Hepatic EROD Activity in Flounder (Platichthys flesus) as an Indicator of Contaminant Exposure in English Estuaries

To investigate the presence of sub-lethal contaminant effects in flounder (Platichthys flesus) populations in English estuaries, 16 sites from 7 estuaries were sampled in September–December 1997. Determination of hepatic ethoxyresorufin O-deethylase (EROD) activity revealed that significant (p<0.05) induction of the mixed function oxygenase (MFO) system was apparent in flounder from several industrialised estuaries compared to the relatively unpolluted reference site – the Alde estuary. The estuaries in increasing order of observed mean EROD activity were: Alde, Southampton Water, Humber, Tyne, Wear, Tees, Mersey. No significant gender differences in EROD induction or other measured variables were discovered for any site. Limited analytical data suggest a close link with EROD induction and hepatic polycyclic aromatic hydrocarbons (PAH)/polychlorinated biphenyls (PCB) concentrations but no strong correlations were discovered between EROD activity induction with any other measured variable across all estuaries. However, in the Tyne estuary strong negative correlations were discovered between mean female EROD and female gonado-somatic index (GSI) and female condition factor (CF) of r=−0.84 and −0.80, respectively. It is suggested that the ‘out of season’ correlation of reproductive parameters with EROD could be linked to contaminant interference, perhaps by xeno-oestrogens. It is clear that flounder populations in English industrialised estuaries are exhibiting widespread sub-lethal contaminant effects and more research is essential to understand the potential implications of this for reproduction and disease that could be affecting the future viability of these populations.