Coral reefs
Coral reefs are one of the most important ecosystems in the world, and have been called 'the rainforests of the sea' owing to the diverse range of plants and animals that they support. Although they cover less than 0.1% of the world's ocean surface, they provide a home for at least 25% of all marine species.
What is a coral reef?
Coral reefs form at depths not exceeding 25 metres, and need warm water between 20 to 28 degrees Celsius. Reefs grow faster in clear water that allows sunlight to penetrate. A coral reef is made up of millions of coral polyps. These are tiny animals, but they contain plants called algae. The algae convert sunlight into energy for the reef itself. The coral polyps make hard calcium carbonate which builds up over thousands of years to form reefs.
Global distribution of coral reefs
Coral reefs are found between 30° north and 30° south of the equator.