SENSITIVITY OF CYTOCHROME-P450 1A INDUCTION IN DAB (LIMANDA-LIMANDA) OF DIFFERENT AGE AND SEX AS A BIOMARKER FOR ENVIRONMENTAL CONTAMINANTSIN THE SOUTHERN NORTH-SEA

The sensitivity of cytochrome P450 1A (CYP1A) 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 south ern North Sea. Mature and juvenile dab from both sexes were collected in autumn and winter during two surveys from four different stations w ith varying levels of polychlorinated biphenyls (PCBs) contamination i n 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 co varied to a large degree with CB153, this congener appears to be a goo d marker for general differences in PCB concentrations. In summer, bot tom water temperature differences of up to 10 degrees C can occur betw een stratified and vertically mixed areas. This was previously shown t o have a strong effect on CYP1A expression. In autumn and winter, stra tification has disappeared, resulting in almost equal water temperatur es between stations of the same survey. CYP1A levels were measured as 7-ethoxyresorufin O-deethylase (EROD) activity and immuno-quantitated CYP1A protein concentrations. Highest levels were also found close to the Dutch coast for mature fish from both sexes in October and for juv enile female and mature male fish in February during the spawning seas on. During this season, gravid female fish had significantly lowered c ontents of CYP1A protein and EROD activity compared to mature males an d juveniles of both sexes. The sensitivity of CYP1A induction in dab a s a biomarker for halogenated aromatic hydrocarbons is highest in matu re males when stratification during autumn is lacking.