Using satellites to track toxic algal blooms from space

As the weather warms, many Albertans look forward to bright summer days spent fishing, boating, swimming or simply enjoying a lakeside stroll. But the sight of a dreaded green sludge can quickly derail those plans.

Algal blooms are a relatively common occurrence in lakes throughout the province and result from numerous factors, including an abundance of nutrients. While not all blooms are harmful, some can be much more than a simple eyesore. An algal bloom is harmful when toxin-producing organisms like blue-green cyanobacteria are present. Blue-green algae produce liver and neurotoxins that can pose a danger to wildlife, livestock and pets. In extreme cases, the algal blooms pose a health risk to humans, and health advisories caution lake-goers to avoid contact with affected lakes.

Aquatic life doesn’t fare any better under a harmful algal bloom. Once the bloom gets going, it spreads like a weed and quickly consumes the available nutrients in the water. When the algae die off come winter, their decomposition robs the water of oxygen and may create a dead zone which is inhospitable to fish and most other aquatic organisms.

With such pronounced impacts to lake ecosystems, recreation, water security and human and animal health, accurate tracking of harmful algal blooms is essential. However, this can prove an enormous challenge.

“Most lakes are inaccessible to traditional monitoring programs, and blooms happen very rapidly. You need a couple days turnaround,” says Rolf Vinebrooke, a professor at the University of Alberta’s Department of Biological Sciences. “Logistically, you can’t sample an entire lake with a boat every week.”

To solve this problem, Vinebrooke is looking to the skies above. In a collaborative initiative funded in part by Alberta Innovates, satellite technology is providing the basis for sophisticated algal bloom monitoring and forecasting.

Satellites collect a wide range of environmental data, which Vinebrooke’s team aims to harness for detecting algae. The first step of the project was to figure out what a lake with an algal bloom looks like to a satellite. In 2023, Alberta Lake Management Society (ALMS) visited six different Alberta lakes several times and collected water samples for comparison with the satellite data.

“The boat crews went out at the very same time the satellite was passing over – within an hour or two – and sampled lakes for things we would be using satellite data for, like how much chlorophyll is floating around in the water,” says Vinebrooke.

By comparing the datasets, the team was able to build a predictive model of algal bloom status. In 2024, they repeated the process, this time to validate that the model could accurately predict a lake’s condition based on the satellite data alone. The hope is to use the model to identify the presence of harmful algal blooms in near-real time. This will allow the government to better prioritize health advisories as well as help lake-goers plan their activities. It will also enable local communities and watershed councils to develop more effective management strategies by helping target to algal hotspots in their lakes.

In addition to detecting blooms as they occur, the team is also interested in knowing the signs a future algal bloom is on its way. To help do so, Alberta Environment and Protected Areas (AEPA) has deployed three state-of-the-art floating observatories which collect lake data at 15-minute intervals. Combined with regional climate data, the information is being used to build a forecasting model using machine learning and artificial intelligence.

“Ideally, the algorithm should apply to a range of other lakes where we can’t put these buoys, though we’ll have to see how generalizable the model is,” says Vinebrooke.

A Google Earth satellite image of Pigeon Lake taken in the summer of 2020. Using the predictive model developed by the team, the image has been colourized to depict the pattern of the algal bloom across the lake.

The team is also looking to the past, using historic satellite data to find out whether algal blooms have become worse. Early findings suggest that while harmful algal blooms are not getting worse on average, the variability from one year to the next has increased dramatically.

“Looking at the satellite data for Pigeon Lake, we see through the 80s, 90s and early 00s that it’s very stable from year to year. Then around 2006 or 2007 we start seeing variability,” says Vinebrooke. “The peaks start going higher, while other years go lower. It’s stunning to see.”

These swings appear to be synchronized across other lakes in the province, which could suggest climate change is the culprit.

“We have a real strong indication that the algal blooms within the province are going to become more unpredictable. As climate change continues, the answer to whether the lake where you live is where you’ll want to be or have water security long term will be more uncertain,” says Vinebrooke.

Tackling a challenge this scale requires a wide range of expertise and resources. Thankfully, the initiative is supported by strong and diverse partners, which include the Alberta Biodiversity Monitoring Institute (ABMI), AEPA, Alberta Health Services, the Alberta Lake Management Society, Associated Environmental Consultants, the Pigeon Lake Watershed Association, Lac La Biche County and Wabamun Watershed Management Council.

“Alberta Innovates really helped us bring together and attract partners within the province. It really made it so we could do these multi-step procedures,” says Vinebrooke.

While the team continues to test and refine the models, ABMI and ALMS are helping develop a web application. The web-based tool will allow the public to easily access the data and observe trends for their lake of interest. In years to come, Albertans may find checking for upcoming algal blooms as easy as checking the weekend weather forecast.

This article is part of Making Waves, an annual Alberta Innovates publication highlighting water solutions we support. You can read more stories from this issue below.