| SS9.01 Ecosystem Science Practiced in an Urbanized Estuary: South San Francisco Bay |
| Dugdale, R, C, Romberg Tiburon Center, San Francisco State University, Tiburon, USA, rdugdale@sfsu.edu |
| Hogue, V, , Romberg Tiburon Center, San Francisco State University, Tiburon, USA, vhogue@sfsu.edu |
| Marchi, A, , Romberg Tiburon Center, San Francisco State University, Tiburon, USA, amarchi@sfsu.edu |
| Wilkerson, F, P, Romberg Tiburon Center, San Francisco State University, Tiburon, USA, fwilkers@sfsu.edu |
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| IMPACT OF ANTHROPOGENIC AMMONIUM ON PHYTOPLANKTON ECOLOGY IN AN URBANIZED ESTUARY: SAN FRANCISCO BAY |
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| South San Francisco Estuary is subjected to the discharge of high levels of ammonium from sewage treatment plants. Long time-series data measured in South Bay show high chlorophyll concentrations occur only when nitrate is high but ammonium concentrations are <4 uM. 15N uptake measurements show nitrate uptake is held low most of the year due to inhibiting ammonium. Spring blooms occur only when ammonium falls to low levels and diatoms are enabled to rapidly take up and grow on nitrate. SFE phytoplankton cannot reach full potential production without access to nitrate. Dilution of anthropogenic ammonium is necessary to reduce the ammonium concentration to levels where the phytoplankton can further reduce these concentrations to the levels where nitrate uptake can occur resulting in a burst of nitrate uptake and biomass formation. This helps explain the low productivity observed during dry years when dilution of anthropogenic ammonium by runoff is strongly reduced. The long term decline in productivity and fisheries in SFE may have resulted from the switch from primary to secondary sewage treatment and resultant discharge of nitrogen primarily as ammonium. |
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