coral bleaching

Coral reefs are sentitive to temperature, needing water that is never cooler than about 20 degree celcius and never warmer than 29 degree celcius. Bleaching of coral reefs has occured due to locally rising sea temperatures, thought to be caused by climate changes brought about by El Nino. These sensitive organisms die in water that is too warm - a rise of only one or two degrees is enough to start the bleaching process. The algae that live inside the polyp die, and the remaining polyp turns white and also dies. By the late 1990s, it was thought that more than half of the Great Barrier Reef had been affected by bleaching.

adapted by: caring for the planet-seas and oceans, by Neil Champion