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How are coral reefs formed?

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sam-jew2 | Student, Grade 9 | eNotes Newbie

Posted November 8, 2008 at 9:53 AM via web

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How are coral reefs formed?

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lynn30k | High School Teacher | (Level 3) Associate Educator

Posted November 8, 2008 at 10:32 AM (Answer #1)

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Coral reefs are formed from what are the hard, limestone "skeletons" of coral. A brown algae living symbiotically with the coral help the coral to produce limestone; the algae provide sugars and oxygen that they produce by photosynthesis.  For this reason, coral reefs only form in relatively shallow, clear, warm water. There are four types of reefs--fringing, platform, barrier, and atolls.  They differ in distance from continents, and age. All usually provide habitats for a wide variety of marine life.

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jwuenschel | (Level 2) Adjunct Educator

Posted November 8, 2008 at 10:41 AM (Answer #2)

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Biologically, coral reefs are formed by the aggregation of the calcium carbonate exoskeletons of corals (also known as polyps).  After settling on a suitable surface, new polyps secrete their exoskeleton around them. Reefs are primarily formed by the growth of new polyps on the skeletons of the dead or old polyps.

Location plays a definitive part in coral reef formation.  Actively growing coral reefs are found in water between 30 degrees south latitude and 30 degrees north latitude with a depth greater than 30 meters and a temperature greater than 22 degrees Celsius.  

The three typs of coral reefs formed are fringing reefs, barrier reefs, and atolls.  Fringing reefs form along shorelines and may be found projecting long distances from land.  Barrier reefs are characterized by a definitive, localized formation of coral seperated from the shoreline by a lagoon.  Atolls are island like structures formed by multiple coral reefs positioned in a ring, surrounding a lagoon.  

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spottedslinky | High School Teacher | (Level 2) Adjunct Educator

Posted November 8, 2008 at 10:46 AM (Answer #3)

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It occurred to me that you might not know what coral is -- the substance that makes up the coral reef. Coral is the term for a colony of polyps, very small organisms that consist mainly of a stomach and mouth, which are fed by many tentacles that catch organisms which float by in the water. They are sort of the "couch potatoes" of the warm water seas. Lucky for us snorkelers, who get to observe them and the tropical fish that feed on them. Of course, it's up to us to make sure the reefs are protected. Remember, they are alive!

Some of my information came from Sydenham & Thomas, What is Coral?  at web site referenced.

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ayushp | Student | (Level 1) eNoter

Posted May 9, 2009 at 6:09 PM (Answer #4)

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Reefs were formed millions of years ago.They form a large collection of corals.There are four types of reefs barrier,atolls,platform and fringing

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georgeisgay | Middle School Teacher | eNotes Newbie

Posted March 18, 2010 at 11:25 AM (Answer #5)

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reefs are formed when me (GeorgeisGay) makes babys with other reefs want to know more information on th details?

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fact-finder | (Level 3) Valedictorian

Posted October 10, 2011 at 4:00 PM (Answer #1)

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The calcium carbonate (chalk) skeletons of dead corals serve as the foundation upon which layers of successively younger animals attach themselves. The coral animal, or polyp, is shaped like a column. Its lower end is attached to the hard floor of the reef and its upper end extends into the water.

There are two kinds of corals—hard and soft—depending on the type of skeleton secreted. The hard-coral polyp deposits a cup-like solid skeleton of calcium carbonate around itself into which the polyp withdraws during the daytime. For this reason, deep sea divers see only the skeletons—and not the polyps—of hard corals.

A coral colony consists of thousands of individuals. Accumulations of dead and living coral polyps, combined with rising water levels, slowly lead to the formation of coral reefs that can be hundreds of meters deep and long. Coral reefs grow only in warm, shallow water.

Sources: Kaplan, Eugene H. Field Guide to Coral Reefs, pp. 78-79; The New Book of Popular Science, vol. 2, p. 270.

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brandon0504 | Student, Undergraduate | (Level 1) eNoter

Posted February 17, 2012 at 2:27 PM (Answer #7)

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Biologically, coral reefs are formed by the aggregation of the calcium carbonate exoskeletons of corals (also known as polyps).  After settling on a suitable surface, new polyps secrete their exoskeleton around them. Reefs are primarily formed by the growth of new polyps on the skeletons of the dead or old polyps.

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strwbrry16 | TA , Grade 5 | (Level 1) Valedictorian

Posted October 22, 2014 at 9:46 AM (Answer #8)

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Coral reefs begin to form when free-swimming coral larvae attach to submerged rocks or other hard surfaces along the edges of islands or continents. As the corals grow and expand, reefs take on one of three major characteristic structures —fringing, barrier or atoll.

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