| Precis||Coral reefs are vital ecosystems, providing a source of income, food and coastal protection for millions of people; and 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 - 29ºC, although they exist in ranges from 18ºC (Florida) to 33ºC (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).
Unfortunately, coral reefs are also among the most vulnerable ecosystems in the world. Disturbances such as bleaching, fishing, pollution, waste disposal, coastal development, sedimentation, SCUBA diving, anchor damage, predator outbreaks, invasive species and epidemic diseases have all acted synergistically to degrade coral reef health and resilience. Today, an estimated 20% of coral reefs worldwide have been destroyed, while 24% are in imminent danger and a further 26% are under longer term danger of collapse (Wilkinson, 2004).