Modulation of CYP1A and genotoxic effects in European seabass (Dicentrarchus labrax) exposed to weathered oil: A mesocosm study

The aim of this study was to assess medium-term toxicity of weathered oil on European seabass. A mesocosm system reproducing an oil spill at sea was applied. Fish were collected after 48 h, 7, 30 and 60 days. Cyp1a gene transcription, EROD and UDPGT activities, bile PAHs metabolites and micronuclei frequency were investigated. A progressive disappearance of low molecular weight n-alkanes and PAHs in the water of the mesocosm occurred during the experimentation. Fishes exposed to oil displayed a significant increase of cyp1a expression and EROD activity during the entire experiment as well as higher concentrations of PAHs metabolites in bile. Micronulei frequency resulted significantly higher during all experiment in oil exposed sea bass compared to controls. The results highlight the environmental risk associated with the release of oil products at sea and confirm the adopted parameters as useful tools for studying the impact of accidental oil spills on fish.

► Cyp1a gene and EROD activity resulted significantly up-regulated in seabass exposed to weathered oil.
► PAHs metabolites in bile displayed a pattern of increase which paralleled EROD activity.
► A genotoxic effect was observed in oil exposed fishes.
► Compounds other than PAHs become bioavailable during the weathering process and heavily contribute to oil toxicity.