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2M - Monitoring of function and structure (WEP/153) Interactions between the pesticides captan, deltamethrin, isoproturon, and pirimicarb and microbial communities of natural sediments. Widenfalk, Anneli1, Svensson, Jonas2, Goedkoop, Willem1, 1 Swedish University of Agricultural Sciences, Uppsala, Uppland, Sweden2 Halmstad University, Halmstad, Halland, Sweden ABSTRACT- Effects of pesticide exposure to microbial communities of fresh water sediments are poorly investigated. Yet, these microorganisms play key roles in the energy, nutrient and contaminant fluxes of aquatic ecosystems. In three microcosm experiments, we exposed microbial communities of a natural sediment with environmentally relevant concentrations of the fungicide captan, the herbicide isoproturon and the insecticides deltamethrin and pirimicarb. Exposure concentrations were calculated Negligible Concentration (NC), Maximum Permissible Concentration (MPC), and 100 times MPC (Crommentuijn et al., J. Environ. Managem., 58: 297-312, 2000). Experimental endpoints were microbial community respiration and biomass, bacterial activity, and denitrification, representing three levels of organization. All the tested pesticides had an inhibiting effect on bacterial activity at MPC-treatments. Surprisingly, for all pesticides except isoproturon, this inhibiting effect was not observed at 100MPC-treatments. We also observed negative effects on microbial biomass in the MPC-treatment with deltamethrin, and in the NC-treatment with isoproturon. Community respiration and denitrification rates were not significantly affected by the tested pesticides. Our study shows that exposure to the tested pesticides may induce toxic responses in sediment microbial communities, at concentrations that are predicted to be environmentally safe. This could in turn lead to negative effects on the function of the aquatic ecosystem. Key words: microbial communities, pesticides, natural sediment, bacterial activity |
