|GILLESPIE, JR., W|
Submitted to: Archives of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/1997
Publication Date: N/A
Interpretive Summary: Insecticides are a necessity in our production of food and fiber. By their nature, they are toxic. Ideally, no insecticide would be transported beyond the crop to which it is applied. However, unexpected weather events or other factors may transport insecticides off the target field. Farmers need in-field and edge of field management practices that will trap and allow processing of insecticides when washoff occurs. Small constructed wetlands placed strategically between fields and water bodies may provide low-cost solutions to eliminate potential contamination. Bio-indicators (aquatic animals and plants) are effective means of measuring success in reducing or eliminating toxicity from insecticides. The laboratory experiments discussed evaluated responses of four aquatic organisms to three insecticides, focusing on sensitive species. Results will allow for more effective field studies of the insecticide processing abilities of constructed wetlands by allowing use of these bio-indicators. Thus, this is a step toward completion of a large goal to provide the farmer with a new management practice as he strives to produce a crop and protect the environment. Toxicologists and water quality scientists will be interested in this particular phase of the research.
Technical Abstract: Laboratory toxicity data contrasting responses of aquatic organisms to insecticides are important for focusing on sensitive species (steepest exposure-response slope) exposed to aqueous concentrations of these agrichemicals in field studies and predicting expected responses. Aqueous 48 h toxicity tests were performed to contrast responses of *Daphnia magna*, *Hyalella azteca*, *Chironomus tentans*, and *Pimephales promelas* to acetylcholinesterase-inhibiting insecticides: chlorpyrifos, aldicarb, and chlordane. As expected, invertebrates tested were 200 times more sensitive than the vertebrate *P. promelas* to chlorpyrifos exposures. *H. azteca* was approximately 3.5 times more sensitive to chlorpyrifos (453% mortality/ug/L) than *D. magna* (128% mortality/ug/L). For both aldicarb and chlordane, *C. tentans* was the most sensitive species tested (2.44 and 2.54% mortality/ug/L, respectively). Differences in chlordane potency for test species varied only by a factor of 2-3 (0.88% mortality/ug/L for *H. azteca* to 2.54% mortality/ug/L for *C. tentans*). While point estimates of population responses such as LC50s are of utility for predicting effects of pesticides in aquatic systems, exposure-response slopes are also useful for extrapolation of laboratory data to diverse field situations, especially where sediment sorption may regulate insecticide exposure or bioavailability.