Sacramento River Phytoplankton Lagrangian Study


We supported a large-scale research study by USGS and university scientists to investigate the effects of Regional San 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.

Regional San temporarily diverted its discharge from the river into storage basins, creating a six-mile wastewater-free parcel of water in the river. Researchers traveled in boats along with the river water for five days, sampling water with and without wastewater.



Results indicate that phytoplankton biomass declined in both the presence and absence of wastewater over time, suggesting that a factor other than wastewater is leading to the decline in phytoplankton biomass. Diatoms, a preferred food source, comprised the bulk of phytoplankton in the presence and absence of diffused wastewater effluent. This suggests that wastewater effluent does not cause a rapid change in phytoplankton species composition in the Sacramento River, from preferred to non-preferred species.

This research is now published in the scientific journal Limnology and Oceanography and is available “open source”:

A river-scale Lagrangian experiment examining controls on phytoplankton dynamics in the presence and absence of treated wastewater effluent high in ammonium. 2017. Tamara E. C. Kraus, Kurt D. Carpenter, Brian A. Bergamaschi, Alexander E. Parker, Elizabeth B. Stumpner, Bryan D. Downing, Nicole M. Travis, Frances P. Wilkerson, Carol Kendall, Timothy D. Mussen. Limnology and Oceanography. Volume 62, Issue 3, Pages 1234–1253.

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