Sources of Particulate Organic Matter in the Mississippi River, USA.
Wissel, Björn; Fry, Brian
Large rivers are conduits for nutrients and sediments from continents to the sea, but can also support productive fisheries within river-floodplain ecosystems. To assay sources of organic matter important for fisheries in the lower Mississippi River, we measured concentrations and stable isotope values of particulate organic carbon and nitrogen over a 2+ year period at Baton Rouge, Louisiana. Mixing models indicated average concentrations of 73 and 38 "mol C/l as soil carbon and labile carbon, respectively, with labile carbon composed of a mixture of phytoplankton and bacteria. The average carbon isotope value for transported soil was ±22.2 %, similar to recent marine sediment values. The combination of high concentrations of labile carbon and high throughput indicates a potentially rich production regime for floodplain food webs linked to the Mississippi River.