Boundary water algae bloom questions, sparks concern

Adam Heathcote has been studying blue-green algal blooms for more than 15 years, including extensive work in lakes in Iowa and southern Minnesota surrounded by farms and other development, where it is common to see severe algal blooms.

But that didn’t prepare him for what he saw last month in the Boundary Waters Canoe Area Wilderness, when he paddled Burnett and Smoke Lakes — two small lakes near Sabil Lake, a popular BWCA entry point north of Toffet, Minn.

“It was as bad a bloom as I’ve seen in Iowa during my entire PhD, in a lake that had two portages in the boundary water,” said Heathcote, who directs the Water and Climate Change Division of St. Croix Watershed Research. Station, part of the Science Museum of Minnesota.

“I’ve never seen a bloom where it’s like a thick, neon-blue, neon-green color, lake-wide, not just [in] A little isolated bay,” Heathcote described. “In two of the three lakes we sampled in the boundary waters, it ran across their entire surface area.”

Heathcote was surprised because these lakes are protected; They’re surrounded by desert.

Every lake has algae. They are a healthy part of the ecosystem. This becomes problematic when algae dominates Cyanobacteriawhich can produce toxins harmful to humans and pets.

Not all algal blooms are poisonous. but Leanne Sethna, a postdoctoral fellow working with Heathcote, said they looked at algae found in boundary waters under a microscope. And they looked at three species of cyanobacteria that produced different types of toxins.

“That’s something we’re really concerned about, and something we really hope to address with this study,” Sethna said.

Minnesota’s most pristine lake

Researchers are studying some of the state’s clearest, most pristine lakes, both within and just outside wilderness areas. They are trying to find out why the algae situation is changing unexpectedly. They documented sections of timber-free canoe routes in the Superior National Forest and cyanobacteria in Elbow and Finger Lakes in Sabil Lake.

Scientists are measuring nutrients and algae, water temperature and oxygen levels. They focused on Burn and Smoke Lakes in part because of past reports of algal blooms there.

Claire owns Shirley Sabil Canoe Outfitters With her husband Dan. He said his family remembers seeing algae in that lake since his grandparents started the business in 1957.

Shirley said these lakes have shallow, muddy bottoms and historically good walleye fishing that doesn’t seem to be affected by algae.

“Nobody ever got sick or reported problems like that,” Shirley said. “So it’s something we’ve lived with for a long time and have always been aware of. But we are excited and grateful that someone is studying it. And we’ll be really interested to hear what they find.”

History in alluvium

Heathcote says there is evidence of algal blooms in shallow northern Minnesota lakes in 18th-century voyageur accounts. But he suspects the area’s blooms are becoming larger, more persistent and more toxic.

To verify this, scientists are extracting sediment cores that slowly build up at the bottom of the lake. Cyanobacteria produce pigments stored in sediments.

“And we can look back through those layers, almost like reading the pages of a book,” Sethna explained.

“We use those layers to understand how nutrients and algae have changed over time. And so we’re using it to understand how cyanobacteria or harmful algal blooms occurred in the past, and from historical conditions to the present day to help us understand why they’re happening now. What kind of factors have changed since.”

Two possible reasons

Scientists have two hypotheses for what blooms in these desert lakes.

One, climate change. The lake is warmer. This allows nutrients accumulated in the sediment to become more readily available to algae at the top of the lake.

Second Theory: Dust. Researchers suspect that nutrients are falling into the lake from the atmosphere and helping to fuel these algae.

“We had to pass the laugh test at first because of course, you think, ‘What could this huge lake of dust be?'” Heathcote admits.

But he says several influential studies have documented the impact of dust on remote, high alpine lakes in Colorado’s Rocky Mountain foothills.

For the first time in Minnesota, Heathcote and his colleagues set up a network of dry deposition monitors to capture and measure nutrients falling from the sky.

Heathcote believes it is likely both global warming and Atmospheric deposition Toxic cyanobacteria are contributing to increased bloom trends in northern Minnesota. This project seeks to ensure

While much research has been done on algal blooms in areas with clear human impact, scientists are still working to understand the more global drivers that are fueling them.

“We don’t really know what we’re going to find out,” Heathcote said. “This is really cutting-edge research. This is the first study of its kind in Minnesota and one of the first of its kind in the world.”

Anyone who sees what they suspect may be a harmful algal bloom in a far northern Minnesota lake is asked to contact researchers at [email protected] or on Twitter @scwrs_mn.