Resuspension of sediment by bottom trawling in the gulf of Maine and potential geochemical consequences

The benthic environment of the Gulf of Maine is characterized by a thick and basin-wide nepheloid layer, classically defined as a near-bottom region of permanent sediment resuspension. The high frequency of commercial bottom trawling in particular regions of the Gulf of Maine, documented by records compiled by the National Marine Fisheries Service, may strongly affect measured resuspension fluxes and contribute to the maintenance of the nepheloid layer. Indirect evidence of the effects of bottom trawling on sediment resuspension is observed in the seasonal collection of large, benthic infaunal worms, along with substantial amounts of resuspended bottom sediment, in a sediment trap deployed 25 m off the bottom in the western gulf region of Wilkinson Basin. These collections appear to be coincident with seasonal periods of intensive bottom trawling in this area. By comparison, the western gulf region of Jordan Basin is typified by significantly reduced annual bottom-trawling activity and very few infaunal worms are found in the seasonal collections of a sediment trap located 25-30 m off the bottom. The extent to which trawling-induced bottom sediment excavation and resuspension occurs has important implications for regional nutrient budgets in terms of the Input of sedimentary nitrogen and silica into the water column via this anthropogenic activity. Sediment mixing and frequent bottom disturbance from trawling activity may also produce changes in the successional organization of soft-sediment infaunal communities The potential effects of trawling require serious examination and quantification to accurately determine the impact of such anthropogenic activity on the benthic ecosystems of continental margin environments.