Lophelia

Lophelia pertusa, the only species in the genus Lophelia, is a 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. pertusa reefs are home to a diverse community, however the species is extremely slow growing and may be harmed by destructive fishing practices, or oil exploration and extraction. Lophelia pertusa is a reef building, deep water coral, but it does not contain zooxanthellae, the symbiotic algae which lives inside most tropical reef building corals. Lophelia lives between 80 metres (260 ft) and over 3,000 metres (9,800 ft) depth, but most commonly at depths of 200–1,000 metres (660–3,280 ft), where there is no sunlight, and a temperature range from about 4–12 °C (39–54 °F). As a coral, it represents a colonial organism, which consists of many individuals. New polyps live and build upon the calcium carbonate skeletal remains of previous generations. Living coral ranges in colour from white to orange-red. Unlike most tropical corals, the polyps are not interconnected by living tissue. Each polyp has up to 16 tentacles and is a translucent pink, yellow or white. Some colonies have larger polyps while others have small and delicate -looking ones. Radiocarbon dating indicates that some Lophelia reefs in the waters off North Carolina may be 40,000 years old, with individual living coral bushes as much as 1,000 years old. The colony grows by the budding off of new polyps. Living polyps are present on the edges of dead coral and fragmentation of coral colonies provides one form of asexual reproduction. Each colony is either male or female and sexual reproduction occurs when these liberate sperm and oocytes into the sea. The larvae do not have a feeding stage, but sustain themselves on their yolks and drift with the plankton, possibly for several weeks. On settling on the seabed, they undergo metamorphosis and develop into polyps which potentially start new colonies. Lophelia reefs can grow to 35 m (115 ft) high. The largest recorded Lophelia reef, Røst Reef, measures 3 km × 35 km (1.9 mi × 21.7 mi) and lies at a depth of 300–400 m (980–1,310 ft) off the Lofoten Islands, Norway. When this is seen in terms of a growth rate of around 1 mm per year, the great age of these reefs becomes apparent. Polyps at the end of branches feed by extending their tentacles and straining plankton from the seawater. The spring bloom of phytoplankton and subsequent zooplankton blooms, provide the main source of nutrient input to the deep sea. This rain of dead plankton is visible on photographs of the seabed and stimulates a seasonal cycle of growth and reproduction in Lophelia. This cycle is recorded in patterns of growth, and can be studied to investigate climatic variation in the recent past. L. pertusa was listed under CITES Appendix II in January 1990, meaning that the United Nations Environmental Programme recognizes that this species is not necessarily currently threatened with extinction but that it may become so in the future. CITES is technically a means of restricting international trade in endangered species, which is not a major threat to the survival of L. pertusa. The OSPAR Commission for the protection of the marine environment of the North-East Atlantic have recognised Lophelia pertusa reefs as a threatened habitat in need of protection. Main threats come from destruction of reefs by heavy deep-sea trawl nets, targeting redfish or grenadiers. The heavy metal 'doors' which hold the mouth of the net open, and the 'footline', which is equipped with large metal 'rollers', are dragged along the sea bed, and have a highly damaging effect on the coral. Because the rate of growth is so slow, it is unlikely that this practice will prove to be sustainable.