Scientists alarmed by Little Cayman coral bleaching

| 19/10/2009

(CNS): Following the recent announcement by the Department of the Environment (DoE) that reefs around Grand Cayman are suffering the adverse affects of coral bleaching, scientists at the Central Caribbean Marine Institute (CCMI) said this week that their visits to reefs around Little Cayman have also confirmed the same problem. Working with the DoE, CCMI visited five sites, including Sailfin Reef, Rock Bottom Wall, Snapshot Reef, Nancy’s Cup of Tea, and Grundy’s Gardens.Bleaching was observed at every site and was found to be affecting corals as shallow as 20 feet and as deep as at least 120 ft on Bloody Bay Wall.

Scientists said that coral bleaching is the loss of a coral’s symbiotic algae population that lives in its tissues. These microscopic algae provide the coral with extra nutrients that help the coral to grow and reproduce. They also give corals their bright and myriad colors. When the algae are lost due to stress, the coral tissue becomes transparent and the coral’s skeleton can be seen through the tissue, making the coral appear bright white, hence the term “bleaching.” Coral bleaching can be caused by a number of different stressors, but the most common stressor is unusually warm water temperatures.

Many different species of corals in the Cayman Islands have been affected, CCMI said, including gorgonians.

“Using transects to quantify the amount of bleaching, it was found that up to 96% of coral cover on Little Cayman reefs was either totally bleached or extremely pale compared to normal coloration," a spokesperson stated. “Expedited permission was granted by the DoE to extract small samples, in order to identify the remaining types of algae that the corals are hosting in their tissues. Since some algae types have been found to be more resistant to thermal stress, identifying whether corals are hosting these more resistant types could help scientists better understand the distribution of bleaching that we are seeing throughout the Cayman Islands.”

At the time of the observations, no mortality associated with bleaching was observed,” Dr. Marilyn Brandt of University of Miami’s Rosenstiel School of Marine and Atmospheric Science noted. “If the stress causing the bleaching (assumed to be high temperature) is removed soon and the corals are not too weakened, it’s possible that they will recover their algae and survive intact,” she said. “However, if the stress continues, the corals may starve or become more susceptible to infections and disease, which could result in significant mortality rates. Therefore, care should be taken to avoid touching or damaging the corals at this time, so that they have the best chance of survival.”

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