An electric reef (also electrified reef) is an artificial reef made from biorock, being limestone that forms rapidly in seawater on a metal structure from dissolved minerals in the presence of a small electric current. The first reefs of this type were created by Wolf Hilbertz and Thomas J. Goreau in the 1980s. By 2011 there were examples in over 20 countries.
Artificial reefs have been built since the 1950s using materials including sunken ships and concrete blocks. While artificial reefs have been effective at boosting fish populations and are valuable areas for benthic organisms and other marine life (e.g. sponges) to colonise, they are less viable for coral restoration due to the slow growth of corals and their susceptibility to environmental changes. [1]
In the 1970s, whilst studying how seashells and reefs grow, Wolf Hilbertz discovered a simple method of creating limestone from minerals dissolved in seawater, which he called biorock. Together with Thomas J. Goreau he realised that this process could be adapted to rapidly create artificial coral reefs during the 1980s. Using the names "Sea-ment" and "sea cement", the process was publicised in the 1992 futurology book titled The Millennial Project. [2]
With others, Hilbertz and Goreau made expeditions to the Saya de Malha bank in 1997 and 2002 where they grew an artificial island around steel structures anchored to the sea floor using this process. [3] In the Maldives, 80% of the electric reefs survived the 1998 warming which killed 95% of the natural reef corals. [4]
Goreau continued the work after Hilbertz's death in 2007. By 2011 there were electric reef projects installed in over 20 countries. [5] [ citation needed ] In 2012, both Goreau and Robert K. Trench published works on how the process could generate building materials as well as restore damaged ecosystems. [6]
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The base of an electrified reef is a welded electrically conductive frame, often made from construction grade rebar or wire mesh which submerged and attached to the seafloor to which an electrical field applied. The frame (cathode) and a much smaller metal plate (anode) placed at a suitable distance from the frame initiates the electrolytic reaction.
Dissolved calcium carbonate and magnesium hydroxide and other minerals naturally found in seawater breakdown in the vicinity of the anode and recombine and precipitate out of the water onto the cathode. The exact composition of the minerals within the crystal formation is depends on their abundance, the climatic conditions and the voltage used. The structure takes on a whitish appearance within days.
This electric field, together with shade and protection offered by the metal/limestone frame soon attracts colonizing marine life, including fish, crabs, clams, octopus, lobster and sea urchins. Once the structure is in place and minerals begin to coat the surface divers transplant coral fragments from other reefs to the frame which soon bond to the newly accreted mineral substrate.
Because of the availability of evolved oxygen at the cathode and the electrochemically facilitated accretion of dissolved ions such as bicarbonate, they start to grow, some three to five times faster than normal and soon the reef takes on the appearance and utility of a natural reef ecosystem.
Shorelines are increasingly susceptible to beach erosion and loss due to climate change which is resulting in rising sea levels and increasingly frequent and more powerful storms. Large structures such as breakwaters constructed to reflect waves to prevent erosion are problematic and can in fact contribute to further beach erosion since for force of waves is doubled due to the reversal of the wave direction vector with the reflected wave carrying sand from the structure's base back out to sea resulting in the structure failing over time. [7]
Common electrified reef used for shore protection mimic the effect of a natural reef which prevent erosion by dissipating wave energy and causing waves to break before they impact the shore. In nature, large reefs, have been shown to dissipate up to 97% of their energy.[ citation needed ] They are based around the same open mesh frameworks as those used for coral restoration. Skeletons of dead coral and algae from the reef are then deposited and help grow beaches. [8] [9] [ dubious ] Because these reefs mimic the properties of natural reefs they solve some of the challenges they have in storm dissipation and their self-healing qualities helps structures survive extreme storms as long as the electricity supply remains in operation. [8]
In Turks and Caicos trials of electrified reefs of coastal protection survived the two worst hurricanes in the history of the islands, which occurred three days apart and damaged or destroyed 80% of the buildings on the island. Sand was observed to build up around the bases of the reef structure. [8] [ dubious ]
In Maldives in 1997, shore protection reefs helped save several buildings, including a hotel, that had risked washing away due to severe beach erosion. The 50-meter-long shore protection reef stabilized and ultimately reversed erosion in several years, even allowing the beach to survive a tsunami in 2004.[ citation needed ]
Electric reef projects had been installed in over 20 countries, in the Caribbean, Indian Ocean, Pacific and Southeast Asia. Projects are located in French Polynesia, Indonesia, Maldives, Mexico, Panama, Papua New Guinea, Seychelles, the Philippines, Thailand and on one of the most remote and unexplored reef areas of the world, the Saya de Malha Bank in the Indian Ocean. [5]
Indonesia has the most reef projects, with sites near over half a dozen islands, including the world's two largest reef restoration projects: Pemuteran with the Karang Lestari and the Gili islands with the Gili Eco Trust. [10]
Non-coral reef projects have been conducted in places such as Barataria Bay, Galveston, seagrasses in the Mediterranean, oyster reefs and salt marshes in New York City, in Port Aransas, and in St. Croix.[ citation needed ]
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Electrolysis of electric reefs enhances coral growth, reproduction and ability to resist environmental stress.[ citation needed ] Coral species typically found on healthy reefs gain a major advantage over the weedy organisms that often overgrow them on stressed reefs.
Biorock can enable coral growth and regrowth even in the presence of environmental stress such as rising ocean temperatures, diseases, and nutrient, sediment, and other types of pollution. Biorock represents the only known method that can sustain and grow natural coral species using only basic conducting elements, typically of a common metal such as steel.
The process accelerated growth on coral reefs by as much as fivefold and restoration of physical damage by as much as 20 times. [11] [12] and the rate of growth can be varied by altering the amount of current flowing into the structure.
In one study, Porites colonies with and without an electric field were compared for 6 months after which time the current to the electric reef was eliminated. Growth differences were significant only during the first 4 months with longitudinal growth being relatively high in the presence of the field. The treatment corals survived at a higher rate. [13]
On Vabbinfaru island in the Maldives, a 12-meter, 2 ton steel cage called the Lotus was secured on the sea floor. As of 2012, coral was so abundant on the structure that the cage is difficult to discern. The 1998 El Nino killed 98% of the reef around Vabbinfaru. Abdul Azeez, who led the Vabbinfaru project, said coral growth on the structure is up to five times that of elsewhere. A smaller prototype device was in place during the 1998 warming event and more than 80% of its corals survived, compared to just 2% elsewhere. [14] However, power is no longer supplied to the project, leaving it vulnerable to the next round of bleaching.[ citation needed ]
Electric reefs require electrical power to maintain them.[ citation needed ] In Maldives, several electric reefs successfully survived a 1998 bleaching event that killed off nearly all local wild coral, however after being depowered they were killed by the bleaching event of 2016. [8]
A study conducted in the Bahamas in 2015 showed that the electric field deterred sharks, specifically the bull shark and the Caribbean reef shark, from swimming and feeding in the area. The electric field is believed to affect sharks because of their electroreception abilities, however species with similar capabilities such as the bar jack and Bermuda chub did not appear to be affected by the electric field. [15]
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 groups.
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 waves, currents, tides, wind-driven water, waterborne ice, or other impacts of storms. The landward retreat of the shoreline can be measured and described over a temporal scale of tides, seasons, and other short-term cyclic processes. Coastal erosion may be caused by hydraulic action, abrasion, impact and corrosion by wind and water, and other forces, natural or unnatural.
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave erosion planing down rock outcrops. However, reefs such as the coral reefs of tropical waters are formed by biotic (living) processes, dominated by corals and coralline algae. Artificial reefs such as shipwrecks and other man-made underwater structures may occur intentionally or as the result of an accident, and are sometimes designed to increase the physical complexity of featureless sand bottoms to attract a more diverse range of organisms. Reefs are often quite near to the surface, but not all definitions require this.
A cay, also spelled caye or key, is a small, low-elevation, sandy island on the surface of a coral reef. Cays occur in tropical environments throughout the Pacific, Atlantic, and Indian oceans, including in the Caribbean and on the Great Barrier Reef and Belize Barrier Reef.
An artificial reef (AR) is a human-created freshwater or marine benthic structure. Typically built in areas with a generally featureless bottom to promote marine life, it may be intended to control erosion, protect coastal areas, block ship passage, block the use of trawling nets, support reef restoration, improve aquaculture, or enhance scuba diving and surfing. Early artificial reefs were built by the Persians and the Romans.
Thomas Fritz Goreau was a marine biologist who worked extensively on the coral reefs of Jamaica, and many other reefs in the Pacific, Caribbean, and Red Sea.
Thomas J. Goreau is a biogeochemist and marine biologist. He is the son of two other renowned marine biologists, Thomas F. Goreau and Nora I. Goreau.
The Saya de Malha Bank or Mesh Skirt Bank, is one of the largest submerged ocean banks in the world, a part of the vast undersea Mascarene Plateau.
Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply and 90% of habitable space on Earth. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats, seagrass meadows, mangroves, rocky intertidal systems, salt marshes, coral reefs, lagoons. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.
Reef Ball Foundation, Inc. is a 501(c)(3) non-profit organization that functions as an international environmental non-governmental organization. The foundation uses reef ball artificial reef technology, combined with coral propagation, transplant technology, public education, and community training to build, restore and protect coral reefs. The foundation has established "reef ball reefs" in 59 countries. Over 550,000 reef balls have been deployed in more than 4,000 projects.
A coral island is a type of island formed from coral detritus and associated organic material. It occurs in tropical and sub-tropical areas, typically as part of a coral reef which has grown to cover a far larger area under the sea. The term low island can be used to distinguish such islands from high islands, which are formed through volcanic action. Low islands are formed as a result of sedimentation upon a coral reef or of the uplifting of such islands.
Wolf Hartmut Hilbertz was a German-born futurist architect, inventor, and marine scientist. Notable contributions to science include the discovery of artificial mineral accretetion / biorock and its use to create electrified reefs.
Coastal engineering is a branch of civil engineering concerned with the specific demands posed by constructing at or near the coast, as well as the development of the coast itself.
Biorock is a cement-like engineering material formed when a small electric current is passed between underwater metal electrodes placed in seawater causing dissolved minerals to accrete onto the cathode to form a thick layer of limestone. This 'accretion process' can be used to create building materials or to create artificial 'electrified reefs' for the benefit of corals and other sea-life. Discovered by Wolf Hilbertz in 1976, biorock was protected by patents and a trademark which have now expired.
Coral reef protection is the process of modifying human activities to avoid damage to healthy coral reefs and to help damaged reefs recover. The key strategies used in reef protection include defining measurable goals and introducing active management and community involvement to reduce stressors that damage reef health. One management technique is to create Marine Protected Areas (MPAs) that directly limit human activities such as fishing.
The Maldives, officially the Republic of Maldives, is a small archipelagic state in South Asia. It lies in the Indian Ocean southwest of Sri Lanka and India, about 700 kilometres (430 mi) from the Asian continent's mainland. The chain of 26 atolls stretches across the Equator from Ihavandhippolhu Atoll in the north to Addu Atoll in the south. The land area is roughly 298 square kilometres. Malé is the capital.
A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.
Gili Eco Trust is a local non governmental organization created in 2000 to protect coral reefs from destructive fishing around the three Gili Islands, off Lombok, Indonesia.
Coral aquaculture, also known as coral farming or coral gardening, is the cultivation of corals for commercial purposes or coral reef restoration. Aquaculture is showing promise as a tool for restoring coral reefs, which are dying off around the world. The process protects young corals while they are most at risk of dying. Small corals are propagated in nurseries and then replanted on the reef.
Coral reef restoration strategies use natural and anthropogenic processes to restore damaged coral reefs. Reefs suffer damage from a number of natural and man-made causes, and efforts are being made to rectify the damage and restore the reefs. This involves the fragmentation of mature corals, the placing of the living fragments on lines or frames, the nurturing of the fragments as they recover and grow, and the transplantation of the pieces into their final positions on the reef when they are large enough.
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