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Coral reefs are vital ecosystems, providing a source of income, food arid coastal protection for millions of people; arid recent studies have shown that coral reef goods and services provide an annual net benefit of US$30 billion to economies worldwide (Cesar et al, 2003). Coral reefs are composed mainly of reef-building corals: colonial animals (polyps) that live symbiotically with the single-celled microalgae (zooxanthellae) in their body tissue and secrete a calcium carbonate skeleton. Coral reefs are formed by hundreds of thousands of these polyps and are found in warm, shallow, clear, low-nutrient tropical and sub-tropical waters, with optimum temperatures of 25-29eC, although they exist in ranges from 18eC (Florida) to 33eC (Persian Gulf) (Buddemeier and Wilkinson, 1994). They are incredibly diverse, covering only 0.2% of the ocean's floor but containing 25% of its species and they are often dubbed the 'tropical rainforests of the oceans' (Roberts, 2003).