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{{Short description|A shoal of rock, coral or other sufficiently coherent material, lying beneath the surface of water}}
{{Short description|Shoal of rock, coral, or other material lying beneath the surface of water}}
{{Other uses}}
{{Other uses}}
{{One source|date=October 2017}}


[[File:Nusa Lembongan Reef.jpg|thumb|Coral reef at [[Nusa Lembongan]], Bali, Indonesia]]
[[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:PamalicanAfterLiftOff.jpg|thumb|[[Pamalican]] island with surrounding reef, [[Sulu Sea]], [[Philippines]]]]
[[File:Reef.jpg|thumb|A reef surrounding an [[islet]]]]
[[File:Reef.jpg|thumb|A reef surrounding an [[islet]]]]
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[[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]] processes—[[deposition (geology)|deposition]] of sand,{{citation needed|reason=for reef formation by deposition of sand|date=February 2021}} wave erosion planing down rock outcrops, etc.—but there are also reefs such as the [[coral reef]]s of tropical waters formed by [[biotic component|biotic]] processes dominated by corals and [[coralline algae]], and [[artificial reef]]s such as shipwrecks and other anthropogenic underwater structures may occur intentionally or as the result of an accident, and sometimes have a designed role in enhancing the physical complexity of featureless sand bottoms, to attract a more diverse assemblage of organisms. Reefs are often quite near to the surface, but not all definitions require this.<ref name="NatGeo" />
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. 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}}.
Earth's largest coral reef system is the [[Great Barrier Reef]] in Australia, at a length of over {{convert|2300|km|abbr=off}}.


== Biotic reef ==
== Etymology ==
The word "reef" traces its origins back to the [[Old Norse]] word ''rif,'' meaning "rib" or "reef". ''Rif'' comes from the Proto-Germanic term ''ribją'' meaning "rib". <ref>{{Cite book |last=Guus Kroonen |url=https://archive.org/details/etymological-dictionary-of-proto-germanic/page/406/mode/2up |title=Etymological Dictionary of Proto-Germanic |date=2013}}</ref>

==Classification==
Reefs may be classified in terms of their origin, geographical location, depth, and [[topography]]. For example a tropical coral fringing reef, or a temperate rocky intertidal reef.

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=== Biotic ===
{{see also|Coral reef#Formation|Sponge reef#Structure of sponge reefs}}
{{see also|Coral reef#Formation|Sponge reef#Structure of sponge reefs}}
[[File:Great-Barrier-Reef-2018-Luka-Peternel.jpg|thumb|Part of [[Great Barrier Reef]]]]
There is a variety of biotic reef types, including [[oyster reef]]s and [[sponge reef]]s, but the most massive and widely distributed are tropical [[coral reef]]s.<ref name="NatGeo" /> 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 [[calcareous]] algae, especially, although not entirely, coralline algae.
A variety of biotic reef types exists, including [[oyster reef]]s and [[sponge reef]]s, but the most massive and widely distributed are tropical [[coral reef]]s.<ref name="NatGeo" /> 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 [[calcareous]] algae, especially, although not entirely, [[coralline algae]].


The preferred substrate for oyster larvae is the shells of oysters so they tend to settle on adult oysters and thereby develop layers building upwards, eventually forming a fairly massive hard stony calcium carbonate structure on which other reef organisms like sponges and seaweeds can grow, and provide a habitat for mobile benthic organisms<ref name="NatGeo" />.
Oyster larvae prefer to settle on adult oysters and thereby develop layers building upwards. These eventually form a fairly massive hard stony calcium carbonate structure on which other reef organisms like [[sponges]] and [[seaweeds]] can grow, and provide a habitat for mobile benthic organisms.<ref name="NatGeo" />


These biotic reef types take on additional names depending upon how the reef lies in relation to the land, if any. Reef types include [[fringing reef]]s, [[barrier reef]]s, and [[atoll]]s. A fringing reef is a reef that is attached to an island. A barrier reef forms a calcareous barrier around an island resulting in a lagoon between the shore and the reef. An atoll is a ring reef with no land present. The reef front (ocean side) is a high energy locale whereas the internal [[lagoon]] will be at a lower energy with fine grained sediments.
These biotic reef types take on additional names depending upon how the reef lies in relation to the land, if any. Reef types include [[fringing reef]]s, [[barrier reef]]s, and [[atoll]]s. A fringing reef is a reef that is attached to an island. Whereas, a barrier reef forms a calcareous barrier around an island, resulting in a [[lagoon]] between the shore and the reef. Conversely, an atoll is a ring reef with no land present.


The reef front, facing the ocean, is a high energy locale. Whereas, the internal lagoon will be at a lower energy with fine grained sediments.
⚫
=== Biotic mound structures ===
⚫
One useful definition distinguishes reefs from mounds as follows: Both are considered to be varieties of organosedimentary buildups – sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. Reefs are held up by a macroscopic skeletal framework. Coral reefs are an example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework. Mounds are built by microorganisms or by organisms that don't grow a skeletal framework. A microbial mound might be built exclusively or primarily by [[cyanobacteria]]. Examples of [[biostrome]]s formed by cyanobacteria occur in the [[Great Salt Lake]] in [[Utah]], and in [[Shark Bay]] on the coast of [[Western Australia]].{{cn|date=March 2021}}


==== Mounds ====
⚫
Cyanobacteria do not have skeletons, and individuals are microscopic. Cyanobacteria can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today; [[stromatolite]]s are microbial mounds with a laminated internal structure. [[Bryozoan]]s and [[crinoid]]s, common contributors to marine sediments during the [[Mississippian (geology)|Mississippian]], for instance, produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate. However, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief.{{cn|date=March 2021}}
⚫
Both mounds and reefs are considered to be varieties of organosedimentary buildups, which are sedimentary features, built by the interaction of organisms and their environment. These interactions have a synoptic relief and whose biotic composition differs from that found on and beneath the surrounding [[sea floor]]. However, reefs are held up by a macroscopic skeletal framework, as what is seen on coral reefs. [[Corals]] and calcareous algae grow on top of one another, forming a three-dimensional framework that is modified in various ways by other organisms and inorganic processes.<ref name=":0">{{Cite web |title=Reading: Shorelines {{!}} Geology |url=https://courses.lumenlearning.com/geo/chapter/reading-shorelines/ |access-date=2024-04-20 |website=courses.lumenlearning.com}}</ref>


Conversely, mounds lack a macroscopic skeletal framework. Instead, they are built by microorganisms or by organisms that also lack a skeletal framework. A microbial mound might be built exclusively or primarily by [[cyanobacteria]]. Examples of [[biostrome]]s formed by cyanobacteria occur in the [[Great Salt Lake]] in [[Utah]], United States, and in [[Shark Bay]] on the coast of [[Western Australia]].<ref name=":0" /><ref>{{Cite journal |last=Wood |first=Rachel |date=2001-12-15 |title=Are reefs and mud mounds really so different? |url=https://www.sciencedirect.com/science/article/pii/S0037073801001464 |journal=Sedimentary Geology |series=Carbonate Mounds: sedimentation, organismal response, and diagenesis |volume=145 |issue=3 |pages=161–171 |doi=10.1016/S0037-0738(01)00146-4 |bibcode=2001SedG..145..161W |issn=0037-0738}}</ref>
The [[Proterozoic]] [[Belt Supergroup]] contains evidence of possible [[microbial mat]] and dome structures similar to stromatolite and chiggen reef complexes.<ref name="Schieber 1998" />


⚫
Cyanobacteria do not have skeletons, and individual organisms are microscopic. However, they can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today. [[Stromatolite]]s, for instance, are microbial mounds with a laminated internal structure. Whereas, [[bryozoan]]s and [[crinoid]]s, common contributors to marine sediments during the [[Mississippian (geology)|Mississippian period]], produce a different kind of mound. Although bryozoans are small and crinoid skeletons disintegrate, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief.<ref name=":0" /><ref>{{Cite journal |last=crossref |title=Chooser |url=https://chooser.crossref.org/ |access-date=2024-04-20 |website=chooser.crossref.org |language=en |doi=10.2307/3514838|jstor=3514838 }}</ref>
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== Geologic reef ==

⚫
Rocky reefs are underwater outcrops of rock projecting above the adjacent unconsolidated surface with varying relief. They can be found in depth ranges from intertidal to deep water, and provide a substrate for a large range of sessile benthic organisms, and shelter for a large range of mobile organisms.<ref name="NOAA fisheries" />
The [[Proterozoic]] [[Belt Supergroup]] contains evidence of possible [[microbial mat]] and dome structures similar to stromatolite and chicken reef complexes.{{clarify|what are chicken reef complexes?|date=November 2024}}<ref name=":0" /><ref>{{Cite journal |last=Schieber |first=Jürgen |date=1998 |title=Possible indicators of microbial mat deposits in shales and sandstones: examples from the Mid-Proterozoic Belt Supergroup, Montana, U.S.A. |url=https://sepm04.sitehost.iu.edu/PDF/JS-J24-microbial_mat_challenge |journal=Sedimentary Geology |volume=120 |issue=1 |pages=105–124|doi=10.1016/S0037-0738(98)00029-3 |bibcode=1998SedG..120..105S }}</ref>

⚫
=== Geologic ===
<!-- target for redirect [[Rocky reef]] -->
⚫
Rocky reefs are underwater outcrops of rock projecting above the adjacent unconsolidated surface with varying relief. They can be found in depth ranges from [[intertidal]] to deep water and provide a substrate for a large range of sessile benthic organisms, and shelter for a large range of mobile organisms.<ref name="NOAA fisheries" /> They are often located in sub-tropical, temperate, and sub-polar latitudes.
{{expand section|relative abundance of rocky vs biotic reef and global distribution, ecological importance|date=February 2021}}
{{expand section|relative abundance of rocky vs biotic reef and global distribution, ecological importance|date=February 2021}}


=== Geologic reef structures ===
==== Structures ====
[[File:Fossil Reef Windley Key 1.jpg|thumb|Fossil [[brain coral]] (''Diploria'') at the [[Windley Key Fossil Reef Geological State Park]]. [[Quarter (United States coin)|US Quarter]] near top for scale.]]
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[[File:Vanatinai, Louisiade Archipelago.jpg|thumb|Reefs off [[Vanatinai]] in the [[Louisiade Archipelago]]]]


Ancient reefs buried within [[stratigraphy|stratigraphic]] sections are of considerable interest to [[geologist]]s because they provide paleo-environmental information about the location in [[history of Earth|Earth's history]]. In addition, reef structures within a sequence of [[sedimentary rock]]s provide a discontinuity which may serve as a trap or conduit for [[fossil fuel]]s or mineralizing fluids to form [[petroleum]] or [[ore]] deposits.
Ancient reefs buried within [[stratigraphy|stratigraphic]] sections are of considerable interest to [[geologist]]s because they provide paleo-environmental information about the location in [[history of Earth|Earth's history]]. In addition, reef structures within a sequence of [[sedimentary rock]]s provide a discontinuity which may serve as a trap or conduit for [[fossil fuel]]s or mineralizing fluids to form [[petroleum]] or [[ore deposit]]s.<ref>{{Cite journal |last1=Gorokhovich |first1=Yuri |last2=Learning |first2=Lumen |title=Coastal Geology: Shorelines |url=https://pressbooks.cuny.edu/gorokhovich/chapter/coastal-geology-shorelines/ |language=en}}</ref>


Corals, including some major extinct groups [[Rugosa]] and [[Tabulata]], have been important reef builders through much of the [[Phanerozoic]] since the [[Ordovician]] Period. However, other organism groups, such as calcifying algae, especially members of the red algae [[Rhodophyta]], and molluscs (especially the [[rudists|rudist]] bivalves during the [[Cretaceous]] Period) have created massive structures at various times. During the [[Cambrian]] Period, the conical or tubular skeletons of [[Archaeocyatha]], an extinct group of uncertain affinities (possibly sponges), built reefs. Other groups, such as the [[Bryozoa]] have been important interstitial organisms, living between the framework builders. The corals which build reefs today, the [[Scleractinia]], arose after the [[Permian–Triassic extinction event]] that wiped out the earlier rugose corals (as well as many other groups), and became increasingly important reef builders throughout the [[Mesozoic]] Era. They may have arisen from a rugose coral ancestor. Rugose corals built their skeletons of [[calcite]] and have a different symmetry from that of the scleractinian corals, whose skeletons are [[aragonite]]. However, there are some unusual examples of well-preserved aragonitic rugose corals in the [[Lopingian|Late Permian]]. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of the rugosan corals (which disappeared in the late Permian).
Corals, including some major extinct groups [[Rugosa]] and [[Tabulata]], have been important reef builders through much of the [[Phanerozoic]] since the [[Ordovician]] Period. However, other organism groups, such as calcifying algae, especially members of the red algae ([[Rhodophyta]]), and molluscs (especially the [[rudists|rudist]] bivalves during the [[Cretaceous]] Period) have created massive structures at various times.
During the [[Cambrian]] Period, the conical or tubular skeletons of [[Archaeocyatha]], an extinct group of uncertain affinities (possibly sponges), built reefs.<ref>{{Cite web |title=Archaeocyathans |url=https://ucmp.berkeley.edu/porifera/archaeo.html#:~:text=The%20first%20archaeocyaths%20appear%20roughly,creation%20of%20the%20first%20reefs. |access-date=2024-04-20 |website=ucmp.berkeley.edu}}</ref> Other groups, such as the Bryozoa, have been important interstitial organisms, living between the framework builders. The corals which build reefs today, the [[Scleractinia]], arose after the [[Permian–Triassic extinction event]] that wiped out the earlier rugose corals (as well as many other groups). They became increasingly important reef builders throughout the [[Mesozoic]] Era.<ref>{{Cite journal |last1=Pruss |first1=Sara B. |last2=Bottjer |first2=David J. |date=2005-09-01 |title=The reorganization of reef communities following the end-Permian mass extinction |url=https://www.sciencedirect.com/science/article/pii/S163106830500045X |journal=Comptes Rendus Palevol |volume=4 |issue=6 |pages=553–568 |doi=10.1016/j.crpv.2005.04.003 |bibcode=2005CRPal...4..553P |issn=1631-0683}}</ref> They may have arisen from a rugose coral ancestor.
Rugose corals built their skeletons of [[calcite]] and have a different symmetry from that of the scleractinian corals, whose skeletons are [[aragonite]].<ref>{{Cite web |date=2021-06-30 |title=Rugose Coral |url=https://www.colorado.edu/cumuseum/2021/06/30/rugose-coral |access-date=2024-04-20 |website=Museum of Natural History |language=en}}</ref> However, there are some unusual examples of well-preserved aragonitic rugose corals in the [[Lopingian|Late Permian]]. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of the rugosan corals (which disappeared in the late Permian).<ref name=":0" />

=== Artificial ===
{{main|Artificial reef}}
An artificial reef is a human-created underwater structure, typically built to promote [[Marine biology#Reefs|marine life]] in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of [[trawling]] nets,<ref name="Gray 2018" /> or improve [[surfing]].<ref name="Bournemouth Echo" />

Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through the [[Rigs-to-Reefs]] program), [[Sinking ships for wreck diving sites|scuttling ships]], or by deploying [[rubble]] or [[construction debris]]. Other artificial reefs are purpose built (e.g. the [[The Reef Ball Foundation|reef balls]]) from [[Polyvinyl chloride|PVC]] or concrete. Shipwrecks become artificial reefs on the seafloor. Regardless of construction method, artificial reefs generally provide stable hard surfaces where [[algae]] and invertebrates such as [[barnacle]]s, corals, and [[oyster]]s attach; the accumulation of attached marine life in turn provides intricate structure and food for [[biocoenosis|assemblages]] of fish.


== See also ==
== See also ==
Line 45: Line 67:
== References ==
== References ==
{{reflist|refs=
{{reflist|refs=

<ref name="Bournemouth Echo" >{{cite web|url=http://www.bournemouthecho.co.uk/news/features/surfreef/surfreefstories/4716058.Optimism_at_Boscombe_surf_reef___s_opening_day/ |title=Optimism at Boscombe surf reef's opening day |publisher=Bournemouthecho.co.uk |date=3 November 2009 |access-date=19 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120318073823/http://www.bournemouthecho.co.uk/news/features/surfreef/surfreefstories/4716058.Optimism_at_Boscombe_surf_reef___s_opening_day/ |archive-date=March 18, 2012 }}</ref>

<ref name="Gray 2018" >{{cite web |url=https://asia.nikkei.com/Life-Arts/Life/Cambodia-volunteers-step-up-battle-against-illegal-fishing |title=Cambodia volunteers step up battle against illegal fishing |website=asia.nikkei.com |publisher=Nikkei Asia |first=Denis D. |last=Gray |date=2 June 2018|access-date=17 March 2021 }}</ref>


<ref name="NatGeo" >{{cite web|url=https://www.nationalgeographic.org/encyclopedia/reef/ |title=Resource Library: Encyclopedic Entry: Reef
<ref name="NatGeo" >{{cite web|url=https://www.nationalgeographic.org/encyclopedia/reef/ |title=Resource Library: Encyclopedic Entry: Reef
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<ref name="NOAA fisheries" >{{cite web |url=https://www.fisheries.noaa.gov/west-coast/habitat-conservation/rocky-reef-west-coast |title=Rocky Reef on the West Coast |website=www.fisheries.noaa.gov |publisher=National Oceanic and Atmospheric Administration |accessdate=3 February 2021 }}</ref>
<ref name="NOAA fisheries" >{{cite web |url=https://www.fisheries.noaa.gov/west-coast/habitat-conservation/rocky-reef-west-coast |title=Rocky Reef on the West Coast |website=www.fisheries.noaa.gov |publisher=National Oceanic and Atmospheric Administration |accessdate=3 February 2021 }}</ref>
<!--

<ref name="Schieber 1998" >{{cite journal |last1=Schieber |first1=Jürgen |title=Possible indicators of microbial mat deposits in shales and sandstones: Examples from the Mid-Proterozoic Belt Supergroup, Montana, U.S.A. |journal=[[Sedimentary Geology (journal)|Sedimentary Geology]] |date=1998 |volume=120 |issue=1–4 |pages=105–124 |doi=10.1016/S0037-0738(98)00029-3 |bibcode=1998SedG..120..105S |url=http://www.uta.edu/paleomap/homepage/Schieberweb/Publications/PDF/sedgeol120.pdf}}</ref>
<ref name="Schieber 1998" >{{cite journal |last1=Schieber |first1=Jürgen |title=Possible indicators of microbial mat deposits in shales and sandstones: Examples from the Mid-Proterozoic Belt Supergroup, Montana, U.S.A. |journal=[[Sedimentary Geology (journal)|Sedimentary Geology]] |date=1998 |volume=120 |issue=1–4 |pages=105–124 |doi=10.1016/S0037-0738(98)00029-3 |bibcode=1998SedG..120..105S |url=http://www.uta.edu/paleomap/homepage/Schieberweb/Publications/PDF/sedgeol120.pdf |access-date=2010-07-06 |archive-date=2011-12-26 |archive-url=https://web.archive.org/web/20111226131037/http://www.uta.edu/paleomap/homepage/Schieberweb/Publications/PDF/sedgeol120.pdf |url-status=dead }}</ref>
-->

}}
}}


== Sources ==
== Sources ==
* Shears N.T. (2007) Biogeography, community structure and biological habitat types of subtidal reefs on the South Island West Coast, New Zealand. ''Science for Conservation 281''. p 53. Department of Conservation, New Zealand. [http://www.doc.govt.nz/upload/documents/science-and-technical/sfc281.pdf]
* Shears N.T. (2007) Biogeography, community structure and biological habitat types of subtidal reefs on the South Island West Coast, New Zealand. ''Science for Conservation 281''. p 53. Department of Conservation, New Zealand. [http://www.doc.govt.nz/upload/documents/science-and-technical/sfc281.pdf]
* “General Information on Reefs.” General Information on Reefs – Reef & Ocean Ecology Lab. Accessed February 1, 2024. <nowiki>https://www.reefoceanlab.org.au/resources/general-information-on-reefs/#:~:text=Rocky%20reefs%20are%20more%20typical,many%20parts%20of%20New%20Zealand</nowiki>.
* “Coral Reefs ~ Marinebio Conservation Society.” MarineBio Conservation Society, November 10, 2023. <nowiki>https://www.marinebio.org/creatures/coral-reefs/#:~:text=Organisms%20responsible%20for%20building%20tropical,and%20the%20Tropic%20of%20Cancer</nowiki>.


== External links ==
== External links ==
Line 62: Line 90:
{{Commons category|Reefs}}
{{Commons category|Reefs}}
* [http://ocean.si.edu/ocean-news/reef-rescue-protect-coral-reefs-your-actions ''Reef Rescue'' - Smithsonian Ocean Portal]
* [http://ocean.si.edu/ocean-news/reef-rescue-protect-coral-reefs-your-actions ''Reef Rescue'' - Smithsonian Ocean Portal]
* [http://www.nature.org/joinanddonate/rescuereef/ Coral Reefs of the Tropics]: facts, photos and movies from [[The Nature Conservancy]]
* [http://www.nature.org/joinanddonate/rescuereef/ Coral Reefs of the Tropics] {{Webarchive|url=https://web.archive.org/web/20110219004025/http://www.nature.org/joinanddonate/rescuereef/ |date=2011-02-19 }}: facts, photos and movies from [[The Nature Conservancy]]
* [http://www.photolib.noaa.gov/reef/ NOAA Photo Library]
* [http://www.photolib.noaa.gov/reef/ NOAA Photo Library]
* [http://www.reef.org/ Reef Environmental Education Foundation]
* [http://www.reef.org/ Reef Environmental Education Foundation]
* [https://web.archive.org/web/20081221021603/http://nosdataexplorer.noaa.gov/nosdataexplorer/ NOS Data Explorer] - A portal to obtain NOAA National Ocean Service data
* [https://web.archive.org/web/20081221021603/http://nosdataexplorer.noaa.gov/nosdataexplorer/ NOS Data Explorer] - A portal to obtain NOAA National Ocean Service data
* [http://www.coexploration.org/bbsr/coral/html/body_reef_formation.htm Reef formation]
* [http://www.coexploration.org/bbsr/coral/html/body_reef_formation.htm Reef formation]
* [http://www.geo.tu-freiberg.de/oberseminar/os06_07/nicol_schulz.pdf Atolls – Distribution, Development and Architecture]
* [https://web.archive.org/web/20180804105935/http://www.geo.tu-freiberg.de/oberseminar/os06_07/nicol_schulz.pdf Atolls – Distribution, Development and Architecture]


{{Coastal geography}}
{{Coastal geography}}

Latest revision as of 07:56, 1 December 2024

For other uses, see Reef (disambiguation).
Coral reef at Nusa Lembongan, Bali, Indonesia
Pamalican island with surrounding reef, Sulu Sea, Philippines
A reef surrounding an islet
Reefs off 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.[1] Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave erosion planning down rock outcrops. However, reefs such as the coral reefs of tropical waters are formed by biotic (living) processes, dominated by corals and coralline algae. Artificial reefs, 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 organisms. Reefs are often quite near to the surface, but not all definitions require this.[1]

Earth's largest coral reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres (1,400 miles).

Etymology

[edit]

The word "reef" traces its origins back to the Old Norse word rif, meaning "rib" or "reef". Rif comes from the Proto-Germanic term ribją meaning "rib". [2]

Classification

[edit]

Reefs may be classified in terms of their origin, geographical location, depth, and topography. For example a tropical coral fringing reef, or a temperate rocky intertidal reef.

Biotic

[edit]
See also: Coral reef § Formation, and Sponge reef § Structure of sponge reefs
Part of Great Barrier Reef

A variety of biotic reef types exists, including oyster reefs and sponge reefs, but the most massive and widely distributed are tropical coral reefs.[1] 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 calcareous algae, especially, although not entirely, coralline algae.

Oyster larvae prefer to settle on adult oysters and thereby develop layers building upwards. These eventually form a fairly massive hard stony calcium carbonate structure on which other reef organisms like sponges and seaweeds can grow, and provide a habitat for mobile benthic organisms.[1]

These biotic reef types take on additional names depending upon how the reef lies in relation to the land, if any. Reef types include fringing reefs, barrier reefs, and atolls. A fringing reef is a reef that is attached to an island. Whereas, a barrier reef forms a calcareous barrier around an island, resulting in a lagoon between the shore and the reef. Conversely, an atoll is a ring reef with no land present.

The reef front, facing the ocean, is a high energy locale. Whereas, the internal lagoon will be at a lower energy with fine grained sediments.

Mounds

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Both mounds and reefs are considered to be varieties of organosedimentary buildups, which are sedimentary features, built by the interaction of organisms and their environment. These interactions have a synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor. However, reefs are held up by a macroscopic skeletal framework, as what is seen on coral reefs. Corals and calcareous algae grow on top of one another, forming a three-dimensional framework that is modified in various ways by other organisms and inorganic processes.[3]

Conversely, mounds lack a macroscopic skeletal framework. Instead, they are built by microorganisms or by organisms that also lack a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria. Examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah, United States, and in Shark Bay on the coast of Western Australia.[3][4]

Cyanobacteria do not have skeletons, and individual organisms are microscopic. However, they can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today. Stromatolites, for instance, are microbial mounds with a laminated internal structure. Whereas, bryozoans and crinoids, common contributors to marine sediments during the Mississippian period, produce a different kind of mound. Although bryozoans are small and crinoid skeletons disintegrate, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief.[3][5]

The Proterozoic Belt Supergroup contains evidence of possible microbial mat and dome structures similar to stromatolite and chicken reef complexes.[clarification needed][3][6]

Geologic

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Rocky reefs are underwater outcrops of rock projecting above the adjacent unconsolidated surface with varying relief. They can be found in depth ranges from intertidal to deep water and provide a substrate for a large range of sessile benthic organisms, and shelter for a large range of mobile organisms.[7] They are often located in sub-tropical, temperate, and sub-polar latitudes.

Structures

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Fossil brain coral (Diploria) at the Windley Key Fossil Reef Geological State Park. US Quarter near top for scale.

Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about the location in Earth's history. In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits.[8]

Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician Period. However, other organism groups, such as calcifying algae, especially members of the red algae (Rhodophyta), and molluscs (especially the rudist bivalves during the Cretaceous Period) have created massive structures at various times.

During the Cambrian Period, the conical or tubular skeletons of Archaeocyatha, an extinct group of uncertain affinities (possibly sponges), built reefs.[9] Other groups, such as the Bryozoa, have been important interstitial organisms, living between the framework builders. The corals which build reefs today, the Scleractinia, arose after the Permian–Triassic extinction event that wiped out the earlier rugose corals (as well as many other groups). They became increasingly important reef builders throughout the Mesozoic Era.[10] They may have arisen from a rugose coral ancestor.

Rugose corals built their skeletons of calcite and have a different symmetry from that of the scleractinian corals, whose skeletons are aragonite.[11] However, there are some unusual examples of well-preserved aragonitic rugose corals in the Late Permian. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Nevertheless, scleractinian corals (which arose in the middle Triassic) may have arisen from a non-calcifying ancestor independent of the rugosan corals (which disappeared in the late Permian).[3]

Artificial

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Main article: Artificial reef

An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets,[12] or improve surfing.[13]

Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or by deploying rubble or construction debris. Other artificial reefs are purpose built (e.g. the reef balls) from PVC or concrete. Shipwrecks become artificial reefs on the seafloor. Regardless of construction method, artificial reefs generally provide stable hard surfaces where algae and invertebrates such as barnacles, corals, and oysters attach; the accumulation of attached marine life in turn provides intricate structure and food for assemblages of fish.

See also

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References

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  1. ^ a b c d "Resource Library: Encyclopedic Entry: Reef". www.nationalgeographic.org. Washington, DC: National Geographic Society. 30 September 2011. Retrieved 15 March 2021.
  2. ^ Guus Kroonen (2013). Etymological Dictionary of Proto-Germanic.
  3. ^ a b c d e "Reading: Shorelines | Geology". courses.lumenlearning.com. Retrieved 2024-04-20.
  4. ^ Wood, Rachel (2001-12-15). "Are reefs and mud mounds really so different?". Sedimentary Geology. Carbonate Mounds: sedimentation, organismal response, and diagenesis. 145 (3): 161–171. Bibcode:2001SedG..145..161W. doi:10.1016/S0037-0738(01)00146-4. ISSN 0037-0738.
  5. ^ crossref. "Chooser". chooser.crossref.org. doi:10.2307/3514838. JSTOR 3514838. Retrieved 2024-04-20.
  6. ^ Schieber, Jürgen (1998). "Possible indicators of microbial mat deposits in shales and sandstones: examples from the Mid-Proterozoic Belt Supergroup, Montana, U.S.A." Sedimentary Geology. 120 (1): 105–124. Bibcode:1998SedG..120..105S. doi:10.1016/S0037-0738(98)00029-3.
  7. ^ "Rocky Reef on the West Coast". www.fisheries.noaa.gov. National Oceanic and Atmospheric Administration. Retrieved 3 February 2021.
  8. ^ Gorokhovich, Yuri; Learning, Lumen. "Coastal Geology: Shorelines". {{cite journal}}: Cite journal requires |journal= (help)
  9. ^ "Archaeocyathans". ucmp.berkeley.edu. Retrieved 2024-04-20.
  10. ^ Pruss, Sara B.; Bottjer, David J. (2005-09-01). "The reorganization of reef communities following the end-Permian mass extinction". Comptes Rendus Palevol. 4 (6): 553–568. Bibcode:2005CRPal...4..553P. doi:10.1016/j.crpv.2005.04.003. ISSN 1631-0683.
  11. ^ "Rugose Coral". Museum of Natural History. 2021-06-30. Retrieved 2024-04-20.
  12. ^ Gray, Denis D. (2 June 2018). "Cambodia volunteers step up battle against illegal fishing". asia.nikkei.com. Nikkei Asia. Retrieved 17 March 2021.
  13. ^ "Optimism at Boscombe surf reef's opening day". Bournemouthecho.co.uk. 3 November 2009. Archived from the original on March 18, 2012. Retrieved 19 June 2012.

Sources

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  • Shears N.T. (2007) Biogeography, community structure and biological habitat types of subtidal reefs on the South Island West Coast, New Zealand. Science for Conservation 281. p 53. Department of Conservation, New Zealand. [1]
  • “General Information on Reefs.” General Information on Reefs – Reef & Ocean Ecology Lab. Accessed February 1, 2024. https://www.reefoceanlab.org.au/resources/general-information-on-reefs/#:~:text=Rocky%20reefs%20are%20more%20typical,many%20parts%20of%20New%20Zealand.
  • “Coral Reefs ~ Marinebio Conservation Society.” MarineBio Conservation Society, November 10, 2023. https://www.marinebio.org/creatures/coral-reefs/#:~:text=Organisms%20responsible%20for%20building%20tropical,and%20the%20Tropic%20of%20Cancer.
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The Wikibook Historical Geology has a page on the topic of: Reefs
Wikimedia Commons has media related to Reefs.
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