Skip to main content
U.S. flag

An official website of the United States government

River discharge controls phytoplankton dynamics in the northern San Francisco Bay estuary

January 1, 1983

Phytoplankton dynamics in the upper reach of the northern San Francisco Bay estuary are usually characterized by low biomass dominated by microflagellates or freshwater diatoms in winter, and high biomass dominated by neritic diatoms in summer. During two successive years of very low river discharge (the drought of 1976-77), the summer diatom bloom was absent. This is consistent with the hypothesis that formation of the diatom population maximum is a consequence of the same physical mechanisms that create local maxima of suspended sediments in partially-mixed estuaries: density-selective retention of particles within an estuarine circulation cell. Because the estuary is turbid, calculated phytoplankton growth rates are small in the central deep channel but are relatively large in lateral shallow embayments where light limination is less severe. When river discharge falls within a critical range (100–350 m3 s−1) that positions the suspended particulate maximum adjacent to the productive shallow bays, the population of neritic diatoms increases. However, during periods of high discharge (winter) or during periods of very low discharge (drought), the suspended particulate maximum is less well-defined and is uncoupled (positioned downstream or upstream) from the shallow bays of the upper estuary, and the population of neritic diatoms declines. Hence, the biomass and community composition of phytoplankton in this estuary are controlled by river discharge.

Publication Year 1983
Title River discharge controls phytoplankton dynamics in the northern San Francisco Bay estuary
DOI 10.1016/0272-7714(83)90103-8
Authors J. E. Cloern, A.E. Alpine, B.E. Cole, R.L.J. Wong, J.F. Arthur, M.D. Ball
Publication Type Article
Publication Subtype Journal Article
Series Title Estuarine, Coastal and Shelf Science
Index ID 70011643
Record Source USGS Publications Warehouse
USGS Organization California Water Science Center; San Francisco Bay-Delta; Pacific Regional Director's Office