Plankton of the Sacramento River

Results of studies on plankton and associated water-quality conditions in the Sacramento river, Calif., from Keswick reservoir to Mayberry Slough over a period of 15 months from the spring of 1960 to the summer of 1961 are summarized in tables and a graph and discussed. Results show a gradual increase in the total number of plankton as the water progresses downstream, a major pulse occurring at Isleton bridge about 35 miles downstream of Sacramento. A statistical evaluation of the number of plankton and of the chemical and physical parameters of water quality and movement shows that water temperature is the most important factor affecting plankton development in the non-tidal stretch of the river. Water temperature, stream flow, and BOD were found to be responsible for about 60 per cent of the variations in numbers of plankton. The diatoms Synedra, Cyclotella, and Melosira were generally the dominant algae, blue-green and other algae never being numerous although at some downstream stations green algae (usually Ankistrodesmus) were abundant in midsummer. Zooplankton was always an insignificant fraction of the total population. A list of 24 references is included.