Contaminant accumulation and multi-biomarker responses in field collected zebra mussels (Dreissena polymorpha) and crayfish (Procambarus clarkii), to evaluate toxicological effects of industrial hazardous dumps in the Ebro river (NE Spain)

Large amounts of industrial waste containing high concentrations of mercury, cadmium and organochlorine residues were dumped in a reservoir adjacent to a chlorine-alkali plant in the village of Flix(Catalonia, Spain), situated at the shore of the lower Ebro river. Effects of these contaminants to aquatic river invertebrates were assessed by integrating analyses of metals and organochlorine residues in field collected zebra mussels and crayfish with a wide range of biomarkers. Biological responses included levels of metallothioneins, activities of ethoxyresorufin-O-deethylase, oxidative stress biomarkers (glutathione content, enzymatic activities of superoxide dismutase, catalase, glutathione s-transferase, glutathione peroxidise and glutathione reductase), levels of lipid peroxidation and of DNA strand breaks. The results obtained evidenced similar response patterns in mussels and crayfish with increasing toxic stress levels from upper parts of the river towards the meander located immediately downstream from the most polluted site, close to the waste dumps. The aforementioned stress levels could be related with concentrations of mercury, cadmium, hexachlorobenzene, polychlorobiphenyls and dichlorodiphenyltrichloroethanes from 4- to 195-fold greater than local background levels. The response of biomarkers to these pollutant concentrations differences was reflected in high activities and levels of antioxidant enzymes, metallothioneins, lipid peroxidation and DNA strand breaks and decreased levels of glutathione.