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Contaminants in Chesapeake Bay Sediments 1984-1991

The primary objectives of this report are to describe the spatial patterns in the distribution of sediment chemical contaminants in Chesapeake Bay and to compare sediment chemical contaminant concentrations in Chesapeake Bay to sediment quality guidelines in order to identify areas where sediment chemical contaminants may adversely impact

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Assessing a Ten-Fold Increase in the Chesapeake Bay Native Oyster Population

The Chesapeake Bay Environmental Model Package (CBEMP) was used to assess the environmental benefits of a ten-fold increase in native oysters in Chesapeake Bay. The CBEMP consists of a coupled system of models including a three-dimensional hydrodynamic model, a three-dimensional eutrophication model, and a sediment diagenesis model. The existing CBEMP benthos submodel was modified to specifically represent the Virginia oyster, Crassostrea virginica. The ten-fold oyster restoration is computed to increase summer-average, bottom, dissolved oxygen in the deep waters of the bay (depth > 12.9 m) by 0.25 g m-3. Summer-average system-wide surface chlorophyll declines by 1 mg m-3. Filtration of phytoplankton from the water column produces net removal of 30,000 kg d-1 nitrogen through sediment denitrification and sediment retention. A significant benefit of oyster restoration is enhancement of submerged aquatic vegetation. Calculated summer-average biomass improves by 25% for a ten-fold increase in oyster biomass. Oyster restoration is most beneficial in shallow regions with limited exchange rather than in regions of great depth, large volume and spatial extent.

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