About

• Coral reefs are huge bustling ecosystems located in shallow, warm, clear and sunny ocean waters. These reefs, though they occupy only a small amount of the ocean's body, house over 25 percent of the ocean's wildlife, including fish, crustaceans, mollusks and sponges. The Great Barrier Reef off the coast of Australia is the world's largest reef and is about 1,600 miles in length. The second largest reef, the Belize Barrier Reef, begins outside of Quintana Roo, Mexico, and extends south toward Belize. Other famous reefs include Pulley Ridge in Florida, the New Caledonia Barrier Reef and the Red Sea Coral Reef.
  
  

Formation

• Coral reefs are made from coral and the limestone and calcium carbonate created from the skeletons of dead marine animals. Corals begin forming by creating polyps that have hard exoskeletons and are similar to sea anemones, aside from this exoskeleton. As these polyps die, new polyps form to extend the size of the coral reef. These colonies begin to house, protect and feed other plants and sea creatures that live or migrate to the shallow, clearer waters of the coral reef colonies, creating a diverse ecosystem.
  
  

Age

• Coral grows at an extremely slow pace. For instance, massive corals grow between 5 and 25 millimeters per year; however, the actual rate of growth can be affected by water temperature, the amount of saline in the water and the availability of food. With the complexity of coral reefs and the varying types of coral, the formation of reefs takes an extremely long time. Some of the oldest coral reefs are thought to have taken approximately 50 million years to grow. Most coral reefs on the planet are thought to have taken between 5,000 and 10,000 years to form. The Great Barrier Reef is thought to be approximately 50,000 years old.
  
  

Environmental Concerns

• There are a number of environmental concerns regarding the depletion of the earth's abundant coral reef ecosystems. Eleven percent of coral reefs in the world have been killed and another 16 percent severely injured. There are a number of things that are causing this damage. Increased tourism and traffic to coral reefs can damage and kill the coral and other sea creatures that rely on that coral. Pollution is also a major concern for coral reefs, as sewage and marine debris continues to take its toll on the reefs. Additionally, global warming, overfishing and ozone depletion all put coral reefs at danger.