Katy O'Donnell
Katy O'Donnell - California Water Science Center
Science and Products
In situ chlorophyll fluorometer validation and comparison study
The Sacramento-San Joaquin Delta (Delta) supplies drinking water to much of California. The Delta also provides irrigation water to the Central Valley and is an important habitat to many aquatic and terrestrial species. In the past decade, there has been an increase in harmful algal blooms (HABs) in the Delta. While some HABs are nontoxic, others contain cyanobacteria that can produce dangerous...
Biogeochemistry Group
The Biogeochemistry (BGC) Group uses an interdisciplinary approach to address surface water quality issues and food web dynamics throughout California, particularly in the Sacramento-San Joaquin Delta and San Francisco Bay.
Causes and Relevance of Phytoplankton Blooms in the Northern Sacramento-San Joaquin Delta
Phytoplankton are an important part of aquatic food webs and ecosystems. These single-celled plants grow faster in the stronger light of spring or summer, resulting in population explosions called phytoplankton blooms. These blooms in turn feed zooplankton (free-floating aquatic microorganisms), providing food for many aquatic species, including fish, shrimp, crabs, and other invertebrates.
Filter Total Items: 22
Phytoplankton Species Composition and Abundance in the Sacramento-San Joaquin River Delta: Microscopic Enumeration of USGS Samples, beginning in 2016 (ver. 2.0, December 2025) Phytoplankton Species Composition and Abundance in the Sacramento-San Joaquin River Delta: Microscopic Enumeration of USGS Samples, beginning in 2016 (ver. 2.0, December 2025)
This dataset contains multiple types of data characterizing phytoplankton in the Sacramento-San Joaquin Delta (California, USA). 1) Bright field microscopy was used to identify and enumerate phytoplankton community composition; 2) Epifluorescent microscopy was used to enumerate picophytoplankton (phytoplankton cells less than 2 microns in diameter) and, 3) a categorical visual index...
Above-water hyperspectral field spectroscopy and associated water quality measurements in the Sacramento-San Joaquin Delta, California, collected in 2024 and 2025 Above-water hyperspectral field spectroscopy and associated water quality measurements in the Sacramento-San Joaquin Delta, California, collected in 2024 and 2025
Broad-area, high-resolution, boat-based water quality mapping surveys of the Sacramento-San Joaquin Delta (Delta) were conducted in June and September of 2024. Each survey was comprised of one day of high-resolution mapping. The regions covered included Discovery Bay and Old and Middle Rivers in the South Delta Tidal Transition Zone. On each day, the route of the mapping survey was...
Water quality and nutrient data from San Joaquin River and Stockton Waterfront, April and August 2024 Water quality and nutrient data from San Joaquin River and Stockton Waterfront, April and August 2024
This dataset records diel changes to water quality parameters, nutrients, and phytoplankton biomass in the south-eastern region of the Sacramento-San Joaquin Delta. Sampling occurred in August 2024 in the Stockton Waterfront (City of Stockton, San Joaquin County, California, USA) and San Joaquin River. Data was collected from approximately 6am to 9pm Pacific Standard Time on August 6, 13...
Assessing spatial variability of nutrients, phytoplankton, and related water quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2023 High resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton, and related water quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2023 High resolution mapping surveys
Broad-area, high-resolution, boat-based water quality mapping surveys of the Sacramento-San Joaquin Delta and Suisun Bay (Delta) of California, USA were conducted under different environmental/flow conditions in May, July, and October of 2023. The spatial and temporal variability of nutrients, phytoplankton, and related water quality parameters were assessed. This dataset includes...
Assessing spatial variability of nutrients, phytoplankton and related water-quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2022 High-resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton and related water-quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2022 High-resolution mapping surveys
Broad-area, high-resolution, boat-based water quality mapping surveys of the Sacramento-San Joaquin Delta and Suisun Bay (Delta) of California, USA were conducted under different environmental/flow conditions in May, July, and October of 2022. The spatial and temporal variability of nutrients, phytoplankton, and related water quality parameters were assessed. This dataset includes...
Above-water hyperspectral field spectroscopy measurements at Franks Tract in the Sacramento-San Joaquin Delta, California Above-water hyperspectral field spectroscopy measurements at Franks Tract in the Sacramento-San Joaquin Delta, California
Hand-held hyperspectral spectroscopy data were collected in 2022 in Franks Tract, a flooded area located in the central Sacramento-San Joaquin Delta of California. The data were collected from a boat and co-located within pixels from the Ocean Land Color Imaging (OLCI) sensor on the Sentinel-3A and 3-B satellites. Data from 16 sites within 7 OLCI pixels were collected on three days: July...
Filter Total Items: 16
Identifying conditions associated with outliers produced by three different chlorophyll fluorometers: A comparison of instrumentation and development of correction formulae Identifying conditions associated with outliers produced by three different chlorophyll fluorometers: A comparison of instrumentation and development of correction formulae
Measurements of chlorophyll concentration reported by fluorometers (fChl) are used in environmental research and monitoring, as inputs to models, and in the interpretation of remote sensing data. Researchers and managers benefit from understanding how to interpret and ensure the accuracy of fChl data collected by in situ fluorometers. Although fChl values produced by different...
Authors
Emily T. Richardson, Tamara E. C. Kraus, Crystal Lee Sturgeon, Katy O’Donnell, Brian A. Bergamaschi
Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—Comparison of four (2018, 2020, 2021, 2022) spring high-resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—Comparison of four (2018, 2020, 2021, 2022) spring high-resolution mapping surveys
Executive Summary This report summarizes results from boat-based, high-resolution water-quality mapping surveys completed before, during, and after upgrades to the EchoWater Resource Recovery Facility (EchoWater Facility), the regional wastewater facility for the City of Sacramento and surrounding areas, near Elk Grove, California. Surveys were completed in the tidal aquatic environments...
Authors
Emily Richardson, Tamara Kraus, Katy O’Donnell, Jeniffer Soto-Perez, Crystal Sturgeon, Elizabeth Stumpner, Brian Bergamaschi
Amphibian and reptile conservation in the United States of America Amphibian and reptile conservation in the United States of America
Wildlife stewardship is of utmost importance in the United States, where management for sustainable natural resources is extended to native species including amphibians and reptiles. The U.S. wildlife conservation framework is a nested system of authorities regulating species and habitats, science-based management and policy decisions, and adaptive management as new knowledge is applied...
Authors
Deanna H. Olson, David S. Pilliod
Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—2018 high resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—2018 high resolution mapping surveys
Executive Summary This study examined the abundance and distribution of nutrients and phytoplankton in the tidal aquatic environments of the Sacramento–San Joaquin Delta (Delta) and Suisun Bay, comprising three spatial surveys conducted in May, July, and October of 2018 that used continuous underway high frequency sampling and measurements onboard a high-speed boat to characterize...
Authors
Brian A. Bergamaschi, Tamara E. C. Kraus, Bryan D. Downing, Elizabeth B. Stumpner, Katy O’Donnell, Jeffrey A. Hansen, Jeniffer Soto Perez, Emily T. Richardson, Angela M. Hansen, Alan Gelber
A simple approach to modeling light attenuation in the Sacramento-San Joaquin Delta using commonly available data A simple approach to modeling light attenuation in the Sacramento-San Joaquin Delta using commonly available data
The diffuse attenuation coefficient of photosynthetically active radiation (KdPAR) is commonly used to predict light attenuation in aquatic productivity models, but obtaining measurements of PAR to compute KdPAR is difficult. In situ calculations of KdPAR require multiple measurements of PAR through the water column, and these measurements are infeasible for real-time recording. Instead
Authors
Emily T. Richardson, Keith Bouma-Gregson, Katy O’Donnell, Brian A. Bergamaschi
A novel boat-based field application of a high-frequency conductometric ammonium analyzer to characterize spatial variation in aquatic ecosystems A novel boat-based field application of a high-frequency conductometric ammonium analyzer to characterize spatial variation in aquatic ecosystems
Documenting dissolved inorganic nitrogen (DIN) concentration and form at appropriate temporal and spatial scales is key to understanding aquatic ecosystem health, particularly as DIN fuels primary productivity. In addition to point and non-point source nutrient inputs, factors such as hydrology, geomorphology, temperature, light, and biogeochemical transformations influence nutrient...
Authors
Emily T. Richardson, Angela Hansen, Tamara E. C. Kraus, Bryan D. Downing, Don Forsberg, John Stillian, Katy O’Donnell, Crystal Lee Sturgeon, Brian A. Bergamaschi
Bay- Delta Water Quality, Nutrient and Phytoplankton Mapping | US Geological Survey Bay- Delta Water Quality, Nutrient and Phytoplankton Mapping | US Geological Survey
Data visualization tool created for California's Bay-Delta Regional Monitoring Program. This web applicaton visualizes nutrients and phytoplankton spatially and temporally.
Science and Products
In situ chlorophyll fluorometer validation and comparison study
The Sacramento-San Joaquin Delta (Delta) supplies drinking water to much of California. The Delta also provides irrigation water to the Central Valley and is an important habitat to many aquatic and terrestrial species. In the past decade, there has been an increase in harmful algal blooms (HABs) in the Delta. While some HABs are nontoxic, others contain cyanobacteria that can produce dangerous...
Biogeochemistry Group
The Biogeochemistry (BGC) Group uses an interdisciplinary approach to address surface water quality issues and food web dynamics throughout California, particularly in the Sacramento-San Joaquin Delta and San Francisco Bay.
Causes and Relevance of Phytoplankton Blooms in the Northern Sacramento-San Joaquin Delta
Phytoplankton are an important part of aquatic food webs and ecosystems. These single-celled plants grow faster in the stronger light of spring or summer, resulting in population explosions called phytoplankton blooms. These blooms in turn feed zooplankton (free-floating aquatic microorganisms), providing food for many aquatic species, including fish, shrimp, crabs, and other invertebrates.
Filter Total Items: 22
Phytoplankton Species Composition and Abundance in the Sacramento-San Joaquin River Delta: Microscopic Enumeration of USGS Samples, beginning in 2016 (ver. 2.0, December 2025) Phytoplankton Species Composition and Abundance in the Sacramento-San Joaquin River Delta: Microscopic Enumeration of USGS Samples, beginning in 2016 (ver. 2.0, December 2025)
This dataset contains multiple types of data characterizing phytoplankton in the Sacramento-San Joaquin Delta (California, USA). 1) Bright field microscopy was used to identify and enumerate phytoplankton community composition; 2) Epifluorescent microscopy was used to enumerate picophytoplankton (phytoplankton cells less than 2 microns in diameter) and, 3) a categorical visual index...
Above-water hyperspectral field spectroscopy and associated water quality measurements in the Sacramento-San Joaquin Delta, California, collected in 2024 and 2025 Above-water hyperspectral field spectroscopy and associated water quality measurements in the Sacramento-San Joaquin Delta, California, collected in 2024 and 2025
Broad-area, high-resolution, boat-based water quality mapping surveys of the Sacramento-San Joaquin Delta (Delta) were conducted in June and September of 2024. Each survey was comprised of one day of high-resolution mapping. The regions covered included Discovery Bay and Old and Middle Rivers in the South Delta Tidal Transition Zone. On each day, the route of the mapping survey was...
Water quality and nutrient data from San Joaquin River and Stockton Waterfront, April and August 2024 Water quality and nutrient data from San Joaquin River and Stockton Waterfront, April and August 2024
This dataset records diel changes to water quality parameters, nutrients, and phytoplankton biomass in the south-eastern region of the Sacramento-San Joaquin Delta. Sampling occurred in August 2024 in the Stockton Waterfront (City of Stockton, San Joaquin County, California, USA) and San Joaquin River. Data was collected from approximately 6am to 9pm Pacific Standard Time on August 6, 13...
Assessing spatial variability of nutrients, phytoplankton, and related water quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2023 High resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton, and related water quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2023 High resolution mapping surveys
Broad-area, high-resolution, boat-based water quality mapping surveys of the Sacramento-San Joaquin Delta and Suisun Bay (Delta) of California, USA were conducted under different environmental/flow conditions in May, July, and October of 2023. The spatial and temporal variability of nutrients, phytoplankton, and related water quality parameters were assessed. This dataset includes...
Assessing spatial variability of nutrients, phytoplankton and related water-quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2022 High-resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton and related water-quality constituents in the California Sacramento-San Joaquin Delta at the landscape scale: 2022 High-resolution mapping surveys
Broad-area, high-resolution, boat-based water quality mapping surveys of the Sacramento-San Joaquin Delta and Suisun Bay (Delta) of California, USA were conducted under different environmental/flow conditions in May, July, and October of 2022. The spatial and temporal variability of nutrients, phytoplankton, and related water quality parameters were assessed. This dataset includes...
Above-water hyperspectral field spectroscopy measurements at Franks Tract in the Sacramento-San Joaquin Delta, California Above-water hyperspectral field spectroscopy measurements at Franks Tract in the Sacramento-San Joaquin Delta, California
Hand-held hyperspectral spectroscopy data were collected in 2022 in Franks Tract, a flooded area located in the central Sacramento-San Joaquin Delta of California. The data were collected from a boat and co-located within pixels from the Ocean Land Color Imaging (OLCI) sensor on the Sentinel-3A and 3-B satellites. Data from 16 sites within 7 OLCI pixels were collected on three days: July...
Filter Total Items: 16
Identifying conditions associated with outliers produced by three different chlorophyll fluorometers: A comparison of instrumentation and development of correction formulae Identifying conditions associated with outliers produced by three different chlorophyll fluorometers: A comparison of instrumentation and development of correction formulae
Measurements of chlorophyll concentration reported by fluorometers (fChl) are used in environmental research and monitoring, as inputs to models, and in the interpretation of remote sensing data. Researchers and managers benefit from understanding how to interpret and ensure the accuracy of fChl data collected by in situ fluorometers. Although fChl values produced by different...
Authors
Emily T. Richardson, Tamara E. C. Kraus, Crystal Lee Sturgeon, Katy O’Donnell, Brian A. Bergamaschi
Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—Comparison of four (2018, 2020, 2021, 2022) spring high-resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—Comparison of four (2018, 2020, 2021, 2022) spring high-resolution mapping surveys
Executive Summary This report summarizes results from boat-based, high-resolution water-quality mapping surveys completed before, during, and after upgrades to the EchoWater Resource Recovery Facility (EchoWater Facility), the regional wastewater facility for the City of Sacramento and surrounding areas, near Elk Grove, California. Surveys were completed in the tidal aquatic environments...
Authors
Emily Richardson, Tamara Kraus, Katy O’Donnell, Jeniffer Soto-Perez, Crystal Sturgeon, Elizabeth Stumpner, Brian Bergamaschi
Amphibian and reptile conservation in the United States of America Amphibian and reptile conservation in the United States of America
Wildlife stewardship is of utmost importance in the United States, where management for sustainable natural resources is extended to native species including amphibians and reptiles. The U.S. wildlife conservation framework is a nested system of authorities regulating species and habitats, science-based management and policy decisions, and adaptive management as new knowledge is applied...
Authors
Deanna H. Olson, David S. Pilliod
Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—2018 high resolution mapping surveys Assessing spatial variability of nutrients, phytoplankton, and related water-quality constituents in the California Sacramento–San Joaquin Delta at the landscape scale—2018 high resolution mapping surveys
Executive Summary This study examined the abundance and distribution of nutrients and phytoplankton in the tidal aquatic environments of the Sacramento–San Joaquin Delta (Delta) and Suisun Bay, comprising three spatial surveys conducted in May, July, and October of 2018 that used continuous underway high frequency sampling and measurements onboard a high-speed boat to characterize...
Authors
Brian A. Bergamaschi, Tamara E. C. Kraus, Bryan D. Downing, Elizabeth B. Stumpner, Katy O’Donnell, Jeffrey A. Hansen, Jeniffer Soto Perez, Emily T. Richardson, Angela M. Hansen, Alan Gelber
A simple approach to modeling light attenuation in the Sacramento-San Joaquin Delta using commonly available data A simple approach to modeling light attenuation in the Sacramento-San Joaquin Delta using commonly available data
The diffuse attenuation coefficient of photosynthetically active radiation (KdPAR) is commonly used to predict light attenuation in aquatic productivity models, but obtaining measurements of PAR to compute KdPAR is difficult. In situ calculations of KdPAR require multiple measurements of PAR through the water column, and these measurements are infeasible for real-time recording. Instead
Authors
Emily T. Richardson, Keith Bouma-Gregson, Katy O’Donnell, Brian A. Bergamaschi
A novel boat-based field application of a high-frequency conductometric ammonium analyzer to characterize spatial variation in aquatic ecosystems A novel boat-based field application of a high-frequency conductometric ammonium analyzer to characterize spatial variation in aquatic ecosystems
Documenting dissolved inorganic nitrogen (DIN) concentration and form at appropriate temporal and spatial scales is key to understanding aquatic ecosystem health, particularly as DIN fuels primary productivity. In addition to point and non-point source nutrient inputs, factors such as hydrology, geomorphology, temperature, light, and biogeochemical transformations influence nutrient...
Authors
Emily T. Richardson, Angela Hansen, Tamara E. C. Kraus, Bryan D. Downing, Don Forsberg, John Stillian, Katy O’Donnell, Crystal Lee Sturgeon, Brian A. Bergamaschi
Bay- Delta Water Quality, Nutrient and Phytoplankton Mapping | US Geological Survey Bay- Delta Water Quality, Nutrient and Phytoplankton Mapping | US Geological Survey
Data visualization tool created for California's Bay-Delta Regional Monitoring Program. This web applicaton visualizes nutrients and phytoplankton spatially and temporally.