Sacramento River Phytoplankton Studies 2016


Some previous research on the Sacramento River found declining phytoplankton concentrations at downstream locations. The cause for the observed phytoplankton decline is not easily discernible, because the loss does not appear to be driven by effluent-derived nutrient concentrations, and while phytoplankton-consuming organisms, such as clams and zooplankton, are present in the river, they are not abundant enough to fully explain the decline. Regional San staff and consultants are conducting four scientific studies to evaluate factors that potentially limit phytoplankton growth within the Sacramento River, both upstream and downstream of the Sacramento Regional Wastewater Treatment Plant (SRWTP). The studies consist of the following:

  • Survey the river between Knights Landing and Isleton to estimate the abundance and diversity of phytoplankton, zooplankton, and clams along the river; changes in phytoplankton growth rates; differences in water chemistry; and other environmental factors
  • Model river flow to identify, for each survey location, the proportion of flow arising from different upstream sources
  • Conduct a controlled mesocosm experiment to determine the relative importance of light availability, clam grazing, zooplankton grazing, river-water sources, and nutrient concentrations on phytoplankton growth
  • Map phytoplankton growth potential in the river, based on the river’s width, depth, and light-availability at different depths

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