Coral Reef

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 geological record indicates that the ancestors of modern coral reef ecosystems were formed at least 350 million years ago. The coral reefs existing today began growing as early as 50 million years ago. Most established coral reefs are between 5,000 and 10,000 years old. Although size sometimes indicates the age of a coral reef, this is not always true. Different species of coral grow at different rates, depending on water temperature, oxygen level, amount of turbulence, and availability of food

How is a coral reef constructed?

Coral reefs are complex, multi-story structures with holes and crevices shared by various creatures. If a coral reef can be thought of as a metropolis of the sea, then a coral colony can be thought of as an apartment building with many different rooms and hallways that house different marine species. Not all coral species build reefs. The actual architects of coral reefs are hard or stony corals, which are referred to as hermatypic or reef-building corals. As the polyps of stony corals grow, they produce limestone for their skeletons. When they die, their skeletons are left behind and are used as foundations for new polyps, which build new skeletons over the old ones. An actual coral mound or tree is composed of layer upon layer of skeletons covered by a thin layer of living polyps.

The best place for coral to grow is in waters with the temperature being between 21 and 29 degrees. They do grow in hotter and colder places, but the growth rate there are very slow. Corals like shallow waters, where there is lots of sunlight filters through to their algae. Its possible to find corals at depths of up to 91 metres, but reef-building corals doesn't grow very well below 18 Ð'- 27 metres. Corals don't grow very well near river openings or costal areas with too much, because corals need salt water to survive.

What do corals need to survive?

 Sunlight: Corals need to grow in shallow water where sunlight