Bleaching — a whitening of corals that occurs when symbiotic algae living within coral tissues are expelled — is an indication of stress caused by environmental triggers such as fluctuations in ocean temperature. Depending on many factors, bleached coral may recover over time or die.
The event is the result of a rise in sea surface temperatures in the Andaman Sea — an area that includes the coasts of Myanmar, Thailand, the Andaman and Nicobar Islands and northwestern Indonesia. According to the National Oceanic and Atmospheric Administration's Coral Hotspots website, temperatures in the region peaked in late May at more than 93 degrees Fahrenheit (34 degrees Celsius). That's 7.2 degrees Fahrenheit (4 degrees Celsius) higher than long-term averages for the area.
"It's a disappointing development particularly in light of the fact that these same corals proved resilient to other disruptions to this ecosystem, including the Indian Ocean Tsunami of 2004," said WCS Indonesia Marine Program Director Stuart Campbell.
Surveys conducted in the wake of the 2004 tsunami revealed that the many reefs of Aceh were largely unaffected by this massive disturbance. Indeed, reefs severely damaged by poor land use and destructive fishing prior to the tsunami had recovered dramatically in the intervening years due to improved management. Government and community-managed areas in the region have been remarkably successful at maintaining fish biomass despite ongoing access to the reefs. But the bleaching and mortality in 2010 have rapidly reversed this recovery and will have a profound effect on reef fisheries.