An artificial reef (AR) is a human-created freshwater or marine
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
structure.
Typically built in areas with a generally featureless bottom to promote
marine life
Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, aquatic plant, plants, algae, marine fungi, fungi, marine protists, protists, single-celled marine microorganisms, microorganisms ...
, it may be intended to control
erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
, protect coastal areas, block ship passage, block the use of
trawling
Trawling is an industrial method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch di ...
nets,
support reef restoration, improve
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. Nelu ...
, or enhance
scuba diving
Scuba diving is a Diving mode, mode of underwater diving whereby divers use Scuba set, breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The word ''scub ...
and
surfing
Surfing is a surface water sport in which an individual, a surfer (or two in tandem surfing), uses a board to ride on the forward section, or face, of a moving wave of water, which usually carries the surfer towards the shore. Waves suita ...
.
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,
such as sinking oil rigs (through the
Rigs-to-Reefs program),
scuttling ships, or by deploying
rubble
Rubble is broken stone, of irregular size, shape and texture; undressed especially as a filling-in. Rubble naturally found in the soil is known also as 'brash' (compare cornbrash)."Rubble" def. 2., "Brash n. 2. def. 1. ''Oxford English Dictionar ...
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.
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.
In some cases, artificial reefs have been developed as artworks.
Artificial reefs generally provide hard surfaces where
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
and invertebrates such as
barnacle
Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...
s,
coral
Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...
s, and
oyster
Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but no ...
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
assemblages of fish.
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.
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.
Considerable research is being done into construction methods and the effects of artificial reefs.
Many of the materials used early on are now considered undesirable.
A 2001 literature review suggested that about half of the reefs studied met their objectives.
Long-term planning and ongoing management were identified as essential factors in success.
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.
History
The construction of artificial reefs began in ancient times.
According to historian
Diodorus Siculus
Diodorus Siculus or Diodorus of Sicily (; 1st century BC) was an ancient Greece, ancient Greek historian from Sicily. He is known for writing the monumental Universal history (genre), universal history ''Bibliotheca historica'', in forty ...
, the
Romans blocked the harbor of
Lilybaeum during the
First Punic War
The First Punic War (264–241 BC) was the first of three wars fought between Rome and Carthage, the two main powers of the western Mediterranean in the early 3rd century BC. For 23 years, in the longest continuous conflict and grea ...
against the
Carthaginians
The Punic people, usually known as the Carthaginians (and sometimes as Western Phoenicians), were a Semitic people, Semitic people who Phoenician settlement of North Africa, migrated from Phoenicia to the Western Mediterranean during the Iron ...
around 250 BC. They built an artificial reef "with stones and construction material" and put poles in the channels using "large timbers and anchors".
Persians
Persians ( ), or the Persian people (), are an Iranian ethnic group from West Asia that came from an earlier group called the Proto-Iranians, which likely split from the Indo-Iranians in 1800 BCE from either Afghanistan or Central Asia. They ...
blocked the mouth of the
Tigris River to thwart Arabian pirates by building an artificial reef.
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
Kelps are large brown algae or seaweeds that make up the order (biology), order Laminariales. There are about 30 different genus, genera. Despite its appearance and use of photosynthesis in chloroplasts, kelp is technically not a plant but a str ...
. 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
South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...
to improve fishing. In the
Philippines
The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...
a traditional native fishing technique known as
fish nests (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
Groupers are a diverse group of marine ray-finned fish in the family Epinephelidae, in the order Perciformes.
Groupers were long considered a subfamily of the seabasses in Serranidae, but are now treated as distinct. Not all members of this f ...
fingerlings to be used as seeds for
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. Nelu ...
. Fish nests were in common use since before 1939.
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
decommissioned ships, subway cars, battle tanks,
armored personnel carriers, oil drilling rigs and beehive-like reef balls.
Purposes
Artificial reef structures (ARs) have a variety of intended uses, ranging from the protection, enhancement and restoration of marine ecosystems to the support of human activities like fishing, recreational diving and surfing. 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.
In fisheries management, artificial reefs may be intended to increase production of species of recreational and commercial interest, enhance fishing yield, and support recreational, artisanal or commercial fisheries. They may be designed to protect benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
habitats from illegal trawling and restore fish stocks.
They may be placed to protect against coastal erosion.
They may also be developed to support eco-tourism, promote recreational activities like scuba diving and surfing, and mitigate tourism pressure on corals.
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. 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.
Artificial reef communities
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
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
-rich upwelling that provides a reliable feeding spot for small fish such as sardine
Sardine and pilchard are common names for various species of small, oily forage fish in the herring suborder Clupeoidei. The term "sardine" was first used in English during the early 15th century; a somewhat dubious etymology says it com ...
s and minnow
Minnow is the common name for a number of species of small freshwater fish, belonging to several genus, genera of the family Cyprinidae and in particular the subfamily Leuciscinae. They are also known in Ireland as wikt:pinkeen, pinkeens.
While ...
s, which draw in pelagic
The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...
predator
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
s such as tuna
A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...
and sharks
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
. Next come creatures seeking protection from the ocean's lethal openness—hole and crevice dwellers such as grouper
Groupers are a diverse group of marine ray-finned fish in the family Epinephelidae, in the order Perciformes.
Groupers were long considered a subfamily of the seabasses in Serranidae, but are now treated as distinct. Not all members of this f ...
, snapper, squirrelfish
Holocentrinae is a subfamily of Holocentridae containing 40 recognized species and one proposed species. Its members are typically known as squirrelfish and all are nocturnal. All three genera in the subfamily are found in the Atlantic and ''Ho ...
, eels and triggerfish. Opportunistic predators such as jack and barracuda
A barracuda is a large, predatory, ray-finned, saltwater fish of the genus ''Sphyraena'', the only genus in the family Sphyraenidae, which was named by Constantine Samuel Rafinesque in 1815. It is found in tropical and subtropical oceans worldw ...
also appear. Over months and years the reef structure becomes encrusted with algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, tunicates, hard and soft coral
Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...
s and sponge
Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...
s.[
]
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
Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
to precipitate onto a metal frame onto which coral planulae can then attach and grow; the process also speeds up post-attachment growth.
3D printing technology has been employed both to create molds to optimize the environment for target species, and to directly create cast ceramic and concrete artificial reefs. Work has also been done to develop environmentally friendly materials. 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.
Restoration and mitigation actions on artificial reefs can include activities such as coral transplantation, larval resettlement, and gardening.
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. 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."
Carbon sequestration
There is interest in the possibility that artificial reefs can be used to support carbon sequestration
Carbon sequestration is the process of storing carbon in a carbon pool. It plays a crucial role in Climate change mitigation, limiting climate change by reducing the amount of Carbon dioxide in Earth's atmosphere, carbon dioxide in the atmosphe ...
and counter climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
. 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
Blue carbon is a concept within climate change mitigation that refers to "biologically driven carbon fluxes and storage in marine systems that are amenable to management". Most commonly, it refers to the role that tidal marshes, mangroves and Seag ...
storage.
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. Another study area is located off Juehua Island in the Bohai Sea
The Bohai Sea ( zh, c=渤海, p=Bó Hǎi, l=Bo Sea) is a gulf/inland sea approximately in area on the east coast of Mainland China. It is the northwestern and innermost extension of the Yellow Sea, to which it connects via the Bohai Strait. It ...
. 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.
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. Estimates suggest that Caribbean seagrass beds can provide substantial pools for global carbon.
Erosion prevention
Some artificial reefs are used to prevent coastal erosion
Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of Wind wave, waves, Ocean current, currents, tides, wind-driven water, waterborne ice, or other impacts ...
.
Geometric and hydrodynamic properties of reefs are particularly important in determining their ability to mitigate coastal erosion.
Artificial reefs to prevent erosion can be designed to act in multiple ways. Some are designed to force waves
United States Naval Reserve (Women's Reserve), better known as the WAVES (for Women Accepted for Volunteer Emergency Service), was the women's branch of the United States Naval Reserve during World War II. It was established on July 21, 1942, ...
to deposit their energy offshore rather than directly on the coastline.
Other reefs are designed to hold sediment
Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
on beaches by trapping the sediment. Reefs are generally custom-designed for each unique zone. Some are designed to support customizable habitat for local target species as well.
Artificial surfing reefs
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). Artificial surfing reefs have been created at
Cable Station Reef (Perth
Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...
, Western Australia
Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...
, 1999)
Narrowneck Reef (Gold Coast, Queensland
The Gold Coast, also known by its initials, GC, is a coastal city and region in the state of Queensland, Australia, located approximately south-southeast of the centre of the list of Australian capital cities, state capital, Brisbane. It is ...
, 2000)
Chevron Reef, also known as Pratte's Reef (El Segundo, California
El Segundo ( , ; ) is a city in Los Angeles County, California, United States. Located on Santa Monica Bay, it was incorporated on January 18, 1917, and is part of the South Bay Cities Council of Governments. The population was 17,272 as of t ...
, 2000, removed 2008).
and Boscombe Surf Reef (Dorset, England, 2009, closed 2011).
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. Some analysts argue that they are fundamentally flawed. While use of stone blocks has raised concerns about possible safety hazards for surfers, it has been suggested that using stone may be structurally preferable.
In addition to improving surfing conditions, objectives of building an artificial surfing reef or multi-purpose reef
A multi-purpose reef, also commonly known as an artificial surfing reef or surf reef, is a structure located offshore designed to induce wave breaking in a manner that creates a wave suitable for surfing or body boarding. Artificial surfing reefs ...
have included stabilizing beachfront, coastal protection and coastal research. Habitat enhancement is sometimes considered as well.
However, different materials are preferred for the construction of artificial surfing reefs and the development of reefs for ecosystem enhancement.
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".
For Pratte's reef, woven polypropylene bags were used in a first phase, and woven polyester bags in a second stage filling an area of approximately 1600 cubic meters. 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. Mount Reef at Mount Maunganui
Mount Maunganui (, ) is a major residential, commercial and industrial suburb of Tauranga located on a peninsula to the north-east of Tauranga's city centre. It was an independent town from Tauranga until the completion of the Tauranga Harb ...
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. 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.
Several projects in Australia have used stone to augment existing sites. Cable Station Reef added limestone rocks to an existing reef. At Burkitts Reef on the Woongarra Coast, large boulders were broken down to fill gaps in an existing boulder and gravel reef. 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. Another artificial stone reef, located in Borth
Borth () is a village, seaside resort and community in Ceredigion, Mid Wales; it is located 7 miles (11 km) north of Aberystwyth, on the Ceredigion Coast Path. The community includes the settlement of Ynyslas and the population was 1,399 ...
, Wales
Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...
, was designed primarily for coastal protection.
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". Even in cases which were initially seen as successful, subsequent changes and deterioration of structures have led to poor outcomes.
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.
Surfing science is a relatively new field.
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.
Recreational dive sites
Thousands of popular wreck diving sites throughout the world are shipwrecks sunk as artificial reefs. Some of these wrecks were sunk deliberately to attract divers. The and in Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, and in North Carolina, and in Grenada
Grenada is an island country of the West Indies in the eastern Caribbean Sea. The southernmost of the Windward Islands, Grenada is directly south of Saint Vincent and the Grenadines and about north of Trinidad and Tobago, Trinidad and the So ...
draw thousands of divers annually.
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.
In Lisbon, 13 artworks by Alexandre Farto ( Vhils) will be placed in an artificial reef off the coast of Albufeira
Albufeira (, ), officially the City of Albufeira (), is a List of cities in Portugal, city and Concelho, municipality of Faro District in the Algarve region of southern Portugal. The population in 2021 was 44,158, in an area of . The city proper ...
as of June 2024. The works are made from parts of decommissioned power stations.
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.
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
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...
and long-term damage to fisheries;
and the potential for the materials used in artificial reefs to degrade and cause damage to the natural habitat. This can include toxicity
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...
from contaminants such as paint
Paint is a material or mixture that, when applied to a solid material and allowed to dry, adds a film-like layer. As art, this is used to create an image or images known as a painting. Paint can be made in many colors and types. Most paints are ...
, oil, and plastics
Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptab ...
, as well as parts of the reef breaking away and becoming ocean waste or washing onto natural reefs and beaches.
Changing populations
Many marine organisms exhibit a high degree of movement or dispersal. The fish attracted to artificial reef zones vary from reef to reef depending on the reef's age, size and structure. 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
The northern red snapper (''Lutjanus campechanus'') is a species of marine ray-finned fish, a snapper belonging to the family (biology), family Lutjanidae. It is native to the western Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico, w ...
''), 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.
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.
The opportunistic use of shipwreck
A shipwreck is the wreckage of a ship that is located either beached on land or sunken to the bottom of a body of water. It results from the event of ''shipwrecking'', which may be intentional or unintentional. There were approximately thre ...
s and oil derricks as artificial reefs creates a new trophic structure for the local ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
. The trophic structure of artificial and natural reefs has been shown to differ strongly. Artificial reefs do not develop the same functions and diversity as natural reefs over time, unless their structure is similar to natural reefs. 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.
As a result, artificial reefs can unbalance the natural ecosystem and affect nearby habitats, in some cases attracting non-native and invasive species that disrupt local ecosystems.
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".
Artificial reefs can show quick increases in local fish population,
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...
and algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
growth. 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).
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. Instead they operate as a type of fish aggregating device
A fish aggregating (or aggregation) device (FAD) is a man-made object used to attract pelagic fish such as marlin, tuna and mahi-mahi (dolphin fish). They usually consist of buoys or floats tethered to the ocean floor. Various types of FADs have be ...
(FAD) bringing in fish, eggs and larvae from other reefs. However, there is some evidence to suggest that artificial reefs can be a source of production as well as attraction. 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."
Concentrating fish on a reef makes for easier fishing.
The increased concentration of fish on artificial reefs can make it easier to harvest fish stocks, with the potential for overfishing
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing Fish stocks, fish stock), resu ...
and long-term damage to fisheries. This has implications for artisanal and industrial fishing management.
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.
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
A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its lo ...
s later demolished the tire containment system, washing tires onto beaches, destroying nearby coral reefs and inhibiting new coral growth. On the Osborne Reef off the coast of Fort Lauderdale, Florida
Fort Lauderdale ( ) is a coastal city located in the U.S. state of Florida, north of Miami along the Atlantic Ocean. It is the county seat of and most populous city in Broward County, Florida, Broward County with a population of 182,760 at the ...
, storms broke the nylon straps holding the original tire bundles together. As of November 2019, 250,000 of an estimated 700,000 tires have been removed.
France
France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
has begun removing its tire reefs. The Ocean Conservancy now includes tire removal during the International Coastal Cleanup in September of each year.
Since 2021, 4Ocean has added collecting tires from the bottom to their cleanup operations as well.
Some attempts to construct artificial surfing reefs have also been problematic. A number of early surfing installations used geotextile bags filled with sand which degraded more quickly than anticipated. Cases such as Pratte's Reef in California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
and Mount Reef at Mount Maunganui
Mount Maunganui (, ) is a major residential, commercial and industrial suburb of Tauranga located on a peninsula to the north-east of Tauranga's city centre. It was an independent town from Tauranga until the completion of the Tauranga Harb ...
in New Zealand have required extensive remediation work to remove materials. In some cases, remediation has cost more than the original installation. It has been argued that this approach to reef construction is fundamentally flawed.
Toxicity
Artificial reefs, particularly opportunistic ones involving materials that were not originally intended for marine use, can 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.
PVCs,
plastics
Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptab ...
,
oil,
paint
Paint is a material or mixture that, when applied to a solid material and allowed to dry, adds a film-like layer. As art, this is used to create an image or images known as a painting. Paint can be made in many colors and types. Most paints are ...
, asbestos
Asbestos ( ) is a group of naturally occurring, Toxicity, toxic, carcinogenic and fibrous silicate minerals. There are six types, all of which are composed of long and thin fibrous Crystal habit, crystals, each fibre (particulate with length su ...
, iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
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 ).
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.
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.
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.
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.
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".
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.
Examples
United States
Florida
Florida is the site of many artificial reefs, 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''.
Osborne Reef
In the early 1970s, more than 2,000,000 used vehicle tires were dumped off the coast of Fort Lauderdale, Florida
Fort Lauderdale ( ) is a coastal city located in the U.S. state of Florida, north of Miami along the Atlantic Ocean. It is the county seat of and most populous city in Broward County, Florida, Broward County with a population of 182,760 at the ...
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, castings of lions or other shapes before entering the water.[
]
Ex-USS ''Massachusetts''
In 1921 the US battleship 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
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
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.
Ex-USS ''Oriskany''
The world's largest artificial reef was created by sinking of the 44,000 ton aircraft carrier off the coast of Pensacola, Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, in 2006.
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 of clear water. Supporters expected the ship to draw recreational divers away from natural reefs, allowing those reefs to recover from damage from overuse.
Ex-USS ''Spiegel Grove''
The ex-USS is located on Dixie Shoal, off the Florida Keys in the Florida Keys National Marine Sanctuary.
Her location is .
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.
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. These artificial reefs attract a huge variety of organisms; according to marine ecologist from Georgia Southern University, "the diversity rivals natural coral reefs."
L Reef
L Reef was established in 1976. It is located roughly east of Ossabaw Island and is 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 culverts. In 2023, on the 21st of December, the DNR unloaded two retired railcars from the Metro Atlanta Rapid Transit Authority. In August 2024, divers discovered soft coral growing on the railcars and counted nine species of game fish.
North Carolina
Ex-USS ''Yancey''
was sunk as an artificial reef off Morehead City, North Carolina in 1990, as AR-302. She is lying on her starboard side at a depth of
Ex-USCGC ''Spar''
was scuttled in June 2004 by Captain Tim Mullane in of water, off Morehead City, North Carolina, where she serves as an artificial reef.
Ex-USS ''Indra''
was sunk as an artificial reef, 4 August 1992 in of water.
Its coordinates are .
Ex-USS ''Aeolus''
was sunk to form an artificial reef in August 1988 as AR-305. The ex-''Aeolus'', is located 18.3 nautical miles from Beaufort Inlet Sea Buoy in of water.
Delaware
Redbird 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.
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.
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.
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:
* at Dunsborough in Western Australia during December 1997.
* at Albany in Western Australia during November 2001.
* in Yankalilla Bay in South Australia during November 2002.
* off the Sunshine Coast in Queensland during July 2005.
* at a site west of the entrance to Port Phillip Bay in Victoria during October 2009.
* off Terrigal on the New South Wales Central Coast during April 2011
* off Hervey Bay on the Queensland Coast on 29 June 2018
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.
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.
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.
Saba and Statia
The AROSSTA project is located in the Caribbean Dutch islands of St. Eustatius and Saba. 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.
Gibraltar
The Gibraltar Artificial Reef, Gibraltar Reef was first proposed by Eric Shaw in 1973. 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. In 2006, a 65-ton wooden boat, ''True Joy'' (also referred to as ''Noah's Ark'') was sunk there as well.
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. The artificial reef, which contains more than 30 scuttled and wrecked vessels, was the first to be constructed in Europe. It continues to be one of the largest.
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. 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.
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 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.
By 2015, Shaw reported that there was "all kinds of life in the new reef from microbiological species to conger and moray eels".
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 , using recycled materials such as concrete, rocks, trees, palms, and iron bars.
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.
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 , the site is designed as an ancient lost city, complete with temples and statues using regional design cues from 800 BC. In 2023, designs for the world's largest ocean restoration and ecotourism project was unveiled in Dubai. The project named Dubai Reefs, aims to use 3D printing technology to create the world's largest artificial reef.
Aqaba, Jordan
Jordan made an under-water military vehicles museum, which is intended to form an artificial reef over time.
Philippines
Underwater Chocolate Hills is an artificial reef project undertaken by Spindrift Reefs Dive Center 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.
Lebanon
In 2018, the Lebanese Army donated 10 stripped tanks to an NGO and sunk them 3 km away from the coast of Sidon, South Lebanon.
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.
See also
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* Types of concrete#Marine habitat concrete, Marine habitat concrete
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References
External links
Eastern Carolina Artificial Reef Association
Organization for Artificial Reefs
Florida Artificial Reef Program
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{{DEFAULTSORT:Reef (artificial)
Artificial reefs,
Ship disposal
Recreational diving