The Sacramento River (SR) is the largest river in California and travels 400 miles from the Klamath Mountains in Oregon to San Francisco Bay. Together with scientists from Regional San, AMS scientists sample 16 stations along a 76-mile stretch between river mile 95 (north of the Feather River confluence) and river mile 19 (north of Rio Vista). At each station we take samples for determining the abundance of the clam Corbicula fluminea, zooplankton, phytoplankton and picoplankton. We also analyze dissolved inorganic nutrients, salinity, turbidity, temperature, chlorophyll a, active fluorescence, and take rate measurements. In addition, we perform incubation experiments to determine grazing rates under different environmental conditions. These measurements will help improve our understanding of the ecology, as well as chemical and physical aspects, of this key waterway, which contributes an important fraction of the freshwater and nutrients that fuel the food webs of the Sacramento-San Joaquin Delta as well as San Francisco Bay. The data collected from this project will be widely disseminated to the public, as well as scientific and regulatory communities.