This years exceptionally strong El Niño event, and the abnormally high water temperatures that it has produced, has triggered what appears to be the largest coral bleaching event ever.  Widespread bleaching is currently underway throughout the Pacific and is expected to continue for months to come.  Researchers have already documented over 99% of the reefs (4 out of the 520 surveyed) in a 1000 mile stretch of the 2300 mile long Great Barrier Reef are currently bleaching, and similar trends are becoming evident throughout the greater Pacific.  “It was the saddest reef trip of my career”, said Terry Hughes, an eminent coral reef ecologist in reference to the expedition during which the extensive bleaching was documented.

Coral bleaching occurs when abnormally high water temperatures stress coral, forcing them to expel the symbiotic algae, called zooxanthellae, that lives within the coral tissue and provides them with their vibrant color.  When coral bleach they become more susceptible to other stressors, compounding the already high levels of stress created by other human-related factors, such as disease, nutrient pollution, and fishing.  Bleaching became a focal concern of coral reef ecologists after the 1998 bleaching events that killed 16% of reefs worldwide.  Given the degree of bleaching already underway, and the magnitude of the current El Niño event, experts fear that this years bleaching could be even more devastating.