Benthic communities can inform about the contamination of large lakes surface sediments: A case-study in Lake Geneva
Les communautés benthiques peuvent nous renseigner sur l'impact de la contamination dans les sédiments de surface des grands lacs: Une étude de cas sur le lac Léman
Résumé
Sediments play a crucial role in biogeochemical cycles and food-webs in lakes. Studying impacts of contaminants on sediment-associated communities would allow to take into consideration specific and functional biodiversity in effect-based studies and monitoring programs, thus opening prospects to evaluate resulting effects on benthic ecological functioning. However, the lack of adequate strategies and methods in sediment-ecotoxicology limits the in situ evaluation of such impacts. To pave the way for implementing relevant sediment ecotoxicological approaches at community level, we initiated a collaborative study combining concepts of ecology, ecotoxicology and chemistry. We examined the spatiotemporal variations in benthic communities collected in surface sediments from eight sampling stations in Lake Geneva, which covered a large range of contamination levels by metals and organic compounds. Structural and functional characteristics of the bacterial communities varied according to the sampling dates and location. Based on the pollution-induced community tolerance (PICT) concept, bacterial tolerance and resistance potential to copper were positively correlated to copper concentrations in sediments. Relative distribution of sensitive/tolerant species in invertebrate communities was also related to the contamination conditions. Overall, our results evidenced the relevance of using benthic communities for the evaluation of sediment quality in lakes, and fresh waters in general.