Coral is a small marine animal from the Anthozoa class that exist as polyps. Coral is usually found in colonies of many similar in size and color individuals. Corals have an important role in marine life and biodiversity because the create the coral reefs found in tropical oceans. Not all corals can create reefs but most coral can secrete a hard exoskeleton of calcium carbonate ( limestone ). The head of a coral reef is wrongly perceived as single organism but is actually formed from thousands of small individual polyps measuring in about a few millimeters in size. After many thousands generations of coral, they lay down a skeleton that is characteristic to their specie. Corals have two ways of reproducing. Their main reproduction method is asexual reproduction of individual polyps but they can also breed sexually by spawning. When spawning, the coral of the same species release gametes all together for a period of a few nights around a full moon.
The coral's main food resource are symbiotic unicellular algae but they can also feed off plankton using their stinging cells found in their tentacles. The most important factor for the coral to survive is sunlight. This is showed because most corals live and grow in clear shallow waters, not more then 60 meters in depth. Corals that do not have symbiotic algae can live in deeper and colder waters. Such corals can be found in the Atlantic ocean, where some corals can live as deep as 3000 meters underwater. Corals are very sensitive to environmental changes. Predictions look very grim for the coral as scientists say that by the year of 2030, half of the total worldwide coral will die in effect to global warming, There are other factors that threat the coral reefs like algae or the increase in nutrients in the water or an increase or decrease in the salinity levels of the water.
