![Manta ray Biorock reef](https://upload.wikimedia.org/wikipedia/commons/9/99/Manta_ray_Biorock_reef.jpg)
An electric reef (also electrified reef) is an
artificial reef
An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing.
Many ...
made from
biorock, being
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
that forms rapidly in
seawater
Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...
on a metal structure from dissolved
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
s 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.
History
Artificial reefs
An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing.
Many re ...
have been built since the 1950s using materials including sunken ships, 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.
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 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 groups.
C ...
s during the 1980s. Using the name "Seacrete", the process was publicised in the 1992
futurology
Futures studies, futures research, futurism or futurology is the systematic, interdisciplinary and holistic study of social and technological advancement, and other environmental trends, often for the purpose of exploring how people will li ...
book titled
The Millennial Project.
With others, Hilbertz and Goreau made expeditions to the
Saya de Malha
The Saya de Malha Bank (also the Sahia de Malha Bank, modern Portuguese: ''saia de malha'', English: ''mesh skirt'') or Mesh Skirt Bank, is one of the largest submerged ocean banks in the world, a part of the vast undersea Mascarene Plateau.
...
bank in 1997 and 2002 where they grew an
artificial island
An artificial island is an island that has been constructed by people rather than formed by natural means. Artificial islands may vary in size from small islets reclaimed solely to support a single pillar of a building or structure to those th ...
around steel structures anchored to the sea floor using this process. In the
Maldives
Maldives (, ; dv, ދިވެހިރާއްޖެ, translit=Dhivehi Raajje, ), officially the Republic of Maldives ( dv, ދިވެހިރާއްޖޭގެ ޖުމްހޫރިއްޔާ, translit=Dhivehi Raajjeyge Jumhooriyyaa, label=none, ), is an archipelag ...
, 80% of the electric reefs survived the 1998 warming which killed 95% of the natural reef corals.
Goreau continued the work after Hilbertz's death in 2007. By 2011 there were electric reef projects installed in over 20 countries.
In 2012, both Goreau and Robert K. Trench published works on how the process could generate building materials as well as restore damaged ecosystems.
Construction process
![Biorock Reef Indonesia](https://upload.wikimedia.org/wikipedia/commons/7/70/Biorock_Reef_Indonesia.jpg)
The base of an electrified reef is a welded electrically conductive frame, often made from construction grade
rebar or
wire mesh
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm
A wire is a flexible strand of metal.
Wire is co ...
which submerged and attached to the seafloor to which an
electrical field
An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field f ...
applied. The frame (
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in wh ...
) and a much smaller metal plate (
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic ...
) placed at a suitable distance from the frame initiates the electrolytic reaction.
Dissolved
calcium carbonate and
magnesium hydroxide
Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk ...
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 which 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
Diver or divers may refer to:
*Diving (sport), the sport of performing acrobatics while jumping or falling into water
*Practitioner of underwater diving, including:
**scuba diving,
**freediving,
**surface-supplied diving,
**saturation diving, a ...
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
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
.
As shore protection
Shorelines are increasingly susceptible to
beach erosion and loss due to
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
which is resulting in rising sea levels and increasingly frequent and more powerful storms. Large structures such as
breakwaters
A breakwater is a permanent structure constructed at a coastal area to protect against tides, currents, waves, and storm surges. Part of a coastal management system, breakwaters are installed to minimize erosion, and to protect anchorages, h ...
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.
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. 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.
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.
In
Turks and Caicos
The Turks and Caicos Islands (abbreviated TCI; and ) are a British Overseas Territory consisting of the larger Caicos Islands and smaller Turks Islands, two groups of tropical islands in the Lucayan Archipelago of the Atlantic Ocean and n ...
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.
In
Maldives
Maldives (, ; dv, ދިވެހިރާއްޖެ, translit=Dhivehi Raajje, ), officially the Republic of Maldives ( dv, ދިވެހިރާއްޖޭގެ ޖުމްހޫރިއްޔާ, translit=Dhivehi Raajjeyge Jumhooriyyaa, label=none, ), is an archipelag ...
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
A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...
in 2004.
Distribution
![Biorock](https://upload.wikimedia.org/wikipedia/commons/c/ca/Biorock.jpg)
Electric reef projects had been installed in over 20 countries, in the
Caribbean,
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...
,
Pacific
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
and
Southeast Asia
Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...
. Projects are located in
French Polynesia,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
,
Maldives
Maldives (, ; dv, ދިވެހިރާއްޖެ, translit=Dhivehi Raajje, ), officially the Republic of Maldives ( dv, ދިވެހިރާއްޖޭގެ ޖުމްހޫރިއްޔާ, translit=Dhivehi Raajjeyge Jumhooriyyaa, label=none, ), is an archipelag ...
,
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
,
Panama
Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Co ...
,
Papua New Guinea
Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
,
Seychelles
Seychelles (, ; ), officially the Republic of Seychelles (french: link=no, République des Seychelles; Creole: ''La Repiblik Sesel''), is an archipelagic state consisting of 115 islands in the Indian Ocean. Its capital and largest city, ...
, the
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
,
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
and on one of the most remote and unexplored reef areas of the world, the
Saya de Malha Bank
The Saya de Malha Bank (also the Sahia de Malha Bank, modern Portuguese: ''saia de malha'', English: ''mesh skirt'') or Mesh Skirt Bank, is one of the largest submerged ocean banks in the world, a part of the vast undersea Mascarene Plateau.
...
in the Indian Ocean.
[
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
The Gili Islands ( id, Tiga Gili hree Gilis Kepulauan Gili ili Islands are an archipelago of three small islands or Gili island triplets — Gili Trawangan, Gili Meno and Gili Air — just off the northwest coast of Lombok, Indones ...
with the Gili Eco Trust.
Non-coral reef projects have been conducted in places such as Barataria Bay
Barataria Bay (french: Baie de Barataria), also Barrataria Bay, is a bay of the Gulf of Mexico, about 15 miles (24 km) long and 12 miles (19 km) wide, in southeastern Louisiana, in Jefferson Parish and Plaquemines Parish, United Stat ...
, Galveston
Galveston ( ) is a coastal resort city and port off the Southeast Texas coast on Galveston Island and Pelican Island in the U.S. state of Texas. The community of , with a population of 47,743 in 2010, is the county seat of surrounding Ga ...
, seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...
es in the Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...
, oyster reefs and salt marsh
A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is domin ...
es in New York City
New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the Un ...
, in Port Aransas
Port Aransas ( ) is a city in Nueces County, Texas, United States. This city is 180 miles southeast of San Antonio. The population was 2,904 at the 2020 census. Port Aransas is the only established town on Mustang Island. It is located north of ...
, and in St. Croix
Saint Croix; nl, Sint-Kruis; french: link=no, Sainte-Croix; Danish and no, Sankt Croix, Taino: ''Ay Ay'' ( ) is an island in the Caribbean Sea, and a county and constituent district of the United States Virgin Islands (USVI), an unincor ...
.
Effectiveness
Electrolysis of electric reefs enhances coral growth, reproduction and ability to resist environmental stress. 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
Stress, either physiological, biological or psychological, is an organism's response to a stressor such as an environmental condition. Stress is the body's method of reacting to a condition such as a threat, challenge or physical and psych ...
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 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 groups.
C ...
s by as much as fivefold and restoration of physical damage by as much as 20 times. and the rate of growth can be varied by altering the amount of current flowing into the structure.
In one study, ''Porites
''Porites'' is a genus of stony coral; they are small polyp stony (SPS) corals. They are characterised by a finger-like morphology. Members of this genus have widely spaced calices, a well-developed wall reticulum and are bilaterally symmetr ...
'' 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.
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
EL, El or el may refer to:
Religion
* El (deity), a Semitic word for "God"
People
* EL (rapper) (born 1983), stage name of Elorm Adablah, a Ghanaian rapper and sound engineer
* El DeBarge, music artist
* El Franco Lee (1949–2016), American po ...
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. However, power is no longer supplied to the project, leaving it vulnerable to the next round of bleaching.
Drawbacks
Electric reefs require electrical power to maintain them. 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.
A study conducted in the Bahamas in 2015 showed that the electric field deterred sharks, specifically the bull shark
The bull shark (''Carcharhinus leucas''), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in ri ...
and the Caribbean reef shark, from swimming and feeding in the area. The electric field is believed to affect sharks because of their electroreception
Electroreception and electrogenesis are the closely-related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to st ...
abilities, however species with similar capabilities such as the bar jack
The bar jack (''Caranx ruber''), also known as the carbonero, red jack, blue-striped cavalla or passing jack, is a common species of inshore marine fish classified in the jack family, Carangidae. The bar jack is distributed through the western ...
and Bermuda chub did not appear to be affected by the electric field.
See also
* Gili Eco Trust
References
Further reading
"Changes in zooxanthellae density, morphology, and mitotic index in hermatypic corals and anemones exposed to cyanide", 2003
Goreau + Hilbertz: "Marine Ecosystem Restoration: Costs and benefits for coral reefs", World Resource Review, 2005
Vaccarella, R. + Goreau: "Applicazione della elettrodeposizione nel recupero die mattes di Posidonia oceanica", 2008
Goreau + Hilbertz, "Bottom-Up Community-Based Coral Reef and Fisheries Restoration in Indonesia, Panama, and Palau", 2008
* [https://web.archive.org/web/20110519062940/http://www.globalcoral.org/Suitability%20of%20mineral%20accretion.pdf Strömberg + Lundälv + Goreau: "Suitability of Mineral Accretion as a Rehabilitation Method for Cold-Water Coral Reefs", 2010]
"Effect of severe hurricanes on Biorock Coral Reef Restoration Projects in Grand Turk, Turks and Caicos Islands", 2010
Goreau, T. J.: "Coral Reef and Fisheries Habitat Restoration in the Coral Triangle", Indonesia 2010
*
External links
Wolf Hilbertz website
* {{Cite web, url=https://newheavendiveschool.com/blog/66-a-new-future-in-electric-coral-reefs, title=A New Future in Electric Coral Reefs, work=New Heaven Diving School, date=23 August 2015
Global Coral Reef Alliance
Biorock.net
CCell
Supplier of equipment
Marine biology