Coral Reefs

These are underwater structures made from calcium carbonate deposits which are secreted by corals. Corals belong to the same group as sea anemones. The reefs only occupy about 0.1% of the world ocean surface and yet they are a vital habitat to over 25% of all marine species- many fish, molluscs and sponges. Coral reefs are very fragile and temperature - sensitive and are under serious threat from climate change and water pollution.