The habitat of deep water corals, also known as cold water corals, extends to deeper, darker parts of the oceans than tropical corals

Coral

Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

, ranging from near the surface to the abyss

Abyssal zone

The abyssal zone is the abyssopelagic layer or pelagic zone that contains the very deep benthic communities near the bottom of oceans. "Abyss" derives from the Greek word ἄβυσσος, meaning bottomless. At depths of 4,000 to 6,000 metres , this zone remains in perpetual darkness and never receives...

, beyond 2000 metres (6,561.7 ft) where water temperatures may be as cold as 4°C. Deep water corals belong to the Phylum Cnidaria

Cnidaria

Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

 and are most often stony corals

Scleractinia

Scleractinia, also called stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton. They first appeared in the Middle Triassic and replaced tabulate and rugose corals that went extinct at the end of the Permian...

, but also include black and horny corals and soft corals

Alcyonacea

The Alcyonacea, or the soft corals are an order of corals which do not produce calcium carbonate skeletons. Soft corals contain minute, spiny skeletal elements called sclerites. Aside from their scientific utility in species identification, sclerites give these corals some degree of support and...

 including the Gorgonians (sea fans). Like tropical corals, they provide habitat to other species, but deep water coral do not require zooxanthellae to survive.

While there are nearly as many species of deep–water corals as shallow-water species, only a few deep-water species develop traditional reefs. Instead, they form aggregations called patches, banks, bioherms, massifs, thickets or groves. These aggregations are often referred to as "reefs," but differ structurally and functionally. Deep sea reefs are sometimes referred to as "mounds," which more accurately describes the large calcium carbonate skeleton that is left behind as a reef grows and corals below die off, rather than the living habitat and refuge that deep sea corals provide for fish and invertebrates. Mounds may or may not contain living deep sea reefs.

Submarine communications cable

Submarine communications cable

A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean....

s and fishing methods such as bottom trawling

Bottom trawling

Bottom trawling is trawling along the sea floor. It is also often referred to as "dragging".The scientific community divides bottom trawling into benthic trawling and demersal trawling...

 tend to break corals apart and destroy reefs. The deep water habitat is designated as a United Kingdom Biodiversity Action Plan

United Kingdom Biodiversity Action Plan

The United Kingdom Biodiversity Action Plan is the governmental response to the Convention on Biological Diversity signed in 1992. When the Biodiversity Action Plans were first published in 1994, the conservation of 391 species and 45 habitats was covered. 1,150 species and 65 habitats are...

 habitat.

Discovery and study

Deep water corals are enigmatic because they construct their reefs in deep, dark, cool waters at high latitudes, such as Norway’s Continental Shelf

Continental shelf

The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...

. They were first discovered by fishermen about 250 years ago, which garnered interest from scientists. Early scientists were unsure how the reefs sustained life in the seemingly barren and dark conditions of the northerly latitudes. It was not until modern times, when manned mini-submarines first reached sufficient depth, that scientists began to understand these organisms. Pioneering work by Wilson (1979) shed light on a colony on the Porcupine Bank

Porcupine Bank

Porcupine Bank is an area of the Irish shelf approximately west of Ireland. The relatively raised area of seabed lies between the deep-water Porcupine Seabight and Rockall Trough....

, off Ireland. The first ever live video of a large deep-water coral reef was obtained in July, 1982, when Statoil

Statoil

Statoil ASA is a Norwegian petroleum company established in 1972. It merged with Norsk Hydro in 2007 and was known as StatoilHydro until 2009, when the name was changed back to Statoil ASA. The brand Statoil was retained as a chain of fuel stations owned by StatoilHydro...

 surveyed a 15 metres (49.2 ft) tall and 50 metres (164 ft) wide reef perched at 280 metres (918.6 ft) water depth near Fugløy Island, north of the Polar Circle

Polar circle

A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is located at a latitude of  N, and the Antarctic Circle is located at a latitude of  S....

, off northern Norway.

During their survey of the Fugløy reef, Hovland and Mortensen also found seabed pockmark

Pockmark

Pockmark may refer to:*acne scarring — resulting from acne or infections such as chicken pox* the scarring of smallpox*Pockmark — a geological formation...

 craters near the reef. Since then, hundreds of large deep-water coral reefs have been mapped and studied. About 60 percent of the reefs occur next to or inside seabed pockmarks. Because these craters are formed by the expulsion of liquids and gases (including methane

Methane

Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

), several scientists hypothesize that there may be a link between the existence of the deep-water coral reefs and nutrients seepage (light hydrocarbon

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

s, such as methane, ethane

Ethane

Ethane is a chemical compound with chemical formula C2H6. It is the only two-carbon alkane that is an aliphatic hydrocarbon. At standard temperature and pressure, ethane is a colorless, odorless gas....

, and propane

Propane

Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...

) through the seafloor. This hypothesis is called the 'hydraulic theory' for deep-water coral reefs.

Lophelia communities support diverse marine life, such as sponges, polychaete worms, mollusks, crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, brittle star

Brittle star

Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...

s, starfish

Sea star

Starfish or sea stars are echinoderms belonging to the class Asteroidea. The names "starfish" and "sea star" essentially refer to members of the class Asteroidea...

, sea urchin

Sea urchin

Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

s, bryozoans, sea spider

Sea spider

Sea spiders, also called Pantopoda or pycnogonids, are marine arthropods of class Pycnogonida. They are cosmopolitan, found especially in the Mediterranean and Caribbean Seas, as well as the Arctic and Antarctic Oceans. There are over 1300 known species, ranging in size from to over in some deep...

s, fish and many other vertebrate and invertebrate species.

The first international symposium for deep water corals took place in Halifax, Canada in 2000. The symposium considered all aspects of deep water corals, including protection methods.

In June 2009, Living Oceans Society led the Finding Coral Expedition on Canada’s Pacific coast in search of deep sea corals. Using one person submarines, a team of international scientists made 30 dives to depths of over 500 meters and saw giant coral forests, darting schools of fish, and a seafloor carpeted in brittle star

Brittle star

Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...

s. During expedition, scientists identified 16 species of corals. This research trip was the culmination of five years of work to secure protection from the Canadian Government for these slow-growing and long-lived animals, which provide critical habitat for fish and other marine creatures.

Taxonomy

Corals are animal

Animal

Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s in the Phylum

Phylum

In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

 Cnidaria

Cnidaria

Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...

 and the class Anthozoa

Anthozoa

Anthozoa is a class within the phylum Cnidaria that contains the sea anemones and corals. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows...

. Anthozoa is broken down into two subclasses Octocorals

Alcyonaria

Octocorallia is a subclass of Anthozoa comprising ~3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians within three orders: Alcyonacea, Helioporacea, and Pennatulacea...

 (Alcyonaria) and Hexacorals

Zoantharia

Zoanthids are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine environments around the world. These animals come in a variety of different colonizing formations and in numerous colors...

 (Zoantharia). Octocorals are soft corals such as sea pen

Sea pen

Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide...

s. Hexacorals include sea anemones and hard bodied corals. Octocorals contain eight body extensions while Hexacorals have six. Most deep water corals are stony corals.

Distribution

Deep water coral are widely distributed within the earth’s oceans, with large reefs/beds in the far North and far South Atlantic, as well as in the tropics in places such as the Florida coast. In the north Atlantic, the principal coral species that contribute to reef formation are Lophelia pertusa, Oculina varicosa, Madrepora oculata, Desmophyllum cristagalli, Enallopsammia rostrata, Solenosmilia variabilis, and Goniocorella dumosa. Four genera (Lophelia, Desmophyllum, Solenosmilia, and Goniocorella) constitute most deep-water coral banks at depths of 400–700 m (1,312.3–2,296.6 ft)

Madrepora oculata occurs as deep as 2,020 m and is one of a dozen species that occur globally and in all oceans, including the Subantarctic (Cairns, 1982). Colonies of Enallopsammia contribute to the framework of deep-water coral banks found at depths of 600 to 800 m in the Straits of Florida (Cairns and Stanley, 1982).

Lophelia pertusa distribution

One of the most common species, Lophelia pertusa

Lophelia pertusa

Lophelia pertusa is a species of cold-water coral which grows in the deep waters throughout the North Atlantic ocean, as well as parts of the Caribbean Sea and Alboran Sea. L...

, lives in the Northeast and Northwest Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 and off Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

’s west coast.

In addition to ocean bottoms, scientists find Lophelia colonies on North Sea oil installations, although oil and gas production may introduce noxious substances into the local environment.

The world's largest known deep-water Lophelia coral complex is the Røst Reef. It lies between 300 and 400 m (984.3 and 1,312.3 ft) deep, west of Røst

Røst

Røst is a municipality in Nordland county, Norway. It is part of the Lofoten traditional region. The administrative centre of the municipality is the village of Røst. Røst was separated from the municipality of Værøy on 1 July 1928.- Environment :...

 island in the Lofoten

Lofoten

Lofoten is an archipelago and a traditional district in the county of Nordland, Norway. Though lying within the Arctic Circle, the archipelago experiences one of the world's largest elevated temperature anomalies relative to its high latitude.-Etymology:...

 archipelago, in Norway, inside the Arctic Circle. Discovered during a routine survey in May 2002, the reef is still largely intact. It is approximately 40 kilometres (24.9 mi) long by 3 kilometres (1.9 mi) wide.

Some 500 km further south is the Sula Reef, located on the Sula Ridge, west of Trondheim

Trondheim

Trondheim , historically, Nidaros and Trondhjem, is a city and municipality in Sør-Trøndelag county, Norway. With a population of 173,486, it is the third most populous municipality and city in the country, although the fourth largest metropolitan area. It is the administrative centre of...

 on the mid-Norwegian Shelf, at 200–300 m (656.2–984.3 ft). It is 13 kilometres (8.1 mi) long, 700 metres (2,296.6 ft)wide, and up to 700 metres (2,296.6 ft) high an area one-tenth the size of the 100 square kilometre Røst Reef.

Discovered and mapped in 2002, Norway's 1,000-year-old and 2 kilometres (1.2 mi) long Tisler Reef lies in the Skagerrak

Skagerrak

The Skagerrak is a strait running between Norway and the southwest coast of Sweden and the Jutland peninsula of Denmark, connecting the North Sea and the Kattegat sea area, which leads to the Baltic Sea.-Name:...

 -- the submarine border between Norway and Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 at a depth of 74–155 m (242.8–508.5 ft). The Tisler Reef contains the world’s only known yellow L. pertusa.
Elsewhere in the northeastern Atlantic, Lophelia is found around the Faroe Islands

Faroe Islands

The Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...

, an island group between the Norwegian Sea

Norwegian Sea

The Norwegian Sea is a marginal sea in the North Atlantic Ocean, northwest of Norway. It is located between the North Sea and the Greenland Sea and adjoins the North Atlantic Ocean to the west and the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a...

 and the Northeast Atlantic Ocean. At depths from 200 to 500 m (656.2 to 1,640.4 ft), L. pertusa is chiefly on the Rockall Bank and on the shelf break north and west of Scotland.
The Porcupine Seabight

Porcupine Seabight

The Porcupine Seabight is a deep-water basin in the Porcupine Bank in the northeastern Atlantic Ocean. It lies southwest of Ireland and is approximately 180 nautical miles by 100 nautical miles . The feature is shaped roughly like an amphitheatre with the deepest point lying to the southwest...

, the southern end of the Rockall Bank, and the shelf to the northwest of Donegal

Donegal

Donegal or Donegal Town is a town in County Donegal, Ireland. Its name, which was historically written in English as Dunnagall or Dunagall, translates from Irish as "stronghold of the foreigners" ....

 all exhibit large, mound-like Lophelia structures. One of them, the Therese Mound, is particularly noted for its Lophelia pertusa and Madrepora oculata colonies. Lophelia reefs are also found along the U.S. East Coast at depths of 500–850 m (1,640.4–2,788.7 ft) along the base of the Florida-Hatteras slope. South of Cape Lookout

Cape Lookout

Cape Lookout can refer to:*Cape Lookout , in the United States*Cape Lookout , in the United States*Cape Lookout...

, NC, rising from the flat sea bed of the Blake Plateau, is a band of ridges capped with thickets of Lophelia. These are the northernmost East Coast Lophelia pertusa growths. The coral mounds and ridges here rise as much as 150 metres (492.1 ft) from the plateau plain. These Lophelia communities lie in unprotected areas of potential oil and gas exploration and cable-laying operations, rendering them vulnerable to future threats.

Lophelia exist around the Bay of Biscay, the Canary Islands, Portugal, Madeira, the Azores, and the western basin of the Mediterranean Sea.

Darwin Mounds

Among the most researched deep-water coral areas in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 are the Darwin Mounds

Darwin Mounds

Darwin Mounds describes a vast field of undersea sand mounds situated off the north west coast of Scotland, first discovered in May 1998, they provide a unique habitat for ancient deep water coral reefs...

. Atlantic Frontier Environmental Network (AFEN) discovered them in 1998 while conducting large-scale regional sea floor surveys north of Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

. They discovered two areas of hundreds of sand and deep-water coral mounds at depths of about 1000 metres (3,280.8 ft) in the northeast corner of the Rockall Trough, approximately 185 kilometres (115 mi) northwest of the northwest tip of Scotland. Named after the research vessel Charles Darwin, the Darwin Mounds have been extensively mapped using low-frequency side-scan sonar. They cover an area of approximately 100 square kilometre and consist of two main fields—the Darwin Mounds East, with about 75 mounds, and the Darwin Mounds West, with about 150 mounds. Other mounds are scattered in adjacent areas. Each mound is about 100 metres (328.1 ft) in diameter and 5 metres (16.4 ft) high. Lophelia corals and coral rubble cover the mound tops, attracting other marine life. The mounds look like 'sand volcanoes', each with a 'tail', up to several hundred meters long, all oriented downstream.
Large congregations of Xenophyophores (Syringammina fragilissima

Syringammina fragilissima

Syringammina fragilissima is a xenophyophore found off the coast of Scotland, near Rockall. It is the largest single-celled organism known, at up to across...

) which are giant unicellular organisms that can grow up to 25 centimetres (9.8 in) in diameter characterize the tails and mounds. Scientists are uncertain why these organisms congregate here. The Darwin Mounds Lophelia grow on sand rather than hard substrate, unique to this area.
Lophelia corals exist in Irish waters as well.

Oculina varicosa distribution

Oculina varicosa is a branching ivory coral that forms giant but slow-growing, bushy thickets on pinnacles up to 30 metres (98.4 ft) in height. The Oculina Banks, so named because they consist mostly of Oculina varicosa, exist in 50–100 m (164–328.1 ft) of water along the continental shelf edge about 26-50 mi off of Florida's central east coast.

Discovered in 1975 by scientists from the Harbor Branch Oceanographic Institution conducting surveys of the continental shelf, Oculina thickets grow on a series of pinnacles and ridges extending from Fort Pierce to Daytona, Florida
Like the Lophelia thickets, the Oculina Banks host a wide array of macroinvertebrates and fishes. They are significant spawning grounds for commercially important food species including gag

Gag

A gag is usually a device designed to prevent speech, often as a restraint device to stop the subject from calling for help. This is usually done by blocking the mouth, partially or completely, or attempting to prevent the tongue, lips, or jaw from moving in the normal patterns of speech. They are...

, scamp

Scamp

Scamp may refer to:* Summercamp Music Festival,* A mischievous perhaps roguish person, especially a playful, impish youngster.* Scamp , a Disney cartoon puppy...

, red grouper

Red grouper

The red grouper is a species of fish in the Serranidae family. It is found in Anguilla, Antigua and Barbuda, Aruba, the Bahamas, Barbados, Belize, Bermuda, Brazil, Cayman Islands, Colombia, Costa Rica, Cuba, Dominica, the Dominican Republic, French Guiana, Grenada, Guadeloupe, Guatemala, Guyana,...

, speckled hind, black sea bass

Black sea bass

The black sea bass is an exclusively marine fish. It is a type of Grouper found more commonly in northern than in southern ranges.It inhabits the coasts from Maine to NE Florida and the eastern Gulf of Mexico....

, red porgy

Red porgy

The red porgy , or common seabream, is a species of fish in the family Sparidae. Although found in a wide variety of locations that range from Europe to the Caribbean, its status is considered endangered. Also known along the Gulf Coast as White Snapper, even though it is not a true...

, rock shrimp, and calico scallop.

Growth and reproduction

Corals must attach to a hard surface in order to begin growing. They are often found growing along bathymetric

Bathymetry

Bathymetry is the study of underwater depth of lake or ocean floors. In other words, bathymetry is the underwater equivalent to hypsometry. The name comes from Greek βαθύς , "deep", and μέτρον , "measure"...

 highs such as seamounts, ridges, pinnacles and mounds, on hard surfaces. Corals are sedentary, so they must live near nutrient-rich water currents. Deep water corals feed on zooplankton

Zooplankton

Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...

 and rely on ocean currents to bring food. The currents also aid in cleaning the corals.

Deep water corals grow more slowly than tropical corals because there are no zooxanthellae to feed them. Lophelia has a linear polyp extension of about 10 millimetre (0.393700787401575 in) per year. By contrast, branching shallow-water corals, such as Acropora

Acropora

Acropora is a genus of scleractinian coral in the Phylum Cnidaria. Some of its species are known as table coral, elkhorn coral and staghorn coral. There are currently 149 described species...

, may exceed 10–20 cm/yr. Reef structure growth estimates are about 1 millimetre (0.0393700787401575 in) per year. Scientists have also found Lophelia colonies on oil installations in the North Sea. Using coral age-dating methods, scientists have estimated that some living deep-water corals date back at least 10,000 years.

Deep water corals use nematocysts on their tentacles to stun prey. Deep water corals feed on zooplankton

Zooplankton

Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...

, crustaceans and even krill

Krill

Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...

.

Coral can reproduce sexually

Sexual reproduction

Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...

 or asexually

Asexual reproduction

Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...

. In asexual reproduction (budding) a polyp divides in two genetically identical pieces. Sexual reproduction requires that a sperm fertilize an egg which grows into larva. Currents then disperse the larvae. Growth begins when the larvae attach to a solid substrate. Old/dead coral provides an excellent substrate for this growth, creating ever higher mounds of coral. As new growth surrounds the original, the new coral intercepts both water flow and accompanying nutrients, weakening and eventually killing the older organisms.

Individual Lophelia pertusa

Lophelia pertusa

Lophelia pertusa is a species of cold-water coral which grows in the deep waters throughout the North Atlantic ocean, as well as parts of the Caribbean Sea and Alboran Sea. L...

colonies are entirely either female or male.

Deep water coral colonies range in size from small and solitary to large, branching tree-like structures. Larger colonies support many life forms, while nearby areas have much less. The gorgonian, Paragorgia arborea, may grow beyond three meters. However, little is known of their basic biology, including how they feed or their methods and timing of reproduction.

Importance

Lophelia reefs can host up to 1,300 species of fish and invertebrates. Fish aggregate on deep sea reefs that is precisely why, as one scientist puts it, “fishermen
trawl them.” Deep sea corals, sponges and other habitat-forming animals provide protection from currents and predators, nurseries for young fish, and feeding, breeding and spawning areas for numerous fish and shellfish species. Rockfish, Atka mackerel, walleye pollock, Pacific cod, Pacific halibut, sablefish, flatfish, crabs, and other economically important species in the North Pacific inhabit these areas. Eighty-three percent of the rockfish found in one study were associated with red tree coral. Flatfish, walleye pollock and Pacific cod appear to be more commonly caught around soft corals. Dense schools of female redfish heavy with young have been observed on Lophelia reefs off Norway, suggesting the reefs are breeding or nursery areas for some species. Oculina reefs are important spawning habitat for several grouper species, as well as other fishes.

Human impact

The primary human impact on deep water corals is from deep water trawling. Trawlers

Trawling

Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl....

 drag nets across the ocean floor, disturbing sediments, breaking and destroying deep water corals. Another harmful method is long line fishing.

Oil and gas exploration also damage deep water coral.

Deep water corals grow slowly, so recovery takes much longer than in shallow waters where nutrients and food-providing zooxanthellae are far more abundant.

In a study during 2001 to 2003, a study of a reef of Lophelia pertusa in the Atlantic off Canada found that the corals were often broken in unnatural ways. And the ocean floor displayed scars and overturned boulders from trawling.

Oculina Banks

Bottom trawling and natural causes like bioerosion and episodic die-offs have reduced much of Florida's Oculina Banks to rubble, drastically reducing a once-substantial fishery by destroying spawning grounds.

In 1980, Harbor Branch Oceanographic Institution scientists called for protective measures. In 1984, the South Atlantic Fishery Management Council (SAFMC) designated a 315 square kilometre area as a Habitat Area of Particular Concern. In 1994, an area called the Experimental Oculina Research Reserve

Experimental Oculina Research Reserve

The Experimental Oculina Research Reserve preserves the Oculina Banks, a reef of ivory bush coral off the coast of Fort Pierce, Florida. Oculina varicosa is a U.S. National Marine Fisheries Service species of concern. Species of concern are those species about which the U.S...

 was completely closed to bottom fishing. In 1996, the SAFMC prohibited fishing vessels from dropping anchors, grapples, or attached chains there. In 1998, the council also designated the reserve as an Essential Fish Habitat. In 2000, the deep-water Oculina Marine Protected Area was extended to 1029 square kilometre. Scientists recently deployed concrete reef balls in an attempt to provide habitat for fish and coral.

Sula and Røst

Scientists estimate that trawling has damaged or destroyed 30 to 50 percent of the Norwegian shelf coral area. The International Council for the Exploration of the Sea

International Council for the Exploration of the Sea

The International Council for the Exploration of the Sea is the world’s oldest intergovernmental science organization. ICES is headquartered in Copenhagen, Denmark, where its multinational Secretariat staff of 51 provide scientific, administrative and secretarial support to the ICES community...

, the European Commission

European Commission

The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....

’s main scientific advisor on fisheries and environmental issues in the northeast Atlantic, recommend mapping and closing Europe’s deep corals to fishing trawlers.

In 1999, the Norwegian Ministry of Fisheries closed an area of 1000 square kilometre at Sula, including the large reef, to bottom trawling. In 2000, an additional area closed, covering about 600 square kilometre. An area of about 300 square kilometre enclosing the Røst Reef, closed in 2002.

Darwin mounds

The European Commission introduced an interim trawling ban in the Darwin Mounds area, in August 2003. A permanent ban is expected to follow.

External references

• http://www.findingcoral.com
• http://www.martinhovland.com/
• http://www.lophelia.org/
• http://www.martinhovland.com
• http://news.nationalgeographic.com/news/2006/05/0501_060501_coral.html. National Geographic. Retrieved on 2008-March-30.
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