Coral reefs are the world’s most diverse marine ecosystems and are home to 25% of known marine species, including 4,000 species of fish, 700 species of coral and thousands of other plants and animals. They are made of thin layers of limestone produced by organisms known as coral polyps and take thousands of years to form. Neat huh?
http://www.sciencedaily.com/releases/2007/05/070515074933.htm
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