A coral reef is a large underwater structure made of dead and living corals. In most healthy reefs, stony corals are predominant. A branch or mound of what we call a coral is actually thousands of tiny animals called polyps. A coral polyp is an invertebrate that can be no bigger than a pinhead to up to a foot in diameter. The reefs are formed in tropical marine areas (30 degrees north and south of the equator). The reef acts as the home of many tropical fish and other animals. Coral reefs systems are a major tourism attraction because of their beauty and color of the corals and their many associated animals.
People look at them while snorkeling and diving. One example of a coral reef is in Malaysia at Pulau Tioman, off the State of Pahang.
Coral reefs are also found in the deep sea away from the continental shelves, around oceanic islands and atolls. The vast majority of these ocean coral islands are volcanic in origin. The few exceptions have tectonic origins where plate movements have lifted the deep ocean floor on the surface.
Coral reefs are fragile ecosystems. Because corals need warm, sunlit water to live, they often grow close to the top of the water. Being so close to land they are often damaged by poisons and dirt that can come from boats and the land nearby. Dirt makes the water more cloudy, which means they receive less sunlight. Poisons can bleach and kill corals. Also, boats and ships cannot always see coral reefs; therefore they often run into the coral, damaging both the boats and coral. Because of this, many countries are trying to restrict building near beaches that have coral reefs nearby, and be more careful about the boats that go around reefs.
(source: https://simple.wikipedia.org/wiki/Coral_reef ) ( CCLP)
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