Coral bleaching

Sea-level rise and increased sea water temperature will cause accelerated beach erosion, degradation of coral reefs and bleaching. (IPCC, 2007)

Oceanic islands fall into two categories: either they are products of volcanism from a stationary magma source creating a linear chain of islands or were once joined to continental land masses and became separated because of tectonic activity. Whether products of volcanism or tectonic uplift, reefs have developed on the foundations of the islands. The coastal reef acts as a natural coastal defence structure that dampens wave energy and blocks saltwater intrusion to coastal aquifers. Since coral reefs shelter coastlines and generate sand, coral reef damage can exacerbate erosion and flooding. In addition to being a barrier, a reef provides a habitat for a diverse range of aquatic life. In terms of biodiversity, coral reefs are the tropical rainforests of aquatic ecosystems. Human populations have historically depended upon reef services such as fisheries and shoreline protection.

A coral bleaching event is triggered whenever temperature anomalies exceed a critical level. Coral reef bleaching is a phenomenon whereby corals lose their pigmentation either through loss of their symbiotic algae or a reduction in chlorophyll concentrations. As a result, corals lose their normal colourful appearance and whiten. In 1998, a year when tropical sea surface temperatures were the highest on record, coral reefs around the world suffered a severe bleaching (loss of symbiotic algae) and subsequent mortality of the reef. These events were likely induced by anthropogenic global warming, which cause steadily rising baseline of marine temperatures, combined with El Niño and La Niña events. Coral bleaching becomes more frequent and severe as the climate continues to warm because reefs are very sensitive to warm sea temperature. Even those reefs with well-enforced legal protection as marine sanctuaries, or those managed for sustainable use, are threatened by global climate change.

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