Be on the lookout for algae blooms on Lake Superior

A team of researchers led by Bob Sterner, director of the Large Lakes Observatory (LLO) at University of Minnesota-Duluth (UMD), has identified two major factors that contribute to the presence of cyanobacterial algae blooms on Lake Superior and one is already in play.

“It’s been a warm year and past blooms have happened in warm years,” said Sterner. “The other factor we’re looking for is a major weather event or historic rainfall.”

Sterner is the lead researcher of a group at UMD that in partnership with the National Park Service has been gathering and examining data on algae blooms along Lake Superior’s southern shore since 2011 to get a better understanding of what causes them. He is also part of a much broader Algal Bloom Response Team that is sharing information and coordinating resources to monitor and help protect the lake from toxic blooms.

The Response Team includes repre-sentatives from Northland College, the Wisconsin DNR, the Environmental Protection Agency, the National Park Service and the Red Cliff Band of Lake Superior Chippewa.

Sterner explains that the broader in-volvement of these agencies improves researchers’ ability to learn of blooms that pop up and respond to gather more information. The public has a part to play in assisting this effort, too.

“Floating green scum indicates a bloom and we’d like people to take photos, note the location, size of the bloom, place and time and, if it can be done safely, collect a water sample,” said Sterner. To report an algae bloom email

The team is not able to test every bloom, but these details are helpful:

• Approximate bloom size
• Duration
• Location with water body name, town name and county name
• Photos for verification, including close-ups and overall views

The first documented Lake Superior bloom occurred in 2012. Another, even larger bloom in 2018 provided an opportunity to gather valuable data. No evidence of toxicity in Lake Superior blooms has yet been seen, but Sterner said certain environmental factors like high nitrogen levels can trigger toxicity.

“Lake Superior is high in nitrogen, but we haven’t seen a toxic bloom yet, so we keep watching,” said Sterner. “We’ve gotten off the ground floor by identifying some underlying causes for these algal blooms, warmer than average lake temperatures and major storm events, but we need to keep going.”

Many UMD students have been part of the research team. PhD candidate Kaitlin Reinl spent many months col-lecting water and sediment samples  and analyzing the data gathered.

“I think most people think of Lake Superior as enormous and pristine, but we’re starting to feel the effects of a changing climate with the lake temperature rising,” said Reinl. “We have an opportunity to be proactive instead of reactive and we need people to be aware of this research and how they can help us.”

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