Influence of temperature and polyaromatic contaminants on CYP1A levels in North Sea dab ( Limanda limanda)

Abstract

Mature specimens ( n = 686) of male dab ( Limanda limanda) were collected at several stations from the southern North Sea during two surveys in 1991 and 1992. Levels of CYP1A protein and 7-ethoxyresorufin O-deethylase (EROD) activity were measured in liver and heart. Elevated CYP1A levels were observed in dab collected from off-shore stations with low bottom water temperatures due to stratification of the water column. Considerably lower CYP1A levels were observed at stations with higher water temperatures. Multiple regression analyses with PCB concentrations in fish and water temperature as independent variables influencing EROD activity or CYP1A protein levels demonstrated significant correlations with both parameters. The water temperature was inversely related to CYP1A levels, whereas PCB concentrations showed a positive relation with CYP1A levels. The effect of water temperature dominated over the effect of PCB contamination. The relationship between water temperature and CYP1A levels was also examined in a laboratory study, where dab were acclimated to 8, 12 and 16 °C for 4 weeks. A three-fold increase in EROD activity in the group acclimated to 8 °C compared to the group acclimated to 16 °C was observed, whereas no differences were observed for CYP1A protein levels. Multiple regression analyses with PCB concentrations and condition factor of fish as independent variables influencing CYP1A levels also demonstrated significant correlations in the field. Thus, differences in water temperature and nutritional status of dab between sampling locations obscured the effects of contamination with polyhalogenated aromatic compounds on CYP1A levels. The results indicate that these factors have to be taken into account when employing CYP1A responses in dab as biomarkers for environmental contamination in the North Sea.