Corals

What are they?

Coral are limestone formations, formed by millions of tiny animals ( mainly coral polyps ). They may be in various shapes. The living coral are in beautiful colours. They leave their limestone 'skeletons' behind ( or rather deposits of them in their shape ). They can even build masses that build up masses till they form an island.

But these reefs can be destroyed. So what? Big deal, no loss. But they are so rich in animal life, and to make a small reef, it takes hundreds of years. But they are being destroyed - they are used for building material, pollution, they are blown to the sky to catch fish, which find that as a hiding place.They are also used for the tourists as souvenirs.

They are generally found in shallow water, in tropical regions, as they cannot live in water colder than 20 degrees. There are three types of reefs : fringing, barrier, atolls.

The first group - fringing reefs are submerged platforms of living coral animals. They extend from the shore.

The barrier reefs follow the shore - parall to it, but do not touch it. They form a barrier between the ocean and the land. It may consist of reefs with water channels between them.

The atolls's are reefs that are ring shaped. They form when a coral builds up on submerged volcano's. They surround a body of water on the surface. Some channels connect them to the open sea.

How do coral form?

We'll answer that in a few paragraphs. The coral belong to a group of animals like sea anemone, hydra, jellyfish. One end has a mouth with tentacles. The other end attaches itself to hard surfaces on the sea bed.

Most live in colonies. They attach themselves to each other. The limestone is deposited when the animals take calcium from the sea water. They deposit them around the lower half of the body. Generation after generation ( with other families coming in ), they build big reefs.

They feed on mainly tiny animals and many kind of larvae of shellfish. They cannot live without algae. The algae are found is the tissue of the polyp. The algae produce a chemical that helps them build their limestone shell's. That's why they live near the surface - for the algae.

Coral reproduce by budding or by eggs. The eggs may float off, but the buds come right out of the parent's body, and stay around the place of the parent. Budding helps the colony build in size.

New colonies occur when the parents lay eggs. The new animals form reefs by budding.

Many marine animals destroy the reegs, but it is balanced by new colonies and the growth of old ones. But later ( 1950's + ), starfish have suddenly grown in number and have destroyed them ( cause of sudden growth : unknown ).

The commercial coral do not live at the surface, they live deeped below ( the precious kind ). In these, they have an internal skeleton rather than an external one.