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Keys coral gets help handling ocean's heat
Last Updated(Beijing Time):2008-03-08 15:43

 Coral can be seen spawning at night during a full moon at the Great Barrier Reef off the north east coast of Australia in this undated hand out photograph released October 19, 2007.

Coral can be seen spawning at night during a full moon at the Great Barrier Reef off the north east coast of Australia in this undated hand out photograph released October 19, 2007.(Xinhua/Reuters Photo)

High water temperatures associated with global warming, along with water pollution and other factors, are stressing and killing coral reefs.

Hot water was at least partly to blame for coral "bleaching" events that killed coral in the Florida Keys in the late 1980s and 1990s - especially on the outer, shallow reefs, said Billy Causey, regional superintendent for the National Marine Sanctuary program in Key West, Florida.

Hurricanes cooled the water and reduced the coral bleaching that was occurring in the Keys during the summer of 2005.

Overall, the Keys reefs have lost 30 percent of their living coral cover in the past 25 years.

Warmer water temperatures, Causey said, are partly to blame. But now, University of Miami researcher Andrew Baker is working to make coral reefs more tolerant of hot water.

Baker, an assistant professor of marine biology and fisheries at Miami's Rosenstiel School of Marine and Atmospheric Science, recently received a three-year, US$150,000 grant from the Pew Institute for Ocean Science to improve the "thermal tolerance" of corals.

When water temperatures rise above approximately 31 degrees Celsius, corals expel the symbiotic algae called zooxanthellae that capture sunlight and, through photosynthesis, allow coral polyps to grow and create the limestone skeletons that build reefs. Without the algae, corals appear white or "bleached." If bleaching persists, coral colonies can die.

At high water temperatures, Baker said, the photosynthetic machinery in zooxanthellae breaks down. The algae produce toxins, and coral polyps expel them.

Baker is cultivating the heat-tolerant strains of zooxanthellae in the lab and working on methods for increasing the natural abundance of heat-tolerant algae on the reefs. Baker hopes to conduct some of his experiments with coral in Biscayne Bay and the Florida Keys.

Separately, Mote Marine Laboratory trains sport divers to record and report coral bleaching in the Florida Keys through its BleachWatch program.

Source:Shanghai Daily 
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