Depletion, degradation, and recovery potential of estuaries and coastal seas.
ABSTRACT Estuarine and coastal transformation is as old as civilization yet has dramatically accelerated over the past 150 to 300 years. Reconstructed time lines, causes, and consequences of change in 12 once diverse and productive estuaries and coastal seas worldwide show similar patterns: Human impacts have depleted >90% of formerly important species, destroyed >65% of seagrass and wetland habitat, degraded water quality, and accelerated species invasions. Twentieth-century conservation efforts achieved partial recovery of upper trophic levels but have so far failed to restore former ecosystem structure and function. Our results provide detailed historical baselines and quantitative targets for ecosystem-based management and marine conservation.
- Conservation Genetics 10/2014; 15(5):1037-1052. · 1.85 Impact Factor
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ABSTRACT: In intertidal soft-bottom ecosystems, ecosystem engineers such as reef-building bivalves, can strongly affect the associated benthic community by providing structure and stabilizing the sediment. Although several engineering species have declined dramatically in the past centuries, the consequences of their loss for the trophic structure of intertidal benthic communities remain largely unclear. In this study, we experimentally test the hypothesis that above- and belowground habitat modifications by ecosystem engineers, facilitate distinctly different, but trophically more diverse benthic communities, using intertidal mussel and tube worm beds as model systems. We constructed a large-scale experiment at two intertidal mudflats in the Dutch Wadden Sea, with distinctly different environmental conditions. At both sites, we applied anti-erosion mats to simulate belowground structure and sediment stabilization by commonly found tube worm beds and crossed this with the addition of adult mussels to investigate effects of aboveground structure. The anti-erosion mats mainly enhanced species and trophic diversity (i.e., feeding guild richness and diversity) of the infaunal community, while the addition of mussels primarily enhanced species and trophic diversity of the epifaunal community, irrespective of location. The effect size of mussel addition was larger at the exposed site in the western Wadden Sea compared to the more sheltered eastern site, probably due to relatively stronger abiotic stress alleviation. We conclude that structure-providing and sediment-stabilizing species such as reef-building bivalves and tube worms, form the foundation for trophically diverse benthic communities. In intertidal soft-bottom ecosystems like the Wadden Sea, their conservation and restoration are therefore critical for overall ecosystem functioning.Journal of Experimental Marine Biology and Ecology 01/2015; 465:41-48. · 2.48 Impact Factor
- Ecological Indicators 09/2014; 44:173-181. · 3.23 Impact Factor
, 1806 (2006);
et al.Heike K. Lotze,
Estuaries and Coastal Seas
Depletion, Degradation, and Recovery Potential of
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Depletion, Degradation, and
Recovery Potential of Estuaries
and Coastal Seas
Heike K. Lotze,1* Hunter S. Lenihan,2Bruce J. Bourque,3Roger H. Bradbury,4
Richard G. Cooke,5Matthew C. Kay,2Susan M. Kidwell,6Michael X. Kirby,7
Charles H. Peterson,8Jeremy B. C. Jackson5,9
Estuarine and coastal transformation is as old as civilization yet has dramatically accelerated over
the past 150 to 300 years. Reconstructed time lines, causes, and consequences of change in 12
once diverse and productive estuaries and coastal seas worldwide show similar patterns: Human
impacts have depleted 990% of formerly important species, destroyed 965% of seagrass and
wetland habitat, degraded water quality, and accelerated species invasions. Twentieth-century
conservation efforts achieved partial recovery of upper trophic levels but have so far failed to
restore former ecosystem structure and function. Our results provide detailed historical baselines
and quantitative targets for ecosystem-based management and marine conservation.
of overexploitation, habitat transformation, and
pollution have obscured the total magnitude of
estuarine degradation and biodiversity loss and
have undermined their ecological resilience (1–5).
This poses potential for disaster, as demonstrated
in numerous fisheries collapses (1–3) and the
recent impacts of the 2004 Asian tsunami and
2005 Hurricane Katrina that were exacerbated by
historical losses of mangroves and wetlands (5–7).
With recognition of their essential role for human
and marine life, estuaries and coastal zones have
become the focus of efforts to develop ecosystem-
based management and large-scale restoration
strategies. To be successful, these approaches re-
the degree and drivers of degradation in an eco-
system context (8, 9).
We reconstructed historical baselines and
quantified the magnitude and causes of change
stuaries and coastal seas have been focal
points of human settlement and marine
resource use throughout history. Centuries
in 12 temperate estuarine and coastal ecosystems
onset of human settlement until today (Table 1).
We used paleontologic, archaeological, historical,
and ecological records (table S1) to quantify
changes in 30 to 80 species per system standard-
ized into 22 guilds and six taxonomic and seven
functional groups, as well as seven water-quality
parameters and species invasions (10). Species
were selected for their economic, structural, or
functional significance throughout history. We
estimated relative abundance of each species over
real time and across seven cultural periods reflect-
ing the stage of cultural and market development
rather than calendar dates (tables S2 and S3).
Relative abundance was quantified as pristine
(100%), abundant (90%), depleted (50%), rare
(10%), or extinct (0%) (table S4). Recovery was
Our estimates are conservative compared with
available absolute abundance records.
was tracked by using arithmetic and multivariate
means of relative abundance of taxonomic and
functional groups (10), all of which yielded
similar results (Fig. 1 and fig. S1). Despite wide
geographic distribution and unique regional
histories, all systems showed similar trajectories
of long periods of slow decline followed by
rapid acceleration over the last 150 to 300 years
(Fig. 1A). Severe resource depletion first began
during Roman times (2500 years B.P.) in the
the Wadden and Baltic Seas, and in the wake of
European colonization in North America and
Australia (Fig. 1A). Substituting cultural periods
for calendar dates revealed low human impacts
during the hunter-gatherer, agricultural, and
market-colonial establishment periods (Fig. 1B),
when exploitation was mainly for subsistence
purposes. However, signs of local resource
depletion were evident in some systems such
as San Francisco Bay (Fig. 1B), where pre-
historic populations depleted highly valued re-
sources such as sea otters (Enhydra lutris), large
1Biology Department, Dalhousie University, 1355 Oxford
Street, Halifax, NS, Canada B3H 4J1.
Environmental Science and Management, Bren Hall 3428,
University of California, Santa Barbara, CA 93106–5131,
Bates College, Lewiston, ME 04240, USA.
Management in Asia-Pacific Program, Research School of
Pacific and Asian Studies, Australian National University,
Canberra, ACT 0200, Australia.
Paleoecology and Archeology, Smithsonian Tropical Re-
search Institute, Unit 0948, APO AA 34002–0948, Republic
of Panama.6Department of Geophysical Sciences, University
of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637,
Florida, Museum Road, P.O. Box 117800, Gainesville, FL
32611–7800, USA.8Institute of Marine Sciences, University
of North Carolina at Chapel Hill, Morehead City, NC 28557,
Scripps Institution of Oceanography, University of California
at San Diego, La Jolla, CA 92093–0244, USA.
2Bren School of
3Department of Anthropology, 155 Pettengill Hall,
5Center for Tropical
7Florida Museum of Natural History, University of
9Center for Marine Biodiversity and Conservation,
*To whom correspondence should be addressed. E-mail:
Table 1. Location and characteristics of study systems. Species richness
(SpR, fish richness as proxy for overall richness) and primary productivity
(PP) represent regional data for large marine ecosystems [table S1 (10)].
Origin indicates the time when the system developed today’s size and
shape. Impact length and human population growth rate were calculated
since beginning of the development period. Human population total and
density refer to today’s population in provinces and countries bordering
the studied systems (10).
(mg CI mj2Idj1)
W. Baltic Sea
N. Adriatic Sea
S. Gulf St. Lawrence
Outer Bay of Fundy
San Francisco Bay
23 JUNE 2006VOL 312 SCIENCE www.sciencemag.org
on August 23, 2007
geese (Anser, Branta, Chen spp.), white sturgeon
(Acipenser transmontanus), and native oyster
(Ostreola conchaphila) (11).
Human impacts escalated into rapid resource
depletion during the market–colonial develop-
ment period and continued in the two global
market periods, 1900–1950 and 1950–2000, in
all systems (Fig. 1B). These were the periods of
(i) rapid human population growth (Fig. 1, C and
of resource use and development of luxury
markets, and (iii) industrialization and technolog-
ical progress toward more efficient but also
unselective and destructive gears (table S2). In
in most and reversed in some systems because of
conservation efforts (Fig. 1B). These general
trends suggest that rapid degradation was driven
by human history rather than natural change and
a slow path to recovery—at least in developed
countries. In developing countries, however,
expected future population growth associated
with growing pressures on coastal ecosystems
may increase degradation.
The degree of degradation, as indicated by
the endpoints of historical trajectories (Fig. 1E),
was independent of system size, species rich-
ness, primary productivity, and human popula-
tion density and growth rate (Table 1, linear
regressions, P 9 0.05). Nevertheless, systems
with the longest history of intense human
impacts and highest total human population
were among the most degraded, including the
Adriatic, Wadden, and Baltic Seas AFig. 1E,
linear regressions, logElength impact^, F(1,10) 0
10.3, P 0 0.009, r20 0.51; logEtotal pop-
ulation^, F(1,10) 0 5.06, P 0 0.048, r20 0.34,
see fig. S1 for alternative measuresZ. The outer
Bay of Fundy, Southern Gulf of St. Lawrence,
Fig. 1. History and present state of 12 estuarine and coastal
ecosystems in North America, Europe, and Australia. (A) Relative
abundance of six taxonomic groups (as arithmetic means) over
real time and (B) cultural periods (Pre, prehuman; HG, hunter-
gatherer; Agr, agricultural; Est, market–colonial establishment;
Dev, market–colonial development; Glo1, global market 1900–
1950; and Glo2, global market 1950–2000). (C) Human
population growth over real time and (D) cultural period (Baltic
and Adriatic, ?10j1; Fundy, ?10; Pamlico, ?102to fit scale).
(E) Present state of relative abundance. Color codes depict study
systems as shown in (E).
Present state of relative abundance
Pre HG Agr Est Dev Glo1Glo2
3000 2500 2000 1500 1000 5000
Pinnipeds & Otters
Waterfowl & Waders
Crocodiles / Alligators
Pre HG Agr Est Dev Glo1Glo2
Pre HG Agr Est Dev Glo1Glo2
Fig. 2. Common patterns of decline in 22 species guilds averaged over 12 study systems for (A)
marine mammals, (B) coastal birds, (C) fish, (D) reptiles, (E) invertebrates, and (F) vegetation. (G)
Degradation of water quality as indicated by the relative increase in eutrophication parameters
[eight systems (10)]. (H) Cumulative increase in recorded species invasions [five systems (10)]. Data
are means T SEM.
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on August 23, 2007
and Massachusetts Bay were consistently
ranked as the least degraded systems (Fig. 1E
and fig. S1).
Detailed time lines for species guilds, taxo-
nomic and functional groups, water-quality
parameters, and species invasions followed sim-
ilar patterns of degradation across study systems
(Fig. 2 and fig. S2). Most mammals, birds, and
reptiles (Fig. 2, A, B, and D) were depleted by
1900 and declined further by 1950 because of
intense exploitation for food, oil, or luxury items
includingfurs,feathers,andivory(2, 12). Among
fish (Fig. 2C), diadromous species such as
salmon and sturgeon were highly desired, easily
accessible, and depleted first, successively
followed by large pelagics such as tuna and
sharks, groundfish such as cod and halibut, and
small pelagics such as herring and sardines.
Oysters were the first invertebrate suffering
depletion (Fig. 2E) because of high value,
accessibility, and destructive exploitation
methods (13). Because of their reef-forming
and filtration capacity, depletion of oysters
reduced the ecosystem_s ability to provide high
water quality and complex habitats. Other
habitat-building filter-feeders including corals,
sponges, and hydrozoans were little affected
until the development period, but rapidly
declined with expanding seafloor trawling
(12). Mussels, crustaceans, and other mobile
invertebrates have been harvested throughout
history, but only recently became targets of
expanding low–trophic level fisheries (2, 14).
Thus, among mammals, fish, and invertebrates,
we see sequential depletion of the most valued
and largest species and subsequent replacement
with smaller, less valuable ones (14).
Over time, 67% of wetlands, 65% of sea-
grasses, and 48% of other submerged aquatic
vegetation (SAV) were lost because of reclama-
tion, eutrophication, disease, destruction, and
direct exploitation (Fig. 2F). Declines in coastal
vegetation caused substantial losses of nursery
habitats, nutrient and sediment sinks, and
coastline protection. By the late 20th century,
91% of the recorded species were depleted; 31%
were rare; and 7% were extinct. Conservation
efforts in the 20th century led to partial recovery
of 12% and substantial recovery of 2% of the
species, especially among pinnipeds, otters, birds,
crocodiles, and alligators (Fig. 2, A, B, and D).
Large whales, sirenia, and sea turtles, however,
remain at low population levels.
Degradation of water quality occurred in two
phases (10). During the development period
(Fig. 2G), primary productivity and sediment
loading strongly increased, mainly driven by
deforestation that mobilized sediments and
nutrients. These trends stabilized during the first
global period (1900–1950) except for increasing
nitrogen loading. In the second global period
increases occurred in nitrogen and phosphorus
loading, primary productivity, eutrophic plank-
ton, oxygen depletion, and losses of epiphytic
diatoms (Cocconeis spp.), commonly associated
with seagrass. These trends reflect coastal
eutrophication driven by nutrient loading from
point and nonpoint sources and losses of filtering
and buffering capacity of vegetation and suspen-
sion feeders (1, 15).
The first identified invasion was by the soft-
shelled clam Mya arenaria, introduced from
North America into the Baltic and North Seas
probably by Norse voyagers before 1245 A.D.
(10, 16). In the following centuries, invasions
were only gradually recorded but increased
during the development and accelerated during
theglobalperiods(Fig.2H), driven by increased
global navigation and commerce (17).
The recorded causes of past changes (10)
highlight priority targets for ecosystem-based
management and marine conservation. Exploi-
tation stands out as the causative agent for 95%
of species depletions and 96% of extinctions in
our study systems, followed by habitat destruc-
tion (Fig. 3A). This is consistent with reported
causes of marine (18) and terrestrial (19)
extinctions worldwide. Pollution, disturbance,
disease, eutrophication, and introduced land
predators were associated with fewer species
losses (Fig. 3A) but contributed to declines of
habitat-building species and may hinder recov-
ery. In our records, which focused on commer-
cially, structurally, and functionally important
species, no depletion or extinction was caused
by invasive species or climate change, although
such cases have been documented (3, 18, 20).
We caution, however, that the relative impor-
tance of these factors may shift in the future
with exploitation becoming more restricted, but
invasions and climate change accelerating (21).
Our results indicate that human impacts do
not act in isolation. In 45% of species depletions
and 42%ofextinctions,multiple humanimpacts
were involved, commonly, exploitation and
habitat loss. Such synergistic effects have been
significant for terrestrial extinctions (19) and
estuarine depletions (22). Cumulative impacts
22% of recoveries resulted from mitigation of a
single human impact, mostly exploitation, 78%
resulted from reduction of at least two impacts,
mostly habitat protection and restricted exploita-
tion but also pollution (Fig. 3A). Reduced
Fig. 3. Causes and
consequences of change
in 12 study systems
(means T SEM). (A) Per-
cent of species deple-
tions (light gray) and
by different human im-
pacts (Expl, exploitation;
Hab, habitat loss; Poll,
pollution; Dist, human
disturbance; Dis, dis-
ease; Eutr, eutrophica-
tion; InPr, introduced
land predators; Inva, in-
vasive species; and Cli,
climate change), and
percent of recoveries
(white) resulting from
impact reduction. (B)
Diversity shift due to
biased losses and gains
across different taxo-
nomic groups (Mam,
mammals; Bir, birds;
Rep, reptiles; Fis, fish;
Inv, invertebrates; Alg,
macroalgae; Pla, higher
plants; Phy, phyto-
plankton; Pro, protozoa;
and ViB, viruses and
bacteria): percent of
recorded species cur-
rently depleted (light
gray), rare (dark gray),
extinct (black), or recovering (white), and number of species invasions (cross-hatched; data for seven
systems). (C) Past, present, and potential future changes in important structural and functional ecosystem
components: large consumers (black), habitat and filter organisms (light gray), eutrophication and invasive
species (dark gray) [cultural periods as in Fig. 1, adapted from (28)]. Future scenarios depict stabilizing (solid
lines), improving (short dashed), or worsening (long dashed) trends.
23 JUNE 2006VOL 312 SCIENCEwww.sciencemag.org
on August 23, 2007
exploitation, habitat protection, and improved
water quality need to be considered together, and
the cumulative effects of multiple human
interventions must be included in both manage-
ment and conservation strategies (22).
Marked shifts in diversity were caused by the
taxonomic bias of almost all extinctions (93%)
and most depletions (81%) affecting large verte-
brates (Fig. 3B) (10). This bias was amplified by
the high incidence of invasions among inverte-
brates, plants, and smaller organisms (Fig. 3B)
(10). Given past trends in depletions, extinctions,
and invasions (Fig. 2), this shift in species
composition is likely to accelerate in the future,
only partly dampened by recent trends in
recovery (Figs. 2 and 3B).
The structure and functioning of estuarine
and coastal ecosystems has been fundamentally
changed by the loss of large predators and
herbivores, spawning and nursery habitat, and
filtering capacity that sustains water quality (Fig.
3C and fig. S2). The erosion of diversity and
complexity has slowly undermined resilience,
giving way to undesirable algal blooms, dead
zones, disease outbreaks, and invasions, and
elevating the potential for disaster (1–7, 21).
Although declines in large vertebrates and
habitat-providing species have slowed in the last
50 to 100 years, trends in small consumers, water
quality, and species invasions continue to de-
teriorate (Figs. 2 and 3C). Together with the
historical degradation of coral reefs (4), kelp
forests (23), and an up-welling system (24), our
results document severe, long-term degradation
of near-shore marine systems worldwide. As
human impacts spread rapidly from the coast to
the shelf, open ocean, and deep sea (25–27), past
trajectories in coastal zones may well forecast
future changes in the entire ocean. Strong
countermeasures are needed to reverse trends
of expanding degradation (Fig. 3C).
Human impacts have pushed estuarine and
coastal ecosystems far from their historical
baseline of rich, diverse, and productive ecosys-
trends and the commonality of causes and
consequences of change provide reference
points and quantitative targets for ecosystem-
based management and restoration. Overex-
ploitation and habitat destruction have been
responsible for the large majority of historical
changes, and their reduction should be a major
management priority. Eutrophication, although
severe in the last phase of estuarine history,
largely followed rather than drove observed
declines in diversity, structure, and functioning.
Despite some extinctions, most species and
functional groups persist, albeit in greatly re-
duced numbers. Thus, the potential for recovery
remains, and where human efforts have focused
on protection and restoration, recovery has oc-
curred, although often with significant lag times
(2, 12). Ourstudynotonlyprovidesbaselineson
the extent of historical degradation, but also a
vision for regenerating resilient estuarine and
coastal ecosystems that can absorb shocks and
disasters in an uncertain future.
References and Notes
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29. We thank all colleagues for sharing data and insight
and B. Worm and R. A. Myers for critical discussions. This
work was initiated as part of the Long-Term Ecological
Records of Marine Environments, Populations and
Communities Working Group supported by the National
Center for Ecological Analysis and Synthesis (funded by
NSF grant DEB-0072909, the University of California, and
the University of California, Santa Barbara). Additional
funding was granted to H.K.L. by the Alfred-Wegener
Institute for Polar and Marine Research, the Sloan
Foundation (Census of Marine Life, History of Marine
Animal Populations Program), and the Lenfest Ocean
Program at the Pew Charitable Trusts.
Supporting Online Material
Materials and Methods
Figs. S1 and S2
Tables S1 to S8
References and Notes
29 March 2006; accepted 3 May 2006
JETLAG Resets the Drosophila Circadian
Clock by Promoting Light-Induced
Degradation of TIMELESS
Kyunghee Koh, Xiangzhong Zheng, Amita Sehgal*
Organisms ranging from bacteria to humans synchronize their internal clocks to daily cycles of light
and dark. Photic entrainment of the Drosophila clock is mediated by proteasomal degradation
of the clock protein TIMELESS (TIM). We have identified mutations in jetlag—a gene coding for an
F-box protein with leucine-rich repeats—that result in reduced light sensitivity of the circadian
clock. Mutant flies show rhythmic behavior in constant light, reduced phase shifts in response to
light pulses, and reduced light-dependent degradation of TIM. Expression of JET along with the
circadian photoreceptor cryptochrome (CRY) in cultured S2Rþ cells confers light-dependent
degradation onto TIM, thereby reconstituting the acute response of the circadian clock to light in a
cell culture system. Our results suggest that JET is essential for resetting the clock by transmitting
light signals from CRY to TIM.
the new day and night cycle. Although the
molecular mechanisms for generating circadian
rhythms through interlocking transcriptional
feedback loops and posttranslational modifica-
tions have been characterized in some detail (1),
few components of the light entrainment path-
way are known (2). Photic entrainment in
Drosophila can be mediated by the visual system
and by CRY, a circadian blue-light photoreceptor
expressed in clock cells (3). When the fly is
exposed to light, CRY binds a core clock protein,
TIM, which leads to subsequent ubiquitination
and degradation of TIM by the proteasome
ravel across time zones often produces
jet lag because it takes some time to re-
synchronize internal circadian clocks to
pathway (4–8). Rapid, light-dependent degrada-
tion of TIM underlies the fly_s ability to reset the
circadian phase to reflect environmental fluctua-
tions in light levels (9, 10). However, the specific
signals that drive the TIM response to light are
In the course of characterizing rest:activity
rhythms of various fly strains, we discovered a
strain with anomalous activity patterns in
constant light (LL). Whereas wild-type flies
Howard Hughes Medical Institute, Department of Neuro-
science, University of Pennsylvania School of Medicine,
Philadelphia, PA 19104, USA.
*To whom correspondence should be addressed. E-mail:
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