Sea cucumbers secrete acidic compounds that may be weakening the structure of the coral communities in which they live.
The main component of a coral reef is calcium carbonate (CaCO3), a mineral that makes up the corals and much of the sand and rubble around them. Many of the organisms living on the reef either add to or absorb CaCO3 from the surrounding environment. In a healthy reef this would be in balance, but when the calcium carbonate is out of whack, the reef may be unhealthy and could cease to grow.
The researchers studied a part of Australia's Great Barrier Reef known as One Tree Reef. In one specific area, called DK13, they found lots of sea cucumbers. They collected these squishy animals and studied them in the lab.
Read more at:
http://www.livescience.com/17692-digestive-acts-sea-cucumbers-dissolving-coral-reefs.html
Showing posts with label coral reefs. Show all posts
Showing posts with label coral reefs. Show all posts
Sunday, January 1, 2012
Monday, December 26, 2011
Are coral reefs being dissolved by sea cucumbers?
Sea cucumbers: Dissolving coral reefs?
Washington, D.C. — Coral reefs are extremely diverse ecosystems that support enormous biodiversity. But they are at risk. Carbon dioxide emissions are acidifying the ocean, threatening reefs and other marine organisms. New research led by Carnegie's Kenneth Schneider analyzed the role of sea cucumbers in portions of the Great Barrier Reef and determined that their dietary process of dissolving calcium carbonate (CaCO3) from the surrounding reef accounts for about half of at the total nighttime dissolution for the reef. The work is published December 23 by the Journal of Geophysical Research.
Reefs are formed through the biological deposition of calcium carbonate (CaCO3). Many of the marine organisms living on and around a reef contribute to either its destruction or construction. Therefore it is crucial that the amount of calcium carbonate remain in balance. When this delicate balance is disrupted, the reef ceases to grow and its foundations can be weakened.
In order to fully understand a reef's ability to deposit carbonate and grow, it is necessary to understand the roles that the various elements of sea life play in this process. This is especially important because increased atmospheric carbon dioxide is predicted to decrease the amount of carbonate available due to acidification.
The research group set out to examine the role that sea cucumbers play in the reef environment.
Schneider's team included Carnegie's Ken Caldeira, as well as Jacob Silverman, of the Israeli Limnology and Oceanography Institute; Maria Byrne and Erika Woolsey, both of the University of Sydney and the latter also from James Cook University; and Hampus Eriksson of Stockholm University.
They studied the growth and dissolution of One Tree Reef, which surrounds One Tree Island in Australia's Great Barrier Reef. Focusing on an area of the reef known as "DK13", they found that sea cucumbers were abundant. They collected some of these sea cucumbers and placed them in aquaria to study the effect on sea water resulting from the sand and rubble transported through their gut system as part of their digestive process.
As part of another ongoing study in this area, the team found that the coral reef was dissolving at night. They found that sea cucumbers play a crucial part in this process. They live off the bits of organic matter in the carbonate sand and rubble that they ingest; in this process, their digestive systems produce acids that dissolve parts of these carbonate minerals. The dissolved carbonate minerals are then released into the surrounding environment. The researchers found that these lowly organisms might be responsible for half of the CaCO3 of the reef observed at night.
The burning of coal, oil, and gas releases CO2 into the atmosphere, which is later absorbed by the ocean, causing the ocean to acidify. Ocean acidification is expected to slow reef growth. With slower reef growth, the dissolution of CaCO3 within the guts of sea cucumbers is expected to become even more important to the reef CaCO3 budget.
"Even though the sea cucumbers dissolve CaCO3 on the reef, in a lagoon such as the one at One Tree Reef, where there is limited seawater exchange with the surrounding ocean, they can be important in recycling of nutrients to support primary productivity. They also increase sea water buffer capacity to partially offset ocean acidification effects, helping to maintain the overall health of the coral reef," Schneider said. "Although sea cucumbers may play a part in reef dissolution, they are also an important part of an incredible marine environment."
This research was supported by the Moore foundation. The authors thank the University of Sydney's One Tree Island Research Station facility.
The Department of Global Ecology was established in 2002 to help build the scientific foundations for a sustainable future. The department is located on the campus of Stanford University, but is an independent research organization funded by the Carnegie Institution. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.
The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
http://www.eurekalert.org/pub_releases/2011-12/ci-scd122211.php
Washington, D.C. — Coral reefs are extremely diverse ecosystems that support enormous biodiversity. But they are at risk. Carbon dioxide emissions are acidifying the ocean, threatening reefs and other marine organisms. New research led by Carnegie's Kenneth Schneider analyzed the role of sea cucumbers in portions of the Great Barrier Reef and determined that their dietary process of dissolving calcium carbonate (CaCO3) from the surrounding reef accounts for about half of at the total nighttime dissolution for the reef. The work is published December 23 by the Journal of Geophysical Research.
Reefs are formed through the biological deposition of calcium carbonate (CaCO3). Many of the marine organisms living on and around a reef contribute to either its destruction or construction. Therefore it is crucial that the amount of calcium carbonate remain in balance. When this delicate balance is disrupted, the reef ceases to grow and its foundations can be weakened.
In order to fully understand a reef's ability to deposit carbonate and grow, it is necessary to understand the roles that the various elements of sea life play in this process. This is especially important because increased atmospheric carbon dioxide is predicted to decrease the amount of carbonate available due to acidification.
The research group set out to examine the role that sea cucumbers play in the reef environment.
Schneider's team included Carnegie's Ken Caldeira, as well as Jacob Silverman, of the Israeli Limnology and Oceanography Institute; Maria Byrne and Erika Woolsey, both of the University of Sydney and the latter also from James Cook University; and Hampus Eriksson of Stockholm University.
They studied the growth and dissolution of One Tree Reef, which surrounds One Tree Island in Australia's Great Barrier Reef. Focusing on an area of the reef known as "DK13", they found that sea cucumbers were abundant. They collected some of these sea cucumbers and placed them in aquaria to study the effect on sea water resulting from the sand and rubble transported through their gut system as part of their digestive process.
As part of another ongoing study in this area, the team found that the coral reef was dissolving at night. They found that sea cucumbers play a crucial part in this process. They live off the bits of organic matter in the carbonate sand and rubble that they ingest; in this process, their digestive systems produce acids that dissolve parts of these carbonate minerals. The dissolved carbonate minerals are then released into the surrounding environment. The researchers found that these lowly organisms might be responsible for half of the CaCO3 of the reef observed at night.
The burning of coal, oil, and gas releases CO2 into the atmosphere, which is later absorbed by the ocean, causing the ocean to acidify. Ocean acidification is expected to slow reef growth. With slower reef growth, the dissolution of CaCO3 within the guts of sea cucumbers is expected to become even more important to the reef CaCO3 budget.
"Even though the sea cucumbers dissolve CaCO3 on the reef, in a lagoon such as the one at One Tree Reef, where there is limited seawater exchange with the surrounding ocean, they can be important in recycling of nutrients to support primary productivity. They also increase sea water buffer capacity to partially offset ocean acidification effects, helping to maintain the overall health of the coral reef," Schneider said. "Although sea cucumbers may play a part in reef dissolution, they are also an important part of an incredible marine environment."
This research was supported by the Moore foundation. The authors thank the University of Sydney's One Tree Island Research Station facility.
The Department of Global Ecology was established in 2002 to help build the scientific foundations for a sustainable future. The department is located on the campus of Stanford University, but is an independent research organization funded by the Carnegie Institution. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.
The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
http://www.eurekalert.org/pub_releases/2011-12/ci-scd122211.php
Monday, October 3, 2011
Coral reef collapse: eight warning signs
Research gives clues to predict problems
September 2011: Coral reefs that have lots of corals and appear healthy may, in fact, be heading toward collapse, according to a study published by the Wildlife Conservation Society.
Using data from coral reef systems across the western Indian Ocean, an international team of researchers identified how overfishing creates a series of at least eight big changes on reefs that precipitate a final collapse. This information can help managers gauge the health of a reef and tell them when to restrict fishing in order to avoid a collapse of the ecosystem and fishery.
The authors say these changes are like a series of light switches, each of which make the reef more degraded and dims the chances of sustained fishery production and recovery.
When the ecological lights go off‘The study identifies eight changes before all of the ecological lights go off and the reef and fishery are gone,' said Dr McClanahan, the lead author on the study and the head of WCS's coral reef research and conservation programme.
The study shows that in well-protected areas, there are typically 1,000 to 1,500kg of reef fish of various species per hectare of coral reef. As the volume is fished down below 1,000kg, the early warning signs - such as increased seaweed growth and urchin activity - begin to appear. The researchers found that between 300-600 kg per hectare, there appeared to be a ‘window' of what is known as maximum sustainable yield, but when the fish stock drops below 300kg per hectare, the reef is in real trouble, they said.
Overfished reefs can appear healthy‘Below 300kg per hectare we see a series of dramatic changes on reefs. This is where you get on a real slippery slope,' McClanahan noted. ‘Strangely, the metric used by most managers to gauge the health of reef system - coral cover - is the last threshold before ecosystem failure. Overfished reefs can appear healthy and then shift to algae dominated seascapes.'
The authors recommend measuring the biomass of fish instead of coral cover to identify the early warning rather than the final sign of reef collapse.
‘The good news is that a reef can likely provide sustainable fisheries even after the first three warning switches are turned off, but it becomes increasingly difficult to maintain a healthy fishery and restore reefs when the final five switches have been turned off,' said Dr McClanahan. ‘This study provides managers and policy makers with a tangible target of where to maintain their fishery.'
People depend on reefs for their livelihoodsReef fisheries with no regulations tended to perform poorly, with some passing all the switches and completely collapsing. No-take marine reserves, where fishing was prohibited, were the best performers and tended to maintain key ecosystem processes such as predation.
‘People depend on reefs for their livelihoods, so we can't prohibit fishing everywhere,' noted Dr Joshua Cinner from James Cook University in Australia. ‘A key finding from our study was that even easily enforceable regulations that restrict gear or the types of species that can be caught helped maintain biomass. These regulations are often more agreeable to fishermen than no-take closures and consequently receive higher levels of support and compliance.'
‘There is no one size fits all solution to save the world's coral reef ecosystems. To be politically and socially sustainable, tangible and objective management targets are critical to help managers make difficult near-term decisions of restricting or altering fishing practices for long-term social and ecological gain,' said Dr Caleb McClennen, director of WCS's marine programme. http://www.wildlifeextra.com/go/news/coral-collapse.html
September 2011: Coral reefs that have lots of corals and appear healthy may, in fact, be heading toward collapse, according to a study published by the Wildlife Conservation Society.
Using data from coral reef systems across the western Indian Ocean, an international team of researchers identified how overfishing creates a series of at least eight big changes on reefs that precipitate a final collapse. This information can help managers gauge the health of a reef and tell them when to restrict fishing in order to avoid a collapse of the ecosystem and fishery.
The authors say these changes are like a series of light switches, each of which make the reef more degraded and dims the chances of sustained fishery production and recovery.
When the ecological lights go off‘The study identifies eight changes before all of the ecological lights go off and the reef and fishery are gone,' said Dr McClanahan, the lead author on the study and the head of WCS's coral reef research and conservation programme.
The study shows that in well-protected areas, there are typically 1,000 to 1,500kg of reef fish of various species per hectare of coral reef. As the volume is fished down below 1,000kg, the early warning signs - such as increased seaweed growth and urchin activity - begin to appear. The researchers found that between 300-600 kg per hectare, there appeared to be a ‘window' of what is known as maximum sustainable yield, but when the fish stock drops below 300kg per hectare, the reef is in real trouble, they said.
Overfished reefs can appear healthy‘Below 300kg per hectare we see a series of dramatic changes on reefs. This is where you get on a real slippery slope,' McClanahan noted. ‘Strangely, the metric used by most managers to gauge the health of reef system - coral cover - is the last threshold before ecosystem failure. Overfished reefs can appear healthy and then shift to algae dominated seascapes.'
The authors recommend measuring the biomass of fish instead of coral cover to identify the early warning rather than the final sign of reef collapse.
‘The good news is that a reef can likely provide sustainable fisheries even after the first three warning switches are turned off, but it becomes increasingly difficult to maintain a healthy fishery and restore reefs when the final five switches have been turned off,' said Dr McClanahan. ‘This study provides managers and policy makers with a tangible target of where to maintain their fishery.'
People depend on reefs for their livelihoodsReef fisheries with no regulations tended to perform poorly, with some passing all the switches and completely collapsing. No-take marine reserves, where fishing was prohibited, were the best performers and tended to maintain key ecosystem processes such as predation.
‘People depend on reefs for their livelihoods, so we can't prohibit fishing everywhere,' noted Dr Joshua Cinner from James Cook University in Australia. ‘A key finding from our study was that even easily enforceable regulations that restrict gear or the types of species that can be caught helped maintain biomass. These regulations are often more agreeable to fishermen than no-take closures and consequently receive higher levels of support and compliance.'
‘There is no one size fits all solution to save the world's coral reef ecosystems. To be politically and socially sustainable, tangible and objective management targets are critical to help managers make difficult near-term decisions of restricting or altering fishing practices for long-term social and ecological gain,' said Dr Caleb McClennen, director of WCS's marine programme. http://www.wildlifeextra.com/go/news/coral-collapse.html
Wednesday, September 21, 2011
Captive Breeding Could Transform the Saltwater Aquarium Trade and Save Coral Reefs, Biologists Say
ScienceDaily (Sep. 20, 2011) — Marine biologists at The University of Texas at Austin Marine Science Institute are developing means to efficiently breed saltwater aquarium fish, seahorses, plankton and invertebrates in captivity in order to preserve the biologically rich ecosystems of the world's coral reefs.
These scientists believe their efforts, and those of colleagues around the world, could help shift much of the $1 billion marine ornamental industry toward entrepreneurs who are working sustainably to raise fish for the aquarium trade.
"It's the kind of thing that could transform the industry in the way that the idea of 'organic' has changed the way people grow and buy fruits and vegetables," says Joan Holt, professor and associate chair of marine science at The University of Texas at Austin. "We want enthusiasts to be able to stock their saltwater tanks with sustainably-raised, coral-safe species."
Holt is a co-author of a recent article, "Advances in Breeding and Rearing Marine Ornamentals," published in the Journal of the World Aquaculture Society in April.
The paper is a complement to Holt's broad-ranging work over the past 10 years to promote captive breeding of ornamentals. She's been a pioneer in developing food sources and tank designs that enable fragile larvae to survive to adulthood.
Holt has also been a vocal critic of the extraordinarily wasteful methods currently used to bring sea creatures from the oceans to the tanks.
"One popular method is to use a cyanide solution," says Holt. "It's squirted into the holes and crevices of the reef and it anesthetizes the fish. They float to the surface. Then the collectors can just scoop them up, and the ones that wake up are shipped out."
This method, says Holt, has a number of unfortunate effects. It bleaches the coral. It kills or harms other species that make the coral their home, particularly those that can't swim away from the cyanide. It can deplete or distort the native populations of the species. And it contributes to 80 percent of traded animals dying before ever reaching a tank.
Unlike the freshwater ornamental market, which relies mostly on fish raised in captivity, the saltwater ornamental market is 99.9 percent wild caught. Holt says this is largely because there's less accumulated knowledge on breeding saltwater fish in captivity. Saltwater species also tend to spawn smaller, less robust larvae, which are harder to rear to maturity, and to rely on various foods, such as plankton, that are not readily available in mass quantities for breeders.
Yet all these difficulties, says Holt, are surmountable.
She and her colleagues in Port Aransas, where the Marine Science Institute is located, have successfully bred in captivity seven species of fish, seahorses and shrimp they've caught from the Gulf of Mexico and the Caribbean, including species that other biologists had tried but failed to rear before. Others have successfully bred popular species like clownfish, gobies, dottybacks, and dragonets, as well as coral, clams, invertebrates, and algae.
Several big aquariums, including SeaWorld, have committed to assisting in the breeding and egg collection effort, and to integrating into their exhibits information about how the aquarium trade impacts the coral reefs.
Holt and her colleagues envision, ultimately, is a "coral-safe" movement. The science, the economics and the social awareness could together result in a sea change in how saltwater aquariums are populated and how saltwater tank enthusiasts think of themselves and their passion.
As more tank-raised ornamentals percolate into the market, Holt believes people will see another advantage to buying sustainably. The fish will simply do better. They'll live longer, be healthier and be easier to care for.
"Species that are bred in captivity should adapt much better to your tank than something that was just caught halfway across the world, in a different system," says Holt. "Good retailers will want to sell these species, and consumers will benefit from buying them."
http://www.sciencedaily.com/releases/2011/09/110920121612.htm
These scientists believe their efforts, and those of colleagues around the world, could help shift much of the $1 billion marine ornamental industry toward entrepreneurs who are working sustainably to raise fish for the aquarium trade.
"It's the kind of thing that could transform the industry in the way that the idea of 'organic' has changed the way people grow and buy fruits and vegetables," says Joan Holt, professor and associate chair of marine science at The University of Texas at Austin. "We want enthusiasts to be able to stock their saltwater tanks with sustainably-raised, coral-safe species."
Holt is a co-author of a recent article, "Advances in Breeding and Rearing Marine Ornamentals," published in the Journal of the World Aquaculture Society in April.
The paper is a complement to Holt's broad-ranging work over the past 10 years to promote captive breeding of ornamentals. She's been a pioneer in developing food sources and tank designs that enable fragile larvae to survive to adulthood.
Holt has also been a vocal critic of the extraordinarily wasteful methods currently used to bring sea creatures from the oceans to the tanks.
"One popular method is to use a cyanide solution," says Holt. "It's squirted into the holes and crevices of the reef and it anesthetizes the fish. They float to the surface. Then the collectors can just scoop them up, and the ones that wake up are shipped out."
This method, says Holt, has a number of unfortunate effects. It bleaches the coral. It kills or harms other species that make the coral their home, particularly those that can't swim away from the cyanide. It can deplete or distort the native populations of the species. And it contributes to 80 percent of traded animals dying before ever reaching a tank.
Unlike the freshwater ornamental market, which relies mostly on fish raised in captivity, the saltwater ornamental market is 99.9 percent wild caught. Holt says this is largely because there's less accumulated knowledge on breeding saltwater fish in captivity. Saltwater species also tend to spawn smaller, less robust larvae, which are harder to rear to maturity, and to rely on various foods, such as plankton, that are not readily available in mass quantities for breeders.
Yet all these difficulties, says Holt, are surmountable.
She and her colleagues in Port Aransas, where the Marine Science Institute is located, have successfully bred in captivity seven species of fish, seahorses and shrimp they've caught from the Gulf of Mexico and the Caribbean, including species that other biologists had tried but failed to rear before. Others have successfully bred popular species like clownfish, gobies, dottybacks, and dragonets, as well as coral, clams, invertebrates, and algae.
Several big aquariums, including SeaWorld, have committed to assisting in the breeding and egg collection effort, and to integrating into their exhibits information about how the aquarium trade impacts the coral reefs.
Holt and her colleagues envision, ultimately, is a "coral-safe" movement. The science, the economics and the social awareness could together result in a sea change in how saltwater aquariums are populated and how saltwater tank enthusiasts think of themselves and their passion.
As more tank-raised ornamentals percolate into the market, Holt believes people will see another advantage to buying sustainably. The fish will simply do better. They'll live longer, be healthier and be easier to care for.
"Species that are bred in captivity should adapt much better to your tank than something that was just caught halfway across the world, in a different system," says Holt. "Good retailers will want to sell these species, and consumers will benefit from buying them."
http://www.sciencedaily.com/releases/2011/09/110920121612.htm
Saturday, August 27, 2011
Map highlights world’s most threatened coral reefs
Pinpoints places to focus conservation management August 2011: A map of the world's corals and their exposure to stress factors, including high temperatures, ultra-violet radiation, weather systems, sedimentation, as well as stress-reducing factors such as temperature variability and tidal dynamics has been created by Wildlife Conservation Society researchers and other marine scientists.
‘The study provides marine park and ecosystem managers with a plan for spatially managing the effectiveness of conservation and sustainability,' said Dr Caleb McClennen, director of the Wildlife Conservation Society's marine programme. ‘The information will help formulate more effective strategies to protect corals from climate change and lead to improved management of reef systems globally.'
http://www.wildlifeextra.com/go/news/coral-map2011.html
The study, say its authors, will help to conserve some of the world's most important coral reefs by identifying reef systems where biodiversity is high and stress is low - in other words, the ecosystems where management has the best chance of success.
The world's coral reefs are under pressure‘Coral reefs around the globe are under pressure from a variety of factors such as higher temperatures, sedimentation, and human-related activities such as fishing and coastal development,' said Joseph M. Maina, WCS conservationist and lead author on the study. ‘The key to effectively identifying where conservation efforts are most likely to succeed is finding reefs where high biodiversity and low stress intersect.'
DYING: Coral bleaching is becoming a worldwide problem
Using a wide array of publicly available data sets from satellites and a branch of mathematics known as fuzzy logic, which can handle incomplete data on coral physiology and coral-environment interactions, the researchers grouped the world's tropical coral reef systems into clusters based on the sum of their stress exposure grades and the factors that reinforce and reduce these stresses.
South East Asia is a ‘high-stress' areaThe first cluster of coral regions - South East Asia, Micronesia, the Eastern Pacific, and the central Indian Ocean - is characterised by high radiation stress (sea surface temperature, ultraviolet radiation, and doldrums weather patterns with little wind) and few stress-reducing factors (temperature variability and tidal amplitude). The group also includes corals in coastal waters of the Middle East and Western Australia (both regions have high scores for reinforcing stress factors such as sedimentation and phytoplankton).
The second cluster - including the Caribbean, Great Barrier Reef, Central Pacific, Polynesia, and the Western Indian Ocean - contained regions with moderate to high rates of exposure as well as high rates of reducing factors, such as large tides and temperature variability.Overall, stress factors such as surface temperature and ultraviolet radiation were the most significant factors - ones that ecosystem management has no control over. What is controllable is the mitigation of human impacts that reinforce radiation stress and where managers decide to locate their protected areas.
Reefs have little chance of surviving climate change‘When radiation stress and high fishing are combined, the reefs have little chance of surviving climate change disturbances because they both work against the survival of corals that are the foundation of the coral reef ecosystem,' said Dr Tim McClanahan, WCS senior conservationist and head of the society's coral reef research and conservation program.
The authors recommend that the study results be used to formulate management strategies that would include activities such as fishing restrictions, the management of watersheds through improved agricultural practices, and reforestation of coastal watersheds that play a role in healthy coral systems.‘The study provides marine park and ecosystem managers with a plan for spatially managing the effectiveness of conservation and sustainability,' said Dr Caleb McClennen, director of the Wildlife Conservation Society's marine programme. ‘The information will help formulate more effective strategies to protect corals from climate change and lead to improved management of reef systems globally.'
http://www.wildlifeextra.com/go/news/coral-map2011.html
Sunday, May 29, 2011
Bubbling sea signals severe coral damage this century
29 May 2011 Last updated at 18:42
This area is on the slope of a dormant volcano, and CO2 emerges from the seafloor naturally Findings from a "natural laboratory" in seas off Papua New Guinea suggest that acidifying oceans will severely hit coral reefs by the end of the century.
Carbon dioxide bubbles into the water from the slopes of a dormant volcano here, making it slightly more acidic.
Coral is badly affected, not growing at all in the most CO2-rich zone.
Writing in journal Nature Climate Change, the scientists say this "lab" mimics conditions that will be widespread if CO2 emissions continue.
The oceans absorb some of the carbon dioxide that human activities are putting into the atmosphere.
This is turning seawater around the world slightly more acidic - or slightly less alkaline.
This reduces the capacity of corals and other marine animals to form hard structures such as shells.
Projections of rising greenhouse gas emissions suggest the process will go further, and accelerate.
"This is the most realistic experiment done to date on this issue," said Chris Langdon, a coral specialist from the Rosenstiel School of Marine and Atmospheric Science in Miami, US.
"So I don't have any qualms about believing that what we found will apply in other parts of the world."
Coral gives way to seagrass around the vents - the shape of things to come? The water becomes progressively more acidic closer to the vents that are bubbling CO2.
This allows the researchers to study the impacts on coral at different levels of acidity.
Seawater has an average pH of about 8.1; this is already about 0.1 lower than before the industrial age and the large-scale human emissions of greenhouse gases associated with it.
The Intergovernmental Panel on Climate Change (IPCC) projects that by the end of the century, emissions may have risen so much that pH may fall to 7.8.
In the Papua New Guinea site, few types of coral grew at pH7.8.
Reefs still formed, but were dominated by one particular type, the Porites, which form massive shapes largely devoid of the branches and fronds that characterise reefs rich in species.
"We saw only a few speces of coral, and none of the structually complex ones that provide a lot of cover for fish," Professor Langdon told BBC News..
ACIDIFYING OCEANS 
- The oceans are thought to have absorbed about half of the extra CO2 put into the atmosphere in the industrial age
- This has lowered its pH by 0.1
- pH is the measure of acidity and alkalinity
- The vast majority of liquids lie between pH 0 (very acidic) and pH 14 (very alkaline); 7 is neutral
- Seawater is mildly alkaline with a "natural" pH of about 8.2
- The IPCC forecasts that ocean pH will fall by "between 0.14 and 0.35 units over the 21st Century, adding to the present decrease of 0.1 units since pre-industrial times"
"The much simpler forms support many fewer species, and theory suggests they create an environment that would be very vulnerable to other stresses."
In an even more acid part of the study site, with a pH of 7.7, the scientists report that "reef development ceased".
Here, seagrasses dominate the floor - but they lack the hard-shelled snails that normally live on their fronds.
This is the second published study of a "natural lab" for ocean acidification.
The first, from a site in Mediterranean, found snails with their shells disintegrating; but the PNG site offers a snapshot of the future that might be more applicable to the world's tropical coral hotspots.
"The results are complex, but their implications chilling," commented Alex Rogers from the University of Oxford, who was not part of the study team.
"Some may see this as a comforting study in that coral cover is maintained, but this is a false perception; the levels of seawater pH associated with a 4C warming completely change the face of reefs.
"We will see the collapse of many reefs long before the end of the century."
The scientific team behind the new research, drawn from Australia, Germany and the US, suggests that the picture from PNG may underplay the threat.
Reefs in the acidic zones of the study site receive regular doses of larvae floating in from nearby healthy corals, replenishing damaged stocks.
This would not be the case if low pH levels pertained throughout the oceans.
In addition, corals at the site are only minimally affected by other threats; there is little fishing, local pollution, or disease.
By contrast, a major survey published earlier this year found that three-quarters of the world's reefs were at risk - 95% in southeast Asia - with exploitative and destructive fishing being the biggest immediate threat.
http://www.bbc.co.uk/news/science-environment-13569442
Saturday, May 14, 2011
Mining to blame for islands to sink beneath waves
13 May 2011
By Sivaramakrishnan Parameswaran
BBC Tamil Service
Two small islands in South Asia's first marine biosphere reserve have sunk into the sea primarily as a result of coral reef mining, experts say.
The islets were in a group in the Gulf of Mannar, between India and Sri Lanka.
The Indo-Pacific region is considered to contain some of the world's richest marine biological resources.
The group's 21 islands and islets are protected as part of the Gulf of Mannar Marine National Park, covering an area of nearly 560 sq km (216 sq miles).
Fishermen had indiscriminately and illegally mined invaluable coral reefs around the islets of Poomarichan and Villanguchalli for many decades, said S Balaji, chief conservator of forests and wildlife for that region of Tamil Nadu state.
"The absence of any regulations prior to 2002 led to illegal mining of the coral reefs, which came to an end when environmental protection laws were enacted," he told the BBC Tamil Service.
Mr Balaji said rising sea level as a result of global warming was also a factor behind the islands' submergence.
But this was questioned by Simon Holgate from the Proudman Oceanographic Laboratory in Liverpool, UK, who said observations showed that the sea level in the region had been rising slower than the global average.
"I think that global sea level rise had little impact on the disappearance of these islands and it must be due to other reasons, possibly the mining of coral reefs," Dr Holgate told BBC News.
Though these islets were only 3-5m (10-15 ft) above sea level, their submergence sounded an alarm bell about the danger many more small islands faced in the long run, according to Mr Balaji, who is also director of the Gulf of Mannar Biosphere Reserve Trust (GOMBRT).
The Gulf of Mannar was chosen as a biosphere reserve by the Indian government in 1989 because of its biological and ecological uniqueness, and the distinctive socio-economic and cultural profile shaped by its geography.
Most of the 21 islands are uninhabited, and the corals were mined for use as a binding material in the construction industry, as they were rich in calcium carbonate.
Rich biodiversity
The biosphere reserve is a storehouse of about 3,600 species of marine flora and fauna.
Many more wait to be studied, said Deepak Samuel, marine biologist and project associate with the Energy and Environment Unit of the UN Development Programme (UNDP).
"The Gulf of Mannar is a unique reserve with ecosystems like coral reefs, mangroves and seagrass," Mr Samuel said.
"It is a nursery for shell and fin fishes, which means the entire breeding and juvenile raising takes places in these three ecosystems."
More than 300,000 fishermen depend on the Gulf of Mannar for their livelihood. It is also the dwelling place for many endemic species, notably the dugong or "sea cow".
Studies have proved that this gulf is home to 117 species of corals belonging to 37 genera, and 13 out of the 14 species of seagrasses in Indian seas.
The area has also been famous for pearl harvesting for over 2,000 years.
According to marine biologists, a quarter of the 2,000-plus fin fish species in Indian waters are in this gulf, making it one of the region's most diverse fish habitats.
The loss of these two islands should be a "wake-up call" for all those in the entire Asia-Pacific region, said Mr Balaji.
Though the lost islets were small, he cautioned that a similar fate may happen to larger islands in the long run as a result of global warming coupled with large scale mining.
Losing the reefs may result in migration of fish populations to other regions, which would result in loss of the gulf's biodiversity, according to Dr Samuel.
"Lost islets are indicators, and can even be considered as a warning," he said.
With the threat of climate change in years to come, factors such as coral mining will have an accelerating effects on the submergence of many island, he warned.
People in the area have gone on record many times as saying that the coral reefs in the Gulf of Mannar saved them from destruction when the devastating tsunami struck in December 2004.
Experts also point out the need to keep the remaining 19 islands and islets "pristine" in order to offer them some protection them from processes such as climate change.
The Indian National Oceanographic Institute point out that very few of the islands and islets in the gulf are in good shape.
Collection of coral by students for research over many decades, and heavy industrial pollution caused by onshore industries, have inflicted an irreversible damage to the coral reefs in this unique marine biosphere.
http://www.bbc.co.uk/news/science-environment-13383182
By Sivaramakrishnan Parameswaran
BBC Tamil Service
Two small islands in South Asia's first marine biosphere reserve have sunk into the sea primarily as a result of coral reef mining, experts say.
The islets were in a group in the Gulf of Mannar, between India and Sri Lanka.
The Indo-Pacific region is considered to contain some of the world's richest marine biological resources.
The group's 21 islands and islets are protected as part of the Gulf of Mannar Marine National Park, covering an area of nearly 560 sq km (216 sq miles).
Fishermen had indiscriminately and illegally mined invaluable coral reefs around the islets of Poomarichan and Villanguchalli for many decades, said S Balaji, chief conservator of forests and wildlife for that region of Tamil Nadu state.
"The absence of any regulations prior to 2002 led to illegal mining of the coral reefs, which came to an end when environmental protection laws were enacted," he told the BBC Tamil Service.
Mr Balaji said rising sea level as a result of global warming was also a factor behind the islands' submergence.
But this was questioned by Simon Holgate from the Proudman Oceanographic Laboratory in Liverpool, UK, who said observations showed that the sea level in the region had been rising slower than the global average.
"I think that global sea level rise had little impact on the disappearance of these islands and it must be due to other reasons, possibly the mining of coral reefs," Dr Holgate told BBC News.
Though these islets were only 3-5m (10-15 ft) above sea level, their submergence sounded an alarm bell about the danger many more small islands faced in the long run, according to Mr Balaji, who is also director of the Gulf of Mannar Biosphere Reserve Trust (GOMBRT).
The Gulf of Mannar was chosen as a biosphere reserve by the Indian government in 1989 because of its biological and ecological uniqueness, and the distinctive socio-economic and cultural profile shaped by its geography.
Most of the 21 islands are uninhabited, and the corals were mined for use as a binding material in the construction industry, as they were rich in calcium carbonate.
Rich biodiversity
The biosphere reserve is a storehouse of about 3,600 species of marine flora and fauna.
Many more wait to be studied, said Deepak Samuel, marine biologist and project associate with the Energy and Environment Unit of the UN Development Programme (UNDP).
"The Gulf of Mannar is a unique reserve with ecosystems like coral reefs, mangroves and seagrass," Mr Samuel said.
"It is a nursery for shell and fin fishes, which means the entire breeding and juvenile raising takes places in these three ecosystems."
More than 300,000 fishermen depend on the Gulf of Mannar for their livelihood. It is also the dwelling place for many endemic species, notably the dugong or "sea cow".
Studies have proved that this gulf is home to 117 species of corals belonging to 37 genera, and 13 out of the 14 species of seagrasses in Indian seas.
The area has also been famous for pearl harvesting for over 2,000 years.
According to marine biologists, a quarter of the 2,000-plus fin fish species in Indian waters are in this gulf, making it one of the region's most diverse fish habitats.
The loss of these two islands should be a "wake-up call" for all those in the entire Asia-Pacific region, said Mr Balaji.
Though the lost islets were small, he cautioned that a similar fate may happen to larger islands in the long run as a result of global warming coupled with large scale mining.
Losing the reefs may result in migration of fish populations to other regions, which would result in loss of the gulf's biodiversity, according to Dr Samuel.
"Lost islets are indicators, and can even be considered as a warning," he said.
With the threat of climate change in years to come, factors such as coral mining will have an accelerating effects on the submergence of many island, he warned.
People in the area have gone on record many times as saying that the coral reefs in the Gulf of Mannar saved them from destruction when the devastating tsunami struck in December 2004.
Experts also point out the need to keep the remaining 19 islands and islets "pristine" in order to offer them some protection them from processes such as climate change.
The Indian National Oceanographic Institute point out that very few of the islands and islets in the gulf are in good shape.
Collection of coral by students for research over many decades, and heavy industrial pollution caused by onshore industries, have inflicted an irreversible damage to the coral reefs in this unique marine biosphere.
http://www.bbc.co.uk/news/science-environment-13383182
Monday, November 15, 2010
Coral near Deep Water Horizon well is dead or dying
Thought to be have damaged by a plume of toxins
November 2010: Communities of dead and dying corals and starfish-like brittle stars have been discovered near the Deep Water Horizon well in the Gulf of Mexico.
On a research ship in the Gulf of Mexico, seven miles south-west of the site of the Deep Water Horizon oil-spill, a team of scientists discovered a community of corals that includes many recently dead colonies and others that clearly are dying.
‘We discovered a community of coral that has been impacted fairly recently by something very toxic,' said the chief scientist on the cruise, Charles Fisher, a professor of biology at Penn State University and a member of the research team that selected the site for study.
Fisher said the research team, on a trip at the beginning of this month, encountered a colony of the hard coral species Madrepora that appeared to be unhealthy at a depth of 1,400 meters.
‘Although some branches of the coral colony appeared normal, other branches clearly were covered in a brown material, apparently sloughing tissue, and were producing abundant mucous,' Fisher said. The scientists sampled pieces of this hard coral and of its immediate environment then, about 400 meters away, they found a seriously stricken community of soft corals.
‘Many colonies appeared recently dead'
‘Within minutes it was evident that this site was unlike any others that we have seen over the course of hundreds of hours of studying the deep corals in the Gulf of Mexico over the last decade with remotely-operated-vehicles (ROVs) and submersibles,' Fisher said. ‘We found that extensive portions of most of the coral colonies were either recently dead or were dying. Most of the soft coral sea fans had extensive areas that were bare of tissue, covered with brown material, and/or had tissue falling off the skeleton.
Many of the colonies appeared recently dead, with no living coral tissue, still covered with decaying material, and also with a notable lack of colonization by other marine life, as would be expected on coral skeletons that had been dead for long periods of time,' Fisher said.
The scientists also found that many of the brittle stars that are the typical symbiotic partners of these types of corals also appeared to be very unhealthy. ‘Many of the dead and dying coral colonies had discoloured and immobile brittle stars - a kind of starfish - still attached,' Fisher said.
The team took a variety of samples that will be analysed for the presence of hydrocarbons and for molecular evidence of genetic damage and physiological stress that could give direct evidence of exposure to oil or dispersants from the Deep Water Horizon disaster. However, Fisher said it is possible that lab results might not be able to provide any new information.
‘For example, a plume of toxic dispersant or oil blowing through this community could have caused damage that resulted in the slow death of the corals without leaving any trace on the sea floor near the corals,' Fisher said.
'We have found a smoking gun'
‘No one yet knows if the signature of whatever toxin killed these corals can be found in their skeletons after the tissue sloughs off. No one even knows if dispersant accumulates in the tissues that it kills.'
‘The compelling evidence that we collected constitutes a smoking gun,' Fisher said. ‘The circumstantial evidence is extremely strong and compelling because we have never seen anything like this - and we have seen a lot; the visual data for recent and ongoing death are crystal clear and consistent over at least 30 colonies; the site is close to the Deep Water Horizon; the research site is at the right depth and direction to have been impacted by a deep-water plume, based on NOAA models and empirical data; and the impact was detected only a few months after the spill was contained.'
http://www.wildlifeextra.com/go/news/deep-sea-corals.html
November 2010: Communities of dead and dying corals and starfish-like brittle stars have been discovered near the Deep Water Horizon well in the Gulf of Mexico.
On a research ship in the Gulf of Mexico, seven miles south-west of the site of the Deep Water Horizon oil-spill, a team of scientists discovered a community of corals that includes many recently dead colonies and others that clearly are dying.
‘We discovered a community of coral that has been impacted fairly recently by something very toxic,' said the chief scientist on the cruise, Charles Fisher, a professor of biology at Penn State University and a member of the research team that selected the site for study.
Fisher said the research team, on a trip at the beginning of this month, encountered a colony of the hard coral species Madrepora that appeared to be unhealthy at a depth of 1,400 meters.
‘Although some branches of the coral colony appeared normal, other branches clearly were covered in a brown material, apparently sloughing tissue, and were producing abundant mucous,' Fisher said. The scientists sampled pieces of this hard coral and of its immediate environment then, about 400 meters away, they found a seriously stricken community of soft corals.
‘Many colonies appeared recently dead'
‘Within minutes it was evident that this site was unlike any others that we have seen over the course of hundreds of hours of studying the deep corals in the Gulf of Mexico over the last decade with remotely-operated-vehicles (ROVs) and submersibles,' Fisher said. ‘We found that extensive portions of most of the coral colonies were either recently dead or were dying. Most of the soft coral sea fans had extensive areas that were bare of tissue, covered with brown material, and/or had tissue falling off the skeleton.
Many of the colonies appeared recently dead, with no living coral tissue, still covered with decaying material, and also with a notable lack of colonization by other marine life, as would be expected on coral skeletons that had been dead for long periods of time,' Fisher said.
The scientists also found that many of the brittle stars that are the typical symbiotic partners of these types of corals also appeared to be very unhealthy. ‘Many of the dead and dying coral colonies had discoloured and immobile brittle stars - a kind of starfish - still attached,' Fisher said.
The team took a variety of samples that will be analysed for the presence of hydrocarbons and for molecular evidence of genetic damage and physiological stress that could give direct evidence of exposure to oil or dispersants from the Deep Water Horizon disaster. However, Fisher said it is possible that lab results might not be able to provide any new information.
‘For example, a plume of toxic dispersant or oil blowing through this community could have caused damage that resulted in the slow death of the corals without leaving any trace on the sea floor near the corals,' Fisher said.
'We have found a smoking gun'
‘No one yet knows if the signature of whatever toxin killed these corals can be found in their skeletons after the tissue sloughs off. No one even knows if dispersant accumulates in the tissues that it kills.'
‘The compelling evidence that we collected constitutes a smoking gun,' Fisher said. ‘The circumstantial evidence is extremely strong and compelling because we have never seen anything like this - and we have seen a lot; the visual data for recent and ongoing death are crystal clear and consistent over at least 30 colonies; the site is close to the Deep Water Horizon; the research site is at the right depth and direction to have been impacted by a deep-water plume, based on NOAA models and empirical data; and the impact was detected only a few months after the spill was contained.'
http://www.wildlifeextra.com/go/news/deep-sea-corals.html
Coral near Deep Water Horizon well is dead or dying
Thought to be have damaged by a plume of toxins
November 2010: Communities of dead and dying corals and starfish-like brittle stars have been discovered near the Deep Water Horizon well in the Gulf of Mexico.
On a research ship in the Gulf of Mexico, seven miles south-west of the site of the Deep Water Horizon oil-spill, a team of scientists discovered a community of corals that includes many recently dead colonies and others that clearly are dying.
‘We discovered a community of coral that has been impacted fairly recently by something very toxic,' said the chief scientist on the cruise, Charles Fisher, a professor of biology at Penn State University and a member of the research team that selected the site for study.
Fisher said the research team, on a trip at the beginning of this month, encountered a colony of the hard coral species Madrepora that appeared to be unhealthy at a depth of 1,400 meters.
‘Although some branches of the coral colony appeared normal, other branches clearly were covered in a brown material, apparently sloughing tissue, and were producing abundant mucous,' Fisher said. The scientists sampled pieces of this hard coral and of its immediate environment then, about 400 meters away, they found a seriously stricken community of soft corals.
‘Many colonies appeared recently dead'
‘Within minutes it was evident that this site was unlike any others that we have seen over the course of hundreds of hours of studying the deep corals in the Gulf of Mexico over the last decade with remotely-operated-vehicles (ROVs) and submersibles,' Fisher said. ‘We found that extensive portions of most of the coral colonies were either recently dead or were dying. Most of the soft coral sea fans had extensive areas that were bare of tissue, covered with brown material, and/or had tissue falling off the skeleton.
Many of the colonies appeared recently dead, with no living coral tissue, still covered with decaying material, and also with a notable lack of colonization by other marine life, as would be expected on coral skeletons that had been dead for long periods of time,' Fisher said.
The scientists also found that many of the brittle stars that are the typical symbiotic partners of these types of corals also appeared to be very unhealthy. ‘Many of the dead and dying coral colonies had discoloured and immobile brittle stars - a kind of starfish - still attached,' Fisher said.
The team took a variety of samples that will be analysed for the presence of hydrocarbons and for molecular evidence of genetic damage and physiological stress that could give direct evidence of exposure to oil or dispersants from the Deep Water Horizon disaster. However, Fisher said it is possible that lab results might not be able to provide any new information.
‘For example, a plume of toxic dispersant or oil blowing through this community could have caused damage that resulted in the slow death of the corals without leaving any trace on the sea floor near the corals,' Fisher said.
'We have found a smoking gun'
‘No one yet knows if the signature of whatever toxin killed these corals can be found in their skeletons after the tissue sloughs off. No one even knows if dispersant accumulates in the tissues that it kills.'
‘The compelling evidence that we collected constitutes a smoking gun,' Fisher said. ‘The circumstantial evidence is extremely strong and compelling because we have never seen anything like this - and we have seen a lot; the visual data for recent and ongoing death are crystal clear and consistent over at least 30 colonies; the site is close to the Deep Water Horizon; the research site is at the right depth and direction to have been impacted by a deep-water plume, based on NOAA models and empirical data; and the impact was detected only a few months after the spill was contained.'
http://www.wildlifeextra.com/go/news/deep-sea-corals.html
November 2010: Communities of dead and dying corals and starfish-like brittle stars have been discovered near the Deep Water Horizon well in the Gulf of Mexico.
On a research ship in the Gulf of Mexico, seven miles south-west of the site of the Deep Water Horizon oil-spill, a team of scientists discovered a community of corals that includes many recently dead colonies and others that clearly are dying.
‘We discovered a community of coral that has been impacted fairly recently by something very toxic,' said the chief scientist on the cruise, Charles Fisher, a professor of biology at Penn State University and a member of the research team that selected the site for study.
Fisher said the research team, on a trip at the beginning of this month, encountered a colony of the hard coral species Madrepora that appeared to be unhealthy at a depth of 1,400 meters.
‘Although some branches of the coral colony appeared normal, other branches clearly were covered in a brown material, apparently sloughing tissue, and were producing abundant mucous,' Fisher said. The scientists sampled pieces of this hard coral and of its immediate environment then, about 400 meters away, they found a seriously stricken community of soft corals.
‘Many colonies appeared recently dead'
‘Within minutes it was evident that this site was unlike any others that we have seen over the course of hundreds of hours of studying the deep corals in the Gulf of Mexico over the last decade with remotely-operated-vehicles (ROVs) and submersibles,' Fisher said. ‘We found that extensive portions of most of the coral colonies were either recently dead or were dying. Most of the soft coral sea fans had extensive areas that were bare of tissue, covered with brown material, and/or had tissue falling off the skeleton.
Many of the colonies appeared recently dead, with no living coral tissue, still covered with decaying material, and also with a notable lack of colonization by other marine life, as would be expected on coral skeletons that had been dead for long periods of time,' Fisher said.
The scientists also found that many of the brittle stars that are the typical symbiotic partners of these types of corals also appeared to be very unhealthy. ‘Many of the dead and dying coral colonies had discoloured and immobile brittle stars - a kind of starfish - still attached,' Fisher said.
The team took a variety of samples that will be analysed for the presence of hydrocarbons and for molecular evidence of genetic damage and physiological stress that could give direct evidence of exposure to oil or dispersants from the Deep Water Horizon disaster. However, Fisher said it is possible that lab results might not be able to provide any new information.
‘For example, a plume of toxic dispersant or oil blowing through this community could have caused damage that resulted in the slow death of the corals without leaving any trace on the sea floor near the corals,' Fisher said.
'We have found a smoking gun'
‘No one yet knows if the signature of whatever toxin killed these corals can be found in their skeletons after the tissue sloughs off. No one even knows if dispersant accumulates in the tissues that it kills.'
‘The compelling evidence that we collected constitutes a smoking gun,' Fisher said. ‘The circumstantial evidence is extremely strong and compelling because we have never seen anything like this - and we have seen a lot; the visual data for recent and ongoing death are crystal clear and consistent over at least 30 colonies; the site is close to the Deep Water Horizon; the research site is at the right depth and direction to have been impacted by a deep-water plume, based on NOAA models and empirical data; and the impact was detected only a few months after the spill was contained.'
http://www.wildlifeextra.com/go/news/deep-sea-corals.html
Sunday, May 30, 2010
Displaced Fish Is Ravaging Caribbean Reefs
One of the prime suspects in the destruction of Caribbean coral has been found guilty, but researchers were wrong about its motive. For years scientists thought that the threespot damselfish was nibbling star coral to death because overfishing had reduced its natural predators. But a new survey shows that the damage is being done because the damselfish was forced from its natural habitat—and in fact the fish is also suffering. The good news is that it might be possible to restore the reefs to health, though that effort could take at least a decade.
The case begins not with the star coral but with another species, the branching staghorn coral (Acropora cervicornis). Once, the dominant coral in the Caribbean, staghorns—and their less-common relative, the elkhorn—were decimated in the 1970s and '80s, the victims of a bacterial infection called white-band disease. More than 90% of the coral died, and populations hit their lowest levels in over 3000 years.
That was bad news for the damselfish (Stegastes planifrons), which survived on the staghorn coral. The ill-tempered fish, which has been known to bite the fingers of divers who approach its territory, nibbles incessantly on the coral—not to eat it but to kill the living tissue so that algae, the fish's favorite food, can grow on the dead coral skeletons. The damselfish never destroyed the staghorn coral, because the coral grew fast enough to recover from the constant nibbling.
But when the damselfish was forced to relocate to star coral (Montastraea), this coral began dying. Many scientists concluded that overfishing had thinned the ranks of damselfish predators, such as snappers and small groupers, and that the population of damselfish had exploded, wreaking havoc on star coral reefs.
But no one had tested this hypothesis. So a team of researchers set up surveys at 10 coral sites in the Florida Keys, Bahamas, and Cayman Islands and off the coasts of Belize and Jamaica. "We wanted to find out if the more heavily fished reefs had more threespot damselfish, and if not, what was controlling the abundance of threespots," says paleontologist Richard Aronson of the Florida Institute of Technology in Melbourne. He explains that the team chose the sites to compare the heavily fished areas, such as off Jamaica, with the moderately fished reefs of the Keys and Bahamas and the protected reefs of the Caymans and Belize.
Damselfish are indeed responsible for the star coral die-off, the team found, but not because their numbers are booming out of control. In fact, the researchers report this week in PLoS ONE, the fish's numbers have declined overall. Aronson says that's because star corals offer fewer places to hide than the staghorn, leaving the damselfish more vulnerable to predation.
So why is star coral dying? Aronson and colleagues conclude that it grows back much slower than the staghorn, so it doesn't recover from the damselfish algae farming. The change has placed all Caribbean reefs—already in jeopardy from pollution, silting, warming waters, and oil spills—in even greater danger. "The threespots have now killed substantial amounts of star coral, and [they] are doing damage that will take decades or centuries to fix," Aronson says.
But the reefs may not be lost. One practical solution, Aronson explains, is to restore the staghorn and elkhorn to the reefs. This can be done via a painstaking aquatic form of tree farming. Biologists first grow nubbins, or small baby coral, on cinder blocks that have been submerged, and then they transplant the growing corals to the reefs. "Once the staghorn is restored, the threespots will move back into their preferred neighborhoods," Aronson says.
The paper "drives home the fundamental importance of disease outbreaks in the changes we've seen on Caribbean coral reefs over the last several decades," says marine biologist John Bruno of the University of North Carolina, Chapel Hill. It's "an important contribution from a group of scientists who know more about these reefs than anyone else in the world."
Phil Berardelli
http://www.sciencemag.org/
The case begins not with the star coral but with another species, the branching staghorn coral (Acropora cervicornis). Once, the dominant coral in the Caribbean, staghorns—and their less-common relative, the elkhorn—were decimated in the 1970s and '80s, the victims of a bacterial infection called white-band disease. More than 90% of the coral died, and populations hit their lowest levels in over 3000 years.
That was bad news for the damselfish (Stegastes planifrons), which survived on the staghorn coral. The ill-tempered fish, which has been known to bite the fingers of divers who approach its territory, nibbles incessantly on the coral—not to eat it but to kill the living tissue so that algae, the fish's favorite food, can grow on the dead coral skeletons. The damselfish never destroyed the staghorn coral, because the coral grew fast enough to recover from the constant nibbling.
But when the damselfish was forced to relocate to star coral (Montastraea), this coral began dying. Many scientists concluded that overfishing had thinned the ranks of damselfish predators, such as snappers and small groupers, and that the population of damselfish had exploded, wreaking havoc on star coral reefs.
But no one had tested this hypothesis. So a team of researchers set up surveys at 10 coral sites in the Florida Keys, Bahamas, and Cayman Islands and off the coasts of Belize and Jamaica. "We wanted to find out if the more heavily fished reefs had more threespot damselfish, and if not, what was controlling the abundance of threespots," says paleontologist Richard Aronson of the Florida Institute of Technology in Melbourne. He explains that the team chose the sites to compare the heavily fished areas, such as off Jamaica, with the moderately fished reefs of the Keys and Bahamas and the protected reefs of the Caymans and Belize.
Damselfish are indeed responsible for the star coral die-off, the team found, but not because their numbers are booming out of control. In fact, the researchers report this week in PLoS ONE, the fish's numbers have declined overall. Aronson says that's because star corals offer fewer places to hide than the staghorn, leaving the damselfish more vulnerable to predation.
So why is star coral dying? Aronson and colleagues conclude that it grows back much slower than the staghorn, so it doesn't recover from the damselfish algae farming. The change has placed all Caribbean reefs—already in jeopardy from pollution, silting, warming waters, and oil spills—in even greater danger. "The threespots have now killed substantial amounts of star coral, and [they] are doing damage that will take decades or centuries to fix," Aronson says.
But the reefs may not be lost. One practical solution, Aronson explains, is to restore the staghorn and elkhorn to the reefs. This can be done via a painstaking aquatic form of tree farming. Biologists first grow nubbins, or small baby coral, on cinder blocks that have been submerged, and then they transplant the growing corals to the reefs. "Once the staghorn is restored, the threespots will move back into their preferred neighborhoods," Aronson says.
The paper "drives home the fundamental importance of disease outbreaks in the changes we've seen on Caribbean coral reefs over the last several decades," says marine biologist John Bruno of the University of North Carolina, Chapel Hill. It's "an important contribution from a group of scientists who know more about these reefs than anyone else in the world."
Phil Berardelli
http://www.sciencemag.org/
Tuesday, February 16, 2010
Coral Fossils Document Past Sea Life
Posted on: Tuesday, 16 February 2010, 06:39 CSTScientists may use fossilized coral reefs in the Great Barrier Reefs to understand how sea levels have changed over the past 20,000 years.
An international team of researchers plan to spend 45 days at sea, gathering core samples from about 40 sites.
Coral, which is described as the "tree of the sea", have growth rings that show seasonal variations.
Researchers say that samples taken of the coral will also help show past sea temperatures, as well as other changes to the reef.
Alan Stevenson, team leader of marine geology at the British Geological Survey (BGS), said the fossilized corals' annual growth rings provided an insight to conditions under waves.
"We can then analyze those rings to build up a very detailed picture of what the ocean was like when they were forming, including temperature and salinity, “ he said.
Stevenson told BBC News that the Great Barrier Reef is about half a million years old.
"Over this time, parts have died out... as sea levels change. Basically, corals drown when it becomes too deep for them."
The team plans to collect samples of fossilized corals that were developed between 20,000 to 10,000 years ago.
"We will core into a 'time capsule' of sediments that holds information on the environmental evolution of the reef since the last glaciation some 20,000 years ago," said Dan Evans, a marine geologist at BGS and science manager for the ECORD Science Operator.
Researchers currently believe that there were three periods in which the sea level rise was accelerated: 19,000, 13,800 and 11,300 years ago.
"By understanding more about the past, we can understand a little bit more about the future," said Stevenson.
The team will gather core samples, some of which are 490 ft below the seabed.
Stevenson said that the expedition would not disturb the live coral in the World Heritage site.
"Obviously, it is a national park and we are in there with the permission of the Great Barrier Reef Marine Park authority. If they were not happy, then we would not be there."
The European Consortium for Ocean Research Drilling (ECORD) and the forms part of the Integrated Ocean Drilling Program (IODP) all are funding the expedition.
---
On the Net:
British Geological Survey (BGS)
Expedition 325 - Great Barrier Reef Environmental Changes
Source: RedOrbit Staff & Wire Reports
http://www.redorbit.com/news/science/1823365/coral_fossils_document_past_sea_life/index.html
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