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What is Coral?

Corals are marine organisms in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.


Types of Coral

Although there are hundreds of different species of corals, they are generally classified as either hard coral or soft coral.

Hard corals

Hard corals or stony corals grow in colonies and are the architects of coral reefs. Including such species as brain coral and elkhorn coral, hard coral create skeletons out of calcium carbonate (also known as limestone), a hard substance that eventually becomes rock. Hard corals are hermatypes, or reef-building corals, and need tiny algae called zooxanthellae to survive.

Soft corals

Soft corals such as sea fingers and sea whips, are soft and bendable and often resemble plants or trees. These corals do not have stony skeletons, but instead grow wood-like cores for support and fleshy rinds for protection. They are referred to as ahermatypes, or non-reef building corals, and they do not always have zooxanthellae. Soft corals are found in both tropical seas and in cool, dark regions.

Sponges Sea

Superficially, sponges and coral have a lot in common. They both just sit there underwater, filtering food particles, living in large colonies that provide habitats for other animals. Divers know that they come in many beautiful colors. But below the surface, sponges and coral are completely different.