Coral Reef Systems

Ecosystems built by colonies of reef forming coral polyps, tiny animals that secrete calcium carbonate skeletons and, over centuries, construct structures large enough to be seen from space, found in warm, shallow, clear waters across the tropics from the Caribbean to the Indo-Pacific and the Red Sea. The reef depends on a symbiotic partnership between the coral polyp and microscopic algae called zooxanthellae living in its tissue, which supply the coral with food through photosynthesis in exchange for shelter, a relationship so central that its breakdown under heat stress causes the whitening known as coral bleaching. Despite covering under one percent of the ocean floor, coral reef systems support roughly a quarter of all known marine species, making them among the most biologically rich ecosystems on Earth.