In situ chlorophyll fluorometer validation and comparison study
Evaluating how environmental conditions affect chlorophyll concentration measurements
Photo: A view of San Francisco from USGS research vessel
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 toxins, posing health risks to people and animals.
To keep the public informed about harmful algal blooms (HABs), the U.S. Geological Survey (USGS) publishes chlorophyll concentration data. Researchers and regulators use this data to:
- Understand the causes of HABs
- Validate remote sensing data
- Create predictive tools
- Guide management actions and regulations
Background
Over the last decade, there has been increasing use of in situ chlorophyll fluorometers that provide continuous, real-time chlorophyll concentration data. More recently, a wealth of in situ chlorophyll fluorescence (fChl) data has been collected in the Delta during boat-based mapping surveys. During each survey, data were collected using three types of chlorophyll fluorometers. These data were collected along with a suite of other in situ water quality measurements.
Additionally, discrete samples were collected and analyzed for chlorophyll-a concentration, and for phytoplankton enumeration (species identification, cell density and biomass) and picophytoplankton enumeration (cell density and biomass).
Objectives
The goal of this study is to identify the reasons for discrepancies between fChl measurements made under different sampling conditions. This goal can be split into two broad objectives:
- Identify conditions and factors leading to fChl sensor disagreements.
- Assess which sensors are best suited to HAB monitoring
Project Scope and Approach
To achieve project goals, scientists will evaluate which environmental conditions affect differences in chlorophyll concentration measurements. Evaluation will be done for each type of in situ chlorophyll fluorometer. Initial assessment of field data guide targeted laboratory studies.
Relevance and Benefits
Understanding the differences between sensors will help the USGS establish quality control procedures, inform users about data quality, and assist researchers in selecting the right sensors for their projects. This work is also important for other aquatic systems since chlorophyll fluorometers are widely used to provide essential information about water quality and ecosystem health nationwide. The insights from this project will enable USGS researchers to better interpret in situ fChl data and guide the use of different sensors, especially as this data is integrated into models and remote sensing interpretations.
Biogeochemistry Group
National Field Manual for the Collection of Water-Quality Data (NFM)
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 toxins, posing health risks to people and animals.
To keep the public informed about harmful algal blooms (HABs), the U.S. Geological Survey (USGS) publishes chlorophyll concentration data. Researchers and regulators use this data to:
- Understand the causes of HABs
- Validate remote sensing data
- Create predictive tools
- Guide management actions and regulations
Background
Over the last decade, there has been increasing use of in situ chlorophyll fluorometers that provide continuous, real-time chlorophyll concentration data. More recently, a wealth of in situ chlorophyll fluorescence (fChl) data has been collected in the Delta during boat-based mapping surveys. During each survey, data were collected using three types of chlorophyll fluorometers. These data were collected along with a suite of other in situ water quality measurements.
Additionally, discrete samples were collected and analyzed for chlorophyll-a concentration, and for phytoplankton enumeration (species identification, cell density and biomass) and picophytoplankton enumeration (cell density and biomass).
Objectives
The goal of this study is to identify the reasons for discrepancies between fChl measurements made under different sampling conditions. This goal can be split into two broad objectives:
- Identify conditions and factors leading to fChl sensor disagreements.
- Assess which sensors are best suited to HAB monitoring
Project Scope and Approach
To achieve project goals, scientists will evaluate which environmental conditions affect differences in chlorophyll concentration measurements. Evaluation will be done for each type of in situ chlorophyll fluorometer. Initial assessment of field data guide targeted laboratory studies.
Relevance and Benefits
Understanding the differences between sensors will help the USGS establish quality control procedures, inform users about data quality, and assist researchers in selecting the right sensors for their projects. This work is also important for other aquatic systems since chlorophyll fluorometers are widely used to provide essential information about water quality and ecosystem health nationwide. The insights from this project will enable USGS researchers to better interpret in situ fChl data and guide the use of different sensors, especially as this data is integrated into models and remote sensing interpretations.