Monitoring of environmental contaminants in freshwater food webs (MILFERSK), 2025

Sammendrag

This report presents data from the fifth year of a five-year period for the MILFERSK program. In 2025, the monitoring program focused on the sampling and analysis of the pelagic food chain in Lake Mjøsa, encompassing the following sample types: zooplankton mainly epipelagic species, Mysis, vendace, E. smelt, and brown trout. Additionally, brown trout from the reference lake, Femunden, were collected. The concentrations of 228 individual compounds/isomers were determined, with frequent detections of specific per- and polyfluoroalkyl substances (PFAS), polybrominated diphenyl ethers (PBDEs), mercury (Hg), and siloxanes exhibiting biomagnifying properties throughout the food chain. Time series of these contaminant groups show declining concentrations in brown trout in Lake Mjøsa. We also observe lower concentrations in the pelagic biota for phthalates and UVcompounds, compared to in 2023 when last pelagic biota was included in the program. Out of the 14 car tyre compounds included in the analysis of pelagic biota in 2025, only DPG and 6PPD Q were detected at low levels in zooplankton and Mysis.