5.2

The tropical coral reef Tropical coral reefs are built by tiny coral polyps, which live in close association with photosynthetic zooxanthellae and are therefore limited in their distribution to areas where abundant light is available and temperatures are warm. The polyps themselves are consumers and require a source of small organisms that they can capture and digest. Changes to biotic or abiotic factors in the oceans can lead to the erosion of coral reefs. Artificial structures can be provided as a substrate on which reef communities can develop.