Abstract
The Norwegian Water Column Monitoring (WCM) 2024 programme assessed the environmental impact of Snorre A and B oil and gas installations using caged mussels, passive samplers (PSDs), and wild fish. Five stations near Snorre A and two reference sites at Hywind Tampen were monitored for five weeks in spring 2024. Chemical (PAHs, metals) and biological (CI, MN, LMS) markers were measured in mussels; PAHs, alkylphenols, and naphthenic acids in PSDs. A weak gradient in alkylated PAH concentrations was found near Snorre A, with mussels accumulating phenanthrenes and PSDs accumulating naphthalenes. The highest PAH in mussels was low (12 ng/g ww) and was influenced by suboptimal station placement. Metals showed no spatial trends, and biological responses in mussels were weak. Wild fish (ling, tusk, saithe) were collected at Snorre A and B, Hywind Tampen, Oseberg, and a coastal site. PAHs, PFAS, radionuclides, and multiple biomarkers were analysed. PAH liver concentrations were generally low, with highest concentrations in coastal saithe. Only ling from Snorre A showed elevated 1-OH phenanthrene. Biomarker responses (e.g., CYP1A, DNA damage) were minimal across locations. For histology, liver granulomas were significantly elevated in tusk from both Snorre A and B compared to the coastal population. However, this could also be due to bacterial infections. Overall, no clear environmental impacts of Snorre A or B installations were observed, with chemical accumulations and biological responses higher in coastal reference fish.