Effects of Wetland Restoration on Mercury Bioaccumulation in the South Bay Salt Pond Restoration Project: Using the Biosentinel Toolbox to Monitor Changes Across Multiple Habitat and Spatial Scales. 2010 Annual Report

摘要

Wetland restoration and management practices that would minimize MeHg bioaccumulation are not well known. Therefore, this project aims to monitor changes in Hg bioaccumulation that may occur after the planned breach of Pond A8, which will return it to muted tidal action. Biosentinel monitoring is being coupled with water and sediment chemistry to understand the processes that cause changes in Hg bioaccumulation and to determine if and how the operation of the A8 Notch causes a direct change in MeHg production in Pond A8 or in Alviso Slough. An increase in the bioavailability of MeHg could negatively impact breeding waterbirds, a result opposite to the management goal of restoring waterbird habitat for the Don Edwards San Francisco Bay National Wildlife Refuge and the SBSP Restoration Project. An increase in MeHg export to surrounding waters, habitats, and the wider Bay also could have important regulatory ramifications. By monitoring across multiple habitats and spatial scales, we will increase the information that managers can draw upon as they attempt to minimize Hg risk while moving forward with restoration. As such, the primary objectives of this project are to: Assess the impact of the A8 notch on Hg cycling within Pond A8 and Alviso Slough mainchannel and adjacent marshes using an integrated biosentinel approach coupled with a stable isotope food web assessment, and process-level water-column and sediment studies. Determine the extent of the effect of the A8 notch implementation over time and with distance from the restoration site, and the relative effect among the different habitats and biosentinel species. Use water column and sediment mercury concentration and speciation data to link the underlying processes of MeHg production to bioaccumulation, and to investigate whether MeHg production potential changes as a function of changes in( a) phytoplankton production, and/or (b) Hg remobilization associated with Alviso Slough sediment scour.