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Fast-growing coral may help reefs survive global warming
mongabay.com
March 13, 2008


Two fast-growing coral species may hold the key to Caribbean reefs surviving global warming, report researchers writing in the journal Science.

Ken Johnson of the Natural History Museum in London and colleagues found that staghorn and elkhorn coral — species that grow 10 times faster than other Caribbean species — did not become dominant in the Caribbean until about a million years ago when half the region's coral species went extinct. Apparently their fast growth rate and reproductive strategy enabled the species to thrive despite change sea levels while others died off.

Looking toward the future, the scientists say that staghorn and elkhorn coral may help coral reefs adapt to rising sea levels caused by climate change.

Caribbean reefs. Image by R. Butler

Scientists are concerned over the potential impact of climate change on coral reef ecosystems. Both increasingly levels of acidity, which reduce the ability of coral to generate their main structural material, and higher sea temperatures, which can cause "bleaching" or expulsion of the symbiotic algae that enable corals to feed, are cited as the primary risks to reefs in a world of higher atmospheric carbon dioxide levels.

Coral bleaching is associated with a variety of physiological stresses, the most important of which is elevated sea surface temperatures. Bleaching causes coral to expel symbiotic zooxanthellae algae living in their tissues -- algae that provide corals with nourishment. Losing their algae leaves coral tissues devoid of color, and thus appearing to be bleached. Corals can recover from short-term bleaching, but prolonged bleaching -- over a week -- can cause irreversible damage and subsequent death. Bleached corals are more vulnerable to disease.