Coral bleaching could result in adaptation to climate change

Bleaching of coral, where the organisms lose their colourful algae with which they live symbiotically, and which is caused by stresses such as increases in sea temperature (see related story), rather than starving the organisms, could be allowing them to adapt to global warming, according to new research.

As sea temperature rises, the effectiveness of the algae may decrease, so that if the coral can rid themselves of these sub optimal algae they can then become hosts to more suitable species which will increase their chances of survival, says the research conducted by the New York-based Wildlife Conservation Society. The study involved the transplantation of corals found off the coast of Panama from shallow to deep water, and visa versa, and showed that corals transplanted upwards generally bleached but ultimately survived by recovering with new algae. In contrast, corals transplanted downwards did not bleach, and did not change their type of algae, although they were poorly adapted to the deeper environment, with the result that a significant number died.

“These findings indicate that bleaching can sometimes help corals respond quickly to environmental change,” said the author’s study, Dr Andrew Baker of the Wildlife Conservation Society’s Osborn Laboratories of Marine Sciences. “The same bleaching that makes corals so fragile may also, during times of extreme environmental stress, help some of them survive.”

However, Baker pointed out that bleaching, particularly as a result of warmer seas, is still a major cause for concern, and will continue to cause high mortality among reef ecosystems in the foreseeable future. “These findings do provide a glimmer of hope for the ability of coral reefs to survive the severe warming and environmental change projected over the next half century,” said Baker. “However, coral reefs are still under assault from global warming, poor water quality, and over-fishing. Much more needs to be done to protect and understand these fragile ecosystems before we lose the ones we have left.”

The results of the study are published in the June 14 issue of Nature.

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