page_title: Reef
hierarchical_section_title: Reef
caption_attribution_description: Pamalican island
context_page_description: A reef is a shoal of rock, sand, coral or similar material, lying beneath the surface of water.
  Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock outcrops, etc.—but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae.
  Artificial reefs sometimes have a role in enhancing the physical complexity of featureless sand bottoms, in order to attract a diverse assemblage of organisms, especially algae and fish.
  Earth's largest coral reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres.
context_section_description: A reef is a shoal of rock, sand, coral or similar material, lying beneath the surface of water.
  Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock outcrops, etc.—but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae. 
  Artificial reefs (e.g. shipwrecks) sometimes have a role in enhancing the physical complexity of featureless sand bottoms, in order to attract a diverse assemblage of organisms, especially algae and fish.
  Earth's largest coral reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres (1,400 miles).
caption: Pamalican island with surrounding reef, Sulu Sea, Philippines
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