Newell, R. I. Horn Point Laboratory, UMCES,
Cornwell, J. C. Horn Point Laboratory, UMCES,
Owens, M. S. Horn Point Laboratory, UMCES,
Tuttle, J. H. Chesapeake Biological Laboratory, UMCES,

Environmental changes in Chesapeake Bay, such as elevated phytoplankton biomass and loss of benthic plants, are often thought to be largely a function of nutrient-driven eutrophication. We propose, however, that oyster populations, which have been reduced to <1% of their historic levels, may have exerted "top-down" control on phytoplankton stocks and also reduced turbidity, thereby increasing light available to benthic plants. In laboratory incubations under oxic and anoxic conditions we measured changes in sediment geochemistry, nutrient fluxes, and denitrification in response to loading by different amounts of algal paste, an experimental analog of oyster biodeposits. Increased organic loading to the sediment under oxidized conditions resulted both in higher rates of coupled nitrification/denitrification and denitrification in the presence of water column nitrate. In contrast, coupled nitrification/denitrification was suppressed under anoxic conditions. Similar incubations in the presence of benthic microalgae showed negligible ammonium fluxes from sediments, with the algal/microbial community efficiently retaining ammonium and fixing nitrogen. Because no DIN was recycled to the water column under oxic conditions we conclude that rehabilitation of oyster stocks will have the beneficial effect of removing phytoplankton from the water column without stimulating further phytoplankton production. Furthermore, nitrogen will be removed from the Bay via increased denitrification.
Day: Monday, Feb. 1
Time: 04:30 - 04:45pm
Location: Hilton of Santa Fe
Code: SS06MO0430H