Short-Term and Interannual Variability in Primary Production in the Low-Salinity Zone of the San Francisco Estuary

• Published in: Estuaries and coasts Vol. 35; no. 4; pp. 913 - 929
• Main Authors: Kimmerer, Wim J., Parker, Alexander E., Lidström, Ulrika E., Carpenter, Edward J.
• Format: Journal Article
• Language: English
• Published: New York Spring Science + Business Media 01-07-2012; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Algae; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomass; Biomass production; Brackish; Brackish water ecosystems; Chlorophyll; Chlorophylls; Coastal Sciences; Coefficients; Earth and Environmental Science; Ecology; Environment; Environmental Management; Estuaries; Fresh water; Freshwater & Marine Ecology; Freshwater fish; Fundamental and applied biological sciences. Psychology; Nutrient flow; Nutrient loading; Photosynthetically active radiation; Phytoplankton; Primary production; Primary productivity; Productivity; Salinity; Synecology; Trophic levels; Water and Health; INE, USA, California, San Francisco Estuary; Chlorophyll; Phytoplankton; Biomass; San Francisco Estuary; Temporal variability; Primary production; Short term; Estuaries; Brackish water environment; Primary productivity; Salinity
• ISSN: 1559-2723; 1559-2731
• DOI: 10.1007/s12237-012-9482-2

We measured primary production during spring–summer 2006–2007 to determine the carbon supply to the low-salinity pelagic food web of the San Francisco Estuary (SFE). Weekly or biweekly samples were taken at three stations of fixed salinity for size-fractionated primary production and biomass, both as chlorophyll and from biovolume based on counts. Error variance in productivity estimates arose mainly from the depth integration of 14 C uptake, showing the importance of productivity measurements at high light levels for estimates of depth-integrated production. Temporal and spatial variability in production were surprisingly small. Combining data from this study with long-term monitoring data, productivity and biomass were variable in time and salinity but without persistent patterns and with infrequent blooms. Production within the low-salinity zone was unresponsive to variation in freshwater flow, in contrast to findings in other estuaries where nutrient loading drives variability in production and other regions of the SFE where production responds to residence time or to stratification. Estimated annual primary production was only 25 and 31 gC m −2 year −1 during 2006 and 2007, only half of it in cells >5 μm. These results imply that phytoplankton provided poor food web support for higher trophic levels, probably contributing to the long-term decline in fish abundance in the brackish to freshwater region of the estuary.