Coral Reefs are the one of the most diverse and beautiful underwater communities. They are known for there exotic plant life and there spectacular animal life. In general coral reefs appear to resemble each other, but each one is very unique. .
So what are coral reefs? Coral reefs are wave- resistant underwater ridge or mound built of fragments of coral, sand and solid limestone. Corals live in all oceans of the world. The largest reefs are found in the warmer portions of the Pacific and Indian oceans. But they are also found in the Caribbean and in the Gulf of Mexico as far north as southern Florida. Reefs are made up of many different species of corals. More than 40 species form large reefs of the West Indies and more than 350 species of coral have been found in the Great Barrier Reef. In which all live in a temperature from 70 to 80 degrees. These corals are made up of tiny organisms called polyps. As the polyps of stony corals grow, they produce limestone for their skeletons. When they die their skeletons are left behind. These are used as foundations for new polyps. An actual coral is composed of layer on layer of dead coral polyps covered by a thin layer of living polyps. Other types of animals and plants add to the architecture of a coral reef. Within the coral animals live single -celled, round algae called zooxanthellae. The photosynthetic zooxanthellae and the green algae transfer some food energy directly to the coral polyps. There are two types of coral , perforate and imperforate. Perforate corals have porous skeletons with connections between the polyps through the skeleton. Imperforate corals have solid skeletons. They have different growth rates. Corals are the slowest species, growing anywhere between 5 and 25 millimeters per year. .
There are three kinds of coral reefs: barriers, fringing, and atolls. Barrier reefs are reefs that are separated from land by a lagoon. These reefs grow parallel to the coast, are large and continuous.