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- Dictionarycoral reef
noun
- 1. a ridge of rock in the sea formed by the growth and deposit of coral: "the small island is enclosed in the middle of the coral reef"
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noun
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A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate e... Wikipedia