Virginia Krause

Mercury poses significant threats to freshwater ecosystems, particularly in regions impacted by historic gold mining, where it may undergo a microbially mediated transformation to neurotoxic methylmercury that bioaccumulates and biomagnifies up aquatic food webs. The focus of this research is to assess the fate and transport of mercury and its conversion to neurotoxic methylmercury in freshwater systems to assist in the development of total maximum daily loads for mercury and reduce concentrations of mercury in fish.

Mercury contamination from historic gold and mercury mining continues to threaten freshwater ecosystems in California, with numerous watersheds listed as mercury-impaired and in need of remediation. Guadalupe Reservoir in Santa Clara County is among these impaired watersheds, where legacy contamination from the New Almaden Mining District has led to record-high fish mercury concentrations. Various remediation strategies have been considered for Guadalupe Reservoir, however, key knowledge gaps regarding the transformation of mercury into methylmercury, the neurotoxic form of mercury that bioaccumulates and biomagnifies up aquatic food webs, and controls of this transformation in the reservoir limit the effectiveness of remediation plans. This research aims to address these knowledge gaps by identifying the primary locations of methylmercury production in the reservoir as well as the key biogeochemical and microbial processes responsible for its production. Results will assist in the ongoing development of remediation strategies and allow for a more targeted plan of action to reduce concentrations of mercury in the water and subsequently the fish.