What is coral bleaching, and how is it related to global warming?
Bleaching occurs when coral polyps, stressed by heat or radiation, expel the symbiotic algae the zooxanthellae that live in the reefs and provide the coral most of their food and oxygen. The reefs turn a whitish color, and the coral have little energy to grow or reproduce. Usually the coral can recover unless the bleaching is severe enough, in which case, whole reefs can be destroyed. Bleaching can be caused by a variety of factors, including diseases and ultraviolet radiation, but scientists are increasingly noting that sudden rises in water temperature are playing a major role. Between 1980 and the present there have been over 60 cases of coral bleaching around the world, and they are becoming increasingly common, especially during El Nino events, which increased sea temperatures in the eastern Pacific by several degrees and caused major bleaching events. Bleaching may become even more widespread if global warming continues to increase the sea temperature.
