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Coral Reef EcosystemsCoral reefs are the most biologically diverse marine ecosystems on earth, rivaled only by the tropicalrainforest on land. Coral reefs are very important to people. The value of coral reefs have been estimated atthirty billion U. S. dollars and perhaps as much as one-hundred and seventy-two billion U.S. dollars each year,it provides food, protection of shorelines, jobs based on tourism and also it provide medicine. Coral reefsoccupy less than one quarter of one percent of the earth’s marine environment and they are home to more thanone-fourth of all known fish species. As unique and valuable as these ecosystems are, they have become one ofthe most threatened coastal ecosystems. A recent World Resources Institute report estimates that nearly sixtypercent of the world's reefs are threatened by increasing human activity. As human population continues toincrease so will the threats to reefs.A coral reef is made up of thin plates of calcium carbonate that has been secreted over thousands ofyears by billions of tiny soft bodies’ animals called polyps. It takes years for some corals to grow an inch. Eachpolyp excretes a calcareous exoskeleton and lives in a symbiotic relationship with a host, zooxanthella thatgives the coral its color. The zooxanthellae take in the carbon dioxide and processes it through photosynthesisand then releases the oxygen as a by-product which is then used by the host, polyp. Millions of polyps grow ontop of the lime stones that are the remaining of the former colonies and they form new reefs.Most coral reefsare surrounded by nutrient-poor ocean waters so their high productivity is surprising. This can be contributed a