Coral Bleaching

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Coral Bleaching

Coral reefs are the most biodiverse ecosystem on the planet. There are more than 25,000 known species of organisms and countless others that have yet to be identified (Helvarg, 2000). Reefs thrive on the shallow edge of tropical seas, most often on the eastern edge of continents along warm water currents that brush the coasts. Reefs cannot live in cold waters and are limited by ocean depth and available sunlight. Coral is the foundation of the reef community, providing a three-dimensional structure where thousands of species of vertebrates and invertebrates live and feed. Some species of coral are hard, while others soft. Some are branched, yet others are compact and rounded. Coral is made up of large communities of tiny jellyfish like polyps. These polyps absorb calcium from the sea water and secrete a hard limestone skeleton. At night the polyps extend sticky, stinging tentacles from their skeletons to capture and consume small floating organisms such as zooplankton. Every coral has a two-stage life cycle: the larva, and the polyp. The larval stage is free swimming, and the polyp is stationary. Ocean currents carry the larva from the stationary parent polyp to any hard, clean, silt-free surface where, if the conditions are perfect, the larva grows into a coral forming polyp, never to move again (Levin, 1999). One of the most valuable resources for coral polyps are algae. Some live on the coral skeletons, but one type in particular, zooxanthellae, lives inside the tissue of the polyps. Zooxanthellae makes up about half the weight of the fleshy polyps and are not only a valuable food resource, but they are responsible for the brilliant colors associated with coral. When coral looses these prec...

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... as Helvarg (2000), Winiarski (19998) and Warrick (1999) have the benefit of being able to describe what coral bleaching is and it’s probable causes in a much more concise and to-the-point fashion.



Gates, R.D., and Edmunds, P.J. 1999. The Physiological Mechanisms of Acclimatization in Tropical Reef Corals. American Zoologist; Vol. 39, No. 1 (Feb. 1999), pp. 30-43.

Huppert, A., and Stone, L. 1998. Chaos in the Pacific’s Coral Reef Bleaching Cycle. The American Naturalist; Vol. 152, No. 3 (Sept. 1998), pp. 447-459.

Levin, T. 1999. To Save a Reef. National Wildlife; Vol. 37, No. 2 (Feb./Mar. 1999), pp. 20-29.

Warrick, J. 1999. Warm Weather Destroyed Corals in ’98, Report Says. Houston Chronicle; March 8, 1999, p. 6.

Winiarski, K. 1998. Coral in Peril as Reefs Suffer Worldwide. USA Today; October 19, 1998, p. 04A.
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