Hepatic microsomal mono-oxygenase activity in flounder Platichthys flesus from polluted sites in Langesundfjord and from mesocosms experimentally dosed with diesel oil and copper

Hepatic ethoxyresorufin 0-de-ethylase (EROD) and benzo(a)pyrene hydroxylase (B(a)PH) activity in flounder Platichthys flesus increased along a pollution gradient in Langesundfjord, examined during the GEEP Workshop. EROD activity in fish from a reference site was around 100 pm01 min-' mg microsomal protein-', increasing 5-fold at 2 moderately polluted sites and a further 2-fold at a more highly polluted site. B(a)PH activity was around 30 pm01 min-' mg protein-' in fish from the reference site, and was more than doubled at the polluted sites. Liver residue concentrations of several industrially-derived chlorinated hydrocarbons also increased along the pollution gradient. The data support the conclusion that fish hepatic mono-oxygenase activity may indicate exposure to organic pollutants in the field. Exposure of flounder to diesel oil and copper in mesocosms over several months dld not induce EROD or B(a)PH. Enzyme activities were all below those at the field reference site (EROD and B(a)PH around 70 and 20 pm01 min-' mg proteln-' respectively). Total PAH concentrations in liver (fluorescence measurements) did not vary with treatment, suggesting that the expenmentally exposed fish &d not accumulate inducing compounds.