sediment using their chemoreceptors to differentiate between the two. Growth of polyps depends on environmental factors such as food availability, water quality, and how the water flows. L. pertusa are considered to be opportunistic feeders since they feed on particles of organic matter that have been broken down. Hence, 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. Conservation status 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 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 recognized 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. Scientists estimate that trawling has damaged or destroyed 30%–50% 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 then closing all of Europe’s deep corals to fishing trawlers. In 1999, the Norwegian Ministry of Fisheries closed an area of at Sula, including the large reef, to bottom trawling. In 2000, an additional area closed, covering about . An area of about enclosing the Røst Reef closed to bottom trawling in 2002. Bottom trawling leads to siltation or sand deposition, which involves the disturbance of underlying sediments and nutrients. This harmful process destroys and decreases the growth of coral reefs, affecting the expansion