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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
... . Excessive macroalgae growth due to overfishing, eutrophication, or loss of key reef herbivores can inhibit coral recruitment and the ability of reefs to recover from disturbance [37,38]. Tropical storms and hurricanes have always impacted reefs, but these events may be increasing in strength or frequency as a result of a changing climate [39]. ...
... Herbivory, macroalgal abundance, and predation. The detrimental effects of macroalgal occupation on potential recruitment and growth of corals has been well recognized [37,38]. Urchins and damselfish are important herbivores that feed on the algae that covers reef framework, and serve as a critical control on macroalgal abundance [3,51]. ...
Full-text available
Live coral cover has declined precipitously on Caribbean reefs in recent decades. Acropora cervicornis coral has been particularly decimated, and few Western Atlantic Acropora spp. refugia remain. Coral Gardens, Belize, was identified in 2020 as a long-term refugium for this species. This study assesses changes in live A. cervicornis coral abundance over time at Coral Gardens to monitor the stability of A. cervicornis corals, and to explore potential threats to this important refugium. Live coral cover was documented annually from 2012-2019 along five permanent transects. In situ sea-surface temperature data were collected at Coral Gardens throughout the study period and compared with calibrated satellite data to calculate Maximum Monthly Mean (MMM) temperatures and Degree Heating Weeks (DHW). Data on bathymetry, sediment, substrate, herbivore abundance, and macroalgal abundance were collected in 2014 and 2019 to assess potential threats to Coral Gardens. Live coral cover declined at all five transect sites over the study period. The greatest loss of live coral occurred between 2016 and 2017, coincident with the earliest and highest maximum average temperatures recorded at the study site, and the passage of a hurricane in 2016. Structural storm damage was not observed at Coral Gardens, though live coral cover declined after the passage of the storm. Uranium-thorium (230Th) dating of 26 dead in situ fragments of A. cervicornis collected in 2015 from Coral Gardens revealed no correlation between coral mortality and tropical storms and hurricanes in the recent past. Our data suggest that several other common drivers for coral decline (i.e. herbivory, predation, sedimentation, pH) may likely be ruled out for Coral Gardens. At the end of the study period, Coral Gardens satisfied most criteria for refugium status. However, the early onset, higher mean, and longer duration of above-average temperatures, as well as intermittent temperature anomalies likely played a critical role in the stability of this refugium. We suggest that temperature stress in 2016 and perhaps 2015 may have increased coral tissue vulnerability at Coral Gardens to a passing hurricane, threatening the status of this unique refugium.
... On coral reefs, living coral cover has declined globally by half since the 1950s (Eddy et al., 2021), and the decline has been even more precipitous in the Caribbean (Gardner et al., 2003). While some studies projected the collapse of reef ecosystems (Pandolfi et al., 2005), other analyses hypothesize that coral reefs will change rather than disappear completely (Hughes et al., 2003;Pandolfi et al., 2011). In this latter view, variability in physiological responses to temperature, acidification and nutrients, as well as rates of adaptation to warming, will drive spatial heterogeneity in the degradation of coral reefs (Pandolfi et al., 2011). ...
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The three‐dimensional structure of habitats is a critical component of species' niches driving coexistence in species‐rich ecosystems. However, its influence on structuring and partitioning recruitment niches has not been widely addressed. We developed a new method to combine species distribution modelling and structure from motion, and characterized three‐dimensional recruitment niches of two ecosystem engineers on Caribbean coral reefs, scleractinian corals and gorgonians. Fine‐scale roughness was the most important predictor of suitable habitat for both taxa, and their niches largely overlapped, primarily due to scleractinians' broader niche breadth. Crevices and holes at mm scales on calcareous rock with low coral cover were more suitable for octocorals than for scleractinian recruits, suggesting that the decline in scleractinian corals is facilitating the recruitment of octocorals on contemporary Caribbean reefs. However, the relative abundances of the taxa were independent of the amount of suitable habitat on the reef, emphasizing that niche processes alone do not predict recruitment rates.
... Impacts of climate change may depend critically on the extent to which a reef is already degraded. Restoring food webs and controlling nutrient runoff from agricultural lots to avoid bacterial blooms provides a first line of defense against the ecological impacts of climate change; however, slowing or reversing global warming trends is essential for the long-term health of all tropical coral reefs (Pandolfi et al. 2005). Post-Cyclone Thomas, and because of concerns raised by climate fluctuations and species extinction, management programs such as the one described above might become a reality in Nayau in the future. ...
... Environmental and ecological conditions can direct the succession of a reef towards alternate stable states (Smith et al., 2010). Under current environmental conditions, many coral reefs tend to follow a successional trajectory that favors the dominance of algae and other organisms that inhibit the recruitment and growth of corals (Pandolfi et al., 2005;Rinkevich, 2005). Coral restoration through transplantation is an increasingly common intervention that is used to accelerate the process of succession to favor the growth and persistence of coral reefs. ...
Full-text available
Introduction: Ecosystem restoration facilitates ecological succession. When a coral reef experiences a disturbance, the community of sessile benthic organisms can follow a successional trajectory that favors the dominance of coral or a change of state to an ecosystem dominated by algae. Objective: To better understand the impact of coral transplants on succession of the sessile benthic community. Methods: To measure and monitor the coral cover (cm²) of Pocillopora spp., and the composition of the associated benthic community, experimental and control coral reef patches were established at the coral restoration site in Golfo Dulce, South Pacific Costa Rica. Thirty Pocillopora spp. colonies were attached to nails on the substrate in an experimental patch. The control coral patch contained nails with non-transplanted colonies. Both treatments were photographed monthly during a period of eight months. Changes in the coverage of coral and other sessile benthic organisms were measured from the images and compared over time between the experimental and control patches. Results: The coral transplants experienced bleaching events in August through September 2019 and January through February 2020. The first bleaching event possibly due to sedimentation, and the second to high temperatures. By the end of the experiment, 83 % of the colonies had survived. The live colonies grew significantly following transplantation; > 67 % of their initial coverage area after eight months. In the experimental patch, the areas of Pocillopora spp., coralline crustose algae (CCA), and cyanobacteria increased while the area of algal turf decreased. The increase in coral coverage and CCA, and decrease in algal turf in the experimental patch could be due to herbivores attracted to transplants. The increase in cyanobacteria in the experimental patch could be the result of higher temperatures and may have been a factor in the death of colonies. Conclusions: The transplantation of Pocillopora spp. colonies in Golfo Dulce changed the early successional trajectory of the sessile benthic community to favor the dominance of coral dominance in the experimental patch. These results may be useful in informing expectations for future restoration efforts.
... Florida's Coral Reef (also known as the Florida reef tract) provides an excellent case of a well-studied reef where major efforts are underway to protect its ecosystem services (Pandolfi et al., 2005;Riegl & Dodge, 2008;Walker & Gilliam, 2013;Lirman et al., 2019). It is threatened by a wide range of stressors (e.g. ...
Coral reef fish assemblages are threatened globally, underscoring the need for data‐driven management to reduce threats and restore populations. Comparing fishery management approaches is aided by a detailed understanding of the key factors controlling species’ abundances. The aims of this study were to assess the importance of biophysical factors compared with fishing impacts on the biomass of reef fishes on Florida’s Coral Reef and to evaluate the potential effects of common management interventions on fish biomass. Fishing impact was estimated using a fishery‐independent modelling approach and the biomass of the snapper–grouper complex as a proxy for the effects of fishing. Using a separate subset of data from underwater fish surveys, estimated fishing impact was then combined with 18 biophysical variables to model the current biomass of all reef fish species, the snapper–grouper complex, grazing species and species collected for aquaria. Models explained between 51 and 64% of the variance in fish biomass for the fish groups. The strongest predictor of biomass in the snapper–grouper complex was fishing impact (accounting for 25.2% of the explained variance), whereas reef complexity was the strongest predictor for all other groups. High‐resolution maps were produced from the statistical models, including maps of current fish biomass and maps of potential biomass under several management scenarios: a no‐take marine reserve, moderate and extensive coral restoration and the addition of artificial benthic structure. Adding structure had the largest single impact on predicted fish biomass (23–72% increase from current estimated levels). However, beneficial synergies emerged when combining habitat‐based management and fishing closures, with some combinations resulting in a reef‐wide averaged 89% increase in biomass relative to current estimated levels. The results suggest that conservation strategies aimed at protecting and increasing structural reef complexity should be an important part of fishery management discussions.
... The cause of this coral decline has been linked to numerous sources including disease outbreaks, thermal stress, ocean acidification, and overfishing from reefs (Jackson et al. 2001;Pandolfi et al. 2003;Hughes et al. 2003;Harborne et al. 2017). Not only have established coral colonies been declining but coral settlement has been inhibited by the rapid proliferation of macroalgal species (Pandolfi et al. 2005;Steneck et al. 2018). This shift from a hard coraldominated reef to an algal-dominated reef has been exacerbated by the loss of reef herbivores including sea urchins and parrotfishes due to disease and overfishing, respectively (Jackson et al. 2014). ...
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Stoplight parrotfish, Sparisoma viride, are hermaphroditic fish that exhibit a complex social structure in which terminal phase (TP) males control a territory of initial phase (IP) individuals (mostly female, rarely male) called a harem. These fish are prolific herbivores that maintain the health of coral reefs by consuming or removing algae that competes with coral for space. In this study, we estimate the influence of food availability, structural complexity, and conspecific density on territory size in S. viride TP males on reef sites in the middle Florida Keys. Divers estimated the territory sizes of both TP and IP individuals by following fish and dropping markers. Divers also estimated the substrate composition, conspecific density, and physical complexity around these territories. TP territories were roughly circular and only overlapped with IP individuals on the outer edges of the TP territory, resulting in TP territories being significantly larger. While TP territory size was positively influenced by the body size of the TP male and negatively influenced by the number of IP individuals, the average ratio of IP:TP individuals was 2.99:1 (± 0.31 SE, range 1–12) for each TP territory regardless of body size. These results suggest that TP males adjust their territory sizes to maintain an apparent optima for the number of females within harems and that the density of conspecifics can potentially influence the timing of sexual transitions in these fish. These results also suggest that S. viride have a polygynous mating structure that is driven by female defense rather than resource defense.
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Dal Lake is not only the centre of tourist attraction, but also an important livelihood source for the local population. The economic activities over the years in and around the lake have intensified, resulting in pollution, eutrophication and encroachment of the lake. The present study examined the multiple economic activities carried out on Dal Lake, estimated the net welfare generated, and subsequently developed a solution focusing on establishing an optimal trade‐off between the economic activities and pollution abatement expenditures incurred by the government. Employing optimization techniques, needed modifications in the configuration of the enterprises and the pollution abatement costs that could maximize the net welfare from Dal Lake were identified. The economic welfare of the three enterprises was maximized at the optimal level of INR 5684.85 million, with a pollution‐abating investment of INR 13.21 million.
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One mechanism giving fleshy algae a competitive advantage over corals during reef degradation is algal-induced and microbially-mediated hypoxia (typically less than 69.5 µmol oxygen L ⁻¹ ). During hypoxic conditions oxygen availability becomes insufficient to sustain aerobic respiration in most metazoans. Algae are more tolerant of low oxygen conditions and may outcompete corals weakened by hypoxia. A key question on the ecological importance of this mechanism remains unanswered: How extensive are local hypoxic zones in highly turbulent aquatic environments, continuously flushed by currents and wave surge? To better understand the concert of biological, chemical, and physical factors that determine the abundance and distribution of oxygen in this environment, we combined 3D imagery, flow measurements, macro- and micro-organismal abundance estimates, and experimentally determined biogenic oxygen and carbon fluxes as input values for a 3D bio-physical model. The model was first developed and verified for controlled flume experiments containing coral and algal colonies in direct interaction. We then developed a three-dimensional numerical model of an existing coral reef plot off the coast of Curaçao where oxygen concentrations for comparison were collected in a small-scale grid using fiberoptic oxygen optodes. Oxygen distribution patterns given by the model were a good predictor for in situ concentrations and indicate widespread localized differences exceeding 50 µmol L ⁻¹ over distances less than a decimeter. This suggests that small-scale hypoxic zones can persist for an extended period of time in the turbulent environment of a wave- and surge- exposed coral reef. This work highlights how the combination of three-dimensional imagery, biogenic fluxes, and fluid dynamic modeling can provide a powerful tool to illustrate and predict the distribution of analytes (e.g., oxygen or other bioactive substances) in a highly complex system.
Surfing has increased in cultural, social, and economic importance through the last century and is now globally significant. Predicated on the natural phenomenon of ocean waves interacting with coasts, surfing’s future is threatened by Earth’s changing climate. This paper provides a comprehensive review of physical processes, including swell generation, wave breaking, and coastal dynamics, relevant for the locations — surf breaks — where surfing occurs and the myriad mechanisms through which each can be affected by a changing climate. We propose an organizing framework for these impacts characterizing them based on their mode of action as direct versus indirect, as well as by their magnitude, and conclude that some impacts (such as sea level rise) may threaten some breaks but on more protracted timelines, whereas other impacts (such as coastal armoring implemented in response to climate change) may pose more immediate, existential threats. This framework underscores the importance of local environmental knowledge of a given surf break for understanding its susceptibility to climate change and informs a Surf Break Vulnerability–Climate Change Assessment Tool (SurfCAT), designed to enable improved wave stewardship by local resource managers and stakeholders in the face of a changing climate.
Coral reefs have experienced a profound shift in community structure in recent decades, a pattern that contrasts with the apparent constancy of Caribbean reef zonation over the past 2 million years. The abrupt decline in branching Acropora palmata and massive frame-builders like Montastrea annularis in the Caribbean is troubling, and similar patterns have been reported from virtually every ocean. As we ponder the future of coral reefs, we must be mindful that our best monitoring records span perhaps half a century – and those are exceedingly rare. “Pristine” reefs may not have existed since Columbus sailed for the new world, and anthropogenic impacts probably extend even farther back in time. Despite the vagaries of evolutionary change, taphonomy and time averaging, the geologic record still represents a unique source of important information about the processes that have controlled community structure and reef building in the absence of human influences. The creation of rigid and elevated structures requires calcification rates that are capable of filling the accommodation space created by rising sea level. This has been complicated over the past three to four decades as accelerated sea-level rise has been joined by a suite of stresses that probably slow accretion. Explaining the recent reef decline and posing realistic models of future change will require an understanding of carbonate cycling in the past, the processes that have been involved and a quantitative assessment of how anthropogenic stresses are affecting both. At the least a look back in time may help to constrain the thresholds at which change might be expected to occur in the future. At best, the context gained from examining the “recent” geological past may provide insights into which possible solutions are most consistent with observed patterns at larger spatial and temporal scales.
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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.