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Coral and Coral Reefs

Updated on November 2, 2013

Corals are animals belonging to the phylum Coelenterata (Cnidaria). These corals secrete an exoskeleton formed of calcium carbonate, which protects the soft body. Generally this exoskeleton is called coral. The corals in general have diverse shapes and sizes, but majority are colonial with very small polyps.Coral colonies are most abundant in tropical seas, through some occur in arctic and temperate seas and most of them flourish at a temperature above 220 C.

Examples: Fungia, Favia and Madrepora

Two special corals:-black corals (Antipathes) and the precious red corals (Corallium) develop based calcium based skeleton. They build skeleton with much different crystal geometrics. The unique mineral formed by these corals makes them prized for jewellery making. These corals are endangered due to discriminate collecting by divers.

Antipathes pennacea (Black coral)
Antipathes pennacea (Black coral) | Source
Corallium rubrum (Red corals)
Corallium rubrum (Red corals)

Corals grow very slowly. The dense solid corals which build reefs grow less than one to two cms each year. When these organisms die their skeleton forms extensive mounds of lime in the sea. These are called coral reefs.

A coral reef is a complex living community in which reef building corals create a physical environment where many other plants and animals thrive. A coral reef takes thousands of years to form. One pound of coral may contain over 37,000 polyp skeletons. Coral reefs are in inhabited by a number of sponges, sea anemones, sea urchins,starfishes, crabs, bivalves etc. The other components in the formation of coral reefs are Tubipora, Millepora, Heliopora, Gorgonians, Alcyonaria, Foraminifera, coralline algae and branching algae.

Types of Coral Reefs

There are general types of reefs can be recognized on the basis of their structure and underlying substratum. They are of three types :

  1. Fringing Reefs
  2. Barrier Reefs
  3. Atoll Reefs

Fringing Reef

They are also known as the shore reefs and built from the sea bottom and project seaward directly from the shore.They are most common type of reef throughout the world. Abundant in East Indies. The zones of the sea between the shore and reef is very shallow. The seaward edge of the reef platform is called reef edge, where the most active coral growth is observed.

Fringing Reef
Fringing Reef
Great Barrier Reefs
Great Barrier Reefs

Barrier Reef

The barrier reefs are similar to fringing reefs, but they are situated in the sea about 1 to 15 km away from shore.The zone of the sea between the shore and reef is very deep and hence navigable. The great barrier reef of Australia is the longest in the world: streching on the north east cost of Australia, is 1200 miles long, 20 to70 miles wide and situiated nearly 90 miles away from the shore. Another relatively long barrier reef is located in the Caribbean Sea off the coast of Belize between Mexico and Guatemala.

The barrier reef consists of same parts as the fringing reef, but the place of inner flat is taken by the lagoon flat.The latter has a thin covering of sand and shows an extraordinary luxuriant coral growth.

Great Barrier Reef
Great Barrier Reef

Atoll Reef

It is also known as coral island or lagoon island, is a circular or horseshoe shaped reef enclosing a lagoon of water which may be small or large up to 50 miles across.

Over 300 atolls are present in the Indo-Pacific, but only 10 are found in the Western Atlantic.Bermuda of Atlantic, Aldabra in the indian Ocean, Lakshadeep islands are examples.

Atoll Reef
Atoll Reef

Conservation of Coral Reef

The coral reef is a balanced system where all things have their own special place and function.The coral reef ecosystem maintain the fertility of the surrounding waters by providing waste materials and nutrients. The abundant,unique and colorful animal life it supports contribute a treasure house of biological wealth.

Reefs are important source of seafood. The reef offers shelter and feeding grounds to many types of fishes and other animals. Reef act as barriers which protests our beaches and shorelines from powerful ocean waves and currents.


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    • profile image


      5 years ago

      Its too good to learn

    • profile image


      5 years ago

      great work. plse add much more informative and interesting aspects concerned with it.

    • deenahere profile imageAUTHOR


      8 years ago from India

      Hai Starstream, Bill and QudsiaP1,

      Thank you very much for your nice comments. Your comments are great motivation for creating good hubs.


    • QudsiaP1 profile image


      8 years ago

      Absolutely gorgeous picture and a very interesting article on coral reefs.

    • bdegiulio profile image

      Bill De Giulio 

      8 years ago from Massachusetts

      Very interesting. Learned a lot about coral. Great selection of pictures. Well done.

    • starstream profile image

      Dreamer at heart 

      8 years ago from Northern California

      Your hub is very informative and the pictures are so lovely. I watched my parents skin dive on the coral reefs as a child. We must save these reefs from further damage. Thanks for sharing.


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