Fact Sheet
Coral Reef

Basic Facts About Coral Reefs

Coral reefs are some of the most diverse ecosystems in the world, housing tens of thousands of marine species. About one-third of all marine fish species live part of their lives on coral reefs. 
Coral Reef, © istockphoto
© istockphoto

Reefs in the Florida Keys, for example, hold at least 45 species of stony coral, 37 species of octocoral, five species of sea  turtles, 500 species of fish, about 1,700 species of mollusks and hundreds of species of sponges. In addition to their incredible value as wildlife habitat, coral reefs protect coastlines from storms and provide billions of dollars of food and jobs every year to people around the world.   

Behavior & Diet

Corals are ancient animals related to jellyfish and anemones. An individual coral is known as a polyp, a very small and simple organism consisting mostly of a stomach topped by a tentacle-bearing mouth. The polyps extend their tentacles at night to sting and ingest tiny organisms called plankton and other small creatures. 

Thousands of identical polyps live together and form a coral colony. Each polyp excretes a calcium carbonate exoskeleton beneath it and, over long periods of time, the skeletons of many coral colonies add up to build the structure of a coral reef. Many other species – fish, invertebrates, algae and microorganisms – make their homes on and around this reef. Reefs only occur in shallow areas that are reachable by sunlight because of the relationship between coral and algae. Various types of microscopic algae, known as Symbiodinium, live inside of the coral, providing them with food and helping them to grow faster. In many ways, reef-building corals are animals that act like plants – they stay in one place and get some of their energy from the sun.

Range

Coral reefs are found all around the world in tropical and subtropical oceans. They are usually found in shallow areas at a depth of less than 150 feet. However, some coral reefs extend even deeper, up to about 450 feet deep. Despite how important coral reefs are to life in the ocean, all of them in the world add up to less than one percent of the sea floor – an area about the size of France.

More on Coral Reef: Coral Reef Fish »

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