What is a coral reef?
A coral reef is a highly diverse tropical ecosystem supporting a huge diversity of marine life. They are one of the most productive environments on Earth and are also one of the most sensitive. There is thought to be in the region of 1-3 million different species with only 93 thousand of these that have been described. The main vertebrates on a reef are fish of which there are around 4 thousand species. Corals are in the Phylum Cnidaria along with jellyfish and anemones. There can be many types of coral; hard, soft, gorgonians and hydrozoans. Figure 1 shows the polyps of a Great star coral partially open and capturing food. Coral reefs rely on light, nutrients and a CO2 source due to the symbiotic algae called zooxanthelle (which photosynthesise using the corals waste products of respiration) that live within the polyps of coral
Figure 2 shows the global distribution of corals; most are found within a band of 30° above and below the equator (Kaiser et al. 2005). Temperature plays a huge role in the distribution of corals the range can be from around 18-36°C. Changes in temperature could have huge consequences for the survival of the coral like causing bleaching. (Hoegh-Guldberg et al. 2007).
Additional threats faced by coral reefs include over fishing, recreational uses and tourism such as diving, eutrophication and others such as construction. All of these effects to coral reefs can be reduced with further knowledge and understanding of the environment.