There are multiple types of reefs that are formed by corals: Fringing Reefs, Barrier Reefs, Atolls and Patch Reefs. Barrier reefs form in close proximity to shorelines to protect coastal towns for natural disasters and large waves. Meanwhile Atolls are circular reefs that enclose a lagoon. These reefs attract fewer species as the water is more murky and has a higher salinity. Another common type of reef is the Patch reef which is formed on shallow patches of sea ground and are surrounded by deeper water. (NOAA)
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What are coral reefs?