Coral Bleaching

Coral bleaching is the loss of the symbiotic zooxanthellae algae that give reef-building corals their color and most of their food, expelled when heat stress (often just 1 to 2 degrees Celsius above the summer maximum for a few weeks) disrupts the symbiosis. Bleached corals can recover if conditions ease but starve and die under prolonged stress. Mass bleaching events have struck the Great Barrier Reef repeatedly since 1998 as ocean temperatures rise.