Assessing the impact of waste water effluents on native fish species from a semi-arid region, NE Spain.

Mediterranean rivers are strongly affected by pollution and water scarcity. Over the summer period, urban and industrial effluents arrive into the rivers with little dilution. In order to assess the water quality, two native fish species, Barbus meridionalis and Squalius laietanus, were collected from six sites along the Ripoll River (Spain). PAH metabolites, alkylphenols (nonylphenol and octylphenol) and the musk galaxolide levels were determined in bile. 7-Ethoxyresorufin-O-deethylase (EROD) and 7-benzyloxy-4-trifluoromethyl-coumarin O-debenzyloxylase (BFCOD) were measured as metabolic biomarkers, and the activity of CYP19 aromatase was determined in the ovaries of B. meridionalis as a biomarker of endocrine disruption. The analysis of bile indicated that fish from the lower course of the river were highly exposed to different pollutants. Accordingly, a significant induction of EROD (9 to 10-fold) and BFCOD (3 to 5-fold) activities were detected in both fish species together with an increased aromatase activity in females of B. meridionalis from the most polluted sites. Considering that sewage treatment plant (STP) effluents are essential for maintaining environmental flows in small Mediterranean rivers, this study highlights the need to improve the efficiency of STPs to protect fish health.