Editing Artificial reef

{{Short description|Human-made underwater structure that functions as a reef}}
[[File:Lake Pontchartrain Basin Foundation Reef Balls, close.jpg|thumb|Reef balls are just one type of structure used in the construction of artificial reefs.]]
An '''artificial reef''' ('''AR''') is a human-created freshwater or marine [[benthic]] structure.<ref name="Seaman2013">{{cite book |last1=Seaman, Jr |first1=William |title=Artificial Habitats for Marine and Freshwater Fisheries |year=2013 |publisher=Academic Press |isbn=978-0-08-057117-1 |url=https://books.google.com/books?id=-6XYBAAAQBAJ&pg=PA61 |language=en}}</ref>
Typically built in areas with a generally featureless bottom to promote [[Marine biology#Reefs|marine life]], it may be intended to control [[#Erosion prevention|erosion]], protect coastal areas, block ship passage, block the use of [[trawling]] nets,<ref name="Gray">{{cite news |last1=Gray |first1=Denis D. |title=Cambodia volunteers step up battle against illegal fishing |url=https://asia.nikkei.com/Life-Arts/Life/Cambodia-volunteers-step-up-battle-against-illegal-fishing |access-date=16 June 2023 |work=Nikkei Asia |date=June 2, 2018}}</ref> support reef restoration, improve [[aquaculture]], or enhance [[scuba diving]] and [[surfing]].<ref name="Airoldi"/> Early artificial reefs were built by the Persians and the Romans.

An opportunity artificial reef is built from objects that were intended for other purposes,<ref name="Carral">{{cite journal |last1=Carral |first1=Luis |last2=Camba Fabal |first2=Carolina |last3=Lamas Galdo |first3=Mª Isabel |last4=Rodríguez-Guerreiro |first4=Mª Jesús |last5=Cartelle Barros |first5=Juan José |title=Assessment of the Materials Employed in Green Artificial Reefs for the Galician Estuaries in Terms of Circular Economy |journal=International Journal of Environmental Research and Public Health |date=28 November 2020 |volume=17 |issue=23 |pages=8850 |doi=10.3390/ijerph17238850 |pmid=33260753 |pmc=7730678 |doi-access=free }}</ref> such as sinking oil rigs (through the [[Rigs-to-Reefs]] program), [[Sinking ships for wreck diving sites|scuttling ships]], or by deploying [[rubble]] or [[construction debris]]. Shipwrecks may become artificial reefs when preserved on the seafloor. A conventional artificial reef uses materials such as concrete, which can be molded into specialized forms (e.g. [[The Reef Ball Foundation|reef balls]]). Green artificial reefs incorporate renewable and organic materials such as vegetable fibres and seashells to improve sustainability and reduce energy consumption, pollution, and greenhouse gas emissions.<ref name="Carral"/> In some cases, artificial reefs have been developed as artworks.

Artificial reefs generally provide hard surfaces where [[algae]] and invertebrates such as [[barnacle]]s, [[coral]]s, and [[oyster]]s attach and spaces where different sizes of fishes can hide. The accumulation of attached marine life in turn provides intricate structures and food for [[biocenose|assemblages]] of fish.<ref name="Seaman2013"/><ref name="Bakx">{{cite news |last1=Bakx |first1=Kyle |title=Concrete solutions Fishermen are sinking boats and dumping concrete in the Gulf of Mexico – to save the fish |url=https://www.cbc.ca/newsinteractives/features/artificial-reef-RGV-carbon-study |work=CBC News |date=May 28, 2023}}</ref> The ecological impact of an artificial reef depends on multiple factors including where it is situated, how it is constructed, and the ages and types of species involved.<ref name="Bracho-Villavicencio"/><ref name="Komyakova">{{cite journal |last1=Komyakova |first1=Valeriya |last2=Chamberlain |first2=Dean |last3=Swearer |first3=Stephen E. |title=A multi-species assessment of artificial reefs as ecological traps |journal=Ecological Engineering |date=1 November 2021 |volume=171 |pages=106394 |doi=10.1016/j.ecoleng.2021.106394 |bibcode=2021EcEng.17106394K |url=https://www.sciencedirect.com/science/article/abs/pii/S0925857421002494 |language=en |issn=0925-8574|url-access=subscription }}</ref><ref name="Macura">{{cite journal |last1=Macura |first1=Biljana |last2=Byström |first2=Pär |last3=Airoldi |first3=Laura |last4=Eriksson |first4=Britas Klemens |last5=Rudstam |first5=Lars |last6=Støttrup |first6=Josianne G. |title=Impact of structural habitat modifications in coastal temperate systems on fish recruitment: a systematic review |journal=Environmental Evidence |date=12 March 2019 |volume=8 |issue=1 |pages=14 |doi=10.1186/s13750-019-0157-3 |bibcode=2019EnvEv...8...14M |s2cid=84831487 |issn=2047-2382|doi-access=free |hdl=11577/3401331 |hdl-access=free }}</ref> While the artificial reefs allow for coral growth, it changes the ecosystem as the relative growth for different species is not always the same. Studies have found that macroalgal, cyanobacterial groups, and coral that are fast growing, grow in artificial reefs at different rates than they would grow in natural reefs.<ref>{{Cite journal |last1=Miller |first1=M. W. |last2=Valdivia |first2=A. |last3=Kramer |first3=K. L. |last4=Mason |first4=B. |last5=Williams |first5=D. E. |last6=Johnston |first6=L. |date=2009-07-28 |title=Alternate benthic assemblages on reef restoration structures and cascading effects on coral settlement |url=https://www.int-res.com/abstracts/meps/v387/p147-156/ |journal=Marine Ecology Progress Series |language=en |volume=387 |pages=147–156 |doi=10.3354/meps08097 |bibcode=2009MEPS..387..147M |issn=0171-8630}}</ref>

Considerable research is being done into construction methods and the effects of artificial reefs.<ref name="Airoldi"/><ref name="Macura"/><ref name="Lima"/> Many of the materials used early on are now considered undesirable.<ref name=" Bracho-Villavicencio"/> A 2001 literature review suggested that about half of the reefs studied met their objectives.<ref name="Baine"/> Long-term planning and ongoing management were identified as essential factors in success.<ref name="Baine">{{cite journal |last1=Baine |first1=Mark |title=Artificial reefs: a review of their design, application, management and performance |journal=Ocean & Coastal Management |date=January 2001 |volume=44 |issue=3–4 |pages=241–259 |doi=10.1016/S0964-5691(01)00048-5|bibcode=2001OCM....44..241B }}</ref><ref name="Brochier">{{cite journal |last1=Brochier |first1=Timothée |last2=Brehmer |first2=Patrice |last3=Mbaye |first3=Adama |last4=Diop |first4=Mamadou |last5=Watanuki |first5=Naohiko |last6=Terashima |first6=Hiroaki |last7=Kaplan |first7=David |last8=Auger |first8=Pierre |title=Successful artificial reefs depend on getting the context right due to complex socio-bio-economic interactions |journal=Scientific Reports |date=17 August 2021 |volume=11 |issue=1 |pages=16698 |doi=10.1038/s41598-021-95454-0 |pmid=34404822 |pmc=8371003 |bibcode=2021NatSR..1116698B |language=en |issn=2045-2322}}</ref><ref name="Lima">{{cite journal |last1=Lima |first1=Juliano Silva |last2=Zalmon |first2=Ilana Rosental |last3=Love |first3=Milton |title=Overview and trends of ecological and socioeconomic research on artificial reefs |journal=Marine Environmental Research |date=1 March 2019 |volume=145 |pages=81–96 |doi=10.1016/j.marenvres.2019.01.010 |pmid=30837123 |bibcode=2019MarER.145...81L |s2cid=73481444 |url=https://www.sciencedirect.com/science/article/abs/pii/S0141113618307888 |language=en |issn=0141-1136|url-access=subscription }}</ref>
A more recent analysis of reefs world wide between 1990 and 2020 concludes that artificial reefs can be useful tools for restoring marine ecosystems if they are strategically designed to suit their specific location and its resource needs.<ref name=" Bracho-Villavicencio"/>

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== History ==
The construction of artificial reefs began in ancient times.
According to historian [[Diodorus Siculus]], the [[Roman Republic|Romans]] blocked the harbor of [[Lilybaeum]] during the [[First Punic War]] against the [[Ancient Carthage|Carthaginians]] around 250 BC. They built an artificial reef "with stones and construction material" and put poles in the channels using "large timbers and anchors".<ref>{{cite book |last1=Samuelsson |first1=Gunnar |title=Crucifixion in antiquity: an inquiry into the background and significance of the New Testament terminology of crucifixion |date=2011 |publisher=Mohr Siebeck |location=Tübingen |isbn=978-3161506949 |page=81 |url=http://khazarzar.skeptik.net/books/crux002.pdf}}</ref><ref name="Knighton">{{cite web |last1=Knighton |first1=Andrew |title=The Awesome Power of the Ancient Roman Navy Was So Great, It Even Won Sieges |url=https://www.warhistoryonline.com/ancient-history/awesome-power-roman-navy.html |website=warhistoryonline |access-date=5 July 2023 |language=en |date=17 January 2018}}</ref><ref>{{cite web|title=Disposal Options for Ships|url=http://192.5.14.110/pubs/monograph_reports/MR1377/MR1377.ch5.pdf|last1=Hess|first1=Ron|last2=Rushworth|first2=Denis|publisher=[[Rand Corporation]]|url-status=dead|archive-url=https://web.archive.org/web/20070629110318/http://192.5.14.110/pubs/monograph_reports/MR1377/MR1377.ch5.pdf|archive-date=29 June 2007|access-date=20 December 2006|last3=Hynes|first3=Michael V.|last4=Peters|first4=John E.}}</ref>
[[Persian Empire|Persians]] blocked the mouth of the [[Tigris River]] to thwart Arabian pirates by building an artificial reef.<ref>{{cite book|last=Williams|first=Thomas Wayne|url=http://etd.vcu.edu/theses/available/etd-08042006-093035/unrestricted/williamstw_phd.pdf|title=A Case Study of Artificial Reef Decision-Making in the Florida Keys|publisher=Virginia Commonwealth University|access-date=20 December 2006|archive-url=https://web.archive.org/web/20060907213433/http://etd.vcu.edu/theses/available/etd-08042006-093035/unrestricted/williamstw_phd.pdf|archive-date=7 September 2006|url-status=dead}}</ref>

Artificial reefs to increase fish yields or for [[algaculture]] began no later than 17th-century Japan, when rubble and rocks were used to grow [[kelp]].<ref>{{cite book |title=Fisheries Technologies for Developing Countries |date=1988 |url=https://nap.nationalacademies.org/catalog/1024/fisheries-technologies-for-developing-countries |access-date=20 December 2006 |publisher=National Academies Press|doi=10.17226/1024 |isbn=978-0-309-03788-4 }} {{dead link|date=April 2015}}</ref> The earliest recorded artificial reef in the United States is from the 1830s, when logs from huts were used off the coast of [[South Carolina]] to improve fishing.<ref>{{Cite web|title=Guidelines For Marine Artificial Reef Materials|url=http://www.gsmfc.org/pubs/SFRP/Guidelines_for_Marine_Artificial_Reef_Materials_January_1997.pdf|publisher=Gulf States Marine Fisheries Commission|url-status=dead|archive-url=https://web.archive.org/web/20070110005135/http://www.gsmfc.org/pubs/SFRP/Guidelines_for_Marine_Artificial_Reef_Materials_January_1997.pdf|archive-date=10 January 2007|access-date=20 December 2006}}</ref> In the [[Philippines]] a traditional native fishing technique known as [[fish nest]]s (natively known by various names like ''gango'', ''amatong'', or ''balirong''), is basically an artificial reef. It uses rocks and waterlogged wood to build mounds inside excavated trenches on shallow tidal waters that attract fish and crustaceans. The mounds are then harvested every few weeks during low tide by surrounding them with nets and dismantling them piece by piece. They are rebuilt after every harvest. Fish nests are often used to capture [[grouper]] [[Juvenile fish|fingerling]]s to be used as seeds for [[aquaculture]]. Fish nests were in common use since before 1939.<ref name="Johannes">{{cite journal |last1=Johannes |first1=R.E. |last2=Ogburn |first2=N.J. |title=Collecting grouper seed for aquaculture in the Philippines |journal=SPC Live Reef Fish Information Bulletin |date=1999 |issue=6 |pages=35–48 |url=https://spccfpstore1.blob.core.windows.net/digitallibrary-docs/files/c6/c69eca99fa56c5ea9cb7df5ec872181b.pdf?sv=2015-12-11&sr=b&sig=OLip3GnWqxu3LVuKMRXTJ%2F%2BxfVmm1aZ%2FrOST6y6u3Cg%3D&se=2021-11-18T08%3A16%3A19Z&sp=r&rscc=public%2C%20max-age%3D864000%2C%20max-stale%3D86400&rsct=application%2Fpdf&rscd=inline%3B%20filename%3D%22LRF6_35_Johannes.pdf%22 |access-date=2021-05-23 |archive-date=2021-09-25 |archive-url=https://web.archive.org/web/20210925145818/https://spccfpstore1.blob.core.windows.net/digitallibrary-docs/files/c6/c69eca99fa56c5ea9cb7df5ec872181b.pdf?sv=2015-12-11&sr=b&sig=OLip3GnWqxu3LVuKMRXTJ%2F%2BxfVmm1aZ%2FrOST6y6u3Cg%3D&se=2021-11-18T08%3A16%3A19Z&sp=r&rscc=public%2C%20max-age%3D864000%2C%20max-stale%3D86400&rsct=application%2Fpdf&rscd=inline%3B%20filename%3D%22LRF6_35_Johannes.pdf%22 |url-status=dead }}</ref><ref name="Monteclaro">{{cite book |last1=Monteclaro |first1=Harold |last2=Anraku |first2=Kazuhiko |last3=Ishikawa |first3=Satoshi |title=Field Guidebook on Philippine Fishing Gears: Fishing Gears in Estuaries |date=2017 |publisher=Research Institute for Humanity and Nature |location=Kyoto |isbn=978-4-906888-31-3 |url=https://www.chikyu.ac.jp/CAPABILITY/img/books/FieldGuidebook_on_PhilippineFishingGears.pdf}}</ref>

Beginning before the 1840s, US fishermen used interlaced logs to build artificial reefs. More recently, refuse such as old refrigerators, shopping carts, ditched cars and out-of-service vending machines replaced the logs in ad hoc reefs. Officially sanctioned projects have incorporated [[Ship commissioning#Ship decommissioning|decommissioned ships]], subway cars, battle tanks, [[Armoured personnel carrier|armored personnel carriers]], oil drilling rigs and beehive-like reef balls.<ref name=ng211/><ref name="Doyle">{{cite journal |last1=Doyle |first1=Martin W. |last2=Havlick |first2=David G. |title=Infrastructure and the Environment |journal=Annual Review of Environment and Resources |date=1 November 2009 |volume=34 |issue=1 |pages=349–373 |doi=10.1146/annurev.environ.022108.180216 |language=en |issn=1543-5938|doi-access=free }}</ref>

==Purposes==
[[File:Snorkeling Reef.JPG|thumb|Artificial reefs can help increase biodiversity in an area.]]
Artificial reef structures (ARs) have a variety of intended uses, ranging from the protection, enhancement and restoration of marine ecosystems<ref name="Bracho-Villavicencio"/> to the support of human activities like fishing, recreational diving and surfing.<ref name="Seaman"/> Artificial reefs can be used as active restoration tools to mitigate environmental damage and habitat loss, restore degraded ecosystems such as kelp forests and coral reefs, and promote biodiversity.<ref name="Bracho-Villavicencio"/><ref name="Seaman"/>
In fisheries management, artificial reefs may be intended to increase production of species of recreational and commercial interest,<ref name="Bracho-Villavicencio"/> enhance fishing yield,<ref name="Paxton"/> and support recreational, artisanal or commercial fisheries. They may be designed to protect [[benthic]] habitats from illegal trawling and restore fish stocks.<ref name="Seaman"/>
They may be placed to protect against coastal erosion.<ref name="Bracho-Villavicencio"/>
They may also be developed to support eco-tourism, promote recreational activities like scuba diving and surfing, and mitigate tourism pressure on corals.<ref name="Seaman"/>

The design and construction of an artificial reef may be very different depending on its proposed location and intended goals. A reef that is designed for one purpose may be unsuitable for others. Early attempts to create artificial reefs frequently failed, or at best, met with mixed results.<ref name="Blacka"/><ref name="Black"/><ref name="Baine"/> More recent reviews of work from 1990–2020 suggest that a correctly implemented artificial reef, designed to fit its target ecosystem, can be useful as a tool for the restoration of marine ecosystems. Reviewers call for better before/after and control comparisons of artificial and natural reefs, increased monitoring of reefs over their lifespan, and attention to the spatial orientation, complexity, and shape of reef substrate, among others.<ref name="Bracho-Villavicencio"/><ref name="Paxton">{{cite journal |last1=Paxton |first1=Avery B. |last2=Shertzer |first2=Kyle W. |last3=Bacheler |first3=Nathan M. |last4=Kellison |first4=G. Todd |last5=Riley |first5=Kenneth L. |last6=Taylor |first6=J. Christopher |title=Meta-Analysis Reveals Artificial Reefs Can Be Effective Tools for Fish Community Enhancement but Are Not One-Size-Fits-All |journal=Frontiers in Marine Science |date=7 May 2020 |volume=7 |doi=10.3389/fmars.2020.00282 |doi-access=free }}</ref><ref name="Seaman">{{cite journal |last1=Seaman |first1=William |title=Artificial habitats and the restoration of degraded marine ecosystems and fisheries |journal=Hydrobiologia |date=1 April 2007 |volume=580 |issue=1 |pages=143–155 |doi=10.1007/s10750-006-0457-9 |s2cid=2331696 |url=https://link.springer.com/article/10.1007/s10750-006-0457-9 |language=en |issn=1573-5117|url-access=subscription }}</ref>

===Artificial reef communities===
[[File:Sarcastic fringehead in plastic tube.JPG|thumb|Human-created objects provide hiding places for marine life, like this [[Sarcastic fringehead]]|alt=]]
On artificial reef structures intended for ecosystem enhancement, reef communities tend to develop in more or less predictable stages. First, where an ocean current encounters a vertical structure, it can create a [[plankton]]-rich upwelling that provides a reliable feeding spot for small fish such as [[sardine]]s and [[minnow]]s, which draw in [[pelagic]] [[predator]]s such as [[tuna]] and [[sharks]]. Next come creatures seeking protection from the ocean's lethal openness—hole and crevice dwellers such as [[grouper]], [[Lutjanidae|snapper]], [[squirrelfish]], [[eel]]s and [[triggerfish]]. Opportunistic predators such as [[Carangidae|jack]] and [[barracuda]] also appear. Over months and years the reef structure becomes encrusted with [[algae]], [[tunicates]], hard and soft [[coral]]s and [[sponge]]s.<ref name=ng211/>

[[File:Manta ray Biorock reef.jpg|thumb|right|alt=|A newly constructed [[electrified reef]] set up by [[Gili Eco Trust]] in [[Indonesia]].]]
An [[electrified reef]] is an artificial reef where a small low voltage electric charge is applied to a sub-sea metallic structures that causes [[limestone]] to precipitate onto a metal frame onto which [[planula|coral planulae]] can then attach and grow; the process also speeds up post-attachment growth.<ref name=GCRA>{{cite web|url=http://www.globalcoral.org/wp-content/uploads/2013/11/BIOROCK_TECHNOLOGY_july1114.pdf |publisher=Global Coral Reef Alliance |title=Biorock Benefits |date=July 2014 |access-date=5 April 2015}}</ref><ref name="Goldberg">{{cite news |last1=Goldberg |first1=Lee |title=Artificial Reefs Built from Sun and Seawater Will Protect the Isle of Man |url=https://www.electronicdesign.com/technologies/power/whitepaper/21243917/electronic-design-artificial-reefs-built-from-sun-and-seawater-will-protect-the-isle-of-man |work=Electronic Design |date=9 June 2022}}</ref>

3D printing technology has been employed both to create molds to optimize the environment for target species,<ref name="Ramos">{{cite book |last1=Ramos |first1=Jorge H. P. |title=Impact of Artificial Reefs on the Environment and Communities |date= 2022 |publisher=IGI Global |isbn=978-1-6684-2346-2 |url=https://books.google.com/books?id=0V1wEAAAQBAJ&pg=PA210 |language=en}}</ref><ref name="3Dreef">{{cite news |title=3D printing technology to aid coral growth in Maldives |url=https://maldivesindependent.com/environment/3d-printing-technology-to-aid-coral-growth-in-maldives-140073 |access-date=16 June 2023 |work=Maldives Independent |date=12 August 2018}}</ref> and to directly create cast ceramic and concrete artificial reefs. Work has also been done to develop environmentally friendly materials.<ref name="Koslow">{{cite news |last1=Koslow |first1=Tyler |title=3D Printing Used to Revive the Coral Reefs of Monaco |url=https://3dprintingindustry.com/news/3d-printing-used-to-revive-the-coral-reefs-ocean-eco-system-of-monaco-60807/ |work=3D Printing Industry |date=26 October 2015}}</ref> For example, Archireef has designed 3D-printed terracotta Reef Tiles, which are nontoxic, biodegradable, and have a pH-level that is compatible with coral. The tiles are small enough to be handled and installed by a diver. An installation in Hong Kong reported a 95 percent coral survival rate after three years, more than four times the survival rate of more traditional restoration methods.<ref name="Boyani">{{cite news |last1=Boyani |first1=Sally |title=These artificial reefs are combating coral degradation |url=https://wired.me/technology/artificial-reefs-coral-degradation/ |work=WIRED Middle East |date=11 September 2023}}</ref>

Restoration and mitigation actions on artificial reefs can include activities such as coral transplantation, larval resettlement, and gardening.<ref name="Bracho-Villavicencio">{{cite journal |last1=Bracho-Villavicencio |first1=Carolina |last2=Matthews-Cascon |first2=Helena |last3=Rossi |first3=Sergio |title=Artificial Reefs around the World: A Review of the State of the Art and a Meta-Analysis of Its Effectiveness for the Restoration of Marine Ecosystems |journal=Environments |date=July 2023 |volume=10 |issue=7 |pages=121 |doi=10.3390/environments10070121 |language=en |issn=2076-3298 |doi-access=free }}</ref>
For example, the [[Coral Restoration Foundation]] in the Florida Keys raises keystone species such as elkhorn ([[Acropora palmata]]) and staghorn ([[Acropora cervicornis]]) in coral tree nurseries and replants the corals onto degrading coral reefs.<ref name="Roberson">{{cite news |last1=Roberson |first1=Julia |title=Restoring Endangered Coral Reefs |url=https://oceanconservancy.org/blog/2016/07/28/restoring-endangered-coral-reefs-2/ |work=Ocean Conservancy |date=July 28, 2016}}</ref> Application of such technologies to artificial reefs could help to restore marine ecosystems. A 2023 review article states: "The implementation of artificial reefs to restore marine ecosystems can be well done, investing resources in studies specifically aimed at determining the appropriate characteristics of ARs for each location."<ref name="Bracho-Villavicencio"/>

=== Carbon sequestration ===
[[File:Artificialreef.JPG|thumb|Constructing an artificial reef using [[Concrete masonry unit|concrete breeze blocks]]<ref>{{cite web | last=Aspinall | first=Richard | title=From concrete to coral: breeze blocks make a splash regenerating reefs | website=The Guardian | date=2016-09-20 | url=http://www.theguardian.com/science/blog/2016/sep/20/from-concrete-to-coral-breeze-blocks-make-a-splash-regenerating-reefs | access-date=2021-01-04}}</ref>]]
There is interest in the possibility that artificial reefs can be used to support [[carbon sequestration]] and counter [[climate change]]. Coastal vegetation ecosystems (mangrove, salt marsh, and seagrass), algal beds, and phytoplankton have been identified as potential [[carbon sinks]]. It is hoped that increasing biomass at artificial reefs can provide another form of [[blue carbon]] storage.<ref name="Shu"/><ref name="Jiang">{{cite news |last1=Jiang |first1=Yifan |title=What makes China's 'blue carbon' plans different? |url=https://chinadialogueocean.net/en/fisheries/18729-what-makes-chinas-blue-carbon-plans-different/ |work=China Dialogue Ocean |date=23 September 2021}}</ref>

RGV Reef, a 1,650-acre artificial reef created in 2017 in the Gulf of Mexico off the coast of Texas, is being studied to assess its potential for carbon capture.<ref name="Curtis">{{cite web |title=Carbon Capture Research Begins at Largest Artificial Reef in Texas |url=https://rgvreef.org/first-of-its-kind-study-could-be-a-gamechanger-in-dealing-with-climate-changer/ |website=RGV Reef|date= October 19, 2022 }}</ref> Another study area is located off Juehua Island in the [[Bohai Sea]]. Biological, physical, social and technological factors must all be considered in calculating carbon capture flow in aquatic systems. Near Juehua Island, M-shaped artificial reefs improved hydrodynamic conditions for creating a carbon sink, but local marine species had limited availability. Development of active marine management strategies and the introduction of appropriate biological species were suggested as ways to increase carbon capture potential.<ref name="Shu">{{cite journal |last1=Shu |first1=Anping |last2=Zhang |first2=Ziru |last3=Wang |first3=Le |last4=Sun |first4=Tao |last5=Yang |first5=Wei |last6=Zhu |first6=Jiapin |last7=Qin |first7=Jiping |last8=Zhu |first8=Fuyang |title=Effects of typical artificial reefs on hydrodynamic characteristics and carbon sequestration potential in the offshore of Juehua Island, Bohai Sea |journal=Frontiers in Environmental Science |date=2022 |volume=10 |doi=10.3389/fenvs.2022.979930 |issn=2296-665X |doi-access=free }}</ref>

In the Caribbean, researchers have found that the placement of [[breeze blocks]] as artificial reefs near tropical [[seagrass meadows]] can create a positive feedback loop. The reef structures attracted fish by providing shelter, and the fish in turn fertilized the seagrass and increased its productivity, providing both food and shelter. The combination of seagrass and reef structures provided added protection from fish nets as well as increasing biomass in the seagrass meadow.<ref name="Ashworth">{{cite web |last1=Ashworth |first1=James |title=Artificial reefs in seagrass meadows could help protect against climate change |website=phys.org |date=July 26, 2023 |url=https://phys.org/news/2023-07-artificial-reefs-seagrass-meadows-climate.html |language=en}}</ref><ref name="Esquivel">{{cite journal |last1=Esquivel |first1=Kenzo E. |last2=Hesselbarth |first2=Maximilian H. K. |last3=Allgeier |first3=Jacob E. |title=Mechanistic support for increased primary production around artificial reefs |journal=Ecological Applications |date=September 2022 |volume=32 |issue=6 |pages=e2617 |doi=10.1002/eap.2617 |pmid=35368128 |bibcode=2022EcoAp..32E2617E |hdl=2027.42/174782 |s2cid=247937506 |url=https://doi.org/10.1002/eap.2617 |language=en |issn=1051-0761|hdl-access=free }}</ref><ref name="Andskog">{{cite journal |last1=Andskog |first1=Mona A. |last2=Layman |first2=Craig |last3=Allgeier |first3=Jacob E. |title=Seagrass production around artificial reefs is resistant to human stressors |journal=Proceedings of the Royal Society B: Biological Sciences |date=26 July 2023 |volume=290 |issue=2003 |doi=10.1098/rspb.2023.0803|pmid=37491960 |pmc=10369039 }}</ref> Estimates suggest that Caribbean seagrass beds can provide substantial pools for global carbon.<ref name="Shayka">{{cite journal |last1=Shayka |first1=Bridget F. |last2=Hesselbarth |first2=Maximilian H. K. |last3=Schill |first3=Steven R. |last4=Currie |first4=William S. |last5=Allgeier |first5=Jacob E. |title=The natural capital of seagrass beds in the Caribbean: evaluating their ecosystem services and blue carbon trade potential |journal=Biology Letters |date=June 2023 |volume=19 |issue=6 |doi=10.1098/rsbl.2023.0075|pmid=37340807 |s2cid=259204507 |pmc=10282569 }}</ref>

===Erosion prevention===
[[File:Oyster reef in the bay made from oyster castles, about 60% complete (22620795960).jpg|thumb|Oyster castle reef, Gandy's Beach shoreline protection project<ref name="Bredes">{{cite journal |last1=Bredes |first1=Amy L. |last2=Miller |first2=Jon K. |last3=Kerr |first3=Laura |last4=Brown |first4=Dana Rose |title=Observations of Wave Height Amplification Behind an Oyster Castle Breakwater System in a High-Energy Environment: Gandys Beach, NJ |journal=Frontiers in Built Environment |date=2022 |volume=8 |doi=10.3389/fbuil.2022.884795 |issn=2297-3362 |doi-access=free }}</ref>]]

Some artificial reefs are used to prevent [[coastal erosion]].<ref name="Brandon">{{cite magazine |last1=Brandon |first1=Elissaveta M. |title=To Fight Coastal Erosion, Design a Bespoke Artificial Reef |url=https://www.wired.com/story/reefy-modular-reef-costal-erosion/ |magazine=Wired |date=March 28, 2023}}</ref><ref name="Cusick">{{cite news |last1=Cusick |first1=Daniel |title='Reef Balls' Gain Traction for Shoreline Protection |url=https://www.scientificamerican.com/article/reef-balls-gain-traction-for-shoreline-protection/ |work=Scientific American |date=May 17, 2022 |language=en}}</ref>
Geometric and hydrodynamic properties of reefs are particularly important in determining their ability to mitigate coastal erosion.<ref name="Escudero">{{cite journal |last1=Escudero |first1=Mireille |last2=Reguero |first2=Borja G. |last3=Mendoza |first3=Edgar |last4=Secaira |first4=Fernando |last5=Silva |first5=Rodolfo |title=Coral Reef Geometry and Hydrodynamics in Beach Erosion Control in North Quintana Roo, Mexico |journal=Frontiers in Marine Science |date=2021 |volume=8 |doi=10.3389/fmars.2021.684732 |issn=2296-7745 |doi-access=free }}</ref><ref name="Kim">{{cite journal |last1=Kim |first1=Taeyoon |last2=Baek |first2=Seungil |last3=Kwon |first3=Yongju |last4=Lee |first4=Jooyong |last5=Cha |first5=Sung Min |last6=Kwon |first6=Soonchul |title=Improved Coastal Erosion Prevention Using a Hybrid Method with an Artificial Coral Reef: Large-Scale 3D Hydraulic Experiment |journal=Water |date=October 2020 |volume=12 |issue=10 |pages=2801 |doi=10.3390/w12102801 |language=en |issn=2073-4441 |doi-access=free }}</ref>
Artificial reefs to prevent erosion can be designed to act in multiple ways. Some are designed to force [[water waves|waves]] to deposit their energy offshore rather than directly on the coastline.

Other reefs are designed to hold [[sediment]] on beaches by trapping the sediment. Reefs are generally custom-designed for each unique zone.<ref name="Morang">{{cite journal |last1=Morang |first1=Andrew |last2=Waters |first2=Jeffrey P. |last3=Stauble |first3=Donald K. |title=Performance of Submerged Prefabricated Structures to Improve Sand Retention at Beach Nourishment Projects |journal=Journal of Coastal Research |date=1 November 2014 |volume=30 |issue=6 |pages=1140–1156 |doi=10.2112/JCOASTRES-D-13-00137.1 |s2cid=128833800 |url=https://doi.org/10.2112/JCOASTRES-D-13-00137.1|url-access=subscription }}</ref><ref name="Blacka"/><ref name="Black"/> Some are designed to support customizable habitat for local target species as well.<ref name="Brandon"/>

===Artificial surfing reefs===
{{Main|Multi-purpose reef}}
[[File:Mega sand container.jpg|thumb|Mega sand container with a by then unprecedented size of 20 m (length) × 4.80 m (diameter) as presented in 1999 on an open day for the public at the construction site for the Gold Coast artificial reef.]]
Some types of artificial reefs, such as surfing reefs, do not have ecosystem enhancement as a major goal. Hoppy's Reef was an early but unsuccessful attempt to create a surfing reef, off [[Hermosa Beach, California]] (1971).<ref>{{cite web |title=Hoppy's Reef |url=https://raisedwaterresearch.com/spot/artificial-reef/us/california/hoppys-reef/ |website=Raised Waves}}</ref> Artificial surfing reefs have been created at
Cable Station Reef ([[Perth]], [[Western Australia]], 1999)<ref name="Bancroft">{{cite book |last1=Bancroft |first1=Stacey |title=Performance Monitoring of the Cable Station Artificial Surfing Reef |date=1999 |publisher=The University of Western Australia |url=http://joas.free.fr/studies/bei/g2s/bancroft_thesis.pdf}}</ref><ref name="BMT">{{cite web |author=BMT Western Australia Pty Ltd |title=Middleton Beach Artificial Surf Reef Environmental Impact Assessment |date=14 September 2018 |url=https://www.epa.wa.gov.au/sites/default/files/Referral_Documentation/Environmental%20Impact%20Assessment_0.pdf |pages=10–17 }}</ref><ref>{{cite web |title=Cables Reef |url=https://raisedwaterresearch.com/spot/artificial-reef/australia/western-australia/cables-reef/ |website=Raised Waves}}</ref>
[[Narrow Neck, Queensland|Narrowneck Reef]] ([[Gold Coast, Queensland]], 2000)<ref name="Jackson">{{cite journal |last1=Jackson |first1=Angus |last2=Tomlinson |first2=Rodger |last3=Corbett |first3=Bobbie |last4=Strauss |first4=Darrell |title=Long Term Performance of a Submerged Coastal Control Structure: A Case Study of the Narrowneck Multi-Functional Artificial Reef |journal=Coastal Engineering Proceedings |date=14 December 2012 |volume=1 |issue=33 |pages=54 |doi=10.9753/icce.v33.structures.54 |url=https://icce-ojs-tamu.tdl.org/icce/article/view/6956 |language=en |issn=2156-1028|doi-access=free }}</ref><ref name="Black">{{cite journal |last1=Black |first1=Kerry |title=Artificial Surfing Reefs for Erosion Control and Amenity: Theory and Application |journal=Journal of Coastal Research |date=2001 |pages=1–14 |jstor=25736269 |url=https://www.jstor.org/stable/25736269 |issn=0749-0208}}</ref><ref>{{cite web |title=Narrowneck |url=https://raisedwaterresearch.com/spot/artificial-reef/australia/queensland/narrowneck/ |website=Raised Water}}</ref>
[[Chevron Reef]], also known as Pratte's Reef ([[El Segundo, California]], 2000, removed 2008).<ref name="Chevron">{{cite web |title=Pratte's Reef |url=https://raisedwaterresearch.com/spot/artificial-reef/us/california/prattes-reef/ |website=Raised Water |access-date=15 August 2023}}</ref><ref name="Leidersdorf">{{cite journal |last1=Leidersdorf |first1=Craig B. |last2=Richmond |first2=Brady |last3=Nelsen |first3=Chad E. |title=The Life and Death of North America's First Man-Made Surfing Reef |journal=Conference on Coastal Engineering Practice 2011 |date=30 August 2011 |pages=212–225 |doi=10.1061/41190(422)18|isbn=9780784411902 }}</ref>
and [[Boscombe Surf Reef]] (Dorset, England, 2009, closed 2011).<ref name="Rendle">{{cite book |last1=Rendle |first1=Emma Jane |title=The Environmental, Social and Economic Impacts of an Artificial Surf Reef – The UK Experience |date=2015 |publisher=Plymouth University |url=https://www.researchgate.net/publication/308695589}}</ref>

The construction of artificial surfing reefs has involved a variety of structures including concrete, rock, and geotextile bags filled with sand. Life expectancy of such materials varies widely. Geotextile structures have been found to degrade more quickly than anticipated under ocean conditions.<ref name="Borrero">{{cite journal |last1=Borrero |first1=Jose Carlos |last2=Mead |first2=Shaw T. |last3=Moores |first3=Andrew |title=Stability considerations and case studies of submerged structures constructed from large, sand filled, geotextile containers |journal=Coastal Engineering Proceedings |date=2010 |volume=1 |issue=32 |pages=60 |doi=10.9753/icce.v32.structures.60 |url=https://icce-ojs-tamu.tdl.org/icce/article/view/1172 |language=en |issn=2156-1028|doi-access=free }}</ref> Some analysts argue that they are fundamentally flawed.<ref name="Gegan">{{cite news |last1=Gegan |first1=Cooper |title=Why Have Most Artificial Reefs Never Really Worked? |url=https://www.theinertia.com/surf/why-have-most-artificial-reefs-never-really-worked/ |work=The Inertia |date=26 May 2023}}</ref> While use of stone blocks has raised concerns about possible safety hazards for surfers,<ref name="Blacka"/> it has been suggested that using stone may be structurally preferable.<ref name="Gegan"/>

In addition to improving surfing conditions, objectives of building an artificial surfing reef or [[multi-purpose reef]] have included stabilizing beachfront, coastal protection and coastal research. Habitat enhancement is sometimes considered as well.<ref name="Loomis">{{cite book |last1=Loomis |first1=Michael |title=Review of artificial surfing reefs and their effectiveness as recreation areas, marine habitats and erosion control devices |date=2003 |publisher=Nova Southeastern University Oceanographic Center |url=https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=094e801343153e9107f2c522e6e21b242f1bcfba}}</ref>
<ref name="Black"/> However, different materials are preferred for the construction of artificial surfing reefs and the development of reefs for ecosystem enhancement.<ref name="Blacka"/>

A 2012 review of artificial reefs indicated that artificial surfing reefs performed poorly in terms of their intended purpose and successfulness, rarely achieving primary or secondary objectives of "Surfing Enhancement".<ref name="Blacka"/>
For Pratte's reef, woven polypropylene bags were used in a first phase, and woven polyester bags in a second stage<ref name="Blacka"/> filling an area of approximately 1600 cubic meters.<ref name="redux">{{cite web |title=Pratt's Reef Redux |url=https://www.surfline.com/templates/article_html.cfm?n=6&id=20360&p=1 |website=Surfline}}</ref> The area involved was too small to be successful. Even after doubling the original budget, the materials used degraded rapidly, and the resulting remediation cost more than the installation.<ref name="Blacka"/>  Mount Reef at [[Mount Maunganui]] in New Zealand used more durable containers and a volume of around 6,000 cubic meters of sand. Although somewhat successful in creating waves, it too deteriorated and had to be removed.<ref name="redux"/><ref name="Maunganui">{{cite web |title=Mount Maunganui |url=https://raisedwaterresearch.com/spot/artificial-reef/new-zealand/north-island/mount-maunganui/ |website=Raised Water}}</ref> The Narrowneck Reef was much larger, at least 60,000 cubic meters, and was somewhat successful in its primary objective of shoreline stabilization, but less so in improving surfing.<ref name="Blacka"/>

Several projects in Australia have used stone to augment existing sites.<ref name="Gegan"/> Cable Station Reef added limestone rocks to an existing reef.<ref>{{cite news |title=Cables Reef Study |url=https://www.surfer.com/features/cablesreef |work=Surfer |date=Oct 11, 2010 |language=en}}</ref> At Burkitts Reef on the Woongarra Coast, large boulders were broken down to fill gaps in an existing boulder and gravel reef.<ref>{{cite web |title=Burkitts Reef |url=https://raisedwaterresearch.com/spot/artificial-reef/australia/queensland/burkitts-reef/ |website=Raised Water}}</ref> At Palm Beach Reef on the Gold Coast of Australia, stone boulders were used to adapt the shape of an existing breakwater and protect added sand.<ref>{{cite web |title=Palm Beach Reef |url=https://raisedwaterresearch.com/spot/artificial-reef/australia/queensland/palm-beach-reef/ |website=Raised Water}}</ref> Another artificial stone reef, located in [[Borth]], [[Wales]], was designed primarily for coastal protection.<ref name="BMT"/><ref name="Gegan"/><ref name="Borth">{{cite news |title=Borth coastal defence and surfing reef opens |url=https://www.bbc.com/news/uk-wales-mid-wales-17286596 |work=BBC News |date=8 March 2012}}</ref>

A major issue is that changes occurring in the lee of submerged reef structures are complex, not well understood, and difficult to model and predict. As of 2012, existing prototypes have been characterized as "trial or experimental only", and predictive models have not achieved "accuracy or reliability", although it has been hoped that "ongoing construction and monitoring of submerged constructed reefs (SCRs) will result in a better understanding of the processes and refined methods for predicting shoreline response".<ref name="Blacka">{{cite book |last1=Blacka |first1=M J |last2=Shand |first2=T D |last3=Carley |first3=J T |last4=Mariani |first4=A |title=A Review of Artificial Reefs for Coastal Protection in NSW WRL Technical Report 2012/08 June 2013 |date=2013 |publisher=Water Research Laboratory |location=Manly Vale, NSW |url=https://www.wrl.unsw.edu.au/sites/wrl/files/uploads/Publications/WRL-TR2012-08-Final-June-Artificial-Reefs.pdf}}</ref> Even in cases which were initially seen as successful, subsequent changes and deterioration of structures have led to poor outcomes.<ref name="Blacka"/>

Surfers' expectations of artificial reefs, particularly "an expectation by the general public of consistent, quality waves during a wide range of environmental conditions" have also led to disappointment.<ref name="Blacka"/><ref name="Mull">{{cite news |last1=Mull |first1=Jeff |title=Pipe Dreams |url=https://www.surfer.com/features/pipe-dreams-artificial-reef |work=Surfer |date=June 2, 2014 |language=en}}</ref>
Surfing science is a relatively new field.<ref name="Scarfe">{{cite journal |last1=Scarfe |first1=Bradley E. |last2=Healy |first2=Terry R. |last3=Rennie |first3=Hamish G. |title=Research-Based Surfing Literature for Coastal Management and the Science of Surfing – A Review |journal=Journal of Coastal Research |date=May 2009 |volume=253 |pages=539–557 |doi=10.2112/07-0958.1 |language=en |issn=0749-0208|doi-access=free }}</ref>
The ability to achieve consistency of surfing waves in a range of conditions in natural environments generally requires wave pre-conditioning or large scale breaking
features or both. The scale of early artificial surfing reefs was too small to achieve such consistency.<ref name="Blacka"/><ref name="Mead">{{cite book |last1=Mead |first1=Shaw |last2=Borrero |first2=Jose |chapter=Surf science and multi-purpose reefs |title=Marine and Coastal Resource Management |date=27 September 2017 |pages=288–311 |doi=10.4324/9780203127087-16|isbn=9780203127087 }}</ref>

===Recreational dive sites===
[[File:Musa 3 (13752182883).jpg| thumb | right | Statue by [[Jason deCaires Taylor]], [[Museo Subacuático de Arte]] ]]
[[File:EDP ArtReef by Vhils, Lisboa 01.jpg|thumb|right|Artwork for the creation of Artreef, Albufeira]]
Thousands of popular [[wreck diving]] sites throughout the world are shipwrecks sunk as artificial reefs.<ref>{{cite web|title=Wrecks and Obstructions Database|url=http://www.nauticalcharts.noaa.gov/hsd/wrecks_and_obstructions.html|website=NOAA|access-date=2016-03-08|archive-date=2021-07-23|archive-url=https://web.archive.org/web/20210723033310/https://www.nauticalcharts.noaa.gov/hsd/wrecks_and_obstructions.html|url-status=dead}}</ref> Some of these wrecks were [[Sinking ships for wreck diving sites|sunk deliberately to attract divers]]. The {{USS|Spiegel Grove}} and {{USS|Oriskany|CV-34|6}} in [[Florida]], {{USS|Indra|ARL-37|6}} and {{USS|Aeolus|ARC-3|6}} in North Carolina, and {{ship||Bianca C.|ship|2}} in [[Grenada]] draw thousands of divers annually.<ref>{{cite web|last1=Gerken|first1=Michael|title=Top 10 Wreck Dives of North Carolina|url=http://www.scubadiving.com/photos/top-10-wreck-dives-north-carolina|website=Scuba Diving|access-date=8 March 2016}}</ref>

In other areas, dive sites have been developed in collaboration with artists as artworks.
For example, the [[Museo Subacuático de Arte]] in the [[Cancún National Marine Park]] contains hundreds of life-size statues, offering divers an alternative to sensitive coral reefs in the region. Each statue is made from a plaster mold of a living person, using a PH neutral "marine cement", by [[Jason deCaires Taylor]].<ref name="Perdomo">{{cite news |last1=Perdomo |first1=Gabriela |title=Mexico's underwater art museum sinks sculptures beneath the sea |url=https://macleans.ca/culture/is-art-better-down-where-its-wetter/ |access-date=6 July 2023 |work=Macleans |date=6 March 2012}}</ref>

In Lisbon, 13 artworks by Alexandre Farto ([[Vhils]]) will be placed in an artificial reef off the coast of [[Albufeira]] as of June 2024. The works are made from parts of decommissioned power stations.<ref name="Romano">{{cite news |last1=Romano |first1=Verónica |title=Taking the plunge to see Portugal's unique underwater exhibition |url=https://www.euronews.com/culture/2023/03/26/taking-the-plunge-to-see-art-a-unique-underwater-exhibition-in-portugal |access-date=6 July 2023 |work=euronews |date=26 March 2023 |language=en}}</ref>

A study in Barbados showed a marked variation in diver satisfaction with artificial reef diving experiences. Novice divers tended to be more satisfied than more experienced divers, who had a strong preference for natural reefs and large shipwrecks.
<ref>{{cite journal|title=The Relationship between Diver Experience Levels and Perceptions of Attractiveness of Artificial Reefs – Examination of a Potential Management Tool |first1=Anne E. |last1=Kirkbride-Smith |first2=Philip M. |last2=Wheeler |first3=Magnus L. |last3=Johnson |date=23 July 2013 |doi=10.1371/journal.pone.0068899 |journal=PLOS ONE |volume=8 |issue=7 |pages=e68899 |pmid=23894372 |pmc=3720904 |bibcode=2013PLoSO...868899K |doi-access=free }}</ref>

== Environmental concerns ==
Environmental concerns about artificial reefs include
possible physical damage to existing natural sites in the installation area;
their potential to disrupt existing patterns of marine life by introducing non-native species and by attracting fish, eggs and larvae from surrounding natural habitats;
their potential to concentrate fish in areas where it becomes easier to catch them,
leading to [[overfishing]] and long-term damage to fisheries;
and the potential for the materials used in artificial reefs to [[environmental degradation|degrade]] and cause damage to the natural habitat. This can include [[toxicity]] from contaminants such as [[paint]], [[oil]], and [[plastics]], as well as parts of the reef breaking away and becoming ocean waste or washing onto natural reefs and beaches.<ref name="Bracho-Villavicencio"/>

===Changing populations===
Many marine organisms exhibit a high degree of movement or dispersal.<ref name="Karnauskas"/> The fish attracted to artificial reef zones vary from reef to reef depending on the reef's age, size and structure.<ref name="Perkol">{{cite journal |last1=Perkol-Finkel |first1=S. |last2=Shashar |first2=N. |last3=Benayahu |first3=Y. |title=Can artificial reefs mimic natural reef communities? The roles of structural features and age |journal=Marine Environmental Research |date=1 March 2006 |volume=61 |issue=2 |pages=121–135 |doi=10.1016/j.marenvres.2005.08.001 |pmid=16198411 |bibcode=2006MarER..61..121P |url=https://www.sciencedirect.com/science/article/abs/pii/S0141113605000590 |issn=0141-1136|url-access=subscription }}</ref>  Preferred habitats vary both between and within species, depending on an organism's developmental stage and behavior. Environments that are well-suited to larval to juvenile stages may differ from those favored by adults. For example, 1–2 year old Red Snapper (''[[Lutjanus campechanus]]''), show a much higher attraction to living in vertical artificial reef structures than older Red Snapper. By ages 6–8, adults return to muddy and sand bottom habitats, which provide a home for the species' pelagic larval phase. Being aware of how organisms relate to the marine habitat is critical to mapping marine resources and understanding how artificial reefs affect marine processes.<ref name="Karnauskas"/>
The siting of artificial reefs should consider the presence of existing natural habitats and the needs of species at multiple developmental stages, including the need for reproductive and early stage habitat.<ref name="Ceccarelli"/><ref name="Karnauskas"/><ref name="Spinner"/>

The opportunistic use of [[shipwreck]]s and oil derricks<ref name="Bull">{{cite news |last1=Love |first1=Milton |last2=Bull |first2=Ann Scarborough |title=Retired oil rigs off the California coast could find new lives as artificial reefs {{!}} GreenBiz |url=https://www.greenbiz.com/article/retired-oil-rigs-california-coast-could-find-new-lives-artificial-reefs |work=GreenBiz |date=May 17, 2019 |language=en}}</ref><ref name="McKinney">{{cite news |last1=McKinney |first1=John |title=After the Oil Runs Out: Rigs to Reefs |url=https://psmag.com/environment/after-the-oil-runs-out-rigs-to-reefs-19272 |work=Pacific Standard |date=July 15, 2010 |language=en}}</ref> as artificial reefs creates a new [[Trophic level|trophic structure]] for the local [[ecosystem]]. The trophic structure of artificial and natural reefs has been shown to differ strongly.<ref name="Simon"/> Artificial reefs do not develop the same functions and diversity as natural reefs over time, unless their structure is similar to natural reefs.<ref name="Perkol"/> For example, the Sint Eustatius reef, nearly 200 years old, has developed a diverse and healthy ecosystem, but it has different and less abundant coral species than a nearby natural reef.<ref name="Urquhart">{{cite news |last1=Urquhart |first1=James |title=For Artificial Coral Reefs, Time Is Not Enough |url=https://hakaimagazine.com/news/for-artificial-coral-reefs-time-is-not-enough/ |work=Hakai Magazine |date=August 4, 2021 |language=en}}</ref><ref name="Hill">{{cite journal |last1=Hill |first1=Claudia E. L. |last2=Lymperaki |first2=Myrsini M. |last3=Hoeksema |first3=Bert W. |title=A centuries-old manmade reef in the Caribbean does not substitute natural reefs in terms of species assemblages and interspecific competition |journal=Marine Pollution Bulletin |date=1 August 2021 |volume=169 |pages=112576 |doi=10.1016/j.marpolbul.2021.112576 |pmid=34119961 |bibcode=2021MarPB.16912576H |issn=0025-326X|doi-access=free }}</ref>

As a result, artificial reefs can unbalance the natural ecosystem and affect nearby habitats,<ref name="Simon">{{cite journal |last1=Simon |first1=Thiony |last2=Joyeux |first2=Jean-Christophe |last3=Pinheiro |first3=Hudson T. |title=Fish assemblages on shipwrecks and natural rocky reefs strongly differ in trophic structure |journal=Marine Environmental Research |date=1 September 2013 |volume=90 |pages=55–65 |doi=10.1016/j.marenvres.2013.05.012 |pmid=23796542 |bibcode=2013MarER..90...55S |url=https://www.sciencedirect.com/science/article/abs/pii/S0141113613000950 |issn=0141-1136|url-access=subscription }}</ref> in some cases attracting non-native and invasive species that disrupt local ecosystems.<ref name="Schulze">{{cite journal |last1=Schulze |first1=Anja |last2=Erdner |first2=Deana L. |last3=Grimes |first3=Candace J. |last4=Holstein |first4=Daniel M. |last5=Miglietta |first5=Maria Pia |title=Artificial Reefs in the Northern Gulf of Mexico: Community Ecology Amid the "Ocean Sprawl" |journal=Frontiers in Marine Science |date=2020 |volume=7 |doi=10.3389/fmars.2020.00447 |issn=2296-7745 |doi-access=free }}</ref>
In 2008, at Palmyra Atoll south of Hawaii, iron leaching from a shipwreck led to increases in algae and a sea anemone called a corallimorph, smothering existing coral to create a "black reef".<ref name="Joosse">{{cite news |last1=Joosse |first1=Tess |title=When Wrecks Become Reefs {{!}} Smithsonian Ocean |url=https://ocean.si.edu/ecosystems/coral-reefs/when-wrecks-become-reefs |work=Smithsonian Ocean |date=2022 |language=en}}</ref>

Artificial reefs can show quick increases in local fish population,<ref name="Polovina">{{cite journal |last1=Polovina |first1=Jeffrey |title=Impacts of Artificial Reefs on Fishery Production in Shimamaki, Japan |journal=Bulletin of Marine Science |date=1989 |volume=44 |issue=2 |pages=997–1003 |url=https://www.academia.edu/26230047}}</ref>
[[coral reef]]<ref name="Prabowo">{{cite journal |last1=Prabowo |first1=B |last2=Rikardi |first2=N |last3=Setiawan |first3=M A |last4=Santoso |first4=P |last5=Arafat |first5=D |last6=Subhan |first6=B |last7=Afandy |first7=A |title=The perspective of high coral growth rate on the artificial reef: what is causing enhancement of coral growth rate on Nyamuk Island, Anambas? |journal=IOP Conference Series: Earth and Environmental Science |date=1 January 2022 |volume=967 |issue=1 |pages=012038 |doi=10.1088/1755-1315/967/1/012038|bibcode=2022E&ES..967a2038P |doi-access=free }}</ref> and [[algae]] growth.<ref name="Marsden">{{cite journal |last1=Marsden |first1=J. Ellen |last2=Marcy-Quay |first2=Benjamin |last3=Dingledine |first3=Natalie |last4=Berndt |first4=Aaron |last5=Adams |first5=Janice |title=Physical and biological evolution of constructed reefs – long-term assessment and lessons learned |journal=Journal of Great Lakes Research |date=1 February 2023 |volume=49 |issue=1 |pages=276–287 |doi=10.1016/j.jglr.2022.10.008 |bibcode=2023JGLR...49..276M |s2cid=253359207 |issn=0380-1330|doi-access=free }}</ref> However, the attraction–production dilemma is the question of whether local increases in fish stocks result from broader-area distributional changes in populations (the attraction hypothesis) or increases in local production (the production hypothesis).<ref name="Roa-Ureta"/>
Some researchers, such as James Bohnsack, a biologist with the [[National Marine Fisheries Service]] (NMFS), have argued that the amount of biomass found on artificial reefs is attracted away from nearby areas rather than developing there. According to this view, artificial reefs do not increase fish populations.<ref name="Smith">{{cite journal |last1=Smith |first1=James A. |last2=Lowry |first2=Michael B. |last3=Suthers |first3=Iain M. |title=Fish attraction to artificial reefs not always harmful: a simulation study |journal=Ecology and Evolution |date=30 September 2015 |volume=5 |issue=20 |pages=4590–4602 |doi=10.1002/ece3.1730 |pmid=26668725 |pmc=4670052 |bibcode=2015EcoEv...5.4590S |issn=2045-7758}}</ref><ref name="Bohnsack">{{cite journal |last1=Bohnsack |first1=James A. |last2=Ecklund |first2=A.-M. |title=Artificial reef research: Is there more than the attraction-production issue? |journal=Fisheries |date=1997 |volume=22 |issue=4 |pages=14–16 |url=https://www.researchgate.net/publication/279561041}}</ref> Instead they operate as a type of [[fish aggregating device]] (FAD) bringing in fish, eggs and larvae from other reefs.<ref name="Ceccarelli">{{cite book |last1=Ceccarelli |first1=D. |last2=Hurley |first2=T. |title=Fish aggregating devices and artificial reefs: Literature review of benefits and negative impacts for the Great Barrier Reef |date=2022 |publisher=Great Barrier Reef Marine Park Authority |location=Townsville |hdl=11017/3952 |isbn=9780645043853 |url=https://hdl.handle.net/11017/3952}}</ref> However, there is some evidence to suggest that artificial reefs can be a source of production as well as attraction.<ref name="Roa-Ureta"/> A 2022 review concluded that "the attraction-production question around ARs ... can only be assessed on a case-by-case basis for each AR, and
validated after their installation."<ref name="Ceccarelli"/>

Concentrating fish on a reef makes for easier fishing.<ref name="Spinner">{{cite news |last1=Spinner |first1=Kate |title=Artificial reefs' effect on fish populations comes under question |url=https://www.heraldtribune.com/story/news/2011/11/14/questions-about-artificial-reefs-effect-on-fish-counts/29060556007/ |work=Sarasota Herald-Tribune |date=November 13, 2011}}</ref><ref name="Karnauskas">{{cite journal |last1=Karnauskas |first1=Mandy |last2=Walter |first2=John F. |last3=Campbell |first3=Matthew D. |last4=Pollack |first4=Adam G. |last5=Drymon |first5=J. Marcus |last6=Powers |first6=Sean |title=Red Snapper Distribution on Natural Habitats and Artificial Structures in the Northern Gulf of Mexico |journal=Marine and Coastal Fisheries |date=January 2017 |volume=9 |issue=1 |pages=50–67 |doi=10.1080/19425120.2016.1255684 |language=en |issn=1942-5120|doi-access=free }}</ref>
The increased concentration of fish on artificial reefs can make it easier to harvest fish stocks, with the potential for [[overfishing]] and long-term damage to fisheries. This has implications for artisanal and industrial fishing management.<ref name="Spinner"/><ref name="Roa-Ureta">{{cite journal |last1=Roa-Ureta |first1=Ruben H. |last2=Santos |first2=Miguel N. |last3=Leitão |first3=Francisco |title=Modelling long-term fisheries data to resolve the attraction versus production dilemma of artificial reefs |journal=Ecological Modelling |date=September 2019 |volume=407 |pages=108727 |doi=10.1016/j.ecolmodel.2019.108727 |bibcode=2019EcMod.40708727R |s2cid=198254212 |url=https://ideas.repec.org/a/eee/ecomod/v407y2019ic2.html|url-access=subscription }}</ref>

=== Debris ===
There are concerns that the placement of opportunity artificial reefs will be abused and become a pretext for disguised ocean dumping. Regulatory measures have been put forward by the U.S. and internationally in an effort to counter abuses, but may provide little protection.<ref name="Macdonald">{{cite journal |last1=Macdonald |first1=John M. |title=Artificial reef debate: Habitat enhancement or waste disposal? |journal=Ocean Development & International Law |date=January 1994 |volume=25 |issue=1 |pages=87–118 |doi=10.1080/00908329409546027 |url=https://www.tandfonline.com/doi/abs/10.1080/00908329409546027 |access-date=16 June 2023 |language=en |issn=0090-8320|url-access=subscription }}</ref><ref name="Airoldi">{{cite journal |last1=Airoldi |first1=Laura |last2=Beck |first2=Michael W. |last3=Firth |first3=Louise B. |last4=Bugnot |first4=Ana B. |last5=Steinberg |first5=Peter D. |last6=Dafforn |first6=Katherine A. |title=Emerging Solutions to Return Nature to the Urban Ocean |journal=Annual Review of Marine Science |date=3 January 2021 |volume=13 |issue=1 |pages=445–477 |doi=10.1146/annurev-marine-032020-020015 |pmid=32867567 |bibcode=2021ARMS...13..445A |hdl=10026.1/16842 |s2cid=221402720 |url=https://www.annualreviews.org/doi/full/10.1146/annurev-marine-032020-020015 |language=en |issn=1941-1405|hdl-access=free }}</ref>

[[File:Tire reef.jpg|thumb|[[Waste tires]] being placed in an array to investigate their effectiveness as a fish habitat, Pokai Bay, Oahu, July 1969.]]
Some artificial reefs have been found to be less stable than originally hoped, breaking into component parts that become ocean refuse, washing onto natural reefs and beaches and damaging them.
In the early 1970s [[waste tires]] were used to create a number of artificial reefs. [[Tropical storm]]s later demolished the tire containment system, washing tires onto beaches, [[coral reef destruction|destroying nearby coral reefs]] and inhibiting new coral growth.<ref>{{cite news|last1=Allen|first1=Greg|title=Fallout from Bad '70s Idea: Auto Tires in Ocean Reef|url=https://www.npr.org/templates/story/story.php?storyId=11462066|access-date=8 March 2016|publisher=NPR|date=5 July 2007}}</ref> On the [[Osborne Reef]] off the coast of [[Fort Lauderdale, Florida]], storms broke the nylon straps holding the original tire bundles together. As of November 2019, 250,000<ref name="2019-11-13 WPLG">{{cite news |last1=Stanwood |first1=Janine |date=2019-11-13 |title=Hundreds of thousands of tires being removed off Fort Lauderdale coast |url=https://www.local10.com/news/2019/11/14/hundreds-of-thousands-of-tires-being-removed-off-fort-lauderdale-coast/ |url-status=live |language=en |location=[[Fort Lauderdale, Florida]] |publisher=[[WPLG]] |archive-url=https://web.archive.org/web/20200807155124/https://www.local10.com/news/2019/11/14/hundreds-of-thousands-of-tires-being-removed-off-fort-lauderdale-coast/ |archive-date=2020-08-07 |access-date=2021-01-08 |quote=Reef project gone wrong; crews now working to remove mass collection of tires}}</ref> of an estimated 700,000 tires have been removed.<ref>{{cite news|last1=Fleshler|first1=David|title=Push is on to remove thousands of tires on ocean floor in Fort Lauderdale|url=http://www.sun-sentinel.com/local/broward/fl-ocean-tire-removal-20160630-story.html|access-date=4 July 2016|publisher=Sun Sentinel|date=30 June 2016}}</ref><ref>{{cite news|last1=Fleshler|first1=David|title=Fixing a catastrophe: Divers removing 90,000 tires from ocean|url=http://www.sun-sentinel.com/local/broward/fl-tire-removal-20150514-story.html|access-date=8 March 2016|publisher=Sun Sentinel|date=15 May 2015}}</ref><ref>{{cite web|title=The Osborne Tire Reef|url=http://www.projectbaseline.org/gulfstream/project-baseline-gulfstream-projects/the-osborne-tire-reef/|website=projectbaseline.org|publisher=Project Baseline|access-date=14 March 2016|url-status=dead|archive-url=https://web.archive.org/web/20160314214913/http://www.projectbaseline.org/gulfstream/project-baseline-gulfstream-projects/the-osborne-tire-reef/|archive-date=14 March 2016}}</ref><ref name=enn>{{cite news|url=http://www.enn.com/top_stories/article/6895 |title=Florida Raises Ill-Fated Artificial Reefs |last=Loney |first=Jim |agency=Reuters |publisher=Enn.com |date=9 July 2007 |access-date=5 April 2015}}</ref>
[[France]] has begun removing its tire reefs.<ref>{{cite news|last1=Ferrer|first1=Sandra|title=France hits reverse on sinking tyres for artificial reefs|url=http://phys.org/news/2015-05-france-reverse-tyres-artificial-reefs.html|access-date=8 March 2016|publisher=Phys.org|date=22 May 2015}}</ref> The [[Ocean Conservancy]] now includes tire removal during the International Coastal Cleanup in September of each year.<ref>{{cite web|last1=Gaskill|first1=Melissa|title=Scuba Divers Left Picking Up Pieces After Tire Artificial Reef Projects Fail|url=http://www.sportdiver.com/scuba-diving-rubber-tire-artificial-reefs-france-florida|website=sportdiver.com|access-date=28 May 2016}}</ref>
Since 2021, [[4Ocean]] has added collecting tires from the bottom to their cleanup operations as well.<ref>{{cite web|url=https://www.today.com/video/inside-the-efforts-to-remove-millions-of-tires-dumped-into-the-ocean-decades-ago-129828421589|title=Inside the efforts to remove millions of tires dumped into the ocean decades ago|website=today.com|date=30 December 2021|access-date=19 March 2023}}</ref>

Some attempts to construct artificial surfing reefs have also been problematic.<ref name="Blacka"/> A number of early surfing installations used geotextile bags filled with sand which degraded more quickly than anticipated.<ref name="Borrero"/>  Cases such as [[Pratte's Reef]] in [[California]] and Mount Reef at [[Mount Maunganui]] in New Zealand have required extensive remediation work to remove materials. In some cases, remediation has cost more than the original installation.<ref name="Blacka"/><ref name="redux"/><ref name="Maunganui"/> It has been argued that this approach to reef construction is fundamentally flawed.<ref name="Gegan"/>

===Toxicity===
Artificial reefs, particularly opportunistic ones involving materials that were not originally intended for marine use, can [[environmental degradation|degrade]] and cause damage to the natural habitat.
If inappropriate materials are used in an artificial reef, they can interfere with the growth of algae which provide a food source for coral, causing the coral to die.<ref name="Pascoe">{{cite news |last1=Pascoe |first1=Robin |title=Dutch zoo works with Delft start-up to restore coral reefs |url=https://www.dutchnews.nl/2022/05/dutch-zoo-works-with-delft-start-up-to-restore-coral-reefs/ |work=DutchNews |date=24 May 2022}}</ref>

[[PVC]]s,<ref name="Zhou">{{cite book |last1=Zhou |first1=Huai Ying |last2=Gu |first2=Tian Long |last3=Yang |first3=Dao Guo |last4=Jiang |first4=Zheng Yi |last5=Zeng |first5=Jian Min |title=New and Advanced Materials |date=21 February 2011 |publisher=Trans Tech Publications Ltd |isbn=978-3-03813-580-7 |url=https://books.google.com/books?id=kAa2DwAAQBAJ&pg=PA12 |language=en}}</ref>
[[plastics]],<ref name="Weiss">{{cite journal |last1=Weiss |first1=Kenneth R. |title=The pileup of plastic debris is more than ugly ocean litter |journal=Knowable Magazine |date=21 September 2020 |doi=10.1146/knowable-120717-211902|doi-access=free |url=https://knowablemagazine.org/article/food-environment/2017/pileup-plastic-debris-more-ugly-ocean-litter |language=en}}</ref><ref name="Gao">{{cite journal |last1=Gao |first1=Shike |last2=Li |first2=Zheng |last3=Wang |first3=Nuo |last4=Lu |first4=Yanan |last5=Zhang |first5=Shuo |title=Microplastics in different tissues of caught fish in the artificial reef area and adjacent waters of Haizhou Bay |journal=Marine Pollution Bulletin |date=January 2022 |volume=174 |pages=113112 |doi=10.1016/j.marpolbul.2021.113112 |pmid=34865856 |bibcode=2022MarPB.17413112G |s2cid=244849554 |url=https://pubmed.ncbi.nlm.nih.gov/34865856/ |issn=1879-3363}}</ref><ref name="Vered">{{cite journal |last1=Vered |first1=Gal |last2=Shenkar |first2=Noa |title=Limited effects of environmentally-relevant concentrations in seawater of dibutyl phthalate, dimethyl phthalate, bisphenol A, and 4-nonylphenol on the reproductive products of coral-reef organisms |journal=Environmental Pollution |date=1 December 2022 |volume=314 |pages=120285 |doi=10.1016/j.envpol.2022.120285 |pmid=36179999 |bibcode=2022EPoll.31420285V |s2cid=252575291 |url=https://www.sciencedirect.com/science/article/abs/pii/S0269749122014993 |issn=0269-7491|url-access=subscription }}</ref>
[[oil]],<ref>{{cite journal |last1=Lewis |first1=Justin P. |last2=Tarnecki |first2=Joseph H. |last3=Garner |first3=Steven B. |last4=Chagaris |first4=David D. |last5=Patterson |first5=William F. |title=Changes in Reef Fish Community Structure Following the Deepwater Horizon Oil Spill |journal=Scientific Reports |date=9 April 2020 |volume=10 |issue=1 |pages=5621 |doi=10.1038/s41598-020-62574-y |pmid=32273520 |pmc=7145834 |bibcode=2020NatSR..10.5621L |issn=2045-2322}}</ref>
[[paint]], [[asbestos]], [[iron]] and other rusting metal, can release [[toxicity|toxic]] contaminants such as Poly-chlorinated biphenols (PCBs) and heavy metals ( Pb, Cu, Ni, Cd, Zn, Ag, and Hg ).<ref name="Johnston">{{cite book |last1=Johnston |first1=R.K. |last2=Halkola |first2=H. |last3=George |first3=R. |last4=In |first4=C. |last5=Gauthier |first5=R. |last6=Wild |first6=W. |last7=Bell |first7=M. |last8=Martore |first8=R. |title=Oceans 2003. Celebrating the Past ... Teaming Toward the Future (IEEE Cat. No.03CH37492) |chapter=Assessing the ecological risk of creating artificial reefs from ex-warships |date=September 2003 |volume=2 |pages=804–811 Vol.2 |doi=10.1109/OCEANS.2003.178419|isbn=0-933957-30-0 |s2cid=42324129 }}</ref><ref name="Galiano">{{cite web |last1=Galiano |first1=Rich |title=Contamination Risks of Artificial Reefs and Shipwrecks ~ New Jersey Scuba Diving |url=https://njscuba.net/marine-biology/marine-biology-contents/contamination-risks-of-artificial-reefs-and-shipwrecks/ |website=New Jersey Scuba Diving}}</ref>
Toxic materials can potentially enter the food chain and affect it at all levels, including fish and humans. However, consumption of seafood from artificial reefs and wrecks is considered unlikely to pose a long-term health risk for humans at average levels of consumption, with the exception of urchins and other grazing shellfish which should be avoided.<ref name="Galiano"/>
[[File:US Navy 100428-N-3154P-149 Sailors assigned to Amphibious Construction Battalion (ACB) 2, use heavy machinery to load oyster shells for two new artificial oyster reef sites in the mud flats of Little Creek Cove.jpg|thumb|Using natural materials, such as oyster shells, can help create more natural artificial reefs.]]
International recommendations state that artificial reefs should use inert materials. Under the 2009 "Specific Guidelines for Assessment of Inert, Inorganic Geological Material" developed by the London Convention and Protocol/UNEP, inert materials cannot cause contamination through leaching, physical and chemical deterioration, or biological activity.<ref name="Santos">{{cite journal |last1=Santos |first1=Jorge |last2=Cifrian |first2=Eva |last3=Rodriguez-Romero |first3=Araceli |last4=Yoris-Nobile |first4=Adrian I. |last5=Blanco-Fernandez |first5=Elena |last6=Castro-Fresno |first6=Daniel |last7=Andres |first7=Ana |title=Assessment of the environmental acceptability of potential artificial reef materials using two ecotoxicity tests: Luminescent bacteria and sea urchin embryogenesis |journal=Chemosphere |date=1 January 2023 |volume=310 |pages=136773 |doi=10.1016/j.chemosphere.2022.136773 |pmid=36220438 |bibcode=2023Chmsp.31036773S |issn=0045-6535|doi-access=free |hdl=10902/26464 |hdl-access=free }}</ref>

Attempts continue to be made to create stable waste-based materials that will not pose a hazard, for use in artificial reefs.  For example, oil and coal fly ash have been stabilized with cement and lime to create experimental artificial reef blocks. However, as with the use of tires, there continue to be environmental concerns about the potential for leaching.<ref name="Valeriya">{{cite journal |last1=Komyakova |first1=Valeriya |last2=Chamberlain |first2=Dean |last3=Jones |first3=Geoffrey P. |last4=Swearer |first4=Stephen E. |title=Assessing the performance of artificial reefs as substitute habitat for temperate reef fishes: Implications for reef design and placement |journal=Science of the Total Environment |date=10 June 2019 |volume=668 |pages=139–152 |doi=10.1016/j.scitotenv.2019.02.357 |pmid=30852192 |bibcode=2019ScTEn.668..139K |s2cid=73726930 |url=https://www.sciencedirect.com/science/article/abs/pii/S0048969719308654 |issn=0048-9697|url-access=subscription }}</ref><ref name="Shu-te">{{cite journal |last1=Shu-te |first1=Kuo |last2=Tsan-chuan |first2=Hsu |last3=Kwang-tsao |first3=Shao |title=Experiences of Coal Ash Artificial Reefs in Taiwan |journal=Chemistry and Ecology |date=March 1995 |volume=10 |issue=3–4 |pages=233–247 |doi=10.1080/02757549508037681 |bibcode=1995ChEco..10..233S |url=https://doi.org/10.1080/02757549508037681 |language=en |issn=0275-7540|url-access=subscription }}</ref><ref>{{cite journal |last1=Davis |first1=Kay L. |last2=Coleman |first2=Melinda A. |last3=Connell |first3=Sean D. |last4=Russell |first4=Bayden D. |last5=Gillanders |first5=Bronwyn M. |last6=Kelaher |first6=Brendan P. |title=Ecological performance of construction materials subject to ocean climate change |journal=Marine Environmental Research |date=1 October 2017 |volume=131 |pages=177–182 |doi=10.1016/j.marenvres.2017.09.011 |pmid=28988853 |bibcode=2017MarER.131..177D |url=https://www.sciencedirect.com/science/article/abs/pii/S0141113617304592 |issn=0141-1136|url-access=subscription }}</ref>

In the United States, best practices for preparing vessels for use in artificial reefs include assuming that divers may access all locations, removing potential hazards to divers, removing all polluting or toxic materials, including [[Polychlorinated biphenyl|PCBs]] (in compliance with applicable water quality standards for class III ocean waters), and clearing debris and floatables.<ref>{{cite book |title=Guidelines and Management Practices for Artificial Reef Siting, Use, Construction, and Anchoring in Southeast Florida |date=2011 |publisher=Southeast Florida Coral Reef Initiative |url=https://www.ncei.noaa.gov/data/oceans/coris/library/NOAA/CRCP/other/other_crcp_publications/SEFCRI/MICCI_Project/MICCI_18_19.pdf}}</ref>
However, if materials over the pollutant threshold are too difficult to remove, permission to bypass their removal can be given by the EPA, as happened in the case of the ex-''[[USS Oriskany]]''. In spite of spending $20 million to decontaminate the vessel, the ship still contained an estimated 700 pounds of PCBs when it was sunk in 2006. Subsequent testing by the [[Florida Fish and Wildlife Conservation Commission]] over a four-year period found elevated levels of PCBs in fish living in the ship's "reef".<ref name="Olsen">{{cite news |last1=Olsen |first1=Erik |title=Out of Commission Above Water, but Not Below It |url=https://www.nytimes.com/2008/08/19/science/earth/19ship.html |work=The New York Times |date=19 August 2008}}</ref><ref>{{cite web |title=Basel Action Network and Sierra Club, Plaintiffs, v. US Envtl. Prot. Agency |url=https://www.biologicaldiversity.org/programs/oceans/pdfs/complaint_%2012-9-11.pdf |website=The Center for Biological Diversity}}</ref><ref name="Merz">{{cite web |last1=Merz |first1=Nina  |date=July 30, 2021 |title=Dear U.S. Navy: Don't Dump Your Ships in Our Oceans |url=https://www.nationalpriorities.org/blog/2021/07/30/dear-us-navy-dont-dump-your-ships-our-oceans/ |website=National Priorities Project |language=en-us }}</ref>

Off the coast of California, an artificial reef has been constructed to lure fish away from a toxic site. Over 35 years, the [[Montrose Chemical Corporation of California]], a maker of [[DDT]], improperly disposed of toxic chemical waste through the sewer system and by dumping barrels of waste into the ocean. As part of remediation efforts by the [[National Oceanic and Atmospheric Administration]] (NOAA), 70,000 tons of quarry rock were placed on the ocean bottom nearer the beach in 2020, creating a new habitat to attract fish and kelp to a safer area.<ref name="Berardelli">{{cite news |last1=Berardelli |first1=Jeff |title=How a shocking environmental disaster was uncovered off the California coast after 70 years – CBS News |url=https://www.cbsnews.com/news/california-environmental-disaster-ocean-ddt-sea-lions/ |work=www.cbsnews.com |date=12 April 2021}}</ref><ref>{{cite news |title=More Than 30 Acres of New Reef Habitat Built Off the Southern California Coast {{!}} NOAA Fisheries |url=https://www.fisheries.noaa.gov/feature-story/more-30-acres-new-reef-habitat-built-southern-california-coast |work=NOAA Fisheries |agency=NOAA |date=December 16, 2020 |language=en}}</ref>

==Examples==

===United States===

===Florida===
Florida is the site of many artificial reefs,<ref>{{cite web |title=The Artificial Reefs of Volusia County, Florida |url=https://www.volusiareefs.org/ |website=Volusia County}}</ref> many created from deliberately sunken ships, including Coast Guard cutters [[USCGC Duane|''Duane'']] and [[USCGC Bibb|''Bibb'']] and the U.S. Navy landing ship [[USS Spiegel Grove (LSD-32)|''Spiegel Grove'']].<ref name="ng211">{{cite web|title=Artificial Reefs|url=https://www.nationalgeographic.com/magazine/2011/02/artificial-reefs/|date=February 2011|work=National Geographic|url-status=dead|archive-url=https://web.archive.org/web/20150505043227/http://ngm.nationalgeographic.com/2011/02/artificial-reefs/harrigan-text|archive-date=May 5, 2015|access-date=5 April 2015}}</ref>

====Osborne Reef====
{{Main|Osborne Reef}}
[[File:Tires540.jpg|thumb|alt=A bed of skummy tires rests piled upon the ocean's floor; a small yellow fish swims by the left.|Tires constituting [[Osborne Reef]] (2007)]]
In the early 1970s, more than 2,000,000 used vehicle tires were dumped off the coast of [[Fort Lauderdale, Florida]] to form an artificial reef. However, the tires were not properly secured to the reef structures, and ocean currents broke them loose, sending them crashing into the developing reef and its natural neighbors.

====Neptune Reef====
[[Neptune Memorial Reef]] was originally conceived as an art project called The Atlantis Reef Project and was envisioned and created by Gary Levine and Kim Brandell. [[Burial at sea]] became a way of financing the project. As of 2011, about 200 "placements" had occurred. Cremated remains are mixed with concrete and either encased in columns or molded into sea-star, brain-coral, {{convert|15|ft|m}} castings of lions or other shapes before entering the water.<ref name=ng211/>

====Ex-USS ''Massachusetts''====
In 1921 the US [[battleship]] {{USS|Massachusetts|BB-2|2}} was scuttled in shallow water off the coast of Pensacola, Florida and then used as a target for experimental artillery. In 1956 the ship was declared the property of the state of [[Florida]] by the [[Florida Supreme Court]]. Since 1993 the wreck has been a [[Florida Underwater Archaeological Preserve]] and is included in the [[National Register of Historic Places]]. She serves as an artificial reef and recreational dive site.<ref name="Roy">{{cite news |last1=Roy |first1=Norm |title=How 'the worst battleship ever made' became a wildlife refuge in the Gulf of Mexico |url=https://taskandpurpose.com/history/wreck-diving-florida-scuba/ |work=Task & Purpose |date=21 April 2020}}</ref>

====Ex-USS ''Oriskany''====
[[File:Oriskany July 2008 -1.jpg|thumb|right|Sea life growing on the remains of {{USS|Oriskany|CV-34|6}}, intentionally sunk in 2006 to become an artificial reef.]]
The world's largest artificial reef was created by sinking of the 44,000 ton aircraft carrier {{USS|Oriskany|CV-34|6}} off the coast of [[Pensacola]], [[Florida]], in 2006.<ref>{{cite news| url=https://www.nytimes.com/2008/08/19/science/earth/19ship.html | work=[[The New York Times]] | first=Erik | last=Olsen | title=Out of Commission Above Water, but Not Below It | date=18 August 2008 |access-date=5 April 2015}}</ref><ref name="Gabriel">{{cite news |last1=Gabriel |first1=Melissa Nelson |title=Oriskany: 10 years as 'The Great Carrier Reef' |url=https://www.pnj.com/story/news/local/2016/04/24/10-years-later-orkisany-reef-international-dive-destination/82957574/ |work=Pensacola News Journal |date=May 16, 2016}}</ref>

====Ex-USNS ''Hoyt S. Vandenberg''====
The second-largest artificial reef is [[USS General Harry Taylor (AP-145)|USNS ''Hoyt S. Vandenberg'']], a former [[World War II]] era [[Troopship|troop transport]] that served as a spacecraft-tracking ship after the war. ''Hoyt S. Vandenberg'' was scuttled seven miles off [[Key West]] on May 27, 2009, in {{convert|140|ft|m}} of clear water.<ref>{{cite web|url=http://my.att.net/s/editorial.dll?fromspage=cg/news/ne_details.htm&eeid=6592684&eetype=article&render=y&ch=ne&s=na |title=WWII-era ship becomes sunken reef off Key West |work=AT&T Online News |date=27 May 2009 |access-date=18 July 2009}} {{dead link|date=April 2015}}</ref> Supporters expected the ship to draw recreational divers away from natural reefs, allowing those reefs to recover from damage from overuse.<ref>{{cite news |url=https://www.nytimes.com/aponline/2009/05/25/us/AP-US-Sinking-The-Vandenberg.html |title=Ship to Become 2nd Largest Intentional Reef |agency=Associated Press |work=[[The New York Times]] |date=25 May 2009 |access-date=25 May 2009}} {{dead link|date=April 2015}}</ref>

====Ex-USS ''Spiegel Grove''====
[[File:Spiegel Grove wreck, large reel on deck, Key Largo, Florida.jpg| thumb|right | Large reel on deck of ''Spiegel Grove'', with diver]]
The ex-USS {{USS|Spiegel Grove|LSD-32|2}} is located on Dixie Shoal, {{convert|6|mi|km}} off the Florida Keys in the Florida Keys National Marine Sanctuary.<ref name="Frink">{{cite news |last1=Frink |first1=Stephen |title=A Photo Diary of the Spiegel Grove |url=https://dan.org/alert-diver/article/a-photo-diary-of-the-spiegel-grove/ |work=Divers Alert Network |date=May 25, 2022}}</ref>
Her location is {{Coord|25|04|00|N|80|18|01|W |region:US_type:landmark |display=inline}}.{{Citation needed|date=April 2021}}

===SS ''United States'' (Planned)===
The ocean liner [[SS United States|SS ''United States'']] is currently planned to be sunk off the coast of [[Destin, Florida|Destin]] and [[Fort Walton Beach, Florida|Fort Walton Beach]] in [[Okaloosa County, Florida]]. Once sunk, she will surpass USS ''Oriskany'' as the world's largest artificial reef, being visible as high as 60 feet and as low as 180 feet, with her funnels removed. ''United States'' is currently in [[Mobile, Alabama]], to be stripped of any hazardous materials and valuable items. <ref>{{cite news |title=SS United States to Become the Largest Artificial Reef |work=The New York Times |date=October 3, 2024 |url=https://www.nytimes.com/2024/10/03/us/ss-united-states-largest-artificial-reef.html |access-date=November 30, 2024}}</ref>

===Georgia===
In 1970, the [[Georgia Department of Natural Resources]] (DNR) began building a network of artificial reefs to provide habitats for [[game fish]]. Georgia generally lacks natural coral reefs because the ocean floor off the coast is generally too sandy and too low-sloping to promote coral growth.<ref name="GPB-Jan-2024">{{cite news |title=WATCH: MARTA train cars splash into ocean off Georgia coast during artificial reef deployment |url=https://www.gpb.org/news/2024/01/03/watch-marta-train-cars-splash-ocean-off-georgia-coast-during-artificial-reef |access-date=10 October 2024 |work=Georgia Public Broadcasting |date=3 January 2024}}</ref><ref name="Atlanta-July-2024">{{cite news |title=A fleet of MARTA train cars find a new home in the ocean as artificial reefs |url=https://www.atlantamagazine.com/news-culture-articles/a-fleet-of-marta-train-cars-find-a-new-home-in-the-ocean-as-artificial-reefs/ |access-date=10 October 2024 |work=Atlanta Magazine |date=23 July 2024}}</ref> These artificial reefs attract a huge variety of organisms; according to marine ecologist from [[Georgia Southern University]], "the diversity rivals natural coral reefs."<ref name="Atlanta-July-2024"/>

====L Reef====
L Reef was established in 1976. It is located roughly {{convert|23|nmi|km mi}} east of [[Ossabaw Island]] and is {{convert|55|-|65|ft}} below the ocean's surface. It contains a variety of different debris, including [[New York City Subway rolling stock|New York City subway cars]], [[M60 tank|M-60 tanks]] formerly used by the [[United States Army]], and concrete [[culvert]]s.<ref name="Smithsonian-Sep-2024">{{cite news |last1=Kuta |first1=Sarah |title=No Longer Full of Commuters, Atlanta's Old Subway Cars Are Now Filled With Fish |url=https://www.smithsonianmag.com/smart-news/no-longer-full-of-commuters-atlantas-old-subway-cars-are-now-filled-with-fish-180985085/ |access-date=10 October 2024 |work=Smithsonian |date=16 September 2024}}</ref> In 2023, on the 21st of December, the DNR unloaded two retired railcars from the [[Metro Atlanta Rapid Transit Authority]].<ref name="GPB-Jan-2024"/> In August 2024, divers discovered soft coral growing on the railcars and counted nine species of game fish.<ref name="Smithsonian-Sep-2024"/>

===North Carolina===

====Ex-USS ''Yancey''====
{{USS|Yancey|AKA-93|6}} was sunk as an artificial reef off [[Morehead City, North Carolina]] in 1990, as AR-302.<ref>{{cite web |title=Sunken Vessel History {{!}} NC DEQ |url=https://www.deq.nc.gov/about/divisions/marine-fisheries/public-information-and-education/coastal-fishing-information/artificial-reefs/sunken-vessel-history |website=North Carolina Department of Environmental Quality}}</ref> She is lying on her starboard side at a depth of {{convert|160|ft|m|abbr=on}}<ref>{{cite web |title=Wreck Desc USS Yancey |url=http://www.ddcbuildsite.com/index.php/diving/dive-sites?id=245 |website=Discovery Diving}}</ref>

====Ex-USCGC ''Spar''====

{{ship|USCGC|Spar|WLB-403|6}} was scuttled in June 2004 by Captain Tim Mullane in {{convert|108|ft|m}} of water, {{convert|30|mi|km|0}} off [[Morehead City, North Carolina]], where she serves as an artificial reef.<ref>{{cite web|last1=Hudy|first1=Paul|title=North Carolina Shipwrecks|url=http://www.nc-wreckdiving.com/shipwrecks.html|website=nc-wreckdiving.com|access-date=15 July 2015}}</ref>

====Ex-USS ''Indra''====

{{USS|Indra|ARL-37|6}} was sunk as an artificial reef, 4 August 1992 in {{convert|60|ft|m}} of water.<br />Its coordinates are {{Coord|34|33|55|N|76|58|30|W|type:landmark|display=inline}}.<ref>{{cite web|author=Mobile Riverine Force Association |title=History of The USS Indra (ARL-37) |url=http://www.mrfa.org/arl-37.htm |date=October 4, 1999 |access-date=October 20, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20150223025710/http://www.mrfa.org/arl-37.htm |archive-date=February 23, 2015 }}</ref>

====Ex-USS ''Aeolus''====
{{USS|Aeolus|ARC-3|6}} was sunk to form an artificial reef in August 1988 as AR-305.<ref name="Jones">{{cite news |last1=Jones |first1=Colin |title=The Sand Tigers of USS Aeolus |url=https://deepbluediver.uk/2020/07/05/the-sand-tigers-of-uss-aeolus/ |work=Deep Blue Diver |date=5 July 2020}}</ref> The ex-''Aeolus'', is located 18.3 nautical miles from Beaufort Inlet Sea Buoy in {{convert|104|ft|-1}} of water.<ref name="Comer">{{cite book |last1=Comer |first1=Amy M. |last2=Love-Adrick |first2=Rachel |title=North Carolina Division of Marine Fisheries Artificial Reef Guide  |date=2016 |publisher=North Carolina Department of Environmental Quality |url=https://www.deq.nc.gov/marine-fisheries/coastal-fishing-information/artificial-reefs/dmf-reef-guide-web/download}}</ref>

===Delaware===

====Redbird Reef====
{{Main|Redbird Reef}}
[[File:NYC subway cars used as artificial reef.jpg|thumb|right|Retired subway cars on a barge before being sunk to form an artificial reef.]]
In the late 2000s, the [[New York City Transit Authority]] decided to retire an outdated fleet of subway cars to make room for new [[R142 (New York City Subway car)|R142]] and [[R142A (New York City Subway car)|R142A]] trains. The obsolete subway cars, (nicknamed "[[Redbird trains|Redbirds]]"), had run on the [[A Division (New York City Subway)|A Division]] (former [[Interborough Rapid Transit Company]] routes) of the [[New York City Subway]] system for 40 years. Each car was stripped, decontaminated, loaded on a barge, and sunk in the Atlantic Ocean off the coast of Delaware, Virginia, South Carolina, Georgia, and Florida. Some cars had number plates removed because of rust, which were then auctioned off on eBay. A total of 1,200 subway cars were sunk for this project.

In September 2007, the NYCTA approved a further contract with [[Weeks Marine]] worth $6 million, to send 1,600 of its retired subway cars to be used as artificial reefs. The old models were sheathed in stainless steel, except for the fiberglass reinforced plastic front ends, which were removed before sinking. The retired fleet included old work trains and cars that were badly damaged beyond repair.<ref>{{cite web |title=More Subway Cars Slated For Reefs |url=https://www.upi.com/Science_News/2007/09/29/More-subway-cars-slated-for-reefs/75341191099046/ |website=United Press International |access-date=22 January 2020}}</ref>

=== Canada ===

==== British Columbia ====
In 2006, a Boeing 737–200 that was deemed no longer airworthy by Air Canada was sunk by the [[Artificial Reef Society of British Columbia]].<ref>{{cite web |title=Boeing 737, 2006 |url=https://artificialreefsocietybc.ca/boeing-737.html |website=Artificial Reef Society British Columbia |access-date=28 January 2023}}</ref>

===Mexico===

====Cancun Underwater Museum====
Since November 2009, artist [[Jason deCaires Taylor]] has created more than 400 life size sculptures off the coast of Cancun, Mexico at the [[Cancun Underwater Museum]]. The coral reefs in this region suffered heavy degradation due to repetitive hurricane abuse. This project was funded by The National Marine Park and the Cancun Nautical Association. It was designed to emulate coral reefs using a neutral ph clay. Taylor constructed unique settings depicting daily activities ranging from a man watching TV to a 1970s replica of a Volkswagen Beetle. This artificial reef relieved pressure from the nearby Manchones Reef.<ref>{{Cite news|url=https://cancuntravel.wordpress.com/2010/04/07/cancun%E2%80%99s-underwater-museum-blooms-in-time-for-spring/|title=Cancun's Underwater Museum Blooms In Time For Spring|date=2010-04-07|work=Cancun Vacation Blog|access-date=2017-10-05|language=en-US}}</ref>

===Australia===
Since the late 1990s, the Australian government has been providing decommissioned warships for use as artificial reefs for recreational scuba diving. So far, seven ships have been sunk:
* {{HMAS|Swan|DE 50|6}} at Dunsborough in Western Australia during December 1997.<ref>{{cite web|title=HMAS Swan – History |url=http://www.michaelmcfadyenscuba.info/viewpage.php?page_id=454 |publisher=Michael McFayden's Scuba Diving Web Site |access-date=5 April 2015}}</ref>
* {{HMAS|Perth|D 38|6}} at Albany in Western Australia during November 2001.<ref>{{cite web|title=Welcome to the official former HMAS Perth Website |url=http://www.hmasperth.com.au/ |access-date=12 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120320234914/http://www.hmasperth.com.au/ |archive-date=March 20, 2012 }}</ref>
* {{HMAS|Hobart|D 39|6}} in Yankalilla Bay in South Australia during November 2002.<ref>{{cite web|title=Dive the Ex-HMAS Hobart |url=http://www.exhmashobart.com.au/index.html |access-date=5 April 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150227163904/http://www.exhmashobart.com.au/index.html |archive-date=27 February 2015 }}</ref>
* {{HMAS|Brisbane|D 41|6}} off the Sunshine Coast in Queensland during July 2005.<ref>{{cite web|title=Ex-HMAS Brisbane Conservation Park |url=http://www.derm.qld.gov.au/parks/ex-hmas-brisbane/index.html |access-date=12 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120511025943/http://www.derm.qld.gov.au/parks/ex-hmas-brisbane/index.html |archive-date=May 11, 2012 }}</ref>
* {{HMAS|Canberra|FFG 02|6}} at a site west of the entrance to Port Phillip Bay in Victoria during October 2009.<ref>{{cite web|title=ex-HMAS Canberra Reef |url=http://www.hmascanberra.com.au/ |publisher=Dive the ex-HMAS Canberra |access-date=5 April 2015}}</ref>
* {{HMAS|Adelaide|FFG 01|6}} off Terrigal on the New South Wales Central Coast during April 2011
* {{HMAS|Tobruk|L 50|6}} off Hervey Bay on the Queensland Coast on 29 June 2018 <ref>{{cite web|title=Ex-HMAS Tobruk scuttled off the Queensland coast to become dive wreck |date=29 June 2018 |url=http://www.abc.net.au/news/2018-06-29/ex-hmas-tobruk-scuttled-off-the-queensland-coast/9923758 |publisher=ABC |access-date=29 June 2018}}</ref>

[[Cooper Reef]] is a purpose-built artificial reef off the coast of Esperance, Western Australia. It is at a depth of 30m and consists of 128 dome-like concrete modules designed to attract fish and enhance [[fish stocks]], thereby creating new fishing and recreation opportunities for tourists, anglers and local families.

===Costa Rica===
At Playa Hermosa, the Playa Hermosa Artificial Reef Project has created an artificial reef using discarded porcelain insulators.<ref name="Arias">{{cite news |last1=Arias |first1=L. |title=Costa Rican Electricity Institute launches construction of artificial reef |url=https://ticotimes.net/2017/01/24/artificial-reef-costa-rica |work=The Tico Times {{!}} Costa Rica News {{!}} Travel {{!}} Real Estate |date=25 January 2017}}</ref><ref>{{cite web |title=Playa Hermosa Artificial Reef Project |url=https://condofish.wordpress.com/ |website=condofish.wordpress.com |access-date=16 June 2023 |language=en}}</ref>

===Curacao===
On Curaçao, Secore International has created 12 artificial reefs using the [[Aquaculture of coral#Economy|cost-effective]] technique with small tetrapod-shaped concrete structures, seeded with coral larvae.<ref name="Dormehl">{{cite news |last1=Dormehl |first1=Luke |title=Our Latest Option To Save Dying Coral Reefs Is… A Concrete Pod? |url=https://www.digitaltrends.com/cool-tech/coral-reef-concrete-pods/ |work=Digital Trends |date=5 January 2018 |language=en}}</ref>

===Canary Islands===
Near Playa de Garcey on Fuerteventura in the [[Canary Islands]], the [[SS American Star (1939)|SS ''America'' (1939)]] lays as a more recent artificial reef. In 1994, while traveling to Thailand, the tugboats' cable on bringing the ship to [[Thailand]], where she would be converted into a floating hotel, snapped. After multiple attempts to re-connect the cables, they were unsuccessful. The next day, she landed off the coast of the Canary Islands, where she deteriorated for years. In 1995, due to the rough waves, she split into two, both sides sank slowly. By 2007, at least 5% of the ship was visible. In 2024, nothing was left, where it had become an artificial reef.<ref>{{cite web|url=https://dev.united-states-lines.org/ss-america-the-wreck-of-the-american-star/|title=SS America: The Wreck of the American Star|website=United States Lines|accessdate=November 30, 2024}}</ref>

===Saba and Statia===
The AROSSTA project is located in the Caribbean Dutch islands of St. Eustatius and Saba.<ref name="AROSSTA">{{cite web |title=Project AROSSTA |url=https://www.vhluas.com/research/research-projects/arossta |website=www.vhluas.com |access-date=16 June 2023 |language=en}}</ref> Based on comparisons of the effectiveness of reef balls, layered cakes, and rock for artificial reefs, researchers have developed MOREEF (Modular Restoration Reef) to provide a more complex internal structure and increase shelter availability.<ref name="van de Water">{{cite news |last1=van de Water |first1=Sebastiaan |title=Droomhuisjes op de zeebodem |url=https://newscientist.nl/blogs/droomhuisjes-op-de-zeebodem/ |work=New Scientist |date=11 December 2019 |language=nl}}</ref>

===Gibraltar===
The [[Gibraltar Artificial Reef|Gibraltar Reef]] was first proposed by Eric Shaw in 1973.<ref name="Vidal">{{cite news |last1=Vidal |first1=John |title=Gibraltar row: Spain 'misinformed' over artificial reef |url=https://www.theguardian.com/environment/2013/aug/22/spain-gibraltar-reef-fishing |access-date=16 June 2023 |work=The Guardian |date=22 August 2013}}</ref> Initial experiments with [[tires]] proved unsuccessful as the tires were swept away by currents or buried underneath sand. In 1974, boats from local marinas and the [[Gibraltar Port Authority]] were donated. The first two were [[barges]] that were sunk in [[Camp Bay, Gibraltar|Camp Bay]].<ref name="Ward">{{cite news |last1=Ward |first1=Jo |title=Giving Gibraltar a helping hand – Gibraltar Insight |url=https://gibraltarinsight.com/2021/06/08/giving-gibraltar-a-helping-hand/ |access-date=16 June 2023 |work=Gibraltar Insight |date=Jun 8, 2021}}</ref> In 2006, a 65-ton wooden boat, ''True Joy'' (also referred to as ''Noah's Ark'') was sunk there as well.<ref>{{cite web |title=Underwater Gibraltar {{!}} Shaun Yeo Photography {{!}} Wrecks {{!}} True Joy |url=https://www.underwatergibraltar.com/true-joy |website=Underwater Gibraltar |access-date=16 June 2023 |language=en}}</ref>

Shaw helped to found the Helping Hand Trust in 1994. The Trust works with researchers from around the world to expand the reef and to conserve, protect and monitor the natural world.<ref>{{cite web |title=Gibraltar Marine Research & Conservation |url=https://www.helpinghand.gi/ |website=Helping Hand Trust |access-date=16 June 2023}}</ref> The artificial reef, which contains more than 30 scuttled and wrecked vessels, was the first to be constructed in Europe.<ref name="Vidal"/><ref name="HHT">{{cite web |title=Gibraltar Artificial Reef Project – A First in Europe |url=https://www.helpinghand.gi/projects/2043-gibraltar-artificial-reef-project-a-first-in-europe |website=Helping Hand Trust |access-date=16 June 2023}}</ref> It continues to be one of the largest.<ref>{{cite book |last1=DG Fisheries and Maritime Affairs  |title=Study to support Impact Assessment of Marine Knowledge 2020 -interim report |date=2020 |publisher=Ernst & Young |url=https://maritime-forum.ec.europa.eu/system/files/Interim%20report_21%2012%202012_final.pdf}}</ref>

Expansion of the Artificial Reef halted after the cargo vessel 'New Flame' collided with the 'Torm Gertrud' and sank in an area known as 'Los Picos'. Los Picos was one of two natural reefs within Gibraltar's EU registered area of special interest, with a high level of biodiversity.<ref name="HHT"/><ref name="Lansford">{{cite book |last1=Lansford |first1=Tom |title=Political Handbook of the World 2022–2023 |date= 2023 |publisher=CQ Press |isbn=978-1-0718-5307-8 |page=1871 |url=https://books.google.com/books?id=IpGREAAAQBAJ&pg=PA1871 |language=en}}</ref> After two years of salvage work, it was determined that attempting to remove the remaining keel and bottom would harm the natural reef. Authorities decided to leave the rest where it was.<ref>{{cite news |title=New Flame wreck removal a success in Gibraltar |url=https://www.ajot.com/news/new-flame-wreck-removal-a-success-in-gibraltar |work=American Journal of Transportation |date=Dec 23, 2009}}</ref><ref>{{cite web |title=Salvage Operation of New Flame concluded |url=https://www.gibraltar.gov.gi/new/sites/default/files/Press%20archives/Press%20Releases/2009/257-2009.pdf |website=The Government of Gibraltar |access-date=16 June 2023|date=3 December 2009}}</ref><ref name="Herbert">{{cite book |last1=Herbert |first1=James |title=The challenges and implications of removing shipwrecks in the 21st century |date=2013 |publisher=Lloyd's |page=19 |url=https://assets.lloyds.com/assets/pdf-risk-reports-wreck-report-final-version/1/pdf-risk-reports-Wreck-Report-Final-version.PDF}}</ref>

In 2013, more than 70 concrete blocks were sunk by the government of Gibraltar (independent of Eric Shaw's trust), each one square meter in size with protruding metal bars. This led to heated debate between the [[United Kingdom]] and [[Spain]], with Gibraltar accusing Spain of over forty incursions into their waters per month<ref>{{cite web|url=http://www.express.co.uk/news/world/443937/GIBRALTAR-We-are-just-one-shot-away-from-military-conflict-warns-MP-amid-new-standoff |title=Gibraltar: We are just one shot away from military conflict, warns MP amid new standoff |work=Daily Express |last=Bennett |first=Owen |date=19 November 2013 |access-date=5 April 2015}}</ref> and Spain accusing Gibraltar of including metal bars in the reef to stop Spanish fishermen trawling the seabed for fish. The dropping led to a diplomatic conflict between the two countries because Gibraltar is a [[British Overseas Territory]].<ref name="Guinand">{{cite news |last1=Guinand |first1=Andy |title=Gibraltar – The Rock of discord – Culture – OCEAN71 |url=http://ocean71.com/culture-en/gibraltar-rock-discord/ |access-date=16 June 2023 |work=Ocean 71 Magazine |date=20 September 2013}}</ref>
By 2015, Shaw reported that there was "all kinds of life in the new reef from microbiological species to conger and moray eels".<ref name="Badcock">{{cite news |last1=Badcock |first1=James |title=Gibraltar's controversial artificial reef 'teeming with life' |url=https://www.telegraph.co.uk/news/worldnews/europe/gibraltar/11614150/Gibraltars-controversial-artificial-reef-teeming-with-life.html |access-date=16 June 2023 |work=The Telegraph |date=18 May 2015}}</ref>

===India===

====Temple Reef====
Experimentation with artificial reef structures at the [[Temple Reef|Temple reef]] dive site off the coast of [[Puducherry (city)|Pondicherry, India]] began as early as 2013. The diving centre Temple Adventures built a Temple-shaped structure in 2015 at a depth of {{convert|18|m|ft}}, using recycled materials such as concrete, rocks, trees, palms, and iron bars.<ref name="Philip">{{cite news |last1=Philip |first1=Annie |title=Delving the depths of marine world |url=https://www.thehindu.com/news/cities/puducherry/delving-the-depths-of-marine-world/article7328200.ece |access-date=16 June 2023 |work=The Hindu |date=17 June 2015 |language=en-IN}}</ref>

The Temple Reef Foundation was founded in 2017 to support marine conservation and the further development of artificial surfing reefs in the area. In 2019 Bennington's Reef was added to the Temple reef dive site using a patented design for cement-dolomite blocks. The initial block was 3D printed, and further blocks were built using molded frames. In 2020, the project began testing a new block prototype that uses eggshell waste, sand, pebbles, and cement, stabilized with iron rebar.<ref name="Pondicherry">{{cite web |title=A Teenager's Action Over Excuses – Building a Sustainable Artificial Reef in Pondicherry |url=https://templeadventures.com/blog/kids-action-excuses-building-sustainable-artificial-reef-pondicherry/ |website=Temple Adventures |access-date=16 June 2023 |date=4 August 2020}}</ref>

===Dubai===

Pearl of Dubai is an art-inspired Lost City off the coast of [[Dubai]]. The site encompasses five acres and is located at the [[World Islands]]. At a depth of {{convert|10|to|20|m|ft}}, the site is designed as an ancient lost city, complete with temples and statues using regional design cues from 800 BC.<ref>{{cite news|url=https://www.telegraph.co.uk/travel/destinations/middleeast/dubai/10937905/The-worlds-largest-underwater-theme-park-planned-in-Dubai.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/travel/destinations/middleeast/dubai/10937905/The-worlds-largest-underwater-theme-park-planned-in-Dubai.html |archive-date=2022-01-12 |url-access=subscription |url-status=live |title=The world's largest underwater theme park planned in Dubai |work=The Telegraph |last=Kim |first=Soo |date=1 July 2014 |access-date=5 April 2015}}{{cbignore}}</ref> In 2023, designs for the world's largest ocean restoration and ecotourism project was unveiled in Dubai.<ref>{{Cite web |last=Skirka |first=Hayley |date=2023-05-09 |title=Designs revealed for Dubai Reefs, world's largest ocean restoration and ecotourism project |url=https://www.thenationalnews.com/travel/2023/05/09/designs-revealed-for-dubai-reefs-worlds-largest-ocean-restoration-and-ecotourism-project/ |access-date=2023-12-02 |website=The National |language=en}}</ref> The project named Dubai Reefs, aims to use 3D printing technology to create the world's largest artificial reef.<ref>{{Cite web |last=Margaret |date=2023-07-06 |title=Vertical farms and 3D-printed reefs part of UAE's plans for food security |url=https://kustreview.com/vertical-farms-and-3d-printed-reefs-part-of-uaes-plans-for-food-security/ |access-date=2023-12-02 |website=Khalifa University Science and Tech Review |language=en-US}}</ref>

===Aqaba, Jordan===

Jordan made an under-water military vehicles museum, which is intended to form an artificial reef over time.<ref>{{cite news|url=https://www.nytimes.com/2019/07/25/world/middleeast/jordan-underwater-museum-military.html |title=Jordan Creates Artificial Reef From Decommissioned Military Vehicles|work=[[The New York Times]]|date=25 July 2019|access-date=25 July 2019}}</ref>

===Philippines===
Underwater Chocolate Hills is an artificial reef project undertaken by Spindrift Reefs Dive Center<ref>{{cite web|title=Spindrift Reefs Dive Center|url=http://spindriftreefs.com|url-status=usurped|archive-url=https://web.archive.org/web/20160109035147/http://spindriftreefs.com/|archive-date=2016-01-09}}</ref> off the coast of [[Panglao Island]] in the Philippines. It consists of broken coral harvested by local divers, who attach it to wire structures. The structures are built in the same shape as the Chocolate Hills, which can be found in the [[Bohol]] Region. The intent is to create a new dive site and new marine habitat.<ref>{{cite web |title=Spindrift Reefs  |url=http://thecoraltriangle.com/travel/spindrift-reefs |archive-url=https://web.archive.org/web/20161111035651/http://thecoraltriangle.com/travel/spindrift-reefs |url-status=usurped |archive-date=November 11, 2016 |website=The Coral Triangle}}</ref>

===Lebanon===

In 2018, the [[Lebanese Army]] donated 10 stripped [[tanks]] to an NGO and sunk them 3&nbsp;km away from the coast of [[Sidon]], South Lebanon.<ref>{{Cite news|url=https://www.bbc.com/news/world-middle-east-44994182|title=Lebanon sinks tanks in Mediterranean to make new reef|work=BBC News|date=28 July 2018}}</ref>

=== Malta ===
Following a gas explosion that occurred on 3 February 1995, the Libyan-owned motor tanker [[Um El Faroud]] was [[Scuttling|scuttled]] off the coast of [[Malta]] as an artificial reef.<ref name="Weinman">{{cite web |last1=Weinman |first1=Steve |title=Tanker is latest Gozo shipwreck attraction |url=https://divernet.com/scuba-news/tanker-is-latest-gozo-shipwreck-addition/ |website=DiverNet |date=4 September 2022}}</ref>

== See also ==
* {{annotated link|Artificial Reef Society of British Columbia}}
* {{annotated link|Artificial reefs in Japan}}
* {{annotated link|Artificial wave}}
* {{annotated link|Cancún Underwater Museum}}
* {{annotated link|Fish aggregating device}}
* {{annotated link|Marine debris}}
* [[Types of concrete#Marine habitat concrete|Marine habitat concrete]]
* {{annotated link|Multi-purpose reef}}
* {{annotated link|Scuttling}}
* {{annotated link|Ship graveyard}}
* {{annotated link|Sinking ships for wreck diving sites}}
* {{annotated link|Spawning bed}}

== References ==
{{Reflist|2}}

==External links==
{{Commons category|Artificial reefs}}
* [http://www.carolinareefs.org/ Eastern Carolina Artificial Reef Association]
* [http://oarreefs.org/reefs.shtml Organization for Artificial Reefs]
* [http://myfwc.com/conservation/saltwater/artificial-reefs/ar-program Florida Artificial Reef Program]
* [http://www.reefball.org/index.htm Reef Ball Foundation]
* {{Cite web|url=http://artificialreefsocietybc.ca|title=Artificial Reef Society of BC|website=Artificial Reefs ARSBC|access-date=2017-10-05}}

{{Earth's landforms}}
{{coastal management}}
{{Corals}}
{{Underwater diving|recdiv}}
{{Recreational dive sites|reesit}}
{{Authority control}}

{{DEFAULTSORT:Reef (artificial)}}
[[Category:Artificial reefs| ]]
[[Category:Ship disposal]]
[[Category:Recreational diving]]