Editing Reef (section)

{{Short description|Shoal of rock, coral, or other material lying beneath the surface of water}}
{{Other uses}}

[[File:Nusa Lembongan Reef.jpg|thumb|Coral reef at [[Nusa Lembongan]], Bali, Indonesia]]
[[File:PamalicanAfterLiftOff.jpg|thumb|[[Pamalican]] island with surrounding reef, [[Sulu Sea]], [[Philippines]]]]
[[File:Reef.jpg|thumb|A reef surrounding an [[islet]]]]
[[File:Vanatinai, Louisiade Archipelago.jpg|thumb|Reefs off [[Vanatinai|Vanatinai Island]] in the [[Louisiade Archipelago]]]]

A '''reef''' is a ridge or [[shoal]] of rock, [[coral]], or similar relatively stable material lying beneath the surface of a natural body of water.<ref name="NatGeo" /> Many reefs result from natural, [[abiotic component|abiotic]] (non-living) processes such as [[deposition (geology)|deposition]] of sand or [[wave erosion]] planning down rock outcrops. However, reefs such as the [[coral reef]]s of tropical waters are formed by [[biotic component|biotic]] (living) processes, dominated by corals and [[coralline algae]]. [[Artificial reef]]s, such as shipwrecks and other man-made underwater structures, may occur intentionally or as the result of an accident. These are sometimes designed to increase the physical complexity of featureless sand bottoms to attract a more diverse range of [[organism]]s. They provide shelter to various aquatic animals which help prevent extinction.<ref>{{Cite journal |last1=Gilby |first1=Ben L. |last2=Olds |first2=Andrew D. |last3=Peterson |first3=Charles H. |last4=Connolly |first4=Rod M. |last5=Voss |first5=Christine M. |last6=Bishop |first6=Melanie J. |last7=Elliott |first7=Michael |last8=Grabowski |first8=Jonathan H. |last9=Ortodossi |first9=Nicholas L. |last10=Schlacher |first10=Thomas A. |date=September 2018 |title=Maximizing the benefits of oyster reef restoration for finfish and their fisheries |url=https://onlinelibrary.wiley.com/doi/10.1111/faf.12301 |journal=Fish and Fisheries |language= |volume=19 |issue=5 |pages=931–947 |doi=10.1111/faf.12301 |issn=1467-2960|url-access=subscription }}</ref> Another reason reefs are put in place is for aquaculture, and fish farmers who are looking to improve their businesses sometimes invest in them.<ref>{{Cite web |last=Geographic |first=National |date= |title=Reef |url=https://education.nationalgeographic.org/resource/reef/ |access-date=2024-12-09 |website=education.nationalgeographic.org |language=en}}</ref> Reefs are often quite near to the surface, but not all definitions require this.<ref name="NatGeo" />

Earth's largest coral reef system is the [[Great Barrier Reef]] in Australia, at a length of over {{convert|2300|km|abbr=off}}.