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Conservation of U.S. coral reefs has been sidetracked by the partial implementation of management plans without clearly achievable goals. Historical ecology reveals global patterns of coral reef degradation that provide a framework for reversing reef decline with ecologically meaningful metrics for success. The authors of this Policy Forum urge action now to address multiple threats simultaneously, because the harmful effects of stressors like overfishing, pollution, poor land-use practices, and global warming are interdependent. Prompt implementation of proven, practical solutions would lead to both short- and long-term benefits, including the return of keystone species and the economic benefits they entail. SCIENCE VOL 307 18 MARCH 2005
oral reefs provide ecosys-
tem goods and services
worth more than $375 bil-
lion to the global economy each
year (1). Yet, worldwide, reefs are
in decline (14). Examination of
the history of degradation reveals
three ways to challenge the cur-
rent state of affairs (5, 6). First,
scientists should stop arguing
about the relative importance of
different causes of coral reef decline: overfish-
ing, pollution, disease, and climate change.
Instead, we must simultaneously reduce all
threats to have any hope of reversing the
decline. Second, the
scale of coral reef
mechanisms such as
protected areas—
has been too small and piecemeal. Reefs must
be managed as entire ecosystems. Third, a lack
of clear conservation goals has limited our
ability to define or measure success.
Large animals, like turtles, sharks, and
groupers, were once abundant on all coral
reefs, and large, long-lived corals created a
complex architecture supporting diverse
fish and invertebrates (5, 6). Today, the most
degraded reefs are little more than rubble,
seaweed, and slime. Almost no large ani-
mals survive, water quality is poor, and
large corals are dead or dying and being
replaced by weedy corals, soft corals, and
seaweed (2, 7, 8). Overfishing of megafauna
releases population control of smaller fishes
and invertebrates, creating booms and busts.
This in turn can increase algal overgrowth,
or overgrazing, and stress the coral archi-
tects, likely making them more vulnerable
to other forms of stress. This linked
sequence of events is remarkably consistent
worldwide (see top figure, this page).
Even on Australia’s Great Barrier Reef
(GBR), the largest and best-managed reef in
the world, decline is ongoing (9). Australia’s
strategy, beginning with the vision to estab-
lish the world’s largest marine park in 1976,
is based on coordinated
management at large
spatial scales. Recently
more than one-third of
the GBR was zoned
“no take,” and new
laws and policies to
reduce pollution and
fishing are in place
(10). Evaluating bene-
fits of increased no-
take zones will require
detailed follow-up, but
smaller-scale studies
elsewhere support in-
creased protection. Two
neighboring countries,
the Bahamas (11) and
Cuba (12), have also
committed to conserve
more than 20% of their
coral reef ecosystems.
By contrast, the Florida
Keys and main Ha-
waiian Islands are far
further down the trajec-
tory of decline (see bottom figure, this
page), yet much less action has been taken.
What is the United States doing to
enhance its coral reef assets? In the Florida
Keys National Marine Sanctuary, the
Governor and the National Oceanic and
Atmospheric Administration (NOAA)
agreed in 1997 to incorporate zoning with
protection from fishing and water quality
controls (13). But only 6% of
the Sanctuary is zoned no take,
and these zones are not strategi-
cally located. Conversion of
16,000 cesspools to centralized
sewage treatment and control of
other land-based pollution have
only just begun. Florida’s reefs
are well over halfway toward
ecological extinction and much
more impaired than reefs of
Belize and all but one of the
Pacific reefs in the figure below (6). Large
predatory fishes continue to decrease (14),
reefs are increasingly dominated by seaweed
(15, 16), and alarming diseases have
emerged (17).
Annual revenues from reef tourism are
$1.6 billion (1), but the economic future of the
Keys is gloomy owing to accelerating ecolog-
ical degradation. Why? Without a clear goal
for recovery, development and ratification of
the management plan became a goal in itself.
Reefs of the northwest Hawaiian Islands
have been partially protected by isolation from
the main Hawaiian Islands (which show
Are U.S. Coral Reefs on
the Slippery Slope to Slime?
J. M. Pandolfi,
* J. B. C. Jackson,
N. Baron,
R. H. Bradbury,
H. M. Guzman,
T. P. Hughes,
C.V. Kappel,
F. Micheli,
J. C. Ogden,
H. P. Possingham,
E. Sala
The slippery slope of coral reef decline through time.
1500 1600 1700 1800 1900 2000 2100
r y
Percent degradation
Main Hawaiian Islands,
Florida Keys
NW Hawaiian Islands,
Outer GBR
Virgin Islands,
Moreton Bay
Jamaica, W Panamá
Bahamas, E Panamá
Cayman Islands,
Belize, N Red Sea
S Red Sea
Torres Strait
Inner GBR
Past and present ecosystem conditions of 17 coral reefs,based on his-
torical ecology (
). The method consists of determining the status of
guilds of organisms for each reef with published data, performing a multi-
variate, indirect gradient analysis on the guild status database, and esti-
mating the location of each reef along a gradient of degradation from pris-
tine to ecologically extinct reefs. Green, Caribbean sites; blue,Australian
and Red Sea sites; red, U.S. reefs from the most recent cultural period.
The Centre for Marine Studies and Department of
Earth Sciences,
Department of Mathematics and
School of Life Sciences,The University of Queensland,
St. Lucia, QLD 4072, Australia.
Center for Marine
Biodiversity and Conservation, Scripps Institution of
Oceanography, La Jolla, CA 92093, USA.
Tropical Research Institute, Balboa, Republic of
National Center for Ecological Analysis and
Synthesis, Santa Barbara CA.
Centre for Resource and
Environmental Studies, Australian National
University, Canberra, ACT 0200, Australia.
Centre for
Coral Reef Biodiversity, School of Marine Biology,
James Cook University, Townsville, QLD 4811,
Hopkins Marine Station, Stanford
University, CA 93950–3094, USA.
Florida Institute of
Oceanography, St. Petersburg, FL 33701, USA.
*Author for correspondence. E-mail: j.pandolfi@
Enhanced online at
Published by AAAS
on November 12, 2010 www.sciencemag.orgDownloaded from
degradation similar to that of the Florida Keys)
and are in relatively good condition (see figure
at the bottom of page 1725). Corals are healthy
(2, 18), and the average biomass of commer-
cially important large predators such as sharks,
jacks, and groupers is 65 times as great (19) as
that at Oahu, Hawaii, Maui, and Kauai. Even in
the northwestern islands, however, there are
signs of decline. Monk seals and green turtles
are endangered (20, 21); large amounts of
marine debris are accumulating, which injure
or kill corals, seabirds, mammals, turtles, and
fishes (2, 18, 22); and levels of contaminants,
including lead and PCBs are high (18).
Until recently, small-scale impacts from
overfishing and pollution could be managed
locally, but thermal stress and coral bleach-
ing are already changing community struc-
ture of reefs. Impacts of climate change may
depend critically on the extent to which a
reef is already degraded (8, 23). Polluted and
overfished reefs like in Jamaica and Florida
have failed to recover from bouts of bleach-
ing, and their corals have been replaced by
seaweed (2). We believe that restoring food
webs and controlling eutrophication pro-
vides a first line of defense against climate
change (8, 23); however, slowing or revers-
ing global warming trends is essential for the
long-term health of all tropical coral reefs.
For too long, single actions such as mak-
ing a plan, reducing fishing or pollution, or
conserving a part of the system were viewed
as goals. But only combined actions
addressing all these threats will achieve the
ultimate goal of reversing the trajectory of
decline (see the table above).
We need to act now to curtail processes
adversely affecting reefs. Stopping overfish-
ing will require integrated systems of no-
take areas and quotas to restore key func-
tional groups. Terrestrial runoff of nutrients,
sediments, and toxins must be greatly
reduced by wiser land use and coastal devel-
opment. Reduction of emissions of green-
house gases are needed to reduce coral
bleaching and disease. Progress on all fronts
can be measured by comparison with the
past ecosystem state through the methods of
historical ecology to determine whether or
not we are succeeding in ameliorating or
reversing decline. Sequential return of key
groups, such as parrot fish and sea urchins
that graze down seaweed; mature stands of
corals that create forest-like complexity; and
sharks, turtles, large jacks, and groupers that
maintain a more stable food web (4, 5, 6, 24)
constitutes success.
This consistent way of measuring recov-
ery (see the figure at the bottom of page
1725) and the possibility of short-term
gains set a benchmark for managing other
marine ecosystems. Like any other success-
ful business, managing coral reefs requires
investment in infrastructure. Hence, we also
need more strategic interventions to restore
species that provide key ecological func-
tions. For example, green turtles and sea
cows not only once helped maintain healthy
seagrass ecosystems, but also were an
important source of high-quality protein for
coastal communities (25).
Our vision of how to reverse the decline
of U.S. reefs rests on addressing all threats
simultaneously (see the table above). By
active investment, major changes can be
achieved through practical solutions with
short- and long-term benefits. Short-lived
species, like lobster, conch, and aquarium
fish will recover and generate income in just
a few years, and benefits will continue to
compound over time. Longer-lived species
will recover, water quality will improve, and
the ecosystem will be more resilient to
unforeseen future threats. Ultimately, we will
have increased tourism, and the possibility of
renewed sustainable extraction of abundant
megafauna. One day, reefs of the United
States could be the pride of the nation.
1. D.Bryant
et al
Reefs at Risk. A Map-Based Indicator of
Threats to the World’s Coral Reefs
(World Resources
Institute,Washington, DC, 1998).
2. C. R.Wilkinson,
Status of Coral Reefs of the World:
(Global Coral Reef Monitoring Network and
Australian Institute of Marine Science, Townsville,
Australia, in press); vol. 1 is available at
3. T.A. Gardener
et al
301, 958 (2003).
4. D. R. Bellwood, T. P. Hughes, C. Folke, M. Nyström,
429, 827 (2004).
5. J. B. C. Jackson
et al
293, 629 (2001).
6. J. M. Pandolfi
et al
301, 955 (2003).
7. T. P. Hughes
et al
265, 1547 (1994).
8. N. Knowlton,
Proc. Natl. Acad. Sci. U.S.A.
98, 5419
9. Great Barrier Reef Marine Park Authority,
The current status of the Great Barrier Reef
10. Great Barrier Reef Marine Park Authority, New Policy
Web site:
11. D. R. Brumbaugh
et al
Proceedings of the Forum 2003
, Nassau, Bahamas, 30 June to 4 July 2003
(College of the Bahamas, Nassau, Bahamas, 2003).
12. R. Estrada
et al
El sistema nacional de areas marinas
protegidas de Cuba
[Center for Protected Areas
(CNAP), Havana, Cuba, 2003].
13. Florida Keys National Marine Sanctuary,
Management Plan/Environmental Impact Statement
(Department of Commerce, National Oceanic and
Atmospheric Administration,Washington, DC, 1995),
vol. 1, pp.1–323.
14. J.A. Bohnsack,
Gulf Caribbean Res.
14, 1 (2003).
15. W. C. Jaap
et al
Environmental Protection Agency/
National Oceanographic and Atmospheric
Administration (NOAA) Coral Reef Evaluation and
Monitoring Project: 2002 Executive Summary
of the Florida Fish and Wildlife Conservation
Commission, Tallahassee, and the University of
Georgia,Athens, 2003).
16. J.W. Porter
et al
., in
The Everglades, Florida Bay, and
Coral Reefs of the Florida Keys: An Ecosystem
, J.W. Porter and K. G. Porter, Eds. (CRC Press,
Boca Raton, FL, 2002), pp. 749–769.
17. C. D. Harvell
et al
296, 2158 (2002).
18. J. Maragos, D. Gulko, Eds.,
Coral Reef Ecosystems of the
Northwestern Hawaiian Islands: Interim Results
Emphasizing the 2000 Surveys
(U.S. Fish and Wildlife
Service and Hawaii Department of Land and Natural
Resources, Honolulu, HI, 2002).
19. A. M. Friedlander, E. E. DeMartini,
Mar. Ecol. Prog. Ser.
230, 253 (2002).
20. International Union for the Conservation of Nature
and Natural Resources,
Red List of Threatened Species
available at
21. NOAA,
22. C. Safina,
Eye of the Albatross
(Holt, New York, 2003).
23. T. P. Hughes
et al
301, 929 (2003).
24. T. Elmqvist
et al
Front. Ecol. Environ.
1, 488 (2003).
25. J. B. C. Jackson,
Coral Reefs
16, S23 (1997).
Supporting Online Material
Threat (time frame) Critical first step Results Benefits
Overfishing Immediate increase of cumulative Increase in short-lived species, Economic viability to lost or
(years) no-take areas of all U.S. reefs to >30%; such as lobsters, conch, weakened fisheries; reduction in
reduce fishing efforts in adjacent areas parrotfish, and sea urchins algal competition with corals
Overfishing Establishment of large fish, shark, turtle, Increase in megafauna Return of key functional
(decades) and manatee breeding programs; populations components and trophic structure
mandatory turtle exclusion devices (TEDs)
and bycatch reduction devices (BRDs)
Pollution Stringent controls over land-based Increase in water quality Reduction in algal competition
(years-decades) pollution with corals; reduced coral disease
Coastal development Moratorium on coastal development Increase in coral reef habitat Increase of coral reef populations
(years-decades) in proximity to coral reefs (i.e., reduced mortality)
Global change International engagement in Reduction in global sea surface Lower incidence of coral bleaching;
(decades) emission caps temperatures and CO
increase calcification potential
Published by AAAS
on November 12, 2010 www.sciencemag.orgDownloaded from
1 SCIENCE Erratum post date 17 JUNE 2005
Post date 17 June 2005
Policy Forum: “Are U.S. coral reefs on the slippery slope to slime?” by J. M.
et al.
(18 Mar. 2005, p. 1725). In the bottom figure on p. 1725,
Caribbean sites are purple (not green as described in the legend), and some
data points are not seen because of superimposed dots. Otherwise, the labels
point to the dots in order. For example, the Bahamas and eastern Panamá are
represented by the purple dot partly showing above the red dot for the Main
Hawaiian islands and Florida Keys. The lettering for the Outer Great Barrier
Reef (Outer GBR) should be black.
on November 12, 2010 www.sciencemag.orgDownloaded from
... The BCG describes six biological condition levels ranging from undisturbed or natural (BCG level 1) to highly disturbed or degraded conditions (BCG level 6) ( Fig. 1). As demonstrated in the present study and noted elsewhere (Jackson et al. 2014, Pandolfi et al. 2003, Pandolfi et al., 2005, undisturbed or natural reefs have largely disappeared from the Caribbean, impressing the urgency for tools such as BCG models to assist natural resource managers and stakeholders evaluate changes in coral reefs. This framework was originally implemented in freshwater systems in the USA to support state biological assessment and criteria programs (Davies and Jackson 2006). ...
... In the last five decades, significant disturbances such as thermal stress, diseases, storms, and pollution have occurred more frequently and with higher intensity, disrupting and eliminating much recovery in the ecological successional process, creating a shifting baseline for "natural" conditions (Alvarez-Filip et al. 2009;Jackson et al. 2011). Community changes in coral species can be subtle because coral species identification is challenging and substantial community changes may occur over decadal, centennial, or millennial timescales (Pandolfi et al. 2005;van Woesik et al. 2012). The potentially slow shift in coral composition emphasizes the importance of establishing and documenting natural reef conditions to help guide and define coral reef conservation and restoration goals, as documented for BCG level 1. ...
As coral reef condition and sustainability continue to decline worldwide, losses of critical habitat and their ecosystem services have generated an urgency to understand and communicate reef response to management actions, environmental contamination, and natural disasters. Increasingly, coral reef protection and restoration programs emphasize the need for robust assessment tools for protecting high-quality waters and establishing conservation goals. Of equal importance is the need to communicate assessment results to stakeholders, beneficiaries, and the public so that environmental consequences of decisions are understood. The Biological Condition (BCG) model provides a structure to evaluate the condition of a coral reef in increments of change along a gradient of human disturbance. Communication of incremental change, regardless of direction, is important for decision makers and the public to better understand what is gained or lost depending on what actions are taken. We developed a narrative (qualitative) Biological Condition Gradient (BCG) from the consensus of a diverse expert panel to provide a framework for coral reefs in US Caribbean Territories. The model uses narrative descriptions of biological attributes for benthic organisms to evaluate reefs relative to undisturbed or minimally disturbed conditions. Using expert elicitation, narrative decision rules were proposed and deliberated to discriminate among six levels of change along a gradient of increasing anthropogenic stress. Narrative rules for each of the BCG levels are presented to facilitate the evaluation of benthic communities in coral reefs and provide specific narrative features to detect changes in coral reef condition and biological integrity. The BCG model can be used in the absence of numeric, or quantitative metrics, to evaluate actions that may encroach on coral reef ecosystems, manage endangered species habitat, and develop and implement management plans for marine protected areas, watersheds, and coastal zones. The narrative BCG model is a defensible model and communication tool that translates scientific results so the nontechnical person can understand and support both regulatory and non-regulatory water quality and natural resource programs.
... The worldwide loss of live coral cover and phase shifts from coral-to algal-dominated reefs has sparked various efforts to facilitate coral reef persistence and resilience (Hughes et al., 2018a;National Academies of Sciences, Engineering, and Medicine [NAS], 2019). A key indicator of coral reef health and area of research includes preventing the transition from coral to macroalgal dominance (Hughes, 1994), where overfishing of herbivorous fish and eutrophication favor algal growth (Pandolfi et al., 2005). Algae are major space competitors with corals (McCook, 2001;McManus and Polsenberg, 2004), where the control of algal cover is important in preventing suffocation of corals, allowing growth of crustose coralline algae (CCA), and providing space for juvenile corals to settle (Edmunds and Carpenter, 2001;Craggs et al., 2019). ...
Full-text available
Increases in sea surface temperature impact animal metabolism, which in turn could influence benthic structure and resulting algal-coral balance. We utilized a long-term coral reef dataset from the west coast of Hawai‘i Island to investigate impacts of annual positive and negative sea surface temperature anomalies (SSTA) on benthic cover [algal turf, macroalgae, crustose coralline algae (CCA), and coral], herbivore density (sea urchins, grazers, browsers, and scrapers) and the relationship between benthic cover and herbivore density. Results showed significantly lower coral cover, but higher CCA cover with positive SSTA. Additionally, the density of sea urchins, grazers and browsers increased with increasing SSTA. Warming disrupted the normal relationship between herbivores and benthic cover on reefs, particularly for grazers where higher densities were coupled with lower algal turf cover only during negative SSTA. The direction of the relationship between benthic cover and herbivore type changed with positive SSTA, where increased algal turf cover was associated with increased herbivore density. Here, herbivores are likely responding accordingly to increases in food availability due to increased metabolism under warming. Despite herbivore populations increasing in density over the past two decades, algal turf cover remains on an upward trajectory. These results indicate that warming can alter herbivore-algal dynamics, where greater herbivore densities may be required to cause a reduction in algal turf cover. Protection of herbivores in addition to reducing nutrient input onto reefs will be essential in driving a reduction in algal turf cover on Hawaiian reefs.
... Despite the clear and well-documented changes to Caribbean reefs, there is ongoing disagreement about the causes of and best remedies for reef decline [20,[38][39][40][41]. The crux of the debate is about the relative importance of local causes-pollution, eutrophication, fishing, and consequent seaweed blooms-compared with regional-to-global causes such as ocean warming and acidification. ...
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Disease, storms, ocean warming, and pollution have caused the mass mortality of reef-building corals across the Caribbean over the last four decades. Subsequently, stony corals have been replaced by macroalgae, bacterial mats, and invertebrates including soft corals and sponges, causing changes to the functioning of Caribbean reef ecosystems. Here we describe changes in the absolute cover of benthic reef taxa, including corals, gorgonians, sponges, and algae, at 15 fore-reef sites (12–15m depth) across the Belizean Barrier Reef (BBR) from 1997 to 2016. We also tested whether Marine Protected Areas (MPAs), in which fishing was prohibited but likely still occurred, mitigated these changes. Additionally, we determined whether ocean-temperature anomalies (measured via satellite) or local human impacts (estimated using the Human Influence Index, HII) were related to changes in benthic community structure. We observed a reduction in the cover of reef-building corals, including the long-lived, massive corals Orbicella spp. (from 13 to 2%), and an increase in fleshy and corticated macroalgae across most sites. These and other changes to the benthic communities were unaffected by local protection. The covers of hard-coral taxa, including Acropora spp., Montastraea cavernosa , Orbicella spp., and Porites spp., were negatively related to the frequency of ocean-temperature anomalies. Only gorgonian cover was related, negatively, to our metric of the magnitude of local impacts (HII). Our results suggest that benthic communities along the BBR have experienced disturbances that are beyond the capacity of the current management structure to mitigate. We recommend that managers devote greater resources and capacity to enforcing and expanding existing marine protected areas and to mitigating local stressors, and most importantly, that government, industry, and the public act immediately to reduce global carbon emissions.
... Despite covering less than one percent of the ocean surface, coral reefs are one of the most biologically diverse and economically important marine ecosystems (Crossland et al. 1991;Costanza et al. 1997Costanza et al. , 2014. Some of the ecosystem services that coral reefs provide include protection for coastlines, fisheries, and tourism (Moberg and Folke 1999;Pandolfi et al. 2005;Brander et al. 2007). Coral reefs are currently under threat due to global environmental change associated with ocean warming (Hughes et al. 2003;Carpenter et al. 2008;Hoegh-Guldberg et al. 2010;Hughes et al. 2018a) and acidification ) in addition to local disturbances such as overfishing (Jackson et al. 2001), eutrophication (Bell 1992;Bruno et al. 2003), and sedimentation (Rogers 1990). ...
Full-text available
Globally, coral reefs are threatened by ocean warming and acidification. The degree to which acidification will impact reefs is dependent on the local hydrodynamics, benthic community composition, and biogeochemical processes, all of which vary on different temporal and spatial scales. Characterizing the natural spatiotemporal variability of seawater carbonate chemistry across different reefs is critical for elucidating future impacts on coral reefs. To date, most studies have focused on select habitats, whereas fewer studies have focused on reef scale variability. Here, we investigate the temporal and spatial seawater physicochemical variability across the entire Heron Island coral reef platform, Great Barrier Reef, Australia, for a limited duration of six days. Autonomous sensor measurements at three sites across the platform were complemented by reef-wide boat surveys and discrete sampling of seawater carbonate chemistry during the morning and evening. Variability in both temporal and spatial physicochemical properties were predominantly driven by solar irradiance (and its effect on biological activity) and the semidiurnal tidal cycles but were influenced by the local geomorphology resulting in isolation of the platform during low tide and rapid flooding during rising tides. As a result, seawater from previous tidal cycles was sometimes trapped in different parts of the reef leading to unexpected biogeochemical trends in space and time. This study illustrates the differences and limitations of data obtained from high-frequency measurements in a few locations compared to low-frequency measurements at high spatial resolution and coverage, showing the need for a combined approach to develop predictive capability of seawater physicochemical properties on coral reefs.
... In addition to military bases, DoD has numerous training areas, particularly in the Pacific, where munitions and UXO can be found in shallow coral reef environments (e.g., Vieques, Puerto Rico; Ordnance Reef, Ohau HI; Kahoolawe HI; Camel Rock in Asan Bay Guam; Island of Farallon de Medinilla, Mariana Islands; Kwajalein Atoll, Johnson Atoll, Midway).Coral reefs clearly co-occur with many military bases and training areas throughout the Caribbean and Pacific Ocean. Range-wide, coral reefs have become at-risk ecosystems from multiple stressor impacts that include land-based sources of pollution, climate change, disease and overuse of reef resources(Wilkinson 1999;Knowlton 2001;Pandolfi et al. 2003Pandolfi et al. , 2005Ramade and Roche 2006;Reopanichkul et al. 2009). Over the last several decades, there has been heightened recognition that coral reefs worldwide are failing. ...
Technical Report
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A technical workshop bringing together a total of over 50 DoD site managers, scientists, regulators, and stakeholders was conducted in May 2018 at the Washington Navy Yard in Washington, DC. The goal of the workshop was to assess progress, questions, and continuing challenges related to understanding and managing environmental risk associated with underwater military munitions (UWMM). The workshop, as well as this report, focused on conventional munitions containing explosives. The workshop report contains 1) an overview of existing scientific evidence regarding environmental risks posed by UWMM; 2) discussion of relevant uncertainties associated with these risks, and 3) evaluation of known and foreseen challenges associated with obtaining site-specific MC concentrations in water column, sediment, and biota to validate risk conclusions at UWMM sites. The workshop provided a venue for open exchange of ideas among participants with varying backgrounds and views and used this exchange to identify data gaps and research priorities.
... Coral reefs are among the most naturally differing and monetarily significant biological systems. Nonetheless, reefs are quickly degraded at a worldwide scale, because of a number of reasons including environmental changes, overexploitation, coral infections and declining water quality Bruno and Selig (2007), Pandolfi et al. (2005) which cause environmental state shift from coral predominance to algae dominant state in a coral reef ecosystem. Current climate change models predict increasing recurrence of mass coral destruction events resulting in phase shift to algae-dominated state that is expected to happen and last for a longer period of time Scheffer et al. (2001), McCook (1999). ...
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The number of coral reefs around the world is slowly declining due to environmental and anthropogenic reason, and Pterois volitans also put extra stress on coral reefs by decreasing the number of herbivorous fishes (parrotfish). Moreover, uncontrolled growth of algae interrupts the growth of corals since corals and algae grow together on algal turf. Here Parrotfish also play an important role in the enhancement of corals by grazing. In this paper, parrotfish and P-volitans are taken as prey and predator, respectively, and the fear effect on the dynamics of the system is investigated. The effect of prey refuge is also shown. Constant harvesting policy for both fishes is included. Stable coexistence region for two parameter spaces: Hopf bifurcation and saddle-node bifurcation, is shown and formulated for the system. Numerical simulations are illustrated to verify the authenticity of the analytical calculations.
Biotic life below water entails life in oceans, seas, rivers, estuaries, lakes, and other bodies that store water and this biotic life below water comprises organisms, both big and small, ranging from large fish, mammals, reptiles, and other tiny species. The marine life is threatened by both environmental and anthropogenic stressors. Ocean warming, acidification, deoxygenation, sea-level rise are the major components of environmental stressors; and anthropogenic stressors include plastic pollution, oil-spills, overfishing, greenhouse gases, etc. Besides, there are land-based pollution sources. In order to sustain life below water, ecosystem-based management (EBM) is suggested to overcome environmental and anthropogenic stressors.
Environmental change is multidimensional, with local anthropogenic stressors and global climate change interacting to differentially impact populations throughout a species’ geographic range. Within species, the spatial distribution of phenotypic variation and its causes (i.e. local adaptation or plasticity) will determine species’ adaptive capacity to respond to a changing environment. However, comparatively little is known about the spatial scale of adaptive differentiation among populations and how patterns of local adaptation might drive vulnerability to global change stressors. To test whether fine-scale (2 - 12 km) mosaics of environmental stress can cause adaptive differentiation in a marine foundation species, eelgrass (Zostera marina), we conducted a three-way reciprocal transplant experiment spanning the length of Tomales Bay, CA. Our results revealed strong home-site advantage in growth and survival for all three populations. In subsequent common garden experiments and feeding assays we show that counter-gradients in temperature, light availability, and grazing pressure from an introduced herbivore contribute to differential performance among populations consistent with local adaptation. Our findings highlight how local-scale mosaics in environmental stressors can increase phenotypic variation among neighboring populations, potentially increasing species resilience to future global change. More specifically, we identified a range-center eelgrass population that is pre-adapted to extremely warm temperatures similar to those experienced by low-latitude range-edge populations of eelgrass, demonstrating how reservoirs of heat-tolerant phenotypes may already exist throughout a species range. Future work on predicting species resilience to global change should incorporate potential buffering effects of local-scale population differentiation and promote a phenotypic management approach to species conservation.
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Ocean warming, fueled by climate change, is the primary cause of coral bleaching events which are predicted to increase in frequency. Bleaching is generally damaging to coral reproduction, can be exacerbated by concomitant stressors like ultraviolet radiation (UVR), and can have lasting impacts to successful reproduction and potential adaptation. We compared morphological and physiological reproductive metrics (e.g., sperm motility, mitochondrial membrane integrity, egg volume, gametes per bundle, and fertilization and settlement success) of two Hawaiian Montipora corals after consecutive bleaching events in 2014 and 2015. Between the species, sperm motility and mitochondrial membrane potential had the most disparate results. Percent sperm motility in M. capitata , which declined to ~ 40% during bleaching from a normal range of 70–90%, was still less than 50% motile in 2017 and 2018 and had not fully recovered in 2019 (63% motile). By contrast, percent sperm motility in Montipora spp . was 86% and 74% in 2018 and 2019, respectively. This reduction in motility was correlated with damage to mitochondria in M. capitata but not Montipora spp . A major difference between these species is the physiological foundation of their UVR protection, and we hypothesize that UVR protective mechanisms inherent in Montipora spp . mitigate this reproductive damage.
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Different human expectations and environmental ethics are key factors preventing the creation of marine reserve networks. People are skeptical about the benefits of no-take marine reserves because they have adjusted to scarcity and have low expectations about the productive capability of marine ecosystems. Pauly (1995) described this as a shifting baseline in which each generation sets its expectations based on its direct experiences and discounts experiences of previous generations. I show evidence of a declining Caribbean baseline based on Nassau grouper landings from Cuba and the U.S., and review common and often conflicting types of conservation ethics existing in North America. No-take marine reserves can help reestablish human expectations about resource productivity by restoring past conditions in places. Leopold’s biotic ethic provides a framework for achieving sustainable resource use based on laws of ecology and human self-interest. Because changing expectations usually requires direct local experience, education, and changes in conservation ethics, implementing successful marine reserve networks will probably be a slow, incremental process. Establishing no-take reserves can help restore human expectations and provide a common basis for conservation by providing a window to the past and a vision for the future.
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A comparison between the northwestern Hawaiian islands (NWHI), a large, remote, and lightly fished area, and the main Hawaiian islands (MHI), an urbanized, heavily fished area, revealed dramatic differences in the numerical density, size, and biomass of the shallow reef fish assemblages. Grand mean fish standing stock in the NWHI was more than 260% greater than in the MHI. The most striking difference was the abundance and size of large apex predators (primarily sharks and jacks) in the NWHI compared to the MHI. More than 54% of the total fish biomass in the NWHI consisted of apex predators, whereas this trophic level accounted for less than 3% of the fish biomass in the MHI. In contrast, fish biomass in the MHI was dominated by herbivores (55%) and small-bodied lower-level carnivores (42%). Most of the dominant species by weight in the NWHI were either rare or absent in the MHI and the target species that were present, regardless of trophic level, were nearly always larger in the NWHI, These differences represent both near-extirpation of apex predators and heavy exploitation of lower trophic levels in the MHI compared to the largely unfished NWHI. The reefs in the NWHI are among the few remaining large-scale, intact, predator-dominated reef ecosystems left in the world and offer an opportunity to understand how unaltered ecosystems are structured, how they function, and how they can most effectively be preserved. The differences in fish assemblage structure in this study are evidence of the high level of exploitation in the MHI and the pressing need for ecosystem-level management of reef systems in the MHI as well as the NWHI.
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Biological diversity appears to enhance the resilience of desirable ecosystem states, which is required to secure the production of essential ecosystem services. The diversity of responses to environmental change among species contributing to the same ecosystem function, which we call response diversity, is critical to resilience. Response diversity is particularly important for ecosystem renewal and reorganization following change. Here we present examples of response diversity from both terrestrial and aquatic ecosystems and across temporal and spatial scales. Response diversity provides adaptive capacity in a world of complex systems, uncertainty, and human-dominated environments. We should pay special attention to response diversity when planning ecosystem management and restoration, since it may contribute considerably to the resilience of desired ecosystem states against disturbance, mismanagement, and degradation.
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History shows that Caribbean coastal ecosystems were severely degraded long before ecologists began to study them. Large vertebrates such as the green turtle, hawksbill turtle, manatee and extinct Caribbean monk seal were decimated by about 1800 in the central and northern Caribbean, and by 1990 elsewhere. Subsistence over-fishing subsequently decimated reef fish populations. Local fisheries accounted for a small fraction of the fish consumed on Caribbean islands by about the mid nineteenth century when human populations were less than one fifth their numbers today. Herbivores and predators were reduced to very small fishes and sea urchins by the 1950s when intensive scientific investigations began. These small consumers, most notably Diadema antillarum, were apparently always very abundant; contrary to speculation that their abundance had increased many-fold due to overfishing. Studying grazing and predation on reefs today is like trying to understand the ecology of the Serengeti by studying the termites and the locusts while ignoring the elephants and the wildebeeste. Green turtles, hawksbill turtles and manatees were almost certainly comparably important keystone species on reefs and seagrass beds. Small fishes and invertebrates feed very differently from turtles and manatees and could and can not compensate for their loss, despite their great abundance long before overfishing began. Loss of megavertebrates dramatically reduced and qualitatively changed grazing and excavation of seagrasses, predation on sponges, loss of production to adjacent ecosystems, and the structure of food chains. Megavertebrates are critical for reef conservation and, unlike land, there are no coral reef livestock to take their place.
BERLIN-- Edelgard Bulmahn has been a major force in German science and higher education since becoming research minister in 1998. She has proposed an overhaul of Germany's university rules--seeking merit pay and "junior professorships" that would free young scientists to pursue independent research--that has polarized the academic community. In a 9 April interview with Science in her Berlin office, Bulmahn discussed these and other topics in laying out her vision for German research.
Coral reefs, with their millions of species, have changed profoundly because of the effects of people, and will continue to do so for the foreseeable future. Reefs are subject to many of the same processes that affect other human-dominated ecosystems, but some special features merit emphasis: (i) Many dominant reef builders spawn eggs and sperm into the water column, where fertilization occurs. They are thus particularly vulnerable to Allee effects, including potential extinction associated with chronic reproductive failure. (ii) The corals likely to be most resistant to the effects of habitat degradation are small, short-lived "weedy" corals that have limited dispersal capabilities at the larval stage. Habitat degradation, together with habitat fragmentation, will therefore lead to the establishment of genetically isolated clusters of inbreeding corals. (iii) Increases in average sea temperatures by as little as 1 degrees C, a likely result of global climate change, can cause coral "bleaching" (the breakdown of coral-algal symbiosis), changes in symbiont communities, and coral death. (iv) The activities of people near reefs increase both fishing pressure and nutrient inputs. In general, these processes favor more rapidly growing competitors, often fleshy seaweeds, and may also result in explosions of predator populations. (v) Combinations of stress appear to be associated with threshold responses and ecological surprises, including devastating pathogen outbreaks. (vi) The fossil record suggests that corals as a group are more likely to suffer extinctions than some of the groups that associate with them, whose habitat requirements may be less stringent.