National Geographic: Early one December morning, Chris Langdon, a biological oceanographer at the University of Miami, zipped up his wet suit and dropped overboard just off Key Largo to inspect a section of Florida's ailing coral reef. His living "laboratory," 15 feet down, is the size of several football fields. Last summer a large bleaching event turned much of the coral white.
Bleaching occurs when water temperatures rise or fall. Even a slight fluctuation can set it off. The result is dramatic and often fatal....