Lethal and sublethal effects of the pyrethroid, bifenthrin, on grass shrimp (Palaemonetes pugio) and sheepshead minnow (Cyprinodon variegatus)

This study investigated the lethal and sublethal effects of the pyrethroid insecticide bifenthrin on adult and larval grass shrimp, Palaemonetes pugio, and adult sheepshead minnows, Cyprinodon variegatus. The effects were determined by conducting 96-h aqueous static renewal tests and 24-h static tests with sediment. Oxidative stress biomarkers, lipid peroxidation, glutathione, and catalase were also assessed. The 96-h aqueous LC50 value for adult shrimp was 0.020 g/L (95% CI: 0.015-0.025 g/L) and for larval shrimp was 0.013 g/L (95% CI: 0.011-0.016 g/L). The 96-h aqueous LC50 for adult sheepshead minnow was 19.806 g/L (95% CI: 11.886-47.250 g/L). The 24-h sediment LC50 for adult shrimp was 0.339 g/L (95% CI: 0.291-0.381 g/L) and for larval shrimp was 0.210 g/L (95% CI: 0.096-0.393 g/L). The oxidative stress assays showed some increasing trends toward physiological stress with increased bifenthrin concentrations but they were largely inconclusive. Given the sensitivity of grass shrimp to this compound in laboratory bioassays, additional work will be needed to determine if these exposure levels are environmentally relevant.