by Paula S. Thompson

Created on: June 13, 2009

60 meters below the surface of the Coral Sea, off the east coast of Queensland, Australia, the Great Barrier Reef expands over 133,000 square miles (over 344,000 square kilometers). Composed of over 2,900 reefs and 900 islands, the Great Barrier Reef is the world's largest structure made by living organisms, composed of and built by billions of tiny coral polyps. This natural wonder of the world is also one of the most complex ecosystems in the world.

With such a diverse ecosystem, the life supported by the Reef is equally diverse. Many of these animals are vulnerable or endangered species, and some may be native to the Reef system.

Among the endangered species in the Reef system are the dugongs. Dugongs are large marine animals, related to the manatee. As a herbivore, it is dependent on seagrasses for food, which can be found on the Reef. It has been hunted for its meat and oil for thousands of years, and many known populations are close to extinction. In addition to dugongs, 30 species of whales, dolphins, and porpoises have been recorded, including the humpback whale, the minke whale, spinner dolphins, and Irrawaddy river dolphins.

Green sea turtles have two genetically distinct populations in the northern and southern parts of the Reef. Other species of sea turtles include leatherback sea turtles, hawksbill turtles, loggerhead sea turtles, flatback turtles, and olive ridley turtles. In addition, 17 species of sea snakes can be found, as well as salt-water crocodiles.

Around 125 species of shark, stingray, skates, and chimera live on the reef, along with 49 species of pipefish, nine species of seahorse, and close to 5,000 species of mollusc, including the giant clam and various cone snails.

215 species of birds are attracted to or roost at the Reef; these include 22 species of seabirds and 32 species of shorebirds. Most resting sites are on the north-most and south-most islands of the Reef.

Over 1,500 species of fish live on the Reef; species include clownfish, red bass, yellow -faced angelfish, blue tuskfishes, and several species of snapper and coral trout.

Over 400 species of coral are found on the Reef. These include 36 genera of soft corals, and approximately 360 species of hard corals, which form the backbone of the Reef. Coral was not recognized as an animal until the mid-18th century; they breed in spawning events effected by rising sea temperatures in spring and summer, the lunar cycle, and the diurnal cycle.

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