Glittering Stones >> Coral

Coral

Corals are very small cnidarians, and most of which form colonies bound together by secreted calcium carbonate. They include the most important reef builders, which found in tropical seas. They obtain much of their energy from symbiotic algae known as zooxanthellae, and so are dependent on sunlight. As a result, they are usually found at and near the surface, though occurring to a depth of at least 50 m. There are two main forms of coral, hard and soft.

Growth

Corals are actually slow growing, and as a result are generally protected through environmental laws. Coral breed by spawning, with its all corals in a region spawning on a few nights around full moon.

Coral reefs grow as atolls, barrier reefs and fringing reefs also called shore reefs. Coral reefs were first described in 1842 in the book according to Coral Reefs by Charles Darwin.

Normally coral reefs live in tropical waters, but also coral exist even in cold waters of the coast of Norway.

The largest collection of coral reefs is of the coast of Queensland and Australia. These reefs are known collectively as the Great Barrier Reef.

Dead coral reefs on land are often mined for marble.

Reddish coral is sometimes used as a gemstone especially in the Tibet. Pure red coral is called as 'fire coral' and it is very rare because of the demand for perfect fire coral for jewellery-making purposes.

Coral is quite sensitive to environmental changes. A coral reef could easily be swamped in algae if there is too much nitrogen in the water. Coral would also die if the water temperature changes by more than its degree or two and becomes too hot or too cold and if the salinity of the water drops. A combination of temperature changes, pollution, and overuse has led to the destruction of many coral reefs around the world.