Beautiful coral reefs are tropical, and grow in warm waters that are shallow.
They are filled with calcareous structures because stony corals are the main constituents of coral reefs, but they include algae, plants, and many organisms. They are like a biome all in itself.
They support a wide variety of animals and plants that inhabit these structures.
The most important reef builders are the stony corals also known as scleratinian corals.
Their distribution depends on water temperature and it should be ~ 20 degrees celcius, shallow as they extend to a maximum depth of 60m, and clear not turbid for maximum photosynthesis to take place by symbionts such as zooxanthellae.
The 3 different types of coral reefs are the atoll, barrier, and fringing reef.
The Atoll reef surrounds a mass of water (lagoon) on top of a submerged volcano.
The Fringing reef is formed when a platform slowly sinks underwater and stops. The platform extends toward sea up to 60 m off the edges of the volcanic island. Such reefs are found in the Maldives, Hawaii, Tahiti, Figi etc.
The Barrier reef like the Great Barrier Reef in Australia, is usually 2000km long. The reef is parallel to and follows the shoreline, and is separated from the mainland by a lagoon.
See attachments for a visual representation.
The reef formation involves 2 phases:
1) A constructive phase: Where the reef grows upward and this happens by the accumulation of calcium carbonate produced by the scleratinian stony corals.
2) A destructive phase: Where the reef becomes weakened, and is almost dying. The agents responsible for the death of the coral reef are the boring sponges such as the Cliona species among the Class Desmospongiae, family Clionidiae, among the phylum Porifera, as well as the boring bivalves in an unsetteling parasitic relationship. However, the bright side of this is that there is a higher chance of generating a new reef from corals, and attracting fish, bivalves, zooxanthellae, molluscs, stony corals,m coraline, algae and many more fauna and flora.
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