WRCA: Water Resources Collections and Archives

San Francisco Bay Fund Inventory of Projects

North Bay Small Fish Mercury Monitoring with a Focus on Napa Sonoma Marsh

Organization: State Coastal Conservancy
2009 Grant Recipient - Napa, Solano, Sonoma, and Marin Counties

Purpose

With the SFF grant funds, the State Coastal Conservancy contracted with the Aquatic Science Center to conduct a biosentinel monitoring study of the San Pablo Bay area, with a focus on the Napa Sonoma Marsh Restoration Project. The monitoring study provides a baseline of methylmercury bioaccumulation in small fish from several sites in the Napa Sonoma Marsh restoration site area, as well as from “control sites” in the San Pablo Bay region. A variety of sites of different habitat types and different stages in the restoration trajectory were monitored with the purpose of documenting the current patterns in bioaccumulation of methylmercury in small fish across these sites.

The information collected from the monitoring study will serve as a basis for future monitoring efforts at the Napa Sonoma Marsh Restoration site and will help the landowner and regulatory agencies assess:

whether or not the project negatively impacts existing aquatic and wetland habitats, and
whether or not the restored habitats increase the risk of mercury bioaccumulation within the Napa Sonoma intertidal landscape.

Documents

North Bay Small Fish Mercury Monitoring with a Focus on Napa-Sonoma Managed Ponds and Sloughs Version 2, Contribution No. 620. October 2010. (30 pps.)
Grenier, L., Greenfield, B., Slotton, D., and Ayers, S. Aquatic Science Center, Oakland, California.

Contact for the Project
Dr. Darell Slotton
University of California, Davis
Phone: (530) 756-1001
Email: dgslotton@ucdavis.edu

San Francisco Estuary Institute
Phone: (510) 746-SFEI
Website: www.sfei.org

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Biosentinel fish were collected with a variety of seines and seining techniques. Samples were maintained in water, field sorted and cleaned, individually measured to mm total length, and placed into size-apportioned composite groups.

The biosentinel mercury monitoring study was designed to ensure that the sampling locations would address important areas for management concerns. The sampling design reflected a balance between achieving a wide spatial coverage and quantifying seasonal variation across a range of important habitat types.

Over 10,000 acres of historic salt ponds and associated habitats are being restored to tidal marsh or managed as ponds in the Napa-Sonoma Marshes Wildlife Area. Monitoring methylmercury (MeHg) bioaccumulation in tidal marsh and managed ponds is needed to understand how tidal restoration and pond management affect bioaccumulation of MeHg.

Small fish were chosen as an appropriate biosentinel, because they reflect MeHg bioaccumulation in near-shore subtidal and intertidal habitats, particularly managed ponds, large sloughs, and the Bay margin. The primary biosentinel species for this project was the Mississippi silverside.