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 the aquatic macroinvertebrate communities have rarely been addressed. Outdoor flow-through stream microcosms were exposed for 1 h in triplicate to approximately 3.1 g/L of total suspended solids spiked with 0.0, 13.6, 136, or 1,365 μg/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) showed a sensitive acute drift reaction with increased drift levels in all FV treatments (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-μg/kg treatments. Temporal pattern of emergence was significantly altered in the 1,365-μg/kg treatment for A. nervosa (p < 0.05). The most sensitive species in terms of total emergence or survival were L. lunatus, which showed a significant effect in the 136- and 1,365-μg/kg treatment, as well as adult and juvenile G. pulex and T. maxima, with a significant effect level in the 1,365-μg/kg treatment (p < 0.05). Total emergence or survival of A. nervosa, P. conspersa, and H. angustipennis decreased with increasing exposure level, but differences from the control were not significant. Neither acute drift nor chronic mortality was observed for Helodes minuta (Coleoptera) and Radix peregra (Gastropoda). This study highlights the ecotoxicological importance and bioavailability of field-relevant levels of particle-associated hydrophobic chemicals transiently introduced into surface waters during runoff events. Received: 26 June 2000/Accepted: 20 November 2000