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Deep-water coral

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Title: Deep-water coral  
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Deep-water coral

Deep-water coral photographed near East Timor

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

  • Deep-sea Corals overview on the Smithsonian Ocean Portal
  • Lophelia.org, a website devoted to the cold-water coral habitats from Heriot-Watt University in Edinburgh, Scotland
  • Deep Sea Corals: Out of Sight, But No Longer Out of Mind report on deep sea corals around the world from Oceana
  • Deep-Sea Corals at the NOAA Habitat Conservation Program
  • Deep-sea Corals at the Woods Hole Oceanographic Institution

External links

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  10. ^ Hovland and Risk, 2003
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  13. ^ a b
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  15. ^ Guihen, D., White, M., and Lundälv, T. (2012). Temperature shocks and ecological implications at a cold-water coral reef. Marine Biodiversity Records 5: 1-10.
  16. ^ Wisshak, M. and Ruggeberg, A. (2006). Colonisation and bioerosion of experimental substrates by benthic foraminiferans from euphotic to aphotic depths (Kosterfjord, SW Sweden). Facies 52: 1–17.
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  29. ^ [1]

References

See also

The European Commission introduced an interim trawling ban in the Darwin Mounds area, in August 2003. A permanent ban is expected to follow [26].

Darwin mounds

In 1999, the Norwegian Ministry of Fisheries closed an area of 1,000 square kilometres (390 sq mi) at Sula, including the large reef, to bottom trawling. In 2000, an additional area closed, covering about 600 square kilometres (230 sq mi). An area of about 300 square kilometres (120 sq mi) enclosing the Røst Reef, closed in 2002.[1]

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, the European Commission’s main scientific advisor on fisheries and environmental issues in the northeast Atlantic, recommend mapping and closing Europe’s deep corals to fishing trawlers.[1]

Sula and Røst

In 1980, Harbor Branch Oceanographic Institution scientists called for protective measures. In 1984, the South Atlantic Fishery Management Council (SAFMC) designated a 315 square kilometres (122 sq mi) area as a Habitat Area of Particular Concern. In 1994, an area called the Experimental Oculina Research Reserve 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 1,029 square kilometres (397 sq mi). Scientists recently deployed concrete reef balls in an attempt to provide habitat for fish and coral.

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.[23]

Oculina Banks

In addition to these managed pressures, deep water coral reefs are also vulnerable to unmanaged pressures (e.g. ocean acidification) and in order to protect these habitats in the long-term methods which assess the relative risks of different pressures are being promoted.[29]

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.

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

Oil and gas exploration also damage deep-water coral.

The primary human impact on deep-water corals is from deep-water trawling. Trawlers drag nets across the ocean floor, disturbing sediments, breaking and destroying deep-water corals. Another harmful method is long line fishing.

Human impact

Deep sea corals together with other habitat-forming organisms hosts a rich fauna of associated organisms.[28] Lophelia reefs can host up to 1,300 species of fish and invertebrates. Various fish aggregate on deep sea reefs. 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.

Photo of crab suspending itself by gripping a branching coral colony
A squat lobster living on a Lophelia reef

Importance

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.[27] However, little is known of their basic biology, including how they feed or their methods and timing of reproduction.

Individual Lophelia pertusa colonies are entirely either female or male.

Coral can reproduce sexually or asexually. 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.

Deep-water corals use nematocysts on their tentacles to stun prey. Deep-water corals feed on zooplankton, crustaceans and even krill.

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 millimetres (0.39 in) per year. By contrast, branching shallow-water corals, such as Acropora, may exceed 10–20 cm/yr. Reef structure growth estimates are about 1 millimetre (0.039 in) per year.[25] Scientists have also found Lophelia colonies on oil installations in the North Sea.[13] Using coral age-dating methods, scientists have estimated that some living deep-water corals date back at least 10,000 years.[26]

Most corals must attach to a hard surface in order to begin growing but sea fans can also live on soft sediments. They are often found growing along bathymetric 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 and rely on ocean currents to bring food. The currents also aid in cleaning the corals.

Bubblegum coral (Paragorgia arborea) at 1257 meters water depth (California).

Growth and reproduction

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 rock shrimp, and calico scallop.[24]

Oculina varicosa is a branching ivory coral that forms giant but slow-growing, bushy thickets on pinnacles up to 30 metres (98 ft) in height. The Oculina Banks, so named because they consist mostly of Oculina varicosa, exist in 50–100 metres (160–330 ft) of water along the continental shelf edge about 26–50 miles (42–80 km) off of Florida's central east coast.

Oculina varicosa distribution

[20] Among the most researched deep-water coral areas in the

Darwin Mounds

Lophelia exist around the Bay of Biscay, the Canary Islands, Portugal, Madeira, the Azores, and the western basin of the Mediterranean Sea.[19]

Discovered and mapped in 2002, Norway's Tisler Reef lies in the Skagerrak on the submarine border between Norway and Sweden at a depth of 90–120 metres (300–390 ft) and covers an area of 2 by 0.2 kilometres (1.24 mi × 0.12 mi).[15] It is estimated to be 8600-8700 years old.[16] The Tisler Reef contains the world’s only known yellow L. pertusa. Elsewhere in the northeastern Atlantic, Lophelia is found around the Faroe Islands, an island group between the Norwegian Sea and the Northeast Atlantic Ocean. At depths from 200 to 500 metres (660 to 1,640 ft), L. pertusa is chiefly on the Rockall Bank and on the shelf break north and west of Scotland.[17] The Porcupine Seabight, the southern end of the Rockall Bank, and the shelf to the northwest of Donegal 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 metres (1,640–2,790 ft) along the base of the Florida-Hatteras slope. South of 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 (490 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.[18]

Some 500 kilometres (310 mi) further south is the Sula Reef, located on the Sula Ridge, west of Trondheim on the mid-Norwegian Shelf, at 200–300 metres (660–980 ft). It is 13 kilometres (8.1 mi) long, 700 metres (2,300 ft) wide, and up to 700 metres (2,300 ft) high,[14] an area one-tenth the size of the 100 square kilometres (39 sq mi) Røst Reef.

The world's largest known deep-water Lophelia coral complex is the Røst Reef. It lies between 300 and 400 metres (980 and 1,310 ft) deep, west of Røst island in the Lofoten 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 (25 mi) long by 3 kilometres (1.9 mi) wide.

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.[13]

’s west coast. Africa and off Brazil, Atlantic Ocean, lives in the Northeast and Northwest Lophelia pertusaOne of the most common species,
Map showing concentration of L. pertusa with greatest density in the Northeast Atlantic
Global distribution of Lophelia pertusa

Map showing concentration of L. pertusa with greatest density in the Northeast Atlantic

Lophelia pertusa distribution

Madrepora oculata occurs as deep as 2,020 metres (6,630 ft) 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 metres (2,000–2,600 ft) in the Straits of Florida (Cairns and Stanley, 1982).

Deep-water corals 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 metres (1,300–2,300 ft).[12]

Photo of pink branching coral
Soft octocoral

Distribution

Corals are animals in the Phylum Cnidaria and the class Anthozoa. Anthozoa is broken down into two subclasses Octocorals (Alcyonaria) and Hexacorals (Zoantharia). Octocorals are soft corals such as sea pens. Hexacorals include sea anemones and hard bodied corals. Octocorals contain eight body extensions while Hexacorals have six. Most deep-water corals are stony corals.

Photo of collected coral branch in sunlight
A specimen of Madrepora oculata coral, collected off the coast of South Carolina.

Taxonomy

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. [11]. During expedition, scientists identified 16 species of corals.brittle starsIn 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 metres (1,600 ft) and saw giant coral forests, darting schools of fish, and a seafloor carpeted in
A rockfish hides in a red tree coral (Primnoa pacifica) in Juan Perez Sound in Haida Gwaii, British Columbia.

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.

Lophelia communities support diverse marine life, such as sponges, polychaete worms, mollusks, crustaceans, brittle stars, starfish, sea urchins, bryozoans, sea spiders, fish and many other vertebrate and invertebrate species.[1]

During their survey of the Fugløy reef, Hovland and Mortensen[6] also found seabed pockmark 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.[7][8] Because these craters are formed by the expulsion of liquids and gases (including methane), several scientists hypothesize that there may be a link between the existence of the deep-water coral reefs and nutrients seepage (light hydrocarbons, such as methane, ethane, and propane) through the seafloor. This hypothesis is called the 'hydraulic theory' for deep-water coral reefs.[9][10]

[5], off northern Norway.Polar Circle, north of the Fugløy Island surveyed a 15 metres (49 ft) tall and 50 metres (160 ft) wide reef perched at 280 metres (920 ft) water depth near Statoil, off Ireland. The first ever live video of a large deep-water coral reef was obtained in July, 1982, when Porcupine Bank shed light on a colony on the [4] Deep-water corals are enigmatic because they construct their reefs in deep, dark, cool waters at high latitudes, such as Norway's

Discovery and study

Contents

  • Discovery and study 1
  • Taxonomy 2
  • Distribution 3
    • Lophelia pertusa distribution 3.1
      • Darwin Mounds 3.1.1
    • Oculina varicosa distribution 3.2
  • Growth and reproduction 4
  • Importance 5
  • Human impact 6
    • Oculina Banks 6.1
    • Sula and Røst 6.2
    • Darwin mounds 6.3
  • See also 7
  • References 8
  • External links 9

Submarine communications cables and fishing methods such as bottom trawling tend to break corals apart and destroy reefs. The deep-water habitat is designated as a United Kingdom Biodiversity Action Plan habitat.[2]

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.[1] 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.

to survive. zooxanthellae Like tropical corals, they provide habitat to other species, but deep-water corals do not require [1]

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