Nutrient Dynamics of the San Francisco Estuary

Over the last few decades, the San Francisco Estuary has experienced a decline in primary productivity that has resulted in the scarcity of food at higher trophic levels. Previous literature has attributed this decline in primary productivity to the increased grazing of the invasive clam, Potamocorbula amurensis. However, there have been occasions of phytoplankton blooms during times of high P. amurensis abundance. This conundrum has been deemed the “clam paradox.” Through a literature review, we have investigated that increased clam grazing is not solely responsible for the decline of primary productivity. Rather, the NH4 excreted from P. amurensis combined with an increase in NH4 discharge from wastewater treatment plants have suppressed the NO3 uptake from phytoplankton and caused the decline in primary productivity. The purpose of this research is to understand the relationship between clam abundance and ammonium discharge within the San Francisco Estuary. Through the Environmental Data Initiative Portal, provided by Jenna Rinde at the California Department of Water Resources, we extracted data from multiple sampling stations over the last eighteen years (2000-2018). This includes data on ammonium, nitrate, chlorophyll a, phytoplankton production, streamflow, and salinity. Using this data, we will conduct descriptive statistical analysis and utilize time series graphs to explore the relationship between NH4 and primary productivity. With the results, we can determine which management techniques can be used to combat the decline of primary productivity and preserve the health of the San Francisco Estuary and estuaries alike.