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Tara Schraga

Tara Schraga is an Oceanographer for the USGS Water Resources Mission Area.

Website: Water Quality of San Francisco Bay https://sfbay.wr.usgs.gov/access/wqdata/

Science and Products

Nutrient status of San Francisco Bay and its management implications

Nutrient enrichment has degraded many of the world’s estuaries by amplifying algal production, leading to hypoxia/anoxia, loss of vascular plants and fish/shellfish habitat, and expansion of harmful blooms (HABs). Policies to protect coastal waters from the effects of nutrient enrichment require information to determine if a water body is impaired by nutrients and if regulatory actions are require
Authors
James E. Cloern, Tara Schraga, Erica Nejad, Charles A. Martin
By
Water Resources Mission Area

Water quality measurements in San Francisco Bay by the U.S. Geological Survey, 1969–2015

The U.S. Geological Survey (USGS) maintains a place-based research program in San Francisco Bay (USA) that began in 1969 and continues, providing one of the longest records of water-quality measurements in a North American estuary. Constituents include salinity, temperature, light extinction coefficient, and concentrations of chlorophyll-a, dissolved oxygen, suspended particulate matter, nitrate,
Authors
Tara Schraga, James E. Cloern
By
Water Resources Mission Area

Ecosystem variability along the estuarine salinity gradient: Examples from long-term study of San Francisco Bay

The salinity gradient of estuaries plays a unique and fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes. We use variability along the salinity gradient of San Francisco Bay to illustrate some lessons about the diversity of spatial structures in estuaries and their variability over time. Spatial patterns of dissolved constituents (e.g., sil
Authors
James E. Cloern, Alan D. Jassby, Tara Schraga, Erica S. Kress, Charles A. Martin
By
Water Resources Mission Area, San Francisco Bay and Sacramento-San Joaquin Delta Estuary

Primary production and carrying capacity of former salt ponds after reconnection to San Francisco Bay

Over 6,110 ha of the commercial production salt ponds surrounding South San Francisco Bay, CA, have been decommissioned and reconnected to the bay, most as part of the largest wetlands restoration program in the western United States. These open water ponds are critical habitat for millions of birds annually and restoration program managers must determine the appropriate balance between retention
Authors
Julien Thébault, Tara Schraga, James E. Cloern, Eric G. Dunlavey
By
Water Resources Mission Area, Ecosystems Mission Area, Toxic Substances Hydrology, Environmental Health Program, California Water Science Center

Ecological values of shallow-water habitats: Implications for the restoration of disturbed ecosystems

A presumed value of shallow-habitat enhanced pelagic productivity derives from the principle that in nutrient-rich aquatic systems phytoplankton growth rate is controlled by light availability, which varies inversely with habitat depth. We measured a set of biological indicators across the gradient of habitat depth within the Sacramento–San Joaquin River Delta (California) to test the hypothesis t
Authors
C.B. Lopez, J. E. Cloern, T.S. Schraga, A.J. Little, L.V. Lucas, J.K. Thompson, J.R. Burau
By
Water Resources Mission Area, Ecosystems Mission Area, Toxic Substances Hydrology, Environmental Health Program, California Water Science Center, San Francisco Bay and Sacramento-San Joaquin Delta Estuary

Intradaily variability of water quality in a shallow tidal lagoon: Mechanisms and implications

Although surface water quality and its underlying processes vary over time scales ranging from seconds to decades, they have historically been studied at the lower (weekly to interannual) frequencies. The aim of this study was to investigate intradaily variability of three water quality parameters in a small freshwater tidal lagoon (Mildred Island, California). High frequency time series of specif
Authors
L.V. Lucas, D.M. Sereno, J.R. Burau, T.S. Schraga, C.B. Lopez, M.T. Stacey, K.V. Parchevsky, V.P. Parchevsky
By
Water Resources Mission Area, Ecosystems Mission Area, Toxic Substances Hydrology, Environmental Health Program, California Water Science Center

Heat wave brings an unprecedented red tide to San Francisco Bay

An exceptional red tide in San Francisco Bay was observed on 8 September 2004. The red tide had chlorophyll concentrations approaching 200 mg/m3 (Figure 1) in red/purple surface streaks containing high abundances of the dinoflagellate Akashiwo sanguinea. Red tides and harmful algal blooms (HABs) are common features of coastal ecosystems, and their growing frequency is a suspected outcome of coasta
Authors
James E. Cloern, Tara S. Schraga, Cary B. Lopez
By
San Francisco Bay and Sacramento-San Joaquin Delta Estuary

Climate anomalies generate an exceptional dinoflagellate bloom in San Francisco Bay

We describe a large dinoflagellate bloom, unprecedented in nearly three decades of observation, that developed in San Francisco Bay (SFB) during September 2004. SFB is highly enriched in nutrients but has low summer‐autumn algal biomass because wind stress and tidally induced bottom stress produce a well mixed and light‐limited pelagic habitat. The bloom coincided with calm winds and record high a
Authors
J. E. Cloern, T.S. Schraga, C.B. Lopez, N. Knowles, Labiosa R. Grover, R. Dugdale
By
Water Resources Mission Area, Ecosystems Mission Area, Toxic Substances Hydrology, Environmental Health Program, California Water Science Center

Detritus fuels ecosystem metabolism but not metazoan food webs in San Francisco estuary's freshwater delta

Detritus from terrestrial ecosystems is the major source of organic matter in many streams, rivers, and estuaries, yet the role of detritus in supporting pelagic food webs is debated. We examined the importance of detritus to secondary productivity in the Sacramento and San Joaquin River Delta (California, United States), a large complex of tidal freshwater habitats. The Delta ecosystem has low pr
Authors
W. V. Sobczak, J. E. Cloern, A.D. Jassby, B.E. Cole, T.S. Schraga, A. Arnsberg
By
Water Resources Mission Area, California Water Science Center

Lessons from monitoring water quality in San Francisco Bay

San Francisco Bay is the defining landscape feature of the place we call ‘The Bay Area,’ but most of us only experience the Bay as we view it from an airplane window or drive across one of its bridges. These views from afar suggest that the Bay is static and sterile, but this impression is deceptive. If you are one of the many thousands of students who have experienced the Bay through a school exc
Authors
J. E. Cloern, T.S. Schraga, C.B. Lopez, R. Labiosa
By
San Francisco Bay and Sacramento-San Joaquin Delta Estuary

Pulsey, patchy water quality in the delta: Implications for meaningful monitoring

Valuable water quality and biological datasets have been gathered in the Sacramento-San Joaquin Delta for decades, most notably by the Interagency Ecological Program’s Environmental Monitoring Program (EMP). These extensive data have provided a means of analyzing and detecting long-term trends in water quality and ecosystem function (Jassby and others 2002; Kimmerer and Orsi 1996; Orsi and Mecum 1
Authors
Lisa V. Lucas, Tara Schraga, Cary B. Lopez, Jon R. Burau, Alan D. Jassby
By
Water Resources Mission Area, California Water Science Center
link
Map showing current San Francisco Bay-Delta water quality sampling station locations.

Sampling Locations for the Water Quality of San Francisco Bay Project

Since 1969, the Water Quality of San Francisco Bay Research and Monitoring Project has conducted water-column sampling along the deep channel of the San Francisco Bay-Delta system. Learn more about when and where we collect data.
By
Water Resources Mission Area, California Water Science Center
link

Sampling Locations for the Water Quality of San Francisco Bay Project

Since 1969, the Water Quality of San Francisco Bay Research and Monitoring Project has conducted water-column sampling along the deep channel of the San Francisco Bay-Delta system. Learn more about when and where we collect data.
Learn More
link
Scientist sample for clams aboard the R/V Polaris in North San Francisco Bay.

Sampling Methods for the Water Quality of San Francisco Bay Project

The Water Quality of San Francisco Bay Research and Monitoring Project measures changes in water quality along the deep channel of the San Francisco Bay-Delta system using submersible sensors and discrete water samples. Learn more about how we collect and measure water-quality data.
By
Water Resources Mission Area, California Water Science Center
link

Sampling Methods for the Water Quality of San Francisco Bay Project

The Water Quality of San Francisco Bay Research and Monitoring Project measures changes in water quality along the deep channel of the San Francisco Bay-Delta system using submersible sensors and discrete water samples. Learn more about how we collect and measure water-quality data.
Learn More
link
R/V David H. Peterson at the Redwood City dock.

Research Vessel David H. Peterson

The Research Vessel David H. Peterson begain service with the U.S. Geological Survey in 2015. Named after a founder of the Water Quality of San Francisco Bay Research and Monitoring Project, this vessel is a high-tech scientific platform for estuarine research. Learn more about how the R/V David H. Peterson makes our research possible.
By
Water Resources Mission Area
link

Research Vessel David H. Peterson

The Research Vessel David H. Peterson begain service with the U.S. Geological Survey in 2015. Named after a founder of the Water Quality of San Francisco Bay Research and Monitoring Project, this vessel is a high-tech scientific platform for estuarine research. Learn more about how the R/V David H. Peterson makes our research possible.
Learn More
link
R/V David H. Peterson at the Redwood City dock.

Water Quality of San Francisco Bay Research and Monitoring Project

Since 1969, the U.S. Geological Survey has maintained a research project in the San Francisco Bay-Delta system to measure and understand how estuarine systems and tidal river deltas function and change in response to hydro-climatic variability and human activities.
By
Water Resources Mission Area, California Water Science Center
link

Water Quality of San Francisco Bay Research and Monitoring Project

Since 1969, the U.S. Geological Survey has maintained a research project in the San Francisco Bay-Delta system to measure and understand how estuarine systems and tidal river deltas function and change in response to hydro-climatic variability and human activities.
Learn More

USGS Measurements of Water Quality in San Francisco Bay (CA), 2016-2021 (ver. 4.0, March 2023)

The U.S. Geological Survey maintains a program of water-quality studies in San Francisco Bay (CA) that began in 1969. This U.S.G.S. Data Release is a continuation of the previously published 1969-2015 dataset (Cloern and Schraga, 2016; Schraga and Cloern, 2017), it will archive and make available all measurements from 2016 and thereafter. Each year, a data file containing the previous years data w
By
Water Resources Mission Area

Phytoplankton Species Composition, Abundance and Cell Size in San Francisco Bay: Microscopic Analyses of USGS Samples Collected 1992-2014

This Data Release makes available measurements of phytoplankton species composition, abundance and cell size made on samples collected in San Francisco Bay (CA) from April 1992 through March 2014. Phytoplankton samples were collected at 31 stations along a 145-km transect where the variability of salinity, temperature, turbidity and nutrient concentrations reflected a broad range of environmental
By
Water Resources Mission Area

USGS Measurements of Water Quality in San Francisco Bay (CA), 1969-2015 (ver. 4.0, March 2023)

The U.S. Geological Survey maintains a program of water-quality studies in San Francisco Bay (CA) that began in 1969. We plan a USGS Data Release to archive and make available all measurements made from 1969 through 2015. Water-quality constituents include salinity, temperature, light attenuation coefficient, and concentrations of chlorophyll-a, dissolved oxygen, suspended particulate matter, nitr

Science and Products