EPA Researchers Develop Forecasting Approach To Predict Harmful Cyanobacterial Blooms For U.S. Lakes
By U.S. EPA
Freshwater cyanobacteria are found in all lakes and reservoirs. Cyanobacteria are naturally occurring and important to water ecosystems. However, excessive growth of these bacteria may cause harmful cyanobacterial blooms (HCBs, also called cyanobacterial harmful algal blooms or cyanoHABs), which may also produce toxins. These toxins can negatively impact people, animals, and the environment through water recreation (swimming and boating), drinking water, livestock, fisheries, and irrigation. Cyanobacterial biomass can result in unsightly surface scums, water taste and odor issues, hypoxia, reduced aquatic diversity, and even socio-economic impacts.
Due to climate and land use pressures, there is concern that HCBs may increase in frequency, extent, and magnitude, but it can be difficult to know when and where HCBs may form. EPA’s Safe and Sustainable Water Resources research uses a range of data sources and methods to characterize HCBs in waterbodies.
One example of this research is a recently published paper from EPA scientists Blake Schaeffer, Wilson Salls, Deron Smith, John Johnston, Mark Myer, and former Oak Ridge Institute for Science and Education (ORISE) participants Natalie Reynolds and Hannah Ferriby. Their work developed a scientific approach for forecasting freshwater HCBs using satellite data. This approach was the first of its kind to successfully forecast high-risk HCB events across 2,192 of the largest lakes in the contiguous U.S.
EPA researcher Wilson Salls preparing instruments on a boat for a satellite overpass.
“There is a lot of ongoing research to forecast HCBs at small scales for lakes, but the novelty of this approach is that it does so at such a broad spatial scale,” Wilson Salls, an EPA environmental scientist, said.
The forecasting approach will be especially useful to water quality managers, as it provides a seven-day advanced notice of blooms. In the paper, the authors demonstrated the approach for the entire 2021 calendar year.
“Our research may be one of the first times that we are examining and predicting water quality analogous to weather forecasting,” Blake Schaeffer, an EPA research scientist, explained.
The researchers applied Bayesian modeling, which is a probabilistic statistical method, in combination with satellite monitoring data and a set of simple environmental predictors to estimate the probability of a cyanobacterial bloom occurring in a given week. It used cyanobacteria presence data sourced from the Cyanobacteria Assessment Network (CyAN) project along with environmental predictor variables from 2017 to 2020. The prediction results were compared against the actual cyanobacteria presence observed in satellite imagery to provide performance statistics for 2021. The model’s overall prediction accuracy was 90%.
“This research provides a tool that uses a large dataset of past HCB information from satellite imagery, and predictors such as lake morphology, lake temperature, and precipitation, to deliver a good prediction of future HCB events,” Mark Myer, an EPA risk assessor, said.
The studied model is in direct response to The Harmful Algal Bloom and Hypoxia Research and Control Amendments Act, which requires EPA to advance the scientific understanding and ability to detect, monitor, assess, and predict HAB and hypoxia events in freshwater across the U.S.
In the future, this approach may be used operationally to forecast HCBs and help water resource managers and associated public health professionals in their planning and response efforts.
“CyAN gave us a powerful tool to provide the monitoring, and many of our state and tribal partners rely on that tool. The new model delivers on the forecasting side and the approach will help those same partners get ahead of blooms and provide better protection for human health and the environment,” Michael Paul, an EPA ecologist, said.
Schaeffer will present this work at the first HABs, Hypoxia, and Nutrients Research Webinar on January 31st at 2:00 p.m. ET. This webinar is free to the public and the recording will be posted on the HABs, Hypoxia, and Nutrients webinar series webpage.
Related Resources
Read the journal article: Forecasting freshwater cyanobacterial harmful algal blooms for Sentinel-3 satellite resolved U.S. lakes and reservoirs
EPA’s Harmful Algal Blooms Research
Registration for the HABs, Hypoxia, and Nutrients Research Webinar Series
Cyanobacteria Assessment Network (CyAN)
Science Matters Story on “American Possibilities: A White House Demo Day”