The Importance of Coral Reefs
Coral reefs are a precious resource in the ocean because of their beauty and biodiversity. Coral reefs provide shelter for a wide variety of marine life, they provide humans with recreation, they are a valuable source of organisms for potential medicines, they create sand for beaches, and serve as a buffer for shorelines. Coral reefs are built by millions of coral polyps, small colonial animals resembling overturned jellyfish that use excess carbon dioxide in the water from the atmosphere and turn it into limestone.
Corals are in fact animals that fall under the phylum Cnidaria and the class Anthozoa. They are relatives of jellyfish and anemones. Corals can exist as individual polyps, or in colonies and communities that contain hundreds to hundreds of thousands of polyps. For example, brain corals consist of colonies of many individual polyps; each individual polyp averages 1-3 mm in diameter. Corals can be divided into two groups: hard coral and soft coral. Hard corals, also known as stony coral, produce a rigid skeleton made of calcium carbonate (CaCO3) in crystal form called aragonite, with reef-building capabilities. Alternatively, soft corals, including sea fans, do not produce a rigid calcium carbonate skeleton and do not form reefs, though they may be present in a reef ecosystem.
Photograph courtesy The Coral Kingdom, Collection/NOAA. (National Geographic)