Estuarine ecosystems important to native and cultured oyster species are particularly sensitive to sea level rise, rising temperatures and ocean acidification. The project will monitor changes in Tomales Bay water conditions, which are likely to be significantly influenced by runoff from anticipated El Niño storms following years of severe drought. This monitoring will further inform an ongoing project (R/HCME-02) to quantify the consequences of terrestrial and marine controls over estuarine acidification for the restoration and health of both native Olympia oysters (Ostrea lurida) and commercial Pacific oysters (Crassostrea gigas). Results will determine whether pH or other factors are more important in explaining patterns observed in the field. Findings will be shared with native oyster restoration groups and local shellfish producers at annual stakeholder meetings to be convened by the researchers, and through outreach materials through the UC Agriculture and Natural Resources Cooperative Extension.