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Methyl Mercury Study

photo of river
Mayberry Farms Wetland project


The DRMS team members determined that information on processes controlling mercury methlyation and bioaccumulation in the Delta is incomplete. Processes important for mercury methylation need to be understood to allow predictions of consequences of island flooding on mercury cycling and accumulation in the Delta. In addition, the Central Valley Regional Water Quality Control Board has required the Department of Water Resources (DWR) to conduct a Mercury/Methyl Mercury monitoring program at the recently constructed Mayberry wetland project.

Project Description

Mercury and methyl mercury will be monitored during the Mayberry Wetland project pre- and post-conversion from seasonal to permanent wetlands to determine if there are changes in concentrations. In addition, methyl mercury and total mercury loads off the wetland will be determined in the post-conversion period. There is concern that creation of wetlands, such as in the Mayberry project, will increase mercury contamination in fish and sediments within and around the Mayberry Wetland. Fish, insects, water and sediment will be monitored for mercury and methyl mercury at the Mayberry project site over a 5 year period to evaluate whether mercury levels increase or decrease as a result of the restoration. It is important not only to document changes in concentrations within the wetlands but to estimate the amount of surrounding area near the discharge that may be affected by methyl mercury.