Modelled bioaccumulation of chemical warfare agents within the Baltic Sea food web

After World War II, some 13 000 t of active chemical warfare agents (CWAs) were destroyed by dumping them into the Bornholm Deep. Recently, due to munition shell and container corrosion, potential CWA leakages are considered as a viable risk to marine organisms. Here, an Ecopath with Ecosim (EwE5.1) - software is used to study the bioaccumulation of a persistent CWA-like contaminant within the Baltic Sea food web with four different scenarios that describe differential water-column mixing and biomass changes in temporal and spatial resolution. In Bornholm, such bioaccumulation is of a particular concern, as the dumpsite coincides with fertile fishing grounds and is one of the main breeding areas for Baltic cod. According to our model, cod accumulated the contaminant most of all fish species studied. However, the magnitude of bioaccumulation, in all species, was very much affected by whether the CWA-contaminant was homogenously mixed within the whole water-column, or existed only in the near-bottom layer. In the latter scenario, the only pelagic groups accumulating the contaminant were fish. The dispersal of the contaminant, also, varied according to the mixing and was more widespread when the contaminant had access to surface water layers and was advected by surface water currents. The effects were more local when the contaminant was restricted to near-bottom water.