Coral reefs are an ecosystem that have the second biggest biodiversity in the world and have been described as the rainforests of the ocean. For years they have been threatened by man. Physical destruction from boats, fishing and pollution. Now their biggest threat may be from climate change.
15% of the world’s reefs have already been lost and 30% may die in the next 30 years.
Coral reefs are a complex ecosystem – tiny sea anemone-like polyps build coral reefs by secreting brittle, limestone skeletons. Algae support the polyps by converting sunlight and carbondioxide into sugars that feed them; the polyps, in turn ooze waste products that nurture the algae.
Coral grows near the surface of the water. Coral forming polyps.
A rise of sea temperatures by as little as 1 or 2°C can cause a major coral bleaching event where the algae, which feed the coral growing polyps, die. A rise of 3 or 4°C will mean that the algae never returns.
Rises in dissolved, acidic, carbon dioxide in the sea water also means that the polyps are unable to form coral through calcification. Coral is made from calcium carbonate which dissolves in acid. Decomposing algae from bleaching events, will increase dissolved carbon dioxide in the water.
Warmer sea water also leaves the reefs more vulnerable to pollutants and diseases.
Australia’s Great Barrier Reef is at the brink of a major bleaching event at the moment with sea water up to 2°C warmer than normal. This will be the third bleaching in six years, increasing the risk that the reef may never recover.
If we lose our coral reefs we lose not only the wildlife that lives there, income from tourism, but also protection for the coasts from the increased number of storms expected from climate change. This was shown after the Boxing Day earthquake off Aceh, Indonesia caused the devastating Tsunami.
Islands protected by unspoilt coral reefs like Surin Island and the Maldives appeared to have suffered less damage and suffered less casualties. The reefs absorbed most of the power of the giant waves.