ORGANOCHLORINE PESTICIDES IN SOIL SEDIMENTS AND AQUATIC ANIMALS IN THE UPPER STEELE BAYOU WATERSHED OF MISSISSIPPI

Soil sediments from 2 depths and tissue samples from 8 species of aquatic animals were collected on or near Yazoo National Wildlife Refuge, Mississippi, and analyzed for organochlorine pesticide residues. Residues of 12 organochlorine pesticides were found in most animal samples, and 0.0 to 4.6 mg/kg of 5 compounds were detected in soil sediments. With the exception of mosquitofish (Gambusia affinis), residues were similarly distributed in soil and animal samples among different watercourses within the watershed. Biomagnification of organochlorine pesticide residues was evident from soil sediments to mosquitofish, a lower secondary consumer and forage fish, to spotted gar (Lepisosteus oculatus), a tertiary consumer. Residues in larger secondary consumers such as carp (Cyprinus carpio) and smallmouth buffalo (Ictiobus bubalus) and tertiary consumers such as water snakes (Nerodia spp.) and cotton-mouths (Agkistrodon piscivorus) demonstrated no clear patterns of accumulation.