Coral Reefs

Coral reefs, also knows as the “rainforests of the sea”, are extremely diverse habitats under the sea that are formed by Coral, an anthozoan in the phylum Cnidaria. Corals live in colonies of other individual coral, called polyps. Corals secrete a hard calcium carbonate skeleton from the base of each polyp. They use this skeleton to grow their community on and when threatened by a predator, they can contract into the structure for protection. Because polyps are always secreting calcium carbonate being added to the skeleton, Coral reefs are always growing, constantly creating new habitat for marine wildlife. Human activity has been negatively affecting the growth and health of the worlds Coral reefs however, destroying over 35 million acres of reefs in the last few decades alone. Coral reefs are very important marine ecosystems that provide habitat for thousands of species, protect the shoreline from the eroding forces of the sea, and provide an unknown amount of resources for pharmaceutical breakthroughs. Although Coral is found all over the world, the Coral that form reefs are found in relatively shallow, warm tropical ocean waters between the latitudes 30 degrees north and 30 degrees south. Waters must be clean and clear in order for Coral to survive. Once Coral larvae settle on a hard substrate colonies will begin to form. Over time these colonies become thickets that continue to grow upward on the skeletal remains of old colonies, steadily forming reefs. These greatly diverse ecosystems are found along tropical coastlines, on the margins of volcanic islands, and as isolated coral atolls. (“Coral Reefs”) There are 3 main types of Coral reefs, with many different species of coral living on each. An Atoll reef is a roughly circular reef system that surrounds a central lagoon. A Barrier reef is a reef system that parallels the shore and is separated by a wide lagoon that contains at least some deep portions. A Fringing reef is a reef system that grows fairly close to shore and has an entirely shallow lagoon or no lagoon at all. Scientists believe that all reefs must have started out as Fringing reefs, yet when the islands surrounded by the reefs started subsiding into the ocean, the reefs were able to grow at a rate where they did not subside with the island. Fringing reefs surround an island that has not subsided at all, an island that has subsided slightly has a Barrier reef around it, and islands that have subsided completely leave behind an Atoll reef. Different species of Coral include Staghorn, Elkhorn, Lettuce, Grooved Brain, Common Brain, Boulder Star, Great Star, Ivory Bush, Mustard Hill, Clubbed Finger, and Massive Scarlet. Coral species tend to be segregated into different zones on the reef separated by competition with other species and environmental conditions. (“Types of Coral Reefs”) Coral reefs are home to thousands of different species of plants and animals that rely on the reef for food, shelter, and protection. The Great Barrier Reef alone is home to over 5,000 species of molluscs, 1,500 species of fish, 500 species of seaweed, 400 species of Coral, and over 200 species of birds. In addition, 30 different species of whales, dolphins, or porpoises live in or visit the waters around the reef. (“Reef Facts”) The plants and animals living in Coral reefs are not the only ones who are affected by the reef. Shoreline-dwelling animals are protected from the eroding forces of the ocean by Coral reefs. Without the reefs many of these animals would lose their habitats. Also, many species of birds use the shallow waters of Coral reefs to hunt for fish. Humans are greatly affected by Coral reefs too. Coral reefs provide humans with fish, snails, crabs, and other animals to hunt and harvest for food. When these animals are sold, it helps stimulate the fragile economy in many developing countries where reefs are found. Also, just like shoreline-dwelling animals, reefs protect humans from