Document Type

Technical Report

Publication Date



Mississippi Alluvial Plain, aquatic ecosystems, water quality


Primary productivity, water quality, and limiting factors of productivity were studied in Lake Chicot from 1 July 1975 to 30 September 1977 to ascertain the ameliorating effects of a comprehensive water quality improvement project. The upper lake receives only limited local run-off, but run-off from 350 square miles of agricultural land enters the lower lake through Connerly Bayou, the principal polluted tributary. Run-off over the predominantly silt and clay soils in the subsidized agricultural area contributes excessive amounts of colloidal silt and clay to the lower lake. Connerly Bayou also contributes additional amounts of nutrients including calcium, magnesium, potassium, sodium, sulfur, chloride, nitrogen, and phosphorus to the south basin. Periodic flooding drastically lowers primary productivity rates and phytoplankton standing crops in the lower lake. The mean primary productivity rate in the upper lake was 150.0 mgC/m2/hr compared to 49.8 mgC/m2/hr and 67.3 mgC/m2/hr at Stations 3 and 4 in the lower lake. Additions of sulfur, nitrogen, phosphorus, and manganese during insitu nutrient bioassay experiments resulted in increases in carbon-14 uptake. All concentrations of selected commercial herbicides and pesticides inhibited photosynthesis.

Report Number