, 17:839

Transport of particulate organic carbon by the Mississippi River and its fate in the Gulf of Mexico


  • John H. Trefry
    • Department of OceanographyFlorida Institute of Technology
  • Simone Metz
    • Department of OceanographyFlorida Institute of Technology
  • Terry A. Nelsen
    • Atlantic Oceanographic and Meteorological LaboratoryNational Oceanic and Atmospheric Administration
  • Robert P. Trocine
    • Department of OceanographyFlorida Institute of Technology
  • Brian J. Eadie
    • Great Lakes Environmental Research LaboratoryNational Oceanic and Atmospheric Administration

DOI: 10.2307/1352752

Cite this article as:
Trefry, J.H., Metz, S., Nelsen, T.A. et al. Estuaries (1994) 17: 839. doi:10.2307/1352752


This study was designed to determine the amount of particulate organic carbon (POC) introduced to the Gulf of Mexico by the Mississippi River and assess the influence of POC inputs on the development of hypoxia and burial of organic carbon on the Louisiana continental shelf. Samples of suspended sediment and supporting hydrographic data were collected from the river and >50 sites on the adjacent shelf. Suspended particles collected in the river averaged 1.8±0.3% organic carbon. Because of this uniformity, POC values (in μmol l−1) correlated well with concentrations of total suspended matter. Net transport of total organic carbon by the Mississippi-Atchafalaya River system averaged 0.48×1012 moles y−1 with 66% of the total organic carbon carried as POC. Concentrations of POC decreased from as high as 600 μmol l−1 in the river to <0.8 μmol l−1 in offshore waters. In contrast, the organic carbon fraction of the suspended matter increased from <2% of the total mass in the river to >35% along the shelf at ≥10 km from the river mouth. River flow was a dominant factor in controlling particle and POC distributions; however, time-series data showed that tides and weather fronts can influence particle movement and POC concentrations. Values for apparent oxygen utilization (AOU) increased from ∼60 μmol l−1 to >200 μmol l−1 along the shelf on approach to the region of chronic hypoxia. Short-term increases in AOU were related to transport of more particle-rich waters. Sediments buried on the shelf contained less organic carbon than incoming river particles. Orgamic carbon and δ13C values for shelf sediments indicated 3 that large amounts of both terrigenous and marine organic carbon are being decomposed in shelf waters and sediments to fuel observed hypoxia.

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© Estuarine Research Federation 1994