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Researchers warn about coral reef deaths
2006-10-25
Researchers warn that more than half of the world's coral reefs could die in less than 25 years, killed off by a deadly cocktail of rising sea temperatures, silt runoff from construction sites, algae and other toxic ingredients. Last year's coral loss in the Caribbean supports predictions that 60 percent of the world's coral alive today could die within a quarter century, University of the Virgin Islands researcher Tyler Smith said on Tuesday. "Given current rates of degradation of reef habitats, this is a plausible prediction, particularly given events in the Virgin Islands this year," Smith said at the National Oceanic and Atmospheric Administration's twice yearly U.S. Coral Reef Task Force meeting in St. Thomas. The coral reefs, hosts for countless marine plants and animals, were made more susceptible to disease and premature death after seas exceeded normal temperatures for nearly three months last year. More than 47 percent of the coral in underwater study sites covering 31 acres around the U.S. Virgin Islands died after abnormally warm seas in 2005, said Jeff Miller, a scientist with the Virgin Islands National Park. A double punch of rising sea temperatures and increased pollutants -- such as construction-site sediment runoff and toxins from boat paints -- have kept coral from recovering, ultimately leading to its death, scientists said at the weeklong meeting. "Think of it as a high school chemistry class," said Billy Causey, NOAA's Caribbean and Gulf Mexico director. "You mix some chemicals together and nothing happens. You crank up the Bunsen burner and all of a sudden things start bubbling around. That's what's happening. That global Bunsen burner is cranking up." This year, Caribbean coral narrowly avoided another widespread episode of bleaching -- which is when stressed coral loose their pigment and are most susceptible to disease -- when sea temperatures only briefly surpassed levels that are healthy for coral. Up to 30 percent of the world's coral reefs have died in the last 50 years, and another 30 percent are severely damaged, said Smith, who studies coral health in the U.S. Virgin Islands and collaborates with researchers globally. "U.S. Virgin Islands coral today is likely at its lowest levels in recorded history," Smith said. Nearly 200 private and government researchers from the Caribbean, Florida and U.S. Pacific islands gathered at the coral meeting. They cited global warming as a potential cause of the abnormally high sea temperatures, yet they couldn't provide definitive answers. "Climate change is an important factor that is influencing coral reefs worldwide," said Mark Eakin, director of NOAA's Coral Reef Watch. "It adds to the other problems that we are having." What their research did show, however, was that the coral started to recover from the warm seas, but then suddenly contracted diseases and died. Scientists say causes of the disease are hard to pinpoint, coming from numerous sources, such as silt runoff from construction sites, which prohibits coral's access to sunlight and ultimately kills the fragile undersea life, and a record increase in fleshy, green algae, which competes with coral for sunlight. "There's not just one stress at a time. What we have is a combination of stressors," said Caroline Rogers, a scientist with the U.S. Geological Survey. "Right now we don't know how to stop some of the coral diseases. But we can do a better job of managing sediment run off. If you anchor on a reef and destroy it, it doesn't matter what the temperature was."
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