Environmental effects and fate of the insecticide bifenthrin in a salt-marsh mesocosm

In the mesocosm experiment, 24 h and 96 h caged shrimp LC50s were 0.061 and 0.051 μg L−1, respectively. The uncaged grass shrimp 28 d LC50 was 0.062 μg L−1. Fifty percent mortality was not reached in the uncaged sheepshead minnow. Bifenthrin did not have a significant effect on the growth of the shrimp, but there was an increasing impact on fish growth. However, it is uncertain as to whether this pattern is a direct effect of the chemical or if it is due to increased food availability resulting from mortality in prey species. The oxidative stress assays were largely inconclusive. Bifenthrin was eliminated rapidly from the water column and readily partitioned to sediments. The LC50s for adult and larval P. pugio were below published Estimated Environmental Concentration (EEC) values and were within the range of bifenthrin concentrations that have been measured in rivers, channels, and creeks.