Main Page | See live article | Alphabetical index


In nautical parlance, a reef is a rock, sandbar, or other feature beneath the surface of the water, shallow enough to be a hazard to ships. See also shoal. Many reefs result from abiotic processes, but the best-known reefs are those of tropical waters developed through biotic processes dominated by corals and algae.

Biotic Reef Types

There are a number of biotic reef types, including oyster reefs, but the most massive and widely distributed are coral reefs, limited to tropical waters. Although corals are major contributors to the framework and bulk material comprising a coral reef, the organisms most responsible for reef growth against the constant assault from ocean waves are calcarous algae.

Coral Reefs

These reefs take various forms described as apron reefs, fringing reefs, patch reefs, ribbon reefs, table reefs, barrier reefs, and atolls.