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MODEL FOR CHANGES IN SEDIMENT AND WATER-COLUMN BIOGEOCHEMISTRY IN RESPONSE TO SEASONALLY HYPOXIC/ANOXIC CONDITIONS BENEATH THE MISSISSIPPI RIVER PLUME
Citation:
Eldridge, P M. AND J. W. Morse. MODEL FOR CHANGES IN SEDIMENT AND WATER-COLUMN BIOGEOCHEMISTRY IN RESPONSE TO SEASONALLY HYPOXIC/ANOXIC CONDITIONS BENEATH THE MISSISSIPPI RIVER PLUME. Presented at Sixth International Symposium on the Geochemistry of the Earth's Surface, Honolulu, HI, May 20-24, 2002.
Description:
Although the bottom waters of many freshwater and marine environments are either permanently oxic or anoxic, there is a growing appreciation that in many bodies of water near-bottom conditions seasonally oscillate between these extremes. Although observational databases for these environments have increased greatly over the last decade, a quantitative understanding of the dynamics of their physical and ecological systems is not well established. For shallow coastal waters with a semi-permanent pycnocline, the transport of oxygen across the pycnocline, and the transport of oxidized and reduced species across the sediment-water interface influence the redox conditions in the hypolimnion. We developed a combined water-column sediment geochemical model of the Louisiana shelf where seasonal hypoxic to anoxic conditions occur. The model shows that while water-column processes are most important to maintaining hypoxia, the onset of hypoxia is controlled by the additional metabolism of the sediments. Knowledge of processes that lead to hypoxic to anoxic conditions is needed to predict the sensitivity of these coastal waters to nutrient loading and the accompanying stimulation of primary production.