Assessment of the effects of wastewater treatment plant effluents on receiving streams using oligochaete communities of the porous matrix

Human activities can disturb the natural dynamics of exchanges between surface water and groundwater in rivers. Such exchanges contribute to the self-purification of the environment and an excess of infiltration can lead to contamination of groundwater. In addition, the porous matrix (coarse surface sediments and hyporheic zone), through which water exchanges occur, is a sink for pollutants. For environmental monitoring programs, it is therefore essential to take into account both the dynamics of vertical hydrological exchanges and the biological quality of this matrix. The functional trait (FTR) method, which is based on the study of oligochaete communities in coarse surface sediments and the hyporheic zone, was proposed as a tool to simultaneously assess the dynamics of vertical hydrological exchanges and the effects of pollutants present in the porous matrix. Here, we applied this method during two different periods (in March and September 2016), upstream and downstream of locations affected by discharges from wastewater treatment plants (WWTP) located in Switzerland. The biological quality of surface sediments and the hyporheic zone was shown to be better upstream of the WWTP in both campaigns. In addition, results suggested that the capacity for self-purification was lower downstream of the WWTP, and that groundwater at these locations was vulnerable to pollution by surface water. The FTR method proved valuable as a field method for detecting the effects of point source contamination on receiving streams. In the near future, this community-based approach will benefit from advances in the use of DNA barcodes for oligochaete species identification

Recommendations from a French-Swiss expert panel for improving the ecotoxicological quality assessment of sediments through the study of benthic communities

International audienceLes sédiments ont un rôle écologique essentiel pour de nombreuses espèces aquatiques.Toutefois, leur capacité à capter les polluants persistants peut participer à long termeà la contamination des milieux aquatiques. Aussi, afin de mieux prendre en compte les impactsécotoxicologiques de la contamination des sédiments et appréhender le risque écologiquequi en découle, il est important de disposer de méthodes d'évaluation robustes. Cet article présentela contribution d'un groupe franco-suisse réunissant chercheurs, gestionnaires et représentantsde bureaux d’études qui ont travaillé ensemble afin de dresser un état des lieux et formulerdes recommandations pour mieux caractériser la contamination des sédiments, les niveauxd’exposition des communautés benthiques et les effets possibles sur ces espèce