Research Studies & Collaborations
In the spring of 2020, Regional San staff studied how environmental conditions can affect phytoplankton living in Delta river channels. Many factors can influence the amount of phytoplankton occurring in Sacramento–San Joaquin River Delta, including nutrient concentrations, water clarity, water flow rates, and grazing by clams and zooplankton. One method to investigate the relative importance of these factors is by measuring how phytoplankton respond to a dramatic change in environmental conditions, such as nutrient concentrations, water clarity, or flow rate.
Regional San staff and collaborators are studying the potential environmental effects of a change in nutrient loading to the Sacramento River in September 2019, which resulted from a wastewater hold at the Sacramento River Wastewater Treatment Plant (SRWTP). This hold, which was planned as part of the EchoWater Project construction process, prevented treated wastewater from entering the Sacramento River for 48 hours. Given the relatively high river flows in 2019, the hold created a zone of wastewater-free river water over 20 miles long in the lower Sacramento River.
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.
We supported a large-scale research study by USGS and university scientists to investigate the effects of SRWTP discharge of treated wastewater on phytoplankton health in the Sacramento River, using a presence and absence study.
This study addressed concerns about reduced phytoplankton abundance and potential changes in relative phytoplankton species abundance reported in the Lower Sacramento River.