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Understanding Phytoplankton Dynamics in San Francisco Bay: Factors Influencing Growth

This overview explores the intricate factors affecting phytoplankton dynamics in San Francisco Bay, including salinity, temperature, turbidity, dissolved oxygen, and chlorophyll levels. Research indicates that phytoplankton growth is influenced by resources, light availability, and nutrient loadings. The study also highlights that the increasing phytoplankton is not directly correlated with nutrient increases, as evidenced by various hypotheses and models analyzing historical data. It emphasizes the complexity of aquatic ecosystems and the ongoing changes they face.

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Understanding Phytoplankton Dynamics in San Francisco Bay: Factors Influencing Growth

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  1. Nutrients Salinity Temperature Turbidity Dissolved Oxygen Chlorophyll www.sfbay.wr.usgs.gov/access/wqdata

  2. North Bay South Bay

  3. Story 1: North Bay USGS + Interagency Ecological Program

  4. Corbula amurensis Interagency Ecological Program

  5. California Department of Fish & Game

  6. Story 2: South Bay Chlorophyll a (mg/L) 1977-1998

  7. Chlorophyll a (mg/L) 1977-2004

  8. Seasonal Kendall Test (Helsel & Hirsch 1992) % per year

  9. Ecologically Important • NOT related to nutrient (N,P) increases

  10. Why is phytoplankton increasing in San Francisco Bay? Four Hypotheses Resources Light Nutrients 1 4 Growth Mortality Impairments Herbicides Metals Transport 2 3

  11. Resources Light Growth 1 Sediment Input (Mt/y) McKee et al. (2006) “sediment yield of the Sacramento River decreased by about half from 1957-2001” (Wright & Schoellhamer 2004).

  12. Growth Impairments Metals 2 City of San Jose, Environmental Services (2006)

  13. Upwelling Intensity Transport 3 NOAA PFEL

  14. Speckled Sanddabs English Sole Mortality 4 California Dept. Fish & Game

  15. Lessons • aquatic ecosystems are in perpetual state of change • unraveling the processes is particularly challenging in estuaries • water quality is influenced by connectivity to the coastal ocean and local watersheds • alien species can be as disruptive as chemical pollution • phytoplankton dynamics are influenced by more than nutrient loadings Thanks to Tara Schraga, Kate Dallas, Alan Jassby, Jan Thompson, Dave Schoellhamer, Kathy Hieb, San Jose Environmental Services, Regional Monitoring Program

  16. Photo: Steve Hager

  17. Chlorophyll varies at time scales from hours to decades

  18. Conceptual Model Resources Light Nutrients Growth Mortality Impairments Herbicides Metals Transport Nancy Monsen

  19. Robin Stewart (USGS): Selenium concentrations in fish Striped Bass White Sturgeon 50 Mean ± SE *** 40 30 * Se conc. (µg/g) 20 10 0 1990 n=25 2000 n=15 1986 n=5 1990 n=10 1999 n=15 1986 n=10 CDFG (data 1986, 1990)

  20. Seasonal Kendall Test for Trends (Helsel & Hirsch 1992) % per year

  21. % per year

  22. Not associated with nutrient increases % per year

  23. Estimated Primary Production (g C/m2-y) 215 120

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