The report summarises the monitoring activities within the National Swedish Contaminant Programme in marine biota.

Few trends are found for the biological variables of the biota included in the programme (age, weight, length, and fulton´s condition factor). This is expected, as samples are selectively selected to avoid trends. However, all variables for Holmöarna in the Bothnian Bay and the fish age at the West Coast sites (Kullen, Fladen and Väderöarna) stands out for herring, cod and perch as having upward trends over the last 10 years. Since many of the contaminants presented in this report bioaccumulate, this is likely to affect the trends presented below.

For the aggregated herring data (on sub-basin scale) on chlorinated pesticides, PCBs, dioxins and furans, brominated flame retardants and perfluorinated substances (PFAS) a general downward trend for the last 10 years (2009-2018) is seen for all sub-basins (Southern and Northern Baltic Proper and Bothnian Sea and Bay) except the West Coast. On the West Coast, changes are small and often non-significant. The contaminant concentrations are in general lowest on the West Coast but the concentration difference between the West Coast and the other sub-basins has shrunken over the last 10 years as the concentrations in the other sub-basins are decreasing towards West Coast levels. The perfluorinated compound FOSA is an exception to this picture, with 2-4 times higher concentrations on the West Coast compared to the Baltic Sea. For the metals, no common patterns are seen for the aggregated herring data across the metals or for each specific metal between sub-basins.