Coral reefs are one of the most biologically diverse and ecologically complex marine communities (3). They are unique in the fact that they are entirely created through biological activity such as the deposition of calcium carbonate occurring over eons of geological time (3). They have one of the oldest marine communities that can be traced as far back as 500 million years (3). Coral reefs are found in shallow tropical waters along the shore of islands and continents, and live in very nutrient poor waters that have certain zones of tolerance to water temperature, salinity, and UV radiation (1). Reefs are mainly composed of calcium carbonate from living and dead corals (1). Coral reefs have so much high productivity and biodiversity among themselves that they are often referred to as the "Tropical Rainforests of the Oceans." (1). Coral reefs are most commonly found in the Caribbean, Western Atlantic, Eastern Pacific, Central and Western Pacific, Indian Ocean, Arabian Gulf, and the Red Sea. The tissues that make up the corals are not what actually give the corals their colors. The reefs are actually clear and receive their coloration from the zooxanthellae living within their tissues (1).
Coral Bleaching occurs when the coral is exposed to some kind of stress like an increase in ocean temperature, solar radiation, exposure to air, and pollution (3). These factors cause the algae contained within the coral to leave, and when this is happening the coral is bleaching (3). It is important to remember that when a coral is being bleached, the entire coral is not being bleached, the polyps of the coral around the edges are still healthy (see picture below) (1). This algae contained within the corals also provide the coral with nutrition, and once this "nutrition" (algae) begins to leave the coral, it will more than likely die (4). The frequency and scale of bleaching disturbances has dramatically increased since the late 70's (1).
