Deepwater

Deepwater Coral

Not all coral species live in tropical, shallow waters. There are many species of deepwater coral that rely solely on their extended polyps for food. Little is known about these species, and new species of deepwater coral are discovered on a regular basis.

Deepwater corals are comparable to trees

Habitat

Deepwater corals grow in all the world’s ocean basins, including the waters of the United Kingdom, Australia, New Zealand, Canada, Ecuador, Japan, Norway, and the United States.They can be found in waters as deep as 6,000m and as cold as -1ºC. However, temperature is an influencing factor of coral distribution, and they are most commonly found in waters ranging from 4 to 12 C. Other factors influencing coral distribution include salinity and competitive interactions with other organisms like sponges and algae.

Cold corals, as they are also called, often are found on seamounts, ocean canyons, and continental shelves and slopes. Corals require a hard surface on which to attach, which could be exposed rock, substrate, or even dead coral. They generally colonize areas where strong currents are found, as corals rely on the steady flow of water to supply them with food, disperse larvae, and to remove wastes and sediments. For this reason, corals are often found specifically on seamounts due to the strong currents.

Importance

Just as with tropical coral reefs, deep water corals are important for a number of reasons, mainly due to their integral role in the functioning of other systems.

• Deepwater coral reefs provide critical habitat to a disproportionate number of marine species. There is high species diversity around cold corals as well as high endemism. Cold corals are essential as nurseries to juvenile fish and the framework of corals create sub-habitats for a variety of marine organisms.
• Cold corals are commercially important in that they provide deep-sea habitats to many commercial fish species. Off the Aleutian Islands, 85% of commercial fisheries are associated with cold corals.
• Corals are also an important resource for new medicines.The chemicals that corals produce have potential to be used in fields such as oncology to create novel medicines such as anti-tumor compounds.
• Another source of coral importance is the use of coral in paleoclimatology. Since deep water corals are so long lived, they provide important clues about past ocean temperatures and chemistry.
• Coral are also used in jewelry, and can support local and commercial industries, though this aspect of coral use is not always sustainable, and can also be a direct, physical threat to the coral.

Threats¦ Bottom Trawling

One of the greatest threats to deep-water coral is the affect of bottom trawling. Bottom trawling has been shown to smooth out the sea floor and destroy habitat for corals. Bottom trawling directly affects reefs by catching coral in fishing nets and removing the coral framework. It also destroys the coral itself by shattering the fragile and easily broken skeletons. If enough coral is removed or damaged, the reef can reach a size where it is not longer sexually viable and does not have enough members to reproduce. Recruitment of larvae becomes sporadic. . This is particularly significant because cold corals are slow growing and take thousands of years to fully develop. .

Bottom trawling has increased in recent years due to the overfishing of shallow waters. However, bottom trawling can be counterproductive in that by destroying deep-water reefs, fishermen also destroy critical habitat for many commercial fish species. The new technology used in these deep-water fisheries has shown an increased, negative affect on coral species, characterized by heavy coral by-catch. However, as coral reefs have been removed, the incidence of by catch has decreased.

Other threats include

• Oil and gas exploration, especially in the event of oil spills
• Climate Change
• Ocean Acidification
• Jewelry or curios made from cold corals

Species

Leiopathes glaberrima

Black corals are the oldest known marine organisms. They live in excess of 4,000 years. Black corals have dark skeletons and irregularly branching, tree-like structures. The coral polyps attach to the base of the skeleton, and their mouths are located at the other end, ringed in tentacles to catch food. . Unlike tropical coral reefs, cold corals do not contain zooxanthellae within their tissues, so they must catch their food on passing currents. They are found in both the Pacific and Atlantic, though their complete distribution is unclear. . Deep-water Black Coral is threatened by habitat degradation and also trade in live corals for aquariums. . While the trade is small, it is not sustainable as slow growing as black coral.

Lophelia pertusa

Lophelia pertusa are stony, deep-water corals mainly occurring mainly on the continental shelf and are one of the few species able to build a coral framework in the deep ocean. They are rarely attached to soil substrata, but occur on soft ocean bottoms greater than 150m and even occasionally on oil industry structures where currents are strong. The skeletons of Lophelia pertusa polyps occur in bush-like colonies that may join together to form a larger reef, joined together by their external calcareous skeletons. . Individual polyps are white, pink, or yellowish, and contain up to 50 tentacles. Within the reef, stony corals are protected against other animals growing in the reef by a layer of mucus. Even so, stony corals are a biodiversity hotspot and provide habitat to a variety of species at the edge of the continental shelf. They are threatened by bottom trawling and oil extraction. . It is also though that deep, cold-water, stony corals are among the first marine organisms to be affect by ocean acidification. . [[File:Lophelia.jpeg.png{775}x{532}px]]