Coral_Reefs

Coral Reefs Coral reefs are underwater structures made from calcium carbonate secreted by corals. Corals are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, and are formed by polyps that live together in groups. The polyps secrete a hard carbonate exoskeleton which provides support and protection for the body of each polyp. Reefs grow best in warm, shallow, clear, sunny and agitated waters. Also coral reef is a reef consisting of coral consolidated into limestone. Often called “rainforests of the sea”, coral reefs form some of the most diverse ecosystems on Earth. They occupy less than one tenth of one percent of the world ocean surface, about half the area of France, yet they provide a home for twenty-five percent of all marine species. Coral reefs are arguably the world’s most beautiful habitats. Scientists have not yet finished counting the thousands of different species of plants and animals that use or live in the coral reef. There are three types of coral reefs: fringing reefs, barrier reefs, and atolls. Fringing reefs are located close to shore, separated from land by only shallow water. Barrier reefs lie farther offshore, separated from land by lagoons more than ten meters deep. Atolls, on the other hand, are formed far offshore and they make a ring-shaped reef that close a circular lagoon. Coral reefs are the largest biological structures on the planet, with the largest being the Great Barrier Reef covering over 2000 kilometers along the east coast of Australia (Focus, 1995). The reef is said to be 500,000 to 2,500,000 years old and is said to be visible from the moon. There is only one problem with this beautiful structure and that is the carelessness of man. Silt from deforested lands and pollution from crowded coastlines choke them, and overuse by coal miners, fisheries, and even tourists deplete and destroy coral reefs. There are many more factors which add to the destruction of the coral reefs, which if not stopped it will destroy all coral reefs. Corals are animals, not plants; sunlight is the key to their survival. They need it to power the millions of microscopic algae, called zooxanthellae, which live in their tissues. The algae provide the corals with food and oxygen in return for raw materials and a secure place to live. This teamwork is what allows the reef to survive in nutrient-poor tropical seas. This relationship is sensitive to such changes in the environment as cloudy waters or extreme temperatures. The stress on the corals can cause them to expel their algae, a phenomenon known as bleaching.