CORAL REEFS

Corals are made of a colony of small creatures: Polyps. These marine animals with tentacles are fixed on a solid axis. This axis is in fact made of the skeletons of dead polyps. The skeletons are made of calcium carbonate (calcareous). The skeleton can be white, pink or blue. The pink coral is very appreciated in jewellery. The polyps live in symbiosis with an alga that lives inside them. The polyps nourish the phosphorus alga. In exchange the alga helps them build their skeleton. The coral reef shelters are very rich in fauna and flora. They can be found in the tropical or sub-tropical waters. They usually grow at rate of 0,5 cm to 1,8 cm per year, mostly along the coasts or by a lagoon, on an atoll. The Coral reefs of the western Pacific are much more diverse than those of the Atlantic and Caribbean. Today, the Coral reefs are under threat, suffering from decline and degradation due to a combination of natural and anthropogenic factors.In several reefs the polyps have been losing their symbiotic alga and ended up dying because their skeleton could not be built any more. Some of the man-made damage is related to pollution and tourism. "Impacts from tourism can often be reduced by raising awareness and changing behaviour among both tourists and local tourism industry workers."The largest coral reef is on the Northern coast of Australia. Click Great Barrier Reef VIDEO