The summer of 2010 brought heat waves to many parts of the planet, including coral reefs in the Caribbean. Global ocean temperatures for the entire year through August were the second warmest on record. These higher than normal water temperatures create stressful conditions for corals. Excessively warm temperatures stress corals, much like they do humans, and the coral responds by expelling the algae that live within their cells and provide them with food and nutrients. This process is called bleaching, since the corals turn a pale white. Prolonged bleaching periods may result in the death of the coral.
This data shows how warmer than normal ocean temperatures accumulated over the summer months of 2010, creating the worst observed bleaching conditions in the Caribbean since records began in 2000. When exposed to 4 weeks or more of excessively warm temperatures, many coral species may begin to bleach. Notice that some parts of the Caribbean went over 16 weeks of heating stress in 2010. It is anticipated that some corals in these areas may not recover. Scientists in the field will be documenting the toll that this bleaching event has taken on corals.