Coral Reefs Ecological Society of America 02.01.01 Coral reefs are the most diverse communities on the planet. These tropical marine communities occupy less than 1% of the ocean floor, but are inhabited by at least 25% of all marine species. Scientists estimate that more than 25,000 described species from thirty-two of the world’s thirty-three animal phyla live in reef habitats - four times the number of animal phyla found in tropical rain forests.     Coral reefs are one of the oldest continuous environments on Earth. Similar marine communities have existed for hundreds of thousands of years. Most of the reefs we see now have been growing for over 5,000 years. Coral reefs are found within the jurisdiction of more than 100 countries and occupy more than 600,000 square kilometers of tropical oceans. They generally require clear, warm water and high light intensity for survival. This limits them to shallow water, with maximum diversity occurring between 10 to 30 meters below the surface. Reefs exist in nutrient-poor environments and for that reason small changes in the nutrient content of the water can adversely affect their survival.   Prepared by the Ecology Society of America   1707 H St., NW   Suite 400   Washington, DC 20006 ©2001 The Aurora Collection, Inc. All Rights Reserved. Site Development by: Interactive Multimedia. Inc.