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Coral reefs and biodiversity
Coral forms range from compact brain corals found in areas of high wave energy, through heavy branching and plate corals in deeper water, off the reef edge, to smaller finely branched corals found behind the reef crest and in the lagoon.
Coral reefs are generally divided into four main types: atolls, barrier reefs, platform reefs, and fringing reefs. Atolls, where reefs form a ring around a lagoon, are mainly found in the Indian and Pacific Oceans. In the Pacific they are grouped into long island chains such as those of Micronesia and Central Polynesia. Barrier reefs are separated from the mainland by a deep channel or lagoon, in which are found platform reefs. Fringing reefs are directly attached to land or separated only by a shallow lagoon.
On an individual reef, the total count of fish species and smaller marine organisms may exceed several thousand, but the number of individual coral species is much lower.
The Indo-Pacific has some 700 reef-building coral species, many times more than the tropical Atlantic (with some 35). In general, reefs in the
Indo-Pacific differ from those of the Atlantic by having many more coral species, and by supporting much richer animal communities on their intertidal reef fiats. The centre of coral diversity is the Southeast Asia region of the
Indo-Pacific, and over 400 species of hard coral are believed to occur in Philippine waters.
Moving away from this region, coral diversity declines. Nevertheless, over 200 coral species are recorded from the northern and central Red Sea, about 200 from Madagascar and Chagos. The east coast of the Malaysian peninsula has 174 identified species, south-east India about 117, the Gulf of Thailand some 601 and the Persian Gulf 57.
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