Acrobat Reader er gratis og kan hjemtages fra Adobes web-sted . Several human activities in the marine environment i.e. dredging, fishery, building activities, discharge of nutrients etc. has been in the focus of the environmental administration for many years. An assessment of the natural processes in relation to the human impacts of the seabed is needed in general to balance the natural resource management and protection policy and the exploitation of the sea. Dependant on the dynamic forces the uppermost part of the sediment by nature will migrate.
Sand migrates close to the seabed and by the current it builds up characteristic ripples.
Mud and organic detritus is transported in suspension and during storms resuspended into the water column. It is obvious that these natural processes are disturbed by any human activities. Damage of the benthic fauna suffered by the passage of the trawl, the change of the physical property characteristics of the seabed sediment and the release of nutrients and heavy metals from the sediment by trawling have been studied in the North Sea by several authors. Most investigations have focused on the damaging effects on the benthic fauna during the physical exploitation of the seabed. Totally the tracks from the use of trawling gear in the North Sea cover an area equivalent to the total North Sea area.