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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Strategies for Improved Water Quality and Ecosystem Integrity within Agricultural Watersheds

Location: Water Quality and Ecology Research

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

Author
item Knight, Scott
item King, Mary
item Cooper, Charles

Submitted to: The International Journal of Earth & Environmental Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2015
Publication Date: 7/27/2015
Publication URL: http://handle.nal.usda.gov/10113/62055
Citation: Knight, S.S., King, M.E., Cooper, C.M. 2015. Suspended sediment impact on chlorophyll a, nitrogen and phosphorus relationships in Moon Lake, MS. The International Journal of Earth & Environmental Sciences. 1(1):1-9.

Interpretive Summary: Waters of the Mississippi Delta are very productive and capable of supporting strong sports fisheries. However, excessive sediments may impact that productivity at a fundamental level. Water was sampled from five sites, bi-weekly from 1982 to 1985 and analyzed for nonpoint source pollutants such as nutrients and sediments that are often associated with agricultural runoff. This study showed that sediment reduces light necessary for plankton to grow and reproduce thus ultimately reducing a lakes ability to produce fish and other aquatic organisms. This research stresses the point that resource managers must also consider sediment as an important pollutant when setting water quality goals.

Technical Abstract: 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.

Last Modified: 8/24/2016
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