Bottom trawling impacts on benthic-pelagic coupling in the North Sea

Bottom trawling has a direct impact on biogeochemical cycling and benthic-pelagic coupling. Despite extensive trawling activities in many shelf seas, the effects on benthic-pelagic exchanges is often not considered in marine ecosystem simulations. In this study, in order to gauge the effects of bottom trawling on North Sea ecosystem productivity, two model simulations were carried out for the period 2000-2005 using the 3D, fully coupled ecosystem model SCHISM-ECOSMO, which allows for coupled simulation of the benthic and pelagic ecosystem. The first simulation includes only natural resuspension while the second experiment also considers a parametrization for bottom trawling induced resuspension. Daily forcing for bottom trawling resuspension rates was generated based on available data of fishing activity including the position, size and engine power of individual vessels, in combination with estimated resuspension rates of various fishing gears in different types of sediment. The results of these simulations were then analyzed with regard to the importance of bottom trawling for the pelagic primary production of the North Sea ecosystem. In addition, we analyzed trawling-induced changes in bottom water oxygen and sedimentary carbon, phosphorus and nitrogen pools.