Abstract
Aquatic sediments are often sinks for contaminants, and buried contaminants from the past 50-100 years are still present in large quantities in Baltic sediments. In addition, a current concern is that nutrients stored in bottom sediments could be released when disturbed, regenerating nutrients into an already eutrophic ecosystem. Whether these contaminants and nutrients remain buried or are subsequently remobilised depends both on biogeochemical processes on the seafloor and resuspension by physical processes (which also alter biogeochemical processes), such as waves and bottom trawling. In the Baltic Sea, bottom trawling is used to catch demersal fish species such as cod, a process that causes substantial disturbance to the sediment. However, the extent and implications of this disturbance have not been investigated. The aim of this project is to determine for the first time the importance of sediment resuspension by trawling in the Baltic Sea. We will do this by combining detailed fishing effort data with field-derived estimates of amounts of sediment, contaminants and nutrients resuspended by trawling, predictions based on an oceanographic model, and assessments of the bioavailability of resuspended contaminants. Incorporation of such data, in conjunction with EU requirements on common fisheries policy, sustainability and conservation will be vital for future sustainable management of the Baltic Sea.
Sweden