Corals are large colonies of tiny animals that grow slowly underwater. Each year, these colonies, or coral reefs, leave behind a layer of calcareous skeleton that is so cruel that it almost looks like a rock. If you looked inside the coral, you would see annual rings very similar to those of a tree. Some coral branches are hundreds of years old. This means they were growing when Christopher Columbus discovered America or even earlier.
Typical brain corals grow primarily in the tropics, where the water stays warm all year round. Because of their hard structure, brain corals can live in ocean currents and strong waves. Thinner plate corals can only survive in sheltered lagoons or deeper water. Large, hard coral heads often serve as “cleaning stations” for certain species of animals and fish. They rub against corals to remove dead skin or parasites.
Ultraviolet light can also damage corals in shallow water where there is no protection. If the depletion of the earth's protective ozone layer allows more ultraviolet radiation to reach the earth, corals could disappear from habitats such as shallow water.