The Mississippi River is the sixth largest river in the world. Rapid depletion of nutrients occurs as salinity increases due to mixing along the plume.
Production is initially light limited near the coast and highest productivity occurs at salinities of ca. 25 ‰. Near-shore production is driven by high nitrate. Nutrient limitation only occurs at salinities >30‰. Paradoxically, the greatest particulate organic carbon (POC) export in the plume seems to occur in areas of low productivity.
Little is known about the plume's contribution to primary productivity in the Gulf of Mexico. Our estimates of the contribution to the basin-wide productivity are based upon in-situ carbon fixation rates and satellite-derived estimates of the plume's area. Our estimates indicate that the plume accounts for 41% of all surface productivity (top 10 m) in the oligotrophic GOM. Additionally, the plume accounts for 13% of total water column productivity in the olig. GOM, while only covering 2.8% of surface area.
Wawrik, B. and J.H. Paul. 2004. Phytoplankton community structure and productivity along the axis of the Mississippi River Plume. Aquat. Microb. Ecol. 35:185-196.
Wawrik, B., John H. Paul, Deborah A. Bronk, David John, Mike Gray. 2004. High rates of ammonium recycling drive phytoplankton productivity in the offshore Mississippi River plume found in the oligotrophic Gulf of Mexico. Aquatic Microbial Ecology 35:175-184.
Wawrik, B., J.H. Paul, L. Campbell, D. Griffin, L. Houchin, A. Fuentes-Ortega, and F. Muller-Karger. 2003. Vertical Structure of the Phytoplankton Community associated with a Coastal Plume in the Gulf of Mexico. Mar. Ecol. Progr. Ser. 251:87-101.