichondria panicea,Littorina littorea
P. Krost et al.
Author's personal copy
As visible in Table 4, different uses exhibit diverse
rates of compatibility towards the set of eleven biotope
types. While compatibility in this case implies no adverse
or even beneficial impacts on the relevant biotope
guaranteeing its near-natural condition, non-compatibility
refers to a change of the respective environment. For cer-
tain combinations the effects are either unknown so far, or
remain potentially compatible or are of an ambiguous na-
ture. Some combinations of use and biotope type do not
occur in Kiel Fjord (here shown as blanks and in a shade
of grey). Ships and their activities on a larger scale pres-
ent the largest harm to most biotope types of higher bio-
diversity, and a similar conclusion may be drawn for fish-
eries and aquaculture. Research endeavors and restricted
access to military areas are by far the most compatible
coastal uses with the multiplicity of biotope types in
Kiel Fjord. Slight touristic uses, i.e. beach life and surf-
ing, are also compatible to the majority of the present
marine life, particularly for area below 2 m water depth.
It is evident that the primarily muddy biotopes (1–3) ap-
pear as the most resilient types towards impacts of anthro-
pogenic uses.
Prioritization of protection
The biotope types with the greatest loss in the area of the
Kiel Fjord are assigned the highest demand for action. We
conclude that the focus of reconstruction activities should be
laid on shallow water areas and stone reefs. This especially
applies to the biotope types stone reefs (11), seagrass
meadows (8) as well as perennial macrophyte population
(7), such as Fucus, in shallow waters.
Tabl e 4 Compatibility matrix of biotope types with uses of Kiel Fjord (+/green refers to compatibility, −/red refers to non-compatibility, ±/yellow
refers to potential compatibility and unknown effects, blank/grey boxes indicate a combination that does not exist in Kiel Fjord)
TYPES
Shipyard
Industrial
Facility
Fishery
Aquaculture
Navy
Military
Restricted Area
Demagnetization
Unit
Local Ferry
Operation
Ferry Terminal
Shipping
Fairway
Sluice
Marina / Yachts
Sailing
Surfing
Beach Life
Research
1
Mud without
rec. biota
+ + + + + + ± + + + + + + + +
2
Mud with
endo-/epibiota
+ + + + + + ± + + - + + + +
3
Mud with occ.
macrophytes
+ + + + + + ± + + - + + + +
4
Sandbank - - + - - - +
5
Sublittoral
sandbank
- - - - ± + ± ± - - - + ± +
6
Sand with
red algae
± + - - + + ± + ± - ± + + + +
7
Sand with algae
and seagrass
- + - - ± + - ± ± - ± ± + + +
8
Seagrass
meadows
- + - - - + - - - - - - ± ± +
9
Mussel beds - + - - + - - - - - ± ± ± +
10
Kelp - - - - - + - - - - - - +
11
Stone Reef - + - - - ± - - - - - - - - +
BIOTOPE ANTHROPOGENIC USES OF KIEL FJORD
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Proposals for biotope reconstruction
Several restoration measures for biotope reconstruction have
been carried out in Kiel Fjord. As characteristic examples, a
stone reef with a diverse community of macroalgae (Fig. 3a) as
compensation measure for harbor construction, transplanted
eelgrass shoots attached to a net (Fig. 3b) and transplanted hard
substrate with attached bladder wrack (Fig. 3c) are depicted
here. These represent a subset of a variety of compensation
measures. Small patches of them are located as stepping stones
at the southern tip of the eastern wildlife corridor (Fig. 4)inan
area near Mönkeberg (Fig. 5a, visible in purple).
Design of benthic wildlife corridors and sublittoral biotope
network
Three main sublittoral wildlife corridors along the shores,
interrupted by ferry pathways and the shipping of Kiel Canal
(Fig. 4, in black), can be designated according to the line of
argument of this study. The eastern shore displays the longest
corridor while the use of the western shore enables two small-
er sectors of connectivity. A shallow area near Mönkeberg
(Fig. 5) at the southern tip of the eastern corridor is the most
restored area with the highest amount of compensation mea-
sures so far. Four depth-layers of Fucus-, seagrass-, mussel-
and red algae-dominated biotopes show the implementation of
a wildlife corridor on a smaller scale. As described biotope
restoration measures serve as stepping stones for the im-
provement of ecological connectivity. A schematic over-
view (Fig. 6) provides a strategy for the design and devel-
opment of further intra- and interconnectivity of biotopes,
here illustrated as ovals of different color (while rectangles
represent the habitat area of stepping stones). Depth-related
belts of bladder-wrack and hard-bottom species in the
shallowest part, sugar kelp and associated species as well
as red algae and associated species with increasing depth
illustrate a sublittoral wildlife corridor in different layers.
Each stretch accommodates a variety of biotope types:
Exemplarily, sublittoral sand rich in macrophytes and
endofauna may cohabit with seagrass meadows and small
hard substrates connected to kelp, seaweed and red algae on
diverse substrate types.
The real-life implementation –as in practice in five sub-
areas of the Inner Kiel Fjord in the near future –requires a
wildlife corridor design on different scales and levels of detail
to accomplish a sublittoral biotope network.
A first step to establish biotope connectivity has been real-
ized at the east coast of Kiel Fjord, off Mönkeberg, between
two artificial reefs Ölberg and Hasselfelde (Fig. 5b). This is an
area of shallow water (< 8 m), the distance between the reefs is
approx. 420 m. From north to south, we find an area with
several seagrass patches, followed by bare sand off a quay
wall and –further south –artificial sand beach. According
to the considerations about dispersal potential of species
and on prioritization of protection we concluded that bladder
wrack (Fucus vesiculosus) and eelgrass (Zostera marina)are
the most important target species. Fucus requires hard sub-
strates. As the dispersal range of Fucus is less than 10 m per
generation, we suggest to have small stone reefs (2 m × 2 m)
in a water depth of 2 m every 50 m, and single stepping
stones with a distance of 5 m in between. This arrangement
of stone reefs and stepping stones is compatible with human
use in this area (chapter 3.6, Table 4). We suggest to trans-
plant patches of eelgrass in order to fill gaps between the
existing meadows. Transplantation is still fairly experimen-
tal, however there is a growing number of successful trans-
plants, in literature (Bondo-Christensen et al. 2005; Zhou
et al. 2014; Ganassin and Gibbs 2008) and in local experi-
ence and evaluation (CRM 2015; Meyer and Nehring 2006).
Seagrass patches should be planted in the southern part of
this area, in a water depth of 3 m. In order to maximize
survival probability, we suggest that bunches of eelgrass with
10 plants each should be transplanted for each patch, with a
distance between bunches of about 0.5 m. The patches
Fig. 3 Representative examples
of biotope restoration measures in
Kiel Fjord (a: stone reef as
compensation measure for harbor
construction with a diverse
community of macroalgae –
biotope type 11, b: transplanted
eelgrass shoots attached to a net –
biotope type 8, c: transplanted
hard substrate with attached
bladder wrack –biotope type 10).
Source: CRM 2016
P. Krost et al.
Author's personal copy
should be placed in a water depth of 3 m and should not be
further apart than 20 m.
Discussion
Biotope typology, distribution and dispersal
The six involved schemes for biotope classification (EUNIS,
FFH, HELCOM, BNatSchG, Red List, B-SH) differ greatly in
numbers, for Inner Kiel Fjord between three and 37 biotope
types. The here characterized eleven biotope types are thus an
approximation to a most practicable yet maximum precise
typology for the study area. For instance, B-SH does not list
muddy substrates at all and does not differentiate between
shallow (Fucus) and deeper (red algae) macrophyte stocks.
On the other hand, numerous biotope types are not practical
in an approach that aims at connecting biotope types within a
fairly small area, and will not fulfill the requirements of com-
munity as Ba species assemblage occupying a well-defined
physical structure –the habitat^(Olenin and Ducrotoy 2006)
because of the limited variety of benthic habitats in Inner Kiel
Fjord. There is no sharp differentiation of biotope types but in
many cases a transition, for example from seagrass meadows
to sublittoral sands with seagrass and algae. The bare sand-
bank is a biotope type not really represented in Kiel Fjord at
the current stage. We included it, nevertheless, as the sand flats
along the western shore of Kiel Fjord present a comparable
situation,and because plans by the municipality exist to create
such structures for leisure purpose.
The actual distribution of biotope types (Fig. 2)withpre-
vailing muddy biotopes (67%, types 1–3) in the central and
deeper areas exhibits only small and fragmented areas of
higher diversity (in green and light-red shades) and thus bears
great potential for improvement. The macrophyte-rich zones
along the northern, eastern and western shores could be en-
larged and connected along the bathymetric profile (cf. sup-
plementary material Fig. A1) and towards deeper areas de-
pending on species mobility range (up 5 m for seagrass, up
to 7 m for reefs, up to 10 m for kelp and up to 12 m for red
algae; cf. Table 3). Moreover, as described above, shallow
areas have experienced the greatest losses, and are only relicts.
The most typical and characteristic species (Table 3)–yet
by no means a complete list –are at the same time species with
a somewhat limited dispersal potential, as this aspect is deci-
sive for the connectivity between biotopes. BConnectivity af-
fects the persistence and dynamics of interacting species^
(Holland and Hastings 2008) and newly created biotope
patches, in form of stepping stones with a relatively large
perimeter in comparison to their sizes, enable an ecological
and genetic exchange (Palumbi 2003). Species that have nei-
ther pelagic reproduction stages (such as many marine
Fig. 4 Potential areas of restoration and resulting wildlife corridors for
the development of a sublittoral biotope network in the Inner Kiel Fjord.
Red arrows indicate regions of potential connectivity (cartography:
Matthias Goerres, Lotta Maack, Solveig Blöcher 2016; coordinate
system: Gauß-Krüger zone 3, EPSG 31467)
Wildlife corridors under water: an approach to preserve marine biodiversity in heavily modified water bodies
Author's personal copy
species, seaweed as well as fish and invertebrates), nor are
able to move themselves actively from one element of a bio-
tope type to the next, typically in the order of some 100 m to
km, highly depend on the proximity to neighboring popula-
tions (cf. Fig. 2). Of particular importance in this context are
those species, which constitute a habitat for other organisms,
i.e. ecosystem engineers. A very important and prominent ex-
ample for these organisms are Fucus species with a pro-
nounced oogamy, producing fertilized eggs of little floatation
and which usually are not transported further than 10 m per
generation from the mother plant (Pehlke et al. 2008). Because
fertilization takes place in the water, fertilized eggs cannot be
transported by the drift of detached plant tissue. Eelgrass
(Zostera marina) is another important habitat building
species and it also has a rather limited dispersal potential.
Marbà et al. (2004) conclude that the seeds travel Ba few
meters at best^after being released from the mother plant,
due to the negative buoyancy. A potential transport way is
posed by detached and floating flowering shoots, which re-
lease seeds at distances from the original stand, and –possibly
and not yet investigated –through seeds ingested by water
birds (Marbà et al. 2004). The same authors, however, con-
clude that sexual reproduction is scarce in the Baltic Sea, and
therefore the asexual, vegetative distribution through
horizontal extension of the rhizomes seems to be the main
dispersal mechanism of eelgrass in Kiel Fjord. Marbà et al.
(2004) report an average annual growth of rhizomes of 26 cm
(22–31 cm), while an average of rhizome elongation of 16 cm
per year was ascertained in an experiment performed in
Limfjord (Denmark) (Cunha et al. 2004). The authors con-
clude that the acreage expansion willbe faster in systems with
many small patches than in systems with few large patches,
and this conclusion adds rational to the idea of eelgrass trans-
plantation in the course of habitat restoration.
Human impacts and compatibility of biodiversity
As indicated by Halpern et al. (2008), the human impact on
the oceans may be derived by the analysis of spatial data on
distribution and intensity. While on a global comparison the
European seas are very strongly affected, the Southern Baltic
shows a medium high to high impact with a variety of
Fig. 5 Maps of restoration measures (a) and the current state of biotope
types (b) in the exemplary location of Mönkeberg (c)asthemost
advanced part of the sublittoral biotope network (cartography: Matthias
Goerres, Lotta Maack, Solveig Blöcher 2016; coordinate system: Gauß-
Krüger zone 3, EPSG 31467)
P. Krost et al.
Author's personal copy
anthropogenic pressures. This assessment provides the oppor-
tunity to link the spatial overview of the investigated area with
the analysis of compatibility in order to improve the coastal
planning and conservation process with biotope- and
ecosystem-based management allocating the required re-
sources via compensation measures (Halpern et al. 2008).
Since a water body which is used as extensively as Kiel
Fjord cannot return to a natural state (the definition of a
HMWB), restoration measures will be limited to an extent
compatible with the legitimate anthropogenic uses of this area.
However, we find that there is a considerable compatibility
between uses and biotopes. And in accordance with European
Directives (WFD and MSFD), the strive for the maximum
ecological potential is obligatory (Dauvin et al. 2008b).
Main incompatibilities in Kiel Fjord are shipping activities
(Kiel is a busy harbor for ferry boats). Without doubt, ship-
ways which require a water depth of 10 m or more will not be
complementary to shallow water biotopes. Many other uses
however, most importantly the military areas, show no
systematic incompatibility with underwater biotopes.
Particularly, the development of connectivity among shallow
water biotopes from the eastern to the western shore appears
almost impossible, due to the shipways and the complete ab-
sence of shallow water areas at the southern end of the fjord.
Water depths suitable for large ships impose a barrier for the
dispersal of benthic species and render shallow areas at the
south-east isolated. In addition, oxygen depleted zones (in
trenches or depressions), sulphidic zones as a result of anoxic
bacterial processes, contaminated and thus uninhabitable
areas, as well as areas of high turbidity can also limit the
dispersal of benthic species. Furthermore, fisheries and aqua-
culture do not match well with nature protection and habitat
restoration, but play a minor role in intensity and required
area. Industrial facilities do not interfere strongly with marine
communities, under the premise that no emissions enter the
marine system. Other partial incompatibilities concern beach
and leisure activities: The fjord is a popular place for
watersports –and particularly sailing with some estimated
2000 boats. Leisure boats, surfing and swimming interfere
with shallow water habitats, down to a water depth of 2–
3 m, which concerns biotope types 7, 10 and 11 and thus
leaves biotopes below (e.g. red algae) unaffected. As visible
in the compatibility matrix (Tab. 4), many uses of Kiel Fjord
do not inevitably collide with the wellbeing of marine species
and communities. In fact, Kiel Fjord encompasses numerous
areas, which in manycases are compatible with nature protec-
tion and habitat restoration.
Implications for the development of a sublittoral biotope
network
There is an ongoing debate on the value of habitats and bio-
topes, and the respective need for protection and even resto-
ration. The current and most widely accepted approach is the
one of ecosystem services (one of many: Daily et al. 2000),
which emphasizes the functional value of nature be it as a
provisioning, a regulating or a cultural service. In the case of
Kiel Fjord and its limited water volume and area, provisioning
and regulating aspects are of minor importance. The cultural
value (as a recreational area for a large population) is im-
mense, however not specific to biotope types, as the value is
conveyed through aesthetic and recreational aspects, such as
beach life and watersports which, except for diving, do not
require specific biotope types. Therefore, we propose to derive
the value and the need for protection of a biotope type on the
base of the deviation of the present state of the respective
biotope (distribution) compared to its pre-industrial
conditions.
Biotopes on muddy sediments occur generally in water
depths of more than 7 to 10 m in Kiel Fjord. In most cases
they are out of reach of –and thus compatible with –anthro-
pogenic uses (we only refer to physical interference; aspects of
Fig. 6 Schematic overview of sublittoral depth-related wildlife corridors
(CRM 2016). Dotted lines schematically indicate the resp. water depths.
Stepping stones act as connectors between major elements of biotope
types. In addition to linking between biotopes of the same type, arrows
also indicate potential vertical connection between different biotope types
Wildlife corridors under water: an approach to preserve marine biodiversity in heavily modified water bodies
Author's personal copy
sediment pollution are not discussed here). As has been point-
ed out before, shallow water biotopes and potentially (hard)/
stone substrates have suffered the greatest damage due to an-
thropogenic reshaping of Kiel Fjord. They therefore should be
restored with priority.
The installation of artificial reefs in Kiel Fjord (14 in Inner
Kiel Fjord) represents a suitable and successful first step.
Periodic monitoring showed that artificial reefs develop a typ-
ical and highly diverse community. Even if the extent of dam-
age in Kiel Fjord remains uncertain, and a complete restora-
tion of the loss might not be possible, we assume an efficient
arrangement of high quality reefs. In contrast to stone reefs, it
seems impossible to compensate for the vast areal loss of
shallow water biotopes in Kiel Fjord. We therefore aim at a
multitude of small units with a high degree of interconnectiv-
ity. A promising nucleus has been established at the east coast
of Inner Kiel Fjord (Fig. 5). Consecutive activities will hope-
fully follow, turning the Inner Kiel Fjord into a model area for
the development of (potentially three large, Fig.4)underwater
wildlife corridors.
Some initial experience has been made in the establishment
of stepping stone and slope areas with near-natural conditions
(Fig. 3). First approaches for seagrass transplantations have
been performed on the base of Bondo-Christensen et al. 2005,
Worm and Reusch 2000,BMTOceanica2013,Ganassinand
Gibbs 2008, and Zhou et al. 2014 as depicted in Fig. 3b,but
more systematic research needs to be done. Other than
seagrass transplants, the transplantation of Fucus has been
successfully performed. Both, the transplantation of stones
with adherent adult Fucus specimen, as well as of seeded
artificial substrates has been successful, and the transplanted
specimen reproduced in their new environment (Sandow and
Krost 2014).
We know very little about minimal sizes of biotope ele-
ments. From the experience gained so far, we have achieved
a good and diverse settlement of seaweed, and sessile animals
on artificial stone reefs, which are typically in a size range of
100 m
2
. Even relatively small biotope ‘resting places’(like
‘stepping stones’) might serve as a connecting element in a
corridor system, while further research is needed for determin-
ing reasonable minimum sizes for the different biotope types.
Even though a complete connectivity for biotope types will
not be achieved within Inner Kiel Fjord, there are many indi-
cations that improved connectivity between biotopes is bene-
ficial for the environmental quality (Damschen et al. 2006;
Damschen and Brudvig 2012; Tewksbury et al. 2002).
However due to a high edge-to-interior ratio of wildlife corri-
dors and its connecting patches, the spread of invasive species
and diseases, such as the pathogen Labyrinthula zosterae,as
well as the propagation of predators and competitors may be
potentially negative or unwanted side effects. While these
aspects also occur in natural habitats, connecting naturally
isolated areas ought to be avoided (Ogden 2015).
Transferability and outlook
The inner part of Kiel Fjord –due to its multiple, multisectoral
and intense uses, combined with a high degree of knowledge
and available scientific data –can function as a model area for
the approach of a sublittoral biotope network. Compensation
measures, required as an integral part of the permission pro-
cedures for relevant sublittoral constructions, can provide at
least partial funding. With regional adaptations, similar ap-
proaches could be applied in other HMWB areas along the
coast of the Baltic Sea, such as Inner Flensburg Fjord and the
estuaries of Trave and Warnow in Germany. An expansion
seaward into areas with biotopes of greater depths (Howell
2010) is necessary in order to ensure the ecological integrity
and connectivity of the marine realm. A restored coastal area
would otherwise attract predators that fail to find prey in the
rather depleted areas of the sea.
Next to the connection between biotopes of the same type,
there are multiple interactions between different biotope types,
may it be migrations of species or fluxes of material and
chemical compounds. This aspect has not been reflected in
this paper extensively, but should play a role in future consid-
erations for optimization of biotope restoration measures.
Integrating the discussed horizontal connectivity with a verti-
cal component from intra- to inter-biotope scale holds poten-
tial as a next phase in order to restore and create a resilient
Baltic seascape (Couling 2016; Elmgren and Hill 1997;
Selkoe et al. 2008).
Conclusions
Despite the fact that Kiel Fjord is classified as a heavily mod-
ified water body according to the EU WFD, there is valuable
marine life that deserves protection. In order to maximize the
efficiency of marine conservation and to reach a good ecolog-
ical state as demanded by EU directives, an approach to opti-
mize connectivity between sublittoral biotopes has been de-
veloped. Following nine consecutive working steps, an effec-
tive and affordable protection of marine biotopes and diversity
can be achieved. Wildlife corridors may be established under
water forming a future sublittoral biotope network in the Kiel
Fjord with high potential for comparably altered coastal areas
and beyond.
Acknowledgements We acknowledge the environmental protection
agency (Umweltschutzamt) of the City of Kiel for their financial contri-
butions to the project and in particular to K.-H. Kweton for his interest
and support. We also thank Carolin Breunig-Lutz (Stadtplanungsamt der
Landeshauptstadt Kiel) for maps and shapefiles from the project
‘Rahmenplan Kieler Förde’, and Birger Treimer (CAU Kiel) for his help
during his internship at CRM. A special thanks goes to Lotta Maack
(CRM) and Solveig Blöcher (CAU Kiel) for substantial support with GIS.
P. Krost et al.
Author's personal copy
References
Beier P, Loe S (1992) A checklist for evaluating impacts to wildlife
movement corridors. Wildl Soc Bull 20(4):434–440
Bing (2016) Bing aerial view maps. https://www.bing.com/maps.
Accessed 15 Aug 2016
BMT Oceanica (2013) Transplanting Posidonia Seagrass in Temperate
Western Australian Waters: A Practical BHow To^Guide. BMT
Oceanica Pty. Ltd., pp. 42. http://www.bmtoceanica.com.au/media/
4865945/Seagrass Transplantation Manual_Rev0_20131024.pdf.
Accessed 26 Oct 2016
Bond M (2003) Principles of wildlife corridor design. Center for
Biological Diversity. pp. 4
Bondo-Christensen P, Díaz Almela E, Diekmann O (2005) Can
transplanting accelerate the recovery of seagrasses? In: Borum J,
Duarte CM, Krause-Jensen D, Greve TM (eds.) European
seagrasses: an introduction to monitoring and management. EU pro-
ject monitoring and managing of European Seagrasses (M&MS),
pp. 77-82
Boström C, Baden S, Bockelmann A-C, Dromph K, Fredriksen S,
Gustafsson C, Krause-Jensen D, Möller T, Nielsen SL, Olesen B,
Olsen J, Pihl L, Rinde E (2014) Distribution, structure and function
of Nordic eelgrass (Zostera marina) ecosystems: implications for
coastal management and conservation. Aquat Conserv Mar
Freshwat Ecosyst 24:410–434
Bundesministerium für Naturschutz (Hrsg) (2009) Gesetz über
Naturschutz und Landschaftspflege. Bundesnaturschutzgesetz –
BNatSchG, Berlin
Costello MJ (2009) Distinguishing marine habitat classification concepts
for ecological data management. Mar Ecol Prog Ser 397:253–268
Couling N (2016) The ocean project –planning a resilient seascape.
International Planning History Society Proceedings 17(4)
CRM, Coastal Research & Management (1998–2016) Reports and im-
pact assessments, unpublished
CRM, Coastal Research & Management (2015) Versetzung von Seegras
vom Fähranleger Kiel-Schilksee zum Ölberg am Ostufer der Kieler
Förde pp 14
CRM, Coastal Research & Management (2016): Rahmenkonzept für
einen Sublitoralen Biotopverbund in der Kieler Förde im Auftrag
und in Zusammenarbeit mit dem Umweltschutzamt Kiel.
Abschlussbericht 31. Oktober 2016. pp. 40
Cunha AH, Duarte CM, Krause-Jensen D (2004) How long time does it
take to recolonize seagrass beds? In: Borum J, Duarte CM, Krause-
Jensen D, Greve TM (eds.) European seagrasses: an introduction to
monitoring and management. EU project monitoring and managing
of European Seagrasses (M&MS), pp. 72-76
Dahl F (1908) Grundsätze und Grundbegriffe der biocenotischen
Forschung. Zool Anz 33:349–353
Daily GC, Söderqvist T, Aniyar S, Arrow K, Dasgupta P, Ehrlich PR,
Folke C, Jansson AM, Jansson B-O, Kautsky N, Levin S,
Lubchenco J, Mäler K-G, Simpson Starrett D, Tilman D, Walker
B (2000) The value of nature and the nature of value. Science
289(5478):395–396
Damschen EI, Brudvig LA (2012) Landscape connectivity strengthens
local–regional richness relationships in successional plant commu-
nities. Ecology 93(4):704–710
Damschen EI, Haddad NM, Orrock JL, Tewksbury JJ, Levey DJ (2006)
Corridors increase plant species richness at large scales. Science
313(5791):1284–1286
Daschkeit A, Sterr H, Kirstein K-G, Krost P (2007) Analyse und
Bewertung ‚erheblich veränderter Küstengewässer‘im Kontext der
Wasserrahmenrichtlinie. Das Beispiel Kieler Förde. In: Gönnert G,
PflügerB,BremerJA(eds)Vonder Geoarchäologie über die
Küstendynamik zum Küstenzonenmanagement. Coastline Reports
9:27–33
Dauvin JC, Bellan G, Bellan-Santini D (2008a) The need for clear and
comparable terminology in benthic ecology. Part I Ecological con-
cepts Aquatic Conservation: Marine and Freshwater Ecosystems
18(4):432–445
Dauvin JC, Bellan G, Bellan-Santini D (2008b) The need for
clear and comparable terminology in benthic ecology. Part
II Application of the European Directives Aquatic
Conservation: Marine and Freshwater Ecosystems 18(4):
446–456
Elmgren R, Hill C (1997) Ecosystem function at low biodiversity –the
Baltic example. In: Ormond RFG, gage JD, angel MV (1997) ma-
rine biodiversity. Patterns and Processes, Cambridge, pp 319–336
European Commission (1992) Habitats Directive. Council Directive 92/
43/EEC on the conservation of natural habitats of wild fauna and
flora. http://ec.europa.eu/environment/nature/legislation/
habitatsdirective/index_en.htm. Accessed 23 Nov 2015
European Commission (2003) Common Implementation Strategy for the
Water Framework Directive (2000/60/EC), Guidance document no.
4, Identification and Designation of Heavily Modified and Artificial
Water Bodies, pp. 118
European Commission (2008) Marine Strategy Framework Directive.
Directive 2008/56/EC of the European Parliament and of the
Council of 17 June 2008 establishing a framework for community
action in the field of marine environmental policy. http://eur-lex.
europa.eu/legal-content/EN/TXT/?uri=CELEX:32008L0056.
Accessed 4 Dec 2016
European Commission (2011) Our life insurance, our natural capital: an
EU biodiversity strategy to:2020 http://eur-lex.europa.eu/legal-
content/EN/ALL/?uri=CELEX:52011DC0244. Accessed 4
Dec 2016
European Commission (2013) Interpretation Manual Of European
Union Habitats. European Commission DG Environment,
ENV B.3, pp. 146
European Environmental Agency (EEA) –European Nature Information
System (EUNIS) (2015) EUNIS habitat types http://eunis.eea.
europa.eu/habitats.jsp. Accessed 10 December 2015
Federal Agency for Nature Conservation (2009) A German red data book
on endangered habitats. Short Version
Ganassin C, Gibbs PJ (2008) A review of seagrass planting as a means of
habitat compensation following loss of seagrass meadow. NSW
Department of Primary Industries - fisheries final report series no.
96, pp. 43
Halpern BS, Walbridge S, Selkoe KA, Kappel CV, Micheli F, D’Agrosa
C, Bruno JF, Casey KS, Ebert C, Fox HE, Fujita R, Heinemann D,
Lenihan HS, Madin EMP, Perry MT, Selig ER, Spalding M, Steneck
R, Watson R (2008) A global map of human impact on marine
ecosystems. Nature 319(5865):948–952
Hartmann-Schröder G (1996) Annelida, Borstenwürmer, Polychaeta
[Annelida, bristleworms, Polychaet]. I: Fischer G (Edt.) (1996) the
fauna of Germany and adjacent seas with their characteristics and
ecology. 2nd edition. pp. 648
HELCOM (1998) Red list of marine and coastal biotopes and biotope
complexes of the Baltic Sea, Belt Sea and Kattegat. Baltic Sea
Environ Proc 75:128
HELCOM (2013) HELCOM HUB –technical report on the HELCOM
underwater biotope and habitat classification. Balt Sea Environ Proc
No 139:96
Holland MD, Hastings A (2008) Strong effect of dispersal network struc-
ture on ecological dynamics. Nature 456:792–795
Howell KL (2010) A benthic classification system to aid in the imple-
mentation of marine protected area networks in the deep/high seas of
the NW Atlantic. Biol Conserv 143(2010):1041–1056
Jedicke E (1990) Biotopverbund –Grundlagen und Maßnahmen einer
neuen Naturschutzstrategie. Eugen Ulmer, Stuttgart, p 254
Jongman RH, Kamphorst D (2002) Ecological Corridors in Land Use
Planning and Development Policies. National approaches for
Wildlife corridors under water: an approach to preserve marine biodiversity in heavily modified water bodies
Author's personal copy
ecological corridors of countries implementing the Pan-European
Landscape and Biological Diversity Strategy. In: Committee for
Activities of the Council of Europe in the Field of Biological and
Landscape Diversity (eds.) (2002) Nature and Environment 125
Karez R, Schories D (2005) Die Steinfischerei und ihre Bedeutung für die
Wiederansiedlung von Fucus vesiculosus in der Tiefe. Rostocker
Meeresbiologische Beiträge 14:95–107
Kögler FC, Ulrich J (1985) Bodengestalt und Sediment der Kieler Förde.
Schriften des naturwissenschaftlichen Vereins Schleswig-Holstein
55:1–33
LLUR, Landesamt für Landwirtschaft, Umwelt und ländliche Räume des
Landes Schleswig-Holstein (2016) Kartieranleitung und
Biotoptypenschlüssel für die Biotopkartierung Schleswig-Holstein
pp 348
MacArthur RH (1965) Patterns of species diversity. Biol Rev 40(4):510–
533
Marbà N, Duarte CM, Alexandre A, Cabaço S (2004) How do seagrasses
grow and spread? In: Borum J, Duarte CM, Krause-Jensen D, Greve
TM (eds.) European seagrasses: an introduction to monitoring and
management. EU project monitoring and managing of European
Seagrasses (M&MS), pp. 11-18
Meyer T, Nehring S (2006) Anpflanzung von Seegraswiesen (Zostera
marina L.) als interne Maßnahme zur Restaurierung der Ostsee.
Rostocker Meeresbiolog. Beitr 15:105–119
Ministerium für Landwirtschaft, Umwelt und Ländliche Räume (Hrsg)
(2009) Landesverordnung über gesetzlich geschützte Biotope.
Biotopverordnung, Kiel
Ogden LE (2015) Do wildlife corridors have a downside? Bioscience
65(4):452
Olenin S, Ducrotoy J-P (2006) The concept of biotope in marine ecology
and coastal management. Mar Pollut Bull 53:20–29
Palumbi SR (2003) Population genetics, demographic connectivity, and
the design of marine reserves. Ecol Appl 13(1):S146–S158
Pehlke C, Selig U, Schubert H (2008) Verbreitung und Ökophysiologie
von Fucus-Beständen der Mecklenburger Bucht (südliche
Ostseeküste). Rostocker Meeresbiologische Beiträge 20:123–142
Riecken U, Finck P, Raths U, Schröder E, Ssymank A (2009) A German
red data book on endangered habitats (short version, July 2009)
Rosenberg DK, Noon BR, Meslow EC (1997) Biological corridors: form,
function, and efficacy. Bioscience 47(10):677–687
Salomidi M, Katsanevakis S, Borja A, Braeckmann U, Damalas D,
Galparsoro I, Mifsud R, Mirto S, Pascual M, Pipitone C, Rabaut
M, Todorova V, Vassilopoulou V, Vega Fernández T (2012)
Assessment of goods and services, vulnerability, and conservation
status of European seabed biotopes: a stepping stone towards
ecosystem-based marine spatial management. Mediterr Mar Sci
13(1):49–88
Sandow V, Krost P (2014) Versetzungsexperimente mit Blasentang
(Fucus vesiculosus) in der Kieler und Lübecker Bucht. RADOST,
Berlin, Berichtsreihe 30:67
Schwarzer K, Themann S (2003) Sediment distribution and geological
buildup of Kiel Fjord (western Baltic Sea). Meyniana 55:91–115
Selkoe KA, Henzler CM, Gaines SD (2008) Seascape genetics and the
spatial ecology of marine populations. Fish Fish 9(4):363–377
Tewksbury JJ, Levey DJ, Haddad NM, Sargent S, Orrock JL, Weldon A,
Danielson BJ, Brinkerhoff J, Damschen EI, Townsend P (2002)
Corridors affect plants, animals, and their interactions in fragmented
landscapes. PNAS 99(20):12923–12926
Waycott M, Duarte CM, Carruthers TJB, Orth RJ, Dennison WC,
Olyamik S, Calladine A, Fourqurean JW, Heck KL Jr, Hughes
AR, Kendrick GA, Kenworthy WJ, Short FT, Williams SL (2009)
Accelerating loss of seagrass across the globe threatens coastal eco-
systems. PNAS 106(30):12377–12381
Wikström S, Daunys D, Leinikki J (2010) A proposed biotope classifica-
tion system for the Baltic Sea. AquaBiota Report 2010:6
Worm B, Reusch TBB (2000) Do nutrient availability and plant density
limit seagrass colonization in the Baltic Sea? Mar Ecol Prog Ser 200:
159–166
Zhou Y, Liu P, Liu B, Liu X, Zhang X, Wang F (2014) Restoring eelgrass
(ZosteramarinaL.) habitats using a simple and effective
transplanting technique. PLoS One 9(4):1–7
P. Krost et al.
Author's personal copy
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