Mass Bleaching Events
Mass bleaching events are primarily caused by elevated sea temperatures. Sea temperature increases of only 1-2° C above the long term average over an extended period of time are enough to trigger these events1. Mass bleaching, or regional bleaching, can be defined as events in which entire reef tracts or regions completely bleach. The isolated bleaching that occurs from sedimentation events, disease, and pollution, although damaging, does not reach the scale and severity of mass bleaching.
The warm sea temperatures that characterize El Niño conditions increase the likelihood of global mass bleaching events.
Map of bleaching events from 1998 through 2007. Image taken from Reefbase. Click image for interactive map on Reefbase site.
The extent and severity of mass bleaching events are increasing as a result of global increases in sea surface temperatures. The number of countries reporting mass bleaching continues to grow, and no region has escaped the effects of warming seas. Many places have experienced bleaching related mortality, while in other regions bleached corals mostly survived. Bleaching events of 1998 effectively destroyed 16% of the world’s reefs2, with most damage occurring throughout the Indian and Western Pacific Oceans3. Since then, bleaching events have occurred on a global scale in association with the El Niño Southern Oscillation (ENSO). This toolkit offers practical solutions for building resilience into coral reef conservation activities during both the planning and management stages in a time of global-scale changes.
Resources
A Reef Manager’s Guide to Coral Bleaching
Global Database on Coral Bleaching
The 1997-98 Mass Coral Bleaching and Mortality Event: 2 Years On
Coral Bleaching & SST Interactive Map