the species which is being targeted and the exact gear that is being used, but for most demersal species, a speed of around 4 knots (7 km/h) is appropriate. Environmental damage Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders, re-suspending sediments and imprinting deep scars on muddy bottoms. Also, the repetitive passage of trawling gear over the same areas creates long-lasting, cumulative impacts that modify the cohesiveness and texture of sediments. It can be asserted nowadays that due to its recurrence, mobility and wide geographical extent, industrial trawling has become a major force driving seafloor change and affecting not only its physical integrity on short spatial scales but also imprinting measurable modifications to the geomorphology of entire continental margins. Bottom fishing has operated for over a century on heavily fished grounds such as the North Sea and Grand Banks. While overfishing has long been recognised as causing major ecological changes to the fish community on the Grand Banks, concern has been raised more recently about the damage which benthic trawling inflicts upon seabed communities. A species of particular concern is the slow growing, deep water coral Lophelia pertusa. This species is home to a diverse community of deep sea organisms, but is easily damaged by fishing gear. On 17 November 2004, the United Nations General Assembly urged nations to consider temporary bans on high seas bottom trawling. A global analysis of the impacts of bottom trawling found that the impact on seabed biota was strongly dependent on the type of gear used, with otter trawls estimated as having the smallest impact and removing 6% of biota per pass while hydraulic dredges had the largest impact and removed 41% of biota per pass. Other research found trawled canyon sediments contained 52 percent less organic matter than the undisturbed seafloor. There were 80 percent fewer sea worms in the trawled region and only half as much diversity of species in the trawled seafloor. Resuspension and biogeochemistry Bottom trawling stirs up the sediment at the bottom of the sea. The suspended solid plumes can drift with the current for tens of kilometres from the source of the trawling, increasing sedimentation rates in deep environments Bottom trawling-induced resuspended sediment mass on the world's continental shelves have been estimated to approximately 22 gigatonnes per year, approximately the same as the sediment