Sensitivity of cytochrome P450 1A induction in dab (Limanda limanda) of different age and sex as a biomarker for environmental contaminants in the southern North Sea.

The sensitivity of cytochrome P450 1A (CYPIA) induction as a biomarker for environmental contaminants in the flatfish dab (Limanda limanda) was evaluated by studying fish of different age and sex from the southern North Sea. Mature and juvenile dab from both sexes were collected in autumn and winter during two surveys from four different stations with varying levels of polychlorinated biphenyls (PCBs) contamination in the southern North Sea. All groups of fish exhibited highest muscle PCB concentrations near the Dutch coast. CB153 was always the dominant congener. Since the concentrations of the other congeners measured covaried to a large degree with CB153, this congener appears to be a good marker for general differences in PCB concentrations. In summer, bottom water temperature differences of up to 10 degrees C can occur between stratified and vertically mixed areas. This was previously shown to have a strong effect on CYPIA expression. In autumn and winter, stratification has disappeared, resulting in almost equal water temperatures between stations of the same survey. CYPIA levels were measured as 7-ethoxyresorufin of O-deethylase (EROD) activity and immunoquantitated CYPIA protein concentrations. Highest levels were also found close to the Dutch coast for mature fish from both sexes in October and for juvenile female and mature male fish in February during the spawning season. During this season, gravid female fish had significantly lowered contents of CYPIA protein and EROD activity compared to mature males and juveniles of both sexes. The sensitivity of CYPIA induction in dab as a biomarker for halogenated aromatic hydrocarbons is highest in mature males when stratification during autumn is lacking.