Science activity

Planned upgrades to the Sacramento Regional wastewater treatment plant (Regional San) between 2019 and 2021 will reduce total nitrogen inputs by >60% and shift the dominant form of nitrogen entering the Delta from ammonium (NH4) to nitrate (NO3). These changes will affect the Delta in ways unforeseeable with existing knowledge. The focus of this project is to quantify the links between wastewater nitrogen and phytoplankton standing stock, community composition and carbon and nitrogen production. Working in collaboration with the other two Operation Baseline projects, we will: 1. validate in situ monitoring approaches for phytoplankton standing stock and community composition (i.e. using size-fractionated chlorophyll-a and diagnostic phytopigments via HPLC) and 2. provide estimates of ambient and nitrogen-saturated phytoplankton NH4 and NO3 uptake rates as well as C uptake. Phytoplankton N and C uptake rates will be made along spatial gradients in nitrogen and water residence time (Task 1) and in three wetland habitats with varying influence from wastewater nitrogen (Task 3). Together with the other proposals, this project will provide much needed baseline characterization of nutrient processes in the Delta prior to Regional San upgrades.