Integrative approach to assess ecological risks of river contamination for wild fish populations

Water pollution is considered as one of the main threat to explain fish declines observed worldwide. Because of human activities, a large array of hazardous substances impairing aquatic organisms and leading to population disturbances are discharged into surface waters. Genotoxic compounds including pesticides, polycyclic aromatic hydrocarbons or heavy metals have been considered as hazardous substances inducing deleterious effects to exposed organisms, as well as progeny developmental defects. The first objective of the present work was to investigate a large panel of biomarkers including a genotoxicity biomarker to assess biological impacts of contamination on wild sticklebacks (Gasterosteus aculeatus). As a second objective, the relationship between the level of primary DNA damage in sperm from fish sampled in polluted rivers and their progeny survival was investigated. Finally, an approach integrating i) chemical analysis, ii) biomarker responses as early warning signals of contamination impacting individuals and iii) the Fish Based Index as an indicator of fish communities "health status" in French rivers was developed to assess ecological risks for fish populations.

Biomarker responses showed some correlations between genotoxicity, biotransformation and oxidative stress biomarkers thus discriminating impacted sites under urban pressures. The relationship between the level of primary DNA damage in sperm and fish reproductive impairment highlight potential long term population disturbances due to environmental genotoxicant exposure. The integrative approach combining chemical analyses, biomarker responses in fish and fish community disturbances provide more valuable information to assess ecological risks than using separately each Line of Evidence separately. When chemical and ecological indexes were not convergent to a clear conclusion, the use of biomarker analyses was relevant to point out biological disturbances at low level of biological organization before fish communities are affected. Thus, such an approach could clearly improve the diagnose of the level of river contamination and biological impacts in order to improve environmental management.