Biochemical markers of environmental contamination in continental aquatic ecosystems. Examples of use and prospects for management.

In addition to conventional chemical analyses, biomarkers are considered as useful tools for monitoring chemical contamination and assessing health of organisms and populations in aquatic ecosystems. Biochemical markers represent sensitive and early warning systems of the exposure of aquatic organisms to pollutants, thus complementing more global studies on field invertebrate populations on a long-term time scale. Among biochemical markers, induction of the enzymatic EthoxyResorufin-O-Deethylase (EROD) activity in fish is specific of exposure to Polycyclic Aromatic Hydrocarbons (PAHs), coplanar PolyChlorinated Biphenyls (PCBs) and dioxins. Moreover, inhibition of AcetylCholinEsterase (AChE) activity can indicate the response of fish to pesticides like organophosphorous compounds and carbamates. Genotoxicity assessment through the measurement of DNA adducts or DNA strand breaks gives rise to relevant information about genetic damage encountered by exposed species. Furthermore, the measure of vitellogenin synthesis in male fish has been successfully used as a biomarker of estrogenic effect of xenobiotics that leads to adverse effects on reproduction. These biomarkers should be integrated in extensive biomonitoring networks in order to complete their validation.