Satellite-Derived Algal Monitoring

With increased attention on harmful algal and cyanobacteria blooms in lakes, there has been a surge in remote-sensing techniques developed to monitor these blooms. Remote-sensing offers unique advantages to traditional techniques, such as the ability to visualize high resolution spatial and temporal variability of blooms, enabling a better understanding of bloom dynamics.

In 2019, a working group was formed consisting of ALMS, the Pigeon Lake Watershed Association (PLWA), Dr. Rolf Vinebrooke from the University of Alberta, Alberta Environment and Parks, and the Alberta Biodiversity Monitoring Institute (ABMI) to begin utilizing satellite imagery to learn more about algal and cyanobacteria bloom dynamics in Pigeon Lake, Alberta. The project began by assessing Sentinel-2 and Sentinel-3 derived chlorophyll-a concentrations in Pigeon Lake using models developed for lakes outside of Alberta. Chlorophyll-a is a pigment found in all algae and cyanobacteria, and its concentration is lake water is used to indicate the abundance of algae and cyanobacteria.

In the summer of 2020, field samples were taken at Pigeon Lake to provide the data necessary to validate a model specific to Pigeon Lake, for the Sentinel-2 and Sentinel-3 satellites. Upon successful model validation, a prototype visualization tool was developed for Pigeon Lake using a Google Earth Engine web application. The visualization tool allows the app user to visualize the distribution of chlorophyll-a concentrations across Pigeon Lake derived from the imagery collected by Sentinel-2 and Sentinel-3, and to also view true-color imagery of the lake. The tool also enables users to interact with satellite-derived bloom metrics such as average chlorophyll-a concentration across the lake, and to compare these values through an open water season, and between years. The web app is still under development, and will be released to the public once ready.


Screenshot of prototype visualization tool, displaying chlorophyll-a concentrations at Pigeon Lake on August 4, 2020.

A current goal of the project is to improve the understanding of algal bloom dynamics at other lakes in Alberta, and to improve the confidence in the integrity of Alberta lake specific chlorophyll-a concentration indices. To address this goal, field samples were collected in the summer of 2021 at Wabamun Lake, Lesser Slave Lake, and Lac La Biche with the assistance of the Wabamun Watershed Management Council (WWMC), Alberta Environment and Parks, the Lesser Slave Watershed Council (LSWC), and Lac La Biche County.


Sentinel-2 satellite imagery of Lac La Biche from August 29, 2021

The trajectory of the project is to develop the visualization tool to enable users to view bloom dynamics in near-real time for multiple lakes in Alberta. The project will also continue to support research into the dynamics of blooms on Alberta lakes, contribute to environmental public health monitoring of blooms, and to provide metrics that enable watershed stewardship groups and government to evaluate lake management initiatives.

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