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what is a coral
4 kinds of coral reef
darwin's volcano
reef structure
manta ray
the solar powered clam
growing a giant clam
   home/species on coral reefs

Coral reefs are home to 1/4 of all marine species.

Species on Coral Reefs
  • Coral reefs create homes to up to 9 million species.
  • Single-celled algae enable coral polyps to build these reefs.

Coral reefs are home to ¼ of all marine species, yet they cover less than 1/10th of the surface of the world’s oceans. Coral polyps enable this diversity to exist by building a 3 dimensional structure with many different habitats. Coral reefs provide shelter, food and other resources for millions of species.

 Coral reef diversity

Fewer than 1000 reef-building coral species exist, but they host a massive diversity of marine life. 35 000 to 60 000 reef dwelling species have been described, but between 1 to 9 million species are estimated live on coral reefs.

Some species spend their entire life on a reef. Others, like sharks, Jacks and manta rays are just visitors that come to the reef to feed, be groomed by cleaner fish or other reasons.
 How coral creates diversity

Coral reefs can be massive structures. For example, the Great Barrier Reef in Australia is 1250 miles (2000 km) long. Coral polyps create a multitude of habitats for other organisms by building these reefs. Many of reef species are totally reliant on coral reefs, and if reefs are lost then the organisms that rely on them will also be lost.

3 factors influence coral reef diversity:

  • Zooxanthellae algae
  • Ecosystem interactions
  • Wave action

Zooxanthellae algae
Coral polyps are simple animals that live within a protective calcium carbonate shell. They grow into rock-like colonies which form the basic structure of a coral reef. Polyps are only able to do this because they have formed a symbiotic relationship with zooxanthellae algae. Polyps provide these single-celled algae with shelter and nutrients. In return, zooxanthellae supply the polyps with enough food to build reefs. Without this symbiosis, coral reefs could not exist. See “What is a Coral?” for more information.

Ecosystem interactions
Coral reefs interact with other ecosystems such as mangroves and seagrass. These interactions increase the health and diversity of all the ecosystems involved. For example, mangroves and seagrass provide nursery habitat for many coral reef fish, and also catch sediment that might otherwise smother a reef. In return, coral reefs shelter these ecosystems from erosion. (See “Reefs & resorts”, “Little fish”, and “How reefs protect the land” for more details).

Wave action
Some parts of a coral reef are very sheltered while others are constantly being pounded by waves. This wave action helps turn coral reefs into a patchwork of habitats that provides homes for many different reef organisms. See “Reef structure” for more detail.

The “Species on Coral Reefs” section explores how coral reefs create diversity and shows some of the species found in this ecosystem.


Frail, T. (2008, January). Great Barrier Reef. Smithsonian magazine. Retrieved 11 September 2008 from http://www.smithsonianmag.com/specialsections/lifelists/lifelist-barrier-reef.html

Knowelton, N. (2008, January 8). Coral reefs. Current biology 18: 18-21. Retrieved 8 September 2008 from http://www.current-biology.com/content/article/fulltext?uid=PIIS0960982207022166

Pauley, G. (1996). Diversity and distribution of reef organisms. In Life and death of coral reefs (Birkeland, C. ed.). Chapman & Hall: New York.

Vernon, J. (2000). Corals of the world, volume 1. Australian Institute of Marine Science: Townsville.

WWF (2008, February 29). Coral Reefs. World Wildlife fund (WWF). Retrieved 8 September 2008 from http://www.panda.org/about_wwf/what_we_do/marine/blue_planet/coasts/coral_reefs/index.cfm

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