A test system to evaluate the susceptibility of Oregon, USA, native stream invertebrates to triclopyr and carbaryl

摘要

The susceptibility of six indigenous macroinvertebrate species representative of U.S.Pacific Northwest streams(Ameletus sp. Brachycentrus americanus, Calineuria californica, Cinygma sp. Lepidostoma unicolor, Psychoglypha sp. Early and late instar) to formulate triclopyr ester(herbicide) and carbaryl (insecticide) was determined using laboratory bioassays. Acute toxicity was expressed as the lethal concentration to 50/100(LC50) and 1/100 (LCl) of the test population based on a 96-h exposure duration. Carbaryl was found to be 1,000 times more toxic than triclopyr for all the organisms tested. The LCl values (7.5, 28.8, 9.0, 3.0, 9.5, 14.8, 33.8 μg/L, respectively, for carbaryl and 1.8, 3.9, 4.0, 4.2, 29.0, 16.1 mg/L, respectively, for triclopyr)were used in the calculation of hazardous concentration to 5/100 of the stream macroinvertebrate community(HC5) based on the lower95/100 confidence limit(HC5/95).