Today here are some facts about how wonderful, unique and big the Great Barrier Reef is. If you want to know more just follow the links.
The Great Barrier Reef is unique as it extends over 14 degrees of latitude, from shallow estuarine areas to deep oceanic waters. Within this vast expanse are a unique range of ecological communities, habitats and species – all of which make the Reef one of the most complex natural ecosystems in the world. (Great Barrier Reef Marine Park Authority).
The Reef comprises 400 different species of coral, 4000 different species of mollusc, and many other kinds of invertebrates. There are 500 species of seaweed, 16 species of sea snake, 1500 species of fish, and 215 bird species, plus dugong and sea turtles.
Individual reefs are of two main types: platform reefs formed from radial growths, and wall reefs resulting from elongated growths, often in areas of strong water currents.
There are also fringing reefs on sub-tidal rock of the main coastline or continental islands. Each reef has a thin layer of living coral capping a structure made up mainly of calcareous sand and rubble from the breakdown and consolidation of coral and other skeletal material.
Many of the present reef areas were once hills on a former coastal plain, and these became islands when the water level rose after the last Ice Age, to be colonised by coral polyps. Each coral polyp lives inside a shell of aragonite (calcium carbonate), and the shells of dead coral are eventually cemented together and covered with more calcium carbonate, from encrusting calcareous algae. The polyps can only grow in shallow warm water, less than about 30 m depth and water temperatures above about 18° C. (Australian Museum).