USGS1985
Conversion of bottomland hardwood forests ℴ agricultural land has reduced habitat and water quality in many lakes in the floodplain of the lower Mississippi River. The objectives of this study were to ascertain current contaminant residue concentrations in fish and sediment from lakes in the Atchafalaya River Basin and to determine the influence of overflow and agricultural land use on contaminant levels. Fish and sediment samples were collected from eight lakes that differed in overflow (no overflow, headwater overflow, backwater overflow) and land-use characteristics (presence or absence of agricultural land). Residue analysis of 24 sediment and 82 fish samples collected from the study lakes showed that contaminant residues were uniformly low. Total DDT concentrations, consisting mainly of DDE, were found in 98% of the fish samples and generally were the highest residues though they rarely exceeded 0.50 μg/g. Dieldrin, α-BHC and γ-BHC, in concentrations rarely exceeding 0.05 μg/g, were detected in about 50% of the fish samples. Total organochlorine pesticide and PCB residues were less than 2.00 μg/g in all fish from all lakes, except for a 3.46 μg/g total in spotted gar ( Lepisosteus oculatus ) from one lake. Sediments were free from pesticide residues except for occasional traces (0.01 μg/g) of α-BHC. Metal residue concentrations in fish and sediment samples were typical of uncontaminated areas. Lake systems in the Atchafalaya River Basin appeared to be relatively uncontaminated by agricultural pesticides, but metal and organic residues in fish were similar from lakes with the same land-use and overflow characteristics.