San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on the most promising avenues for attempting to reduce methylmercury (MeHg) contamination in Bay Area aquatic food webs and identifying the scientific information that is most urgently needed to support these efforts. Concern for human exposure to MeHg in the region has led to advisories for consumption of sport fish. Striped bass from the Bay have the highest average Hg concentration measured for this species in USA estuaries, and this degree of contamination has been constant for the past 40 years. Similarly, largemouth bass in some Bay Area reservoirs have some of the highest Hg concentrations observed in the entire US. Bay Area wildlife, particularly birds, face potential impacts to reproduction based on Hg concentrations in the tissues of several Bay species. Source control of Hg is one of the primary possible approaches for reducing MeHg accumulation in Bay Area aquatic food webs. Recent findings (particularly Hg isotope measurements) indicate that the decades-long residence time of particle-associated Hg in the Bay is sufficient to allow significant conversion of even the insoluble forms of Hg into MeHg. Past inputs have been thoroughly mixed throughout this shallow and dynamic estuary. The large pool of Hg already present in the ecosystem dominates the fraction converted to MeHg and accumulating in the food web. Consequently, decreasing external Hg inputs can be expected to reduce MeHg in the food web, but it will likely take many decades to centuries before those reductions are achieved. Extensive efforts to reduce loads from the largest Hg mining source (the historic New Almaden mining district) are underway. Hg is spread widely across the urban landscape, but there are a number of key sources, source areas, and pathways that provide opportunities to capture larger quantities of Hg and reduce loads from urban runoff. Atmospheric deposition is a lower priority for source control in the Bay Area due to a combination of a lack of major local sources and Hg isotope data indicating it is a secondary contributor to food web MeHg. Internal net production of MeHg is the dominant source of MeHg that enters the food web. Controlling internal net production is the second primary management approach, and has the potential to reduce food web MeHg more effectively and within a much shorter time-frame. MeHg cycling and control opportunities vary by habitat. Controlling net MeHg production and accumulation in the food web of upstream reservoirs and ponds is very promising due to the many features of these ecosystems that can be manipulated. The most feasible control options in tidal marshes relate to the design of flow patterns and subhabitats in restoration projects. Options for controlling MeHg production in open Bay habitat are limited due primarily to the highly dispersed distribution of Hg throughout the ecosystem. Other changes in these habitats may also have...

Following the 2007 M/V Cosco Busan oil spill in San Francisco Bay, California, legislation was enacted to provide for the closure of fisheries by the California Department of Fish and Game (DFG) after oil spills in marine waters. This legislation (DFG Code Section 5654) facilitated a partnership between the state's primary oil spill responder, the Department of Fish and Game, Office of Spill Prevention and Response (DFG/OSPR), and the state's Office of Environmental Health Hazard Assessment (OEHHA), the agency responsible for determining whether fish caught in California waters can be safely consumed. A fisheries closure protocol established as a result of the statute stipulates the role of staff at both agencies, from the initial spill responders to data evaluation and reopening of a closed fishery. OEHHA staff is required to assess the need for fisheries closure following a spill event. When a fisheries closure is deemed necessary for more than 48 hours, OEHHA will select species and chemicals for analysis, determine sampling strategies, conduct a risk assessment on the safety of fish and shellfish consumption, and work with DFG/OSPR to modify closure boundaries, if indicated. Relevant case study information from California spills, including the T/V Dubai Star is shown.

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