Monitoring and Assessment of Environmental Mercury and Mercury Bioaccumulation in South Baylands

The potential exists to inadvertently increase the risk of mercury (Hg) accumulating in South Bay fish and wildlife through hydrological modification of salt ponds as part of the South Bay Salt Pond Restoration Project (SBSPRP). The concern is that management actions will favor conversion of Hg into toxic methylmercury (MeHg) and its uptake into local food webs. Concerns about possible mercury poisoning exist throughout San Francisco Bay (SFEI 2004, CalFed Bay-Delta Program 2005). Concentrations of Hg in sediment and water tend to be greater in South Bay due to past local mercury mining (Beutel and Abu-Saba 2004). The Alviso Pond and Slough Complex are especially worrisome because they contain more Hg than most other areas of South Bay (SFEI 2005) and because they are slated for early management actions by the SBSPRP. The mercury problem is complex. The production of MeHg depends on many environmental factors besides the total amount of Hg. The uptake of MeHg into food webs and its bioaccumulation vary within and among species and habitats. Threshold concentrations of MeHg toxicity are not well known for most wildlife species, and habitat designs or management practices that would minimize MeHg bioaccumulation are also unknown. Although data are being collected about mercury concentrations at various very little is known about the associated processes governing Hg physical transport, Hg methylation, and bioacccumulation. Key questions include (a) how much legacy Hg is contained in sediments of different habitats; (b) how readily the available Hg can or will be converted to MeHg; c) how effectively any MeHg will be incorporated into local food webs; and d) how answers to these questions might be influenced by different management actions. Solution Pathway Bayland managers need to know how their actions affect the risk of mercury toxicity in wildlife. The risk can be assessed most directly by monitoring Hg in 'biosentinel' wildlife species that represent the baylands. Coupling such a monitoring effort to studies of MeHg production and uptake is essential if we are to understand how the risk of Hg bioaccumulation can be reduced, and thus develop effective management options. Santa Clara Valley Water District (SCVWD) seek $737,575 for a scientific effort to develop indicators of Hg problems, employ the indicators to survey the magnitude and extent of the problem for South Baylands (beginning with Pond A8 and Alviso Slough), and, where necessary, implement research to understand the problem. The proposed work would be …