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Coral Reefs

Coral reefs are generally found in warm and shallow waters of the world’s tropical oceans. They are formed from calcium carbonate produced by colonies of tiny coral polyps with the assistance of symbiotic alga, and also by the exoskeletons of marine organisms such as anemones, starfish and molluscs.

Each colony of coral can be made up of thousands of polyps that live by digesting small microscopic organisms. Colonies grow through both sexual and asexual reproduction.

The are three main types of coral reef. The first are known as fringing reefs. As the name suggests, they are found on the coast or are separated from the mainland by a narrow channel.

A second type is the barrier reef. These are large reefs that are separated from the coast by a broad expanse of water and grow parallel to the coast, in some instances for many hundreds of kilometres.

Finally there are atolls. These are reef formations found on the continental shelf or in the open ocean surrounded by deep water. They usually form when a volcanic island on the continental shelf subsides and is covered by the sea. As the island continues to subside, the coral continuously grows upward.


Prepared by: Turnbull, P.
Created: 3 November 2001
Modified: 1 December 2001

Published by South Seas, 1 February 2004
Comments, questions, corrections and additions: Paul.Turnbull@jcu.edu.au
Prepared by: Paul Turnbull
Updated: 28 June 2004
To cite this page use: http://nla.gov.au/nla.cs-ss-biogs-P000117

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