Fire Corals:

The fire, or stinging corals, belong to the Hydrozoa class. Fire produce hard, smooth skeletons containing many tiny polyps. The skeleton is light brown in colour because of zooxanthellae, which is a dangerous poison, that is very harmful to skin. Fire corals reproduce jellyfish, and the fertilized egg then becomes a planula larva, that develops into a new coral colony.

Stony Corals:

Stony corals are the hardest type of corals. They remove calcium from sea water and deposit it under the living tissue, as a white, external skeleton of calcium, also known as a limestone. Stony corals use to be abundant in ancient seas, but today, are only found in limestone formations, and there is small population of these corals. The reef-forming corals have very rapid skeletal growth, while non-reef forming corals have a very slow skeletal growth.

Soft Corals:

Soft corals lack axial skeletons. They receive their support from a gelatinous, spicule-filled mesoglea. These soft corals form colonies that are rubbery and that have shapes the are irregular.

Gorgonian Coral:

This group includes corals commonly known as sea feathers, sea fans, and the red coral. The corals of the gorgonian group are often part of reefs. The body of this type of coral, consists, of an erect central rod of organic material called gorgonin, surrounded by a cylinder of calcareous spicules and by the polyp organisms. The spicules gives the coral an orange or purple colour, and sometimes yellow or brown colours may be given, which is caused by zooxanthellae.

Branching Coral Colonies:

A colony of very small individual animals called coral polyps. Branching corals are considered hard corals, since they have a hard calcium carbonate skeleton. They have bright colours due to the algae that lives in their body tissues. They produce the food that the corals need to survive.

TYPES OF CORAL REEFS

Fringing Reefs:

Fringe reefs form a border or fringe of coral along a shoreline. They grow on the shelves of rock that extend from the coast's shore into the sea. A fringe reef is separated from the shore by a narrow stretch of shallow water. This place of coral growth includes rows of coral with sandy passages between the rows

Barrier reefs:

Grow parallel to the land, but are separated from the shoreline by a larger area of calm water called a lagoon. They act as barriers between the lagoon and the waters of the open sea. The regions of coral formation include zones found in fringing reefs, patch reefs, small reefs, back reefs, or the shoreward side of the reef.

Atolls:

Atolls are annular reefs that develop near or at the surface of the water when islands that are surrounded by reefs subside. An atoll is a ring of coral which surrounds nothing but water. There are two types of atolls , deep sea atolls, and those found on the continental shelf. There are three steps in the formation of an atoll. First, a fringe reef grows around a volcanic island, then, as the island begins to sink, a lagoon appears, which means the stretch of water between the island and the coral reef widens, which means the reef is now a barrier reef. When the island disappears completely, the coral atoll now surrounds a shallow lagoon, and the channels between the stretches of coral connect the lagoon with the open sea.

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