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Bleached Coral

January 4, 2018

A coral at Dongsha Atoll in the South China Sea shows the effects of “bleaching.” The phenomenon occurs when ocean temperatures rise and the colorful symbiotic algae hosted in coral tissue are driven out, revealing the corals’ underlying white skeletons. Sometimes bleaching can be fatal. In 2015, about 40 percent of the corals at Dongsha Atoll died following a severe bleaching event. Tom DeCarlo, a graduate student in the MIT-WHOI Joint Program in Oceanography, led a study that showed that two factors combined to cause the devastation: First, ocean temperatures rose by 3.6 degrees Fahrenheit. Second, winds that ordinarily would have brought cooling waters from the open ocean to the reefs, died down. (Photo by Tom DeCarlo, Woods Hole Oceanographic Institution)