Acute and chronic effects of particle-associated fenvalerate on stream macroinvertebrates: A runoff simulation study using outdoor microcosms

Agricultural edge-of-field runoff usually contaminates surface waters with particle-associated pesticides. However, the acute and chronic effects on t he aquatic macroinvertebrate communities have rarely been addressed. Outdoo r flow-through stream microcosms were exposed for 1 h in triplicate to appr oximately 3.1 g/L of total suspended solids spiked with 0.0, 13.6, 136, or 1,365 mug/kg of the pyrethroid insecticide fenvalerate (FV). The effects on eight species typical of agricultural streams were monitored for 93 days. Gammarus pulex (Amphipoda) and Hydropsyche angustipennis (Trichoptera) show ed a sensitive acute drift reaction with increased drift levels in all FV t reatments (p < 0.05). The caddisfly species Anabolia nervosa, Plectrocnemia conspersa, and Limnephilus lunatus as well as the dipteran species Tipula maxima were less sensitive, with a significant increase in drift in the 136 - and 1,365-mug/kg treatments. Temporal pattern of emergence was significan tly altered in the 1,365-mug/kg treatment for A. nervosa (p < 0.05). The mo st sensitive species in terms of total emergence or survival were L. lunatu s, which showed a sig nificant effect in the 136- and 1,365-mug/kg treatmen t, as well as adult and juvenile G. pulex and T. maxima, with a significant effect level in the 1,365-mug/kg treatment (p < 0.05). Total emergence or survival of A. nervosa, P. conspersa, and H. angustipennis decreased with i ncreasing exposure level, but differences from the control were not signifi cant. Neither acute drift nor chronic mortality was observed for Helodes mi nuta (Coleoptera) and Radix peregra (Gastropoda). This study highlights the ecotoxicological importance and bioavailability of field-relevant levels o f particle-associated hydrophobic chemicals transiently introduced into sur face waters during runoff events.