What Are Coral Reefs?

Coral reef seems like plants but in actually coral reef are made up of marine invertebrate animals that are related to anemones and jelly fishes.
Single coral animal is a polyp. Polyp are shallow water organisms have a soft body covered by a calcareous skeleton.The polyps extract calcium salts from sea water to form these hard polyp are usually look like soft round mouth covered with tentacles.
Polyp doesn't always act alone.Many species of coral grow in colonies with hundreds or thousands of polyp acting as a single organism.

There are three types of coral reef :

1)Fringing Coral : Also called shore reefs.

Fringing reefs are reefs that grow directly from a shore. They are located very close to land, and often form a shallow lagoon between the beach and the main body of the reef.
The fringing reef is by far the most common of the three major types of coral reefs, with numerous examples in all major regions of coral reef development.
Fringing reefs can be seen at the New Hebrides Society islands off Australia and off the southern coast of Florida.
Height of island >. Height of reef

2) Barrier Reef :

Barrier reefs are extensive linear reef complexes that parallel a shore, and are separated from it by lagoon.
This is the largest (in size, not distribution) of the three reefs.
Barrier reefs are far less common than fringing reefs or atolls, although examples can be found in the tropical Atlantic as well as the Pacific.
Height of island = Height of reef
The Great Barrier Reef of Australia - World's largest reef, 1200mile long.It is ta very large comlex consist many reefs.

3) Atoll Reef:

An atoll is a roughly circular (annular) oceanic reef system surrounding a large (and often deep) central lagoon.
Atolls are located at great distances from deep see platforms, where the submarine features may help in formation of atolls, such as a submerged island or a volcanic cone which may reach a level suitable for coral growth.
Island submerged in water in this case.
Atoll are more common in Pacific Ocean than any other ocean
An atoll may have any one of the following three forms-

True atoll—a circular reef enclosing a lagoon with no island;
An atoll surrounding a lagoon with an island
A coral island or an atoll island which is, in fact, an atoll reef, built by the process of erosion and deposition of waves with island crowns formed on them.

Death of Coral due to excessive Carbon dioxide in the atmosphere is called coral bleaching .Because carbon dioxide change the ph of ocean .
There will be symbiosis association between zooxanthalle( algae ) and coral.So,with change in ph, symbiosis association is destroyed and zooxanthalle is removed from coral .Coral without zooxanthalle is considered as dead.

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