Worst coral reef die-off in 11,000 years
December 18, 2006
Two new studies by scientists at the Australian Research Council Centre of Excellence for Coral Reef Studies at James Cook University suggest that coral reefs may be in worse shape than previously thought. The first, appearing in the journal Geology indicates that the current large scale coral die-offs are now occurring more frequently than at any time in the last 11,000 years. The second, published in Current Biology, suggests that the loss of a single "keystone" species can trigger a rapid shift in the health of a reef.
The first study, led by Associate Professor John Pandolfi of the Australian Research Council Centre of Excellence in Coral Reef Studies and The University of Queensland, examined fossilized reefs of the Huon Peninsula in Papua New Guinea and determined that past reef die-offs occurred about every 1500 years due to some catastrophic event -- a rate that is exceeded by the current decline in coral reefs;
"The cause of some of these events was volcanic, but others may have been due to bleaching, disease, or something else - we just don't know. Regardless, what is clear is that the frequency of die-off was so much lower than it is today. The frequency of reef events in the fossils is at least an order of magnitude less than it is today" said Pandolfi.
Pandolfi said the results show that the ancient reefs "recovered rapidly after these events, taking as little as 100 years to be repopulated by the corals that normally occurred there."
Pandolfi said that he hopes his ongoing research will help reef managers better understand what they need to do to help current reefs bounce back from impact events.
Single species found to be crucial to reef recovery
One area the needs further exploration is the role of individual species in coral reef ecology. The Current Biology did just this and determined that reefs may be more fragile than previously thought.
Using experimental plots on the Great Barrier Reef to simulate overfishing, David R. Bellwood, Terry P. Hughes, and Andrew S. Hoey found that a single species plays a key role in reef recovery. Loss of this species could leave reefs more susceptible to damage from algae.
In the experimental plots, the researchers "intentionally triggered a phase shift to algal dominance on a healthy reef" and then "filmed the reef's recovery with remote underwater digital videos cameras." They found that "only two of the 27 herbivorous fish species present on the reefs had any significant impact on its recovery from algal overgrowth." Surprisingly, the dominant browser was a rare batfish, Platax pinnatus, species previously unknown as an algae eater. "Meanwhile," reported a statement from Cell Press, publisher of Current Biology, "parrotfishes and surgeonfishes, which are the routine consumers of seaweed on coral reefs, were unable to reverse runaway algal blooms."
The research demonstrates the importance of a single rare species in the recovery of coral reefs and suggests that the loss of this keystone species could undermine the regenerative capacity of coral reef ecosystems.
Great Barrier Reef shark populations collapsing finds study. Coral reef shark populations are declining rapidly due to fishing according to research published in the December 5th issue of the journal Current Biology. The paper says that "no-take zones" -- areas where fishing is prohibited -- can be effective in protecting sharks but only when the no-take regulations are strictly enforced. Examining two common species of sharks on the Great Barrier Reef in Australia, the researchers found that both populations are in the midst of a rapid population decline -- 7% per year for white tip sharks and 17% per year for gray reef sharks, showing that current shark conservation strategies are not effective.
Coral reefs can be saved from global warming. The outlook for coral reefs -- often termed the rainforests of the sea -- is dire. Overfishing, pollution, damage from anchors, mining for construction materials, and over-collection for the pet trade are all over-shadowed by climate change which could decimate reefs by higher water temperatures and increasingly acidic conditions which could render many coral species incapable of forming carbonate support structures. Nevertheless a new report from the World Conservation Union (IUCN) and The Nature Conservancy says that measures can be taken to help increase the survival chances for coral reefs. The report, "Coral Reef Resilience and Resistance to Bleaching", outlines strategies for helping reefs to be better adapt to the impacts of climate change.
Some corals can adapt to ocean acidification. While scientists warn that increasing ocean acidity will doom marine animals that build skeletons and structural elements out of calcium carbonate, new research has found that corals can change their skeletons, building them out of different minerals depending on the chemical composition of the seawater around them. However, the research provides further evidence that corals are extremely sensitive to rapid environmental change and will be negatively affected by increased carbon dioxide levels in the short-term.
Increasingly acidic oceans damaging to marine life. Carbon dioxide emissions are altering ocean chemistry and putting sea life at risk according to a new report released today. The report, "Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers," summarizes known effects of increased atmospheric carbon dioxide on marine organisms that produce calcium carbonate skeletal structures, such as corals. Oceans worldwide absorbed approximately 118 billion metric tons of carbon between 1800 and 1994 according to the report, resulting in increased ocean acidity, which reduces the availability of carbonate ions needed for the production of calcium carbonate structures.
Global warming may cause permanent damage to coral reefs. Global warming has had a more devastating impact on coral reefs than previously believed says a new study published in the Proceedings of the National Academy of Sciences. The research, the first to show the long-term impact of rising sea temperatures on coral and fish communities, suggests that "large sections of coral reefs and much of the marine life they support may be wiped out for good," according to a news release from the University of Newcastle upon Tyne, an institution involved in the project.
Coral reefs decimated by 2050, Great Barrier Reef's coral 95% dead. Australia's Great Barrier Reef could lose 95 percent of its living coral by 2050 should ocean temperatures increase by the 1.5 degrees Celsius projected by climate scientists. The startling and controversial prediction, made last year in a report commissioned by the World Worldwide Fund for Nature (WWF) and the Queensland government, is just one of the dire scenarios forecast for reefs in the near future. The degradation and possible disappearance of these ecosystems would have profound socioeconomic ramifications as well as ecological impacts says Ove Hoegh-Guldberg, head of the University of Queensland's Centre for Marine Studies.
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