2010 Coral Bleaching

In Brief: Some Caribbean coral reefs experienced over 16 weeks of heating stress during 2010, which will likely result in large-scale coral reef mortality.

Shallow-water coral reef ecosystems are some of the most diverse and economically important ecosystems in the world. These ecosystems support fisheries that feed hundreds of millions of people. Coral reefs are also popular tourist destinations; Southeast Florida alone gets an annual $4.4 billion boost from coral reef tourism. While these reefs host some of Earth’s most visually stunning species, it is the microscopic, single-celled organisms called zooxanthellae on which everything else in the coral reef relies. Zooxanthellae live in coral skeletons and use their photosynthetic ability to manufacture sugars from the sun, which they give to the coral for energy. These sugars can be likened to “rent” paid by the zooxanthellae to the coral, and this “rent” meets about 90 percent of the coral’s energy needs. Coral reefs require warm waters to survive, which is why they are only found in shallow tropical and subtropical oceans. If the water becomes too warm, however, corals expel the zooxanthellae and “bleach,” losing their primary food source. Without living coral, coral reef ecosystems fall apart.

Sea surface temperatures in the tropical and subtropical Atlantic are the warmest they have been since record keeping began in the 1880s. The northern hemisphere summer (June, July and August) of 2009 logged the warmest summer global sea-surface temperatures on record; the 2010 January through August period has been the second warmest on record for that period. The 2010 warm season in the Caribbean has been particularly hard on coral. Coral begin bleaching after four weeks of high water temperatures. If warm conditions wane soon after, coral can recover.

This year, however, some corals in the Caribbean have experienced over 16 weeks of high stress conditions. Visit the NOAA Environmental Visualization Laboratory for an animation of this year’s Caribbean water temperature fluctuations and corresponding coral stress: www.nnvl.noaa.gov/MediaDetail.php?MediaID=547&MediaTypeID=2. Many reefs are not expected to recover from this year’s bleaching. Researchers are in the process of assessing damages.

(Sources: National Oceanic and Atmospheric Administration: NOAA News. “NOAA: Warmest Global Sea Surface Temperatures for August and Summer.” 16 September 2009. Accessed Online 6 February 2010 and Government of Australia: Great Barrier Reef Marine Park Authority. “What is Coral Bleaching?” Accessed Online 6 February 2010 NOAA Environmental Visualization Laboratory. “Warm Oceans Threaten Caribbean Corals.” Accessed Online 8 October 2010 and University of Florida; IFAS Extension. “The Importance and Status of Florida Coral Reefs: Questions and Answers.” 2009. Accessed Online 8 October 2010 )

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