Occurrence of regulated pollutants in populated Mediterranean basins: Ecotoxicological risk and effects on biological quality

Chemical stressors co-occur in mixtures into watercourses and this complicates predicting their effects on their ecological status. Our knowledge of river basin specific pollutants (RBSPs) is still limited, but it remains necessary to ensure the good chemical and ecological status. We performed an exercise on Mediterranean river sites exposed to urban and industrial pressures in order to, i) prioritize the occurring chemicals, ii) assessing the site's specific chemical risk (RQ), and iii) relating the chemical risk to the biological quality, using as evidences invertebrates and diatom indices. Mediterranean rivers suffer from strong pressures which lead to a poor dilution ability, which makes the inhabiting biota highly vulnerable. The most frequent pollutants in the 89 sites surveyed included pharmaceutical products such as the antibiotics azithromycin, clarithromycin, and erythromycin, and the anti-inflammatory diclofenac, and products of industrial origin such as perfluorinated PFOS, nickel, and nonylphenol. Both the diatom index IPS and the macroinvertebrate index IBMWP hold strong negative correlations to RQ, indicating a significant contribution of chemicals to biological impairment. Chemical contaminants (but not nutrients or dissolved organic carbon) were associated with significant changes to the taxonomic composition of invertebrate communities, but not to that of diatom communities. Our analyses indeed reveal that the impact of co-occurring chemicals translates onto negative effects in the biological quality. Our approach may be of use to evidence impacts on water resources and water quality in rivers under strong human pressure.This research was co-funded by the projects CLIMALERT (PCIN-2017-068) and CEX2018-000794-S of the Spanish Ministry of Science and Innovation. Researchers are part of the Consolidated Research Groups ICRAENV 2017SGR 1124 and 2017SGR 1404 - Water and Soil Quality Unit. ICRA is part of the CERCA programme