INSECTICIDE CONCENTRATIONS IN ECOSYSTEM COMPONENTS OF AN INTENSIVELY CULTIVATED WATERSHED IN MISSISSIPPI

Concentrations of three currently used insecticides (fenvalerate, permethrin, and methyl parathion) were documented in major watershed components of Moon Lake, Mississippi and its 166 km2 watershed over a three year period. Moon Lake (10.1 km2), an oxbow of the Mississippi River, receives flow through a series of wetlands from a flatland watershed intensively cultivated in cotton, soybeans, and rice. None of the three insecticides were detected in watershed soils, but they were found sporadically in wetland and lake sediments, water and fish. Twenty-six percent of the 110 fish collected had measurable concentrations of the insecticides. Detection of all three insecticides, especially methyl parathion, in fish tissue suggested that they have sufficient persistence for uptake and, perhaps, bioaccumulation. The occurrence of banned organochlorine insecticides in the ecosystem was also observed, especially during runoff, and it also indicated the importance of watershed management practices on long term water quality.