The South Bay Salt Pond Restoration Project plans to convert 50-90% of the former salt evaporation ponds of South San Francisco Bay into tidal marsh habitat. This large-scale habitat restoration may change the distribution, bioavailability, and bioaccumulation of methylmercury. The South Bay is known to already have high methylmercury levels in biota, with methylmercury concentrations in several waterbird species above known toxicity thresholds where avian reproduction is impaired.
Our goal was to monitor changes in mercury chemistry in sediment and water, and in methylmercury bioaccumulation that occurred before and after restoration activities associated with the opening of Pond A8 to Alviso Slough, which turned the Pond A8/A7/A5 Complex into a relatively deep and large pond with muted tidal action. The restoration of the Pond A8/A7/A5 Complex began in fall 2010 and the Pond A8 Notch was opened to muted tidal action on June 1, 2011. In fall 2010, internal levees between Ponds A8, A7, and A5 were breached and water depths were substantially increased by flooding the Pond A8/A7/A5 Complex in February 2011.
This report synthesizes biosentinel data from three related mercury projects: (1) the Pond A8 Mercury Study funded by the Resource Legacy Fund and the South Bay Salt Pond Restoration Project, (2) the Shoals Mercury Study funded by the USGS Research Augmentation for the South Bay Salt Pond Restoration Project, and (3) the Alviso Slough Mercury Study funded by the Resource Legacy Fund.