Coral Reef

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  • Topic: Coral, Coral reef, Cnidaria
  • Pages : 8 (2578 words )
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  • Published : July 30, 2003
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CORAL REEFS

Almost every one of us have heard and most of you have seen the Coral reefs but did you know what actually these are: As a mariner its important to know about the marine life, that was one reason I have chosen this topic for my today's short presentation.

GM, my scheme of presentation will be as flashed:

DEFINATION OF CORAL REEF
DIFFERENCE BETWEEN CORAL AND CORAL POLYP
WHERE WE CAN FIND CORAL
CONSTRUCTION OF CORAL REEFS
CONDITIONS FOR GROWTH OF CORAL REEFS
TYPES OF CORAL REEFS
THREAT TO CROAL REEFS
WHAT SHOULD A MARINER DO IN CORAL RICH AREAS
FUTURE OF CORAL REEFS
CONCLUSION

What is a coral reef?
Coral reefs are huge structures made of limestone that is deposited by living things. There are thousands of species that live in coral reefs, but only a fraction actually produces the limestone that builds the reef. Coral reefs support over 25% of all known marine species. They are one of the most complex ecosystems on the planet, and are home to over 4,000 different types of fish, 700 species of coral and thousands of other plants and animals.

A good way to imagine a coral reef is to think of it as a bustling city or community, with the buildings made of coral, and thousands of inhabitants coming and going, carrying out their business. In this sense, a coral reef is like a metropolis under the sea.

What is coral?
Although coral is often mistaken for a rock or a plant, it is actually composed of tiny, fragile animals called coral polyps. When we say "coral" we are actually referring to these animals and the skeletons they leave behind after they die.

Although there are hundreds of different species of corals, they are generally classified as "hard coral" or "soft coral". Hard corals grow in colonies and are the architects of coral reefs. They include such species as brain coral and elkhorn coral. Their skeletons are made out of calcium carbonate (also known as limestone) which is hard and eventually becomes rock. Hard corals are hermatypes or reef-building corals and need tiny algae called zooxanthellae (pronounced zo-zan-THEL-ee) to survive. Generally, when we talk about "coral" we are referring to hard 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.

What is a coral polyp?
A coral polyp is a spineless animal. Coral polyps can be the size of a pinhead while others are larger, sometimes a foot in diameter. One coral branch or mound is covered by thousands of these animals. They are invertebrates (spineless animals) and are cousins of anemones and jellyfish. When thousands of these animals are grouped together, they are referred to as coral colonies. Each coral "tree" or "mound" is one colony of coral polyps. A polyp has a sac-like body and an opening or mouth encircled by stinging tentacles called cnidae. The polyp uses calcium carbonate from seawater to build itself a hard, cup-shaped skeleton. This limestone skeleton protects the soft, delicate body of the polyp. Coral polyps are usually nocturnal, meaning that they stay inside their skeletons during the day. At night, polyps extend their tentacles out to feed.

Where do corals live?
Coral reefs are found in over 100 countries. Most reefs are located between the tropics of Cancer and Capricorn, in places such as the Pacific Ocean, the Indian Ocean, the Caribbean, the Red Sea and the Arabian Gulf. Corals are also found farther from the equator in places where warm currents flow out of the tropics, such as Florida and southern Japan. Worldwide, coral reefs cover an estimated 284,300 square kilometers (110,000 square miles).

How old are coral reefs?
The...
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