Ethoxyresorufin-O-deethylase (EROD) and vitellogenin (VTG) in flounder (Platichthys flesus): system interaction, crosstalk and implications for monitoring.

The extent to which biological systems interact in fish from multi-contaminant areas needs to be understood for full interpretation of monitoring data. This study investigates the interaction between two biomarkers, ethoxyresorufin-O-deethylase (EROD) activity and plasma vitellogenin (VTG) in the European flounder (Platichthys flesus). Flounder were exposed to several waterborne EROD inducers and estrogenic chemicals on their own and in binary combinations. Each experimental exposure was for 10 days. The estrogenic chemicals suppressed PAH-mediated EROD induction. Ethynylestradiol (EE2) and nonylphenol (NP) had threshold concentrations of EROD inhibition similar to those at which they induced VTG production. Estradiol (E2), however, showed an ability to suppress EROD at a concentration much lower than that at which VTG was induced. This established that, although EE2 is a more potent VTG inducer than E2, it is less potent in its ability to inhibit EROD activity. The PAH, dibenz[a,h]anthracene (DbA), showed no effect on the VTG induction caused by EE2 and E2. A small effect was noted with NP at threshold concentrations for VTG induction. Archived data on flounder hepatic EROD activity collected during estuarine monitoring were reassessed in light of the project findings. It is hypothesised that published EROD monitoring data may be an underestimation of effects if it is assumed that estrogen-mediated MFO suppression is occurring in wild populations. A greater understanding of system interaction and other factors, including genetics, that influence biomarker response to contaminants would be required to interpret biomarker monitoring data.

EROD activity measured in flatfish from the area of the Sea Empress oil spill.

Dab (Limanda limanda) and plaice (Pleuronectes platessa) were collected at five stations near to the site of the Sea Empress oil spill within two weeks of the incident and a further fourteen stations three months after the spillage. Ethoxyresorufin-O-deethylase (EROD) activity was determined in the livers of the specimens to determine whether induction could be detected. Statistically significant inter-site differences in EROD levels in both species were demonstrated. Elevated levels of EROD activity in dab were found at the two stations nearest to the incident up to three months after the spill but no clear relationship to putative contaminant levels was determined. EROD levels in plaice showed a generally similar pattern of induction as in dab. Correlation of EROD levels with other variables showed that sexual maturity had the greatest influence on dab during the study period. The plaice specimens were sexually immature and, therefore, did not demonstrate a corresponding relationship. It was concluded that, for EROD monitoring purposes, fish should be sampled during their sexually inactive phase and that close attention needs to be paid to other variables (depth, temperature, GSI, length, influential contaminants etc.) when interpreting the results.

Hepatic ethoxyresorufin O-deethylase (EROD) activity in flounder (Platichthys flesus) from contaminant impacted estuaries of the United Kingdom: continued monitoring 1999-2001.

The determination of hepatic ethoxyresorufin O-deethylase (EROD) has been used to assess the induction of the mixed function oxygenase system (MFO) of flounder (Platichthys flesus) in UK estuaries. Induction of the MFO system denotes possible exposure to certain organic contaminants (e.g. polycyclic aromatic hydrocarbons, polychlorinated biphenyls) and its measure has been incorporated in national monitoring programmes. This study presents EROD monitoring data from 5 UK estuaries taken between 1999 and 2001 and builds on data from previous years. The results reveal that for all sampled estuaries EROD values have been significantly (p < 0.05) elevated on the majority of occasions in comparison with the reference estuary, the Alde in Suffolk, UK. However, the limited temporal scale of the reported monitoring does not allow any conclusions to be drawn with respect to trends in the data. Possible factors influencing the data (size, gender, seasonality, reproductive status, etc.) are discussed and recommendations for continued monitoring are made.