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Suspended sediment impact on chlorophyll a, nitrogen and phosphorus relationships in Moon Lake, MS

Scott S. Knight, Mary E. King, Charles M. Cooper
The International Journal of Earth & Environmental Sciences 2015 v.1 no.1 pp. 1-9
agricultural runoff, alluvial plains, chlorophyll, ecosystem services, nitrogen, nitrogen content, nonpoint source pollution, nutrients, oxbow lakes, phosphorus, pollution load, primary productivity, river deltas, sediments, surface water, suspended sediment, turbidity, water quality, Mississippi, Mississippi River
Moon Lake, MS is a 947 ha. oxbow lake of the Mississippi River Alluvial Plain also known as the Mississippi Delta. Water was sampled from five sites, bi-weekly from 1982 to 1985. Analysis of surface water quality reviled loading of nutrients from nonpoint source pollution associated with agricultural runoff. Significant negatives correlation was found between total phosphorus and chlorophyll a which seems counterintuitive until the effects of sediment on light availability are considered. As expected, Secchi depth was positively related to chlorophyll a and negatively correlated to total phosphorus and nitrogen. Significant positive correlations were found between total sediments and both total nitrogen and total phosphorus; however, a significant negative correlation was found between total sediments and chlorophyll a. The strong association of phosphorous with total sediments, the negative correlation of Secchi depth to phosphorus and nitrogen and the positive correlation to chlorophyll a indicate that Moon Lake primary productivity is driven by light availability rather than nutrients. The connection of productivity to sediment effects on light is important to ecosystem services of Delta oxbow lakes.