Coral bleach-out in Belize

The highest sea surface temperatures ever recorded, related both to the 1997-98 El Nino/Southern Oscillation and to global warming, caused severe bleaching of corals worldwide in 1998. This thermal anomaly induced mass mortality of scleractinian corals on lagoonal reefs in Belize, the first time that a coral population in the Caribbean has collapsed completely from bleaching. Cores extracted from the Belizean reefs showed that these events were unprecedented over at least the past 3,000 years. Coral bleaching occurs when coral colonies under physiological stress expel their symbiotic algae (zooxanthellae). Usually a response to high temperature and/or high incident solar radiation, bleaching has become more frequent on coral reefs worldwide over the past two decades. Bleaching-related mass coral mortalities, involving population collapses that can lead to local extirpation, have occurred several times recently in the Indo-Pacific. In contrast, bleaching in the Caribbean has until now been followed by substantial recovery of the affected coral populations.