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Coral Reef Bleaching

Coral Bleaching
Coral Bleaching

Photo: Andy Bruckner, NOAA NMFS

Coral reefs, sometimes called "rainforests of the seas", are found throughout the world's oceans. Not only do reefs provide food and habitat for many species to grow, live, and reproduce, but they also are essential for supporting fisheries, coastal protection, and tourism. Today, many coral reefs are threatened by overfishing and pollution, as well as ocean acidification, disease, and warmer ocean temperatures. Warmer-than-average temperatures cause corals to become stressed. This can lead to mass bleaching (indicated by a white or pale color) of coral colonies and reefs. If ocean temperatures increase just 1°-2°C (1.8°-3.6°F) above average and persist for a month or more, this frequently leads to severe damage or death of corals. Even if corals survive a mass bleaching event, their vulnerability to infectious disease increases and their ability to reproduce decreases. Experts have estimated that bleaching and disease from high ocean temperatures have destroyed nearly one-third of the world's coral reefs.

In 2005, warmer-than-average ocean temperatures in the Caribbean contributed to record-breaking mass coral bleaching, with 50-95% of coral colonies being severely affected. This was the worst bleaching event ever seen in many Caribbean countries. Unfortunately, Caribbean corals are at risk from warming ocean temperatures again this year. Warming in 2010 already has caused mass coral bleaching and mortality in Southeast Asia and the Coral Triangle.

For information on current coral reef environment conditions, please visit NOAA's Coral Reef Watch (CRW).