Mystery in Minnesota: Dogs dying from toxic algae blooms

ELIZABETH DUNBAR, Minnesota Public Radio News

Layla was an energetic 4-year-old springer spaniel just reaching her prime. Jack Lundbohm figures she would have been the perfect dog for last fall’s grouse-hunting season.

But Layla died one day last August, after splashing along the shore of Lake of the Woods for nearly two hours. She had been playing with Lundbohm’s 5-year-old grandson, Gus, and not long after the boy took a break from throwing sticks and tennis balls, Layla “was not only dead but as rigid as a bronze statue,” Lundbohm said.

She was the 18th dog in Minnesota to have died from suspected blue-green algae poisoning since the Minnesota Pollution Control Agency started tracking the issue a little more than a decade ago.

Last summer, the state recorded its first two cases of human illness linked to toxic algae.

Sickness and death from blue-green algae are troubling, though rare. But the lake conditions that increase the chances of seeing both are not.

Across Minnesota each summer, sky-blue waters transform into pea-green soup, a sign of possible toxins. It’s happening more often — and farther north — than ever before, suggesting that climate change is a key player.


Biologists in the state say they’re even beginning to see blooms of blue-green algae on northern lakes so remote that you’d have to carry a canoe several miles to reach them.

Wilderness spots far removed from most human interaction have typically been safe from such toxic blooms — until now.

“The fingers do start pointing to climate change and how that is changing how our lakes are behaving to produce blue-green algal blooms,” said Mark Edlund, a biologist with the Science Museum of Minnesota’s St. Croix Watershed Research Station.

The warming temperatures and more intense rains Minnesota has seen under climate change are altering lakes in ways that give blue-green algae a boost. The longer growing season that’s a byproduct of global warming offers blue-green algae warmer temperatures and more opportunities to thrive.

Blue-green algae, or cyanobacteria, are sometimes, but not always, toxic. And they have an amazing track record: They were the earliest forms of life on the planet and have outlived trilobites, pteranodons and woolly mammoths.

“They’ve adapted to living in just about any condition, from hot springs to crusts on the walls of old buildings,” Edlund said.

Scientists still have a long way to go before they understand cyanobacteria toxins, said Wayne Carmichael, a professor emeritus of aquatic biology and toxicology at Wright State University in Dayton, Ohio.

“We still lack a tremendous amount of knowledge about the exact toxicity of these, and as you get better and better testing, you find what we call analogs: molecules with similar structure to the compound that we’ve already defined,” said Carmichael, who has studied toxic algae for 45 years. “Are they also toxic? And if so, how toxic?”

Carmichael said while global warming can exacerbate problem blue-green algae, farming and urban development have historically been the primary driver. “That’s where we should be putting our focus. The problem is that’s heavily tied up in politics,” he said.

Meanwhile, scientists are finding more evidence suggesting blue-green algae are unstoppable, at least without drastic measures.


In Minnesota’s lakes, blue-green algae thrive best under warm, dry, calm conditions with access to plenty of their favorite foods: phosphorus and nitrogen. Those nutrients exist in lakes naturally, deposited when aquatic plants and fish die and decompose.

They are also deposited when rainstorms wash leaves, soil and fertilizer into streams and lakes. Over the years, farming, industry and urban development have caused those nutrient levels in Minnesota’s waters to spike. Blue-green algal blooms are especially common in southern Minnesota, where row crops dominate the landscape.

A few blue-green algal blooms were blamed for livestock deaths in Minnesota as early as the late 1800s.

“In the southern lakes in the corn belt, they’re blooming all the time, and it’s land use,” said Adam Heathcote, a limnologist who works with Edlund at the St. Croix lab.

Two southern Minnesota lakes — Lake Benton, north of Pipestone, and Fox Lake, west of Fairmont — have been havens for algae. Dogs died on both lakes — in 2004 and 2009 — when the waters were pea-green and toxic.

Lake Benton’s water in 2004 “looked like opaque paint,” the dog’s owner told the local newspaper. “The water was absolutely consistently green. You could have taken it out and painted your house with it. That’s what the dog looked like.

“It looked almost funny, like something you’d see in a comic book. It looked like she had been dipped in paint.”

On Fox Lake in 2009, it was likely toxic algae that killed Sady, a 3-year-old black Lab. She died roughly five hours after swimming. Photos of the lake show mats of blue-green algae floating on the surface.

Sady had been a wedding gift from a Minnesota Marine to his sister. The next year, the Marine was killed in Iraq. Sady’s death hit the family hard.

“That dog was what we had left of him,” the Marine’s brother-in-law told The Associated Press.

Both incidents were textbook cases of harmful algal blooms: They happened in shallow to medium-depth, nutrient-rich lakes in the middle of farm country. But some of the more recent suspected cases are not so predictable.

Lake of the Woods, for example, has seen a spike in toxic blue-green algae in the past two to three decades, despite major reductions in the phosphorus coming into the lake from paper mills. That change was mandated by the Clean Water Act in 1972, Heathcote said.

“We don’t really have a handle on why these northern lakes are starting to bloom,” he said.


Scientists know cyanobacteria are thriving in Lake of the Woods despite lower phosphorus levels because they’ve analyzed the layers of mud deposited on the lake bottom over time.

“Every lake in Minnesota has somewhere between 6 feet and 75 feet of mud that’s accumulated since the glaciers left, 10,000 years ago,” said Edlund, Heathcote’s colleague.

In March, their team collaborated with the Red Lake Nation to collect a sediment core from Upper Red Lake. They drilled a hole in the ice, pushed a tube deep into the mud, capped it off and brought it back to the lab.

The researchers have sliced the long, cylindrical slab in half lengthwise. Edlund guesses that a place on the core where the color changes shows when settlers arrived to the watershed and cleared the land for farming. The scientists will slice the mud crosswise and use radioisotopes to date the sediment.

Then, they will analyze everything trapped inside, including fossilized algae.

“It will tell you what that lake was like,” Edlund said. “What the algae were like, what the nutrients were like. We might even be able to tell you what the fish were like.”

In past core samples, scientists have found rare isotopes like cesium-137, which showed up during the atomic bomb testing era. Blue-green algae species are there, too, and Edlund said that, as water quality worsens in lakes, “we typically will see increases in the numbers and types of blue-green algae.”

Edlund and other scientists from several institutions plan to test a group of Minnesota lakes to better understand cyanobacteria and their toxins. That project, funded by state lottery money, includes some lakes in the central and forested regions of the state where blue-green algae have historically been less common.

At the same time, Edlund, Heathcote and other scientists are taking a deeper look at Lake of the Woods because they want to understand the exact cause of the upward trend in algal blooms.

So far, it appears related to the way nutrients from the bottom of the lake — deposited decades ago by industrial pollution — are suspended upward into the water column, where cyanobacteria enjoy a splendid feast. The algae grow and multiply, forming green mats massive enough to show up on satellite images.

Jack Lundbohm, Layla’s owner, said his grandfather built one of the first cabins along Lake of the Woods’ Birch Beach in the 1940s. “We’ve been going there all our lives,” he said.

The water turns green pretty much every summer, but Lundbohm said he didn’t start seeing that signature surface scum from cyanobacteria until recently.

“The blue-green algae is a totally different beast,” he said. “When it blooms, it’s an awful sight. It floats in the water like a big raft. It’s almost metallic blue and green in color, and when you drive through with your boat it has a very strong metallic odor that you just have to wish you’d never smelled before.”

Lundbohm’s experiences on the lake through the years parallel Edlund and Heathcote’s research into industrial waste on Lake of the Woods and the river that feeds it.

One spring fishing trip, in particular, left an impression.

It was the 1970s. Lundbohm was still in college. He cast his line out into the Rainy River from a dock near the point where it flows into the lake. He guesses he was probably 80 miles by river to International Falls, where a giant paper mill flushed its waste into the water. When he reeled in, his line was covered in muck.

“You could squeeze it out and tell it was paper,” he said. “It was incredible to think there was that much sludge collecting on my line every time I reeled it in.”

Lake of the Woods’ recent blue-green algae spike initially perplexed scientists, because they knew the source of the pollution — wastewater — had been cut off by Clean Water Act regulations.

Now, they have a new hypothesis: Climate change creates more opportunities for “internal loading” of phosphorus — when old phosphorus on the lake bottom is released.

On Lake of the Woods, legacy phosphorus from paper mills, rather than new pollution, is leaking out of the bottom sediment, fueling blue-green algae growth. A longer open-water season and wind storms that follow long periods of calm seem to be the problem’s two primary climate drivers, the scientists say.

Under calm conditions, the lake separates into a warm layer and a cold layer. When the layers remain separate for longer than usual, the colder bottom layer is choked of oxygen, which causes phosphorus from the sediment to leak out and become available to blue-green algae.

Wind storms mix up the lake and bring more phosphorus out of the darkness and closer to the surface, where algae can grab it and combine it with sunlight to grow. The more ice-free days in a lake’s year, the more chances for these processes to repeat themselves.

Edlund and Heathcote hope that learning more about what’s happening on other lakes, especially Upper Red Lake, will help confirm the role climate change has had in increased blue-green algae in northern Minnesota’s lakes.

Heavier rainstorms in the Midwest consistent with climate change in the Midwest are likely making the problem worse. Intense rains are tough for the ground to absorb, which means more rain is running off into lakes and streams, bringing along soil, leaves and anything else in its path. That adds to the phosphorus problem.

Those conditions, combined with the unique skillset cyanobacteria possess, seem to be turning more clearwater lakes green — a change that’s hard to reverse, said Kathy Cottingham, a freshwater ecologist at Dartmouth College in New Hampshire.

Scientists already knew that cyanobacteria, unlike other algae, can pull nitrogen from the air to use as fuel, Cottingham said. And they have gas vesicles that allow them to move up and down within the water column, so they can bring phosphorus up from the bottom of the lake, she said.

“I sometimes refer to this as bringing phosphorus to the party,” Cottingham said. “They have a lot of ways of making a living that some of the other organisms don’t have access to.”


Despite its name, the water in the Mud River was clear on the day in September 2014 when Lisa Newton walked Petey, an 11-year-old beagle, and Zeus, a 10-month-old chocolate Lab, along its shore in the town of Grygla, roughly an hour southwest of Lake of the Woods.

Petey, a rescue dog, drank from the river that day. When they got home, he laid down on his favorite napping spot on the entryway rug. Newton’s teenage daughter, Marisa, arrived home a little while later and screamed. Petey was dead, a pool of saliva on the floor.

“Old age,” Newton thought at the time. She buried Petey.

“He got along good with everybody, and everybody in town knew Petey when he would bark and howl,” she said. “He was a really good dog.”

The next morning, Newton walked Zeus, her daughter’s dog, along the same river trail. He played in the river and drank from it.

“We got back to the house and I put laundry in, and when I came back up, I looked at him and his eyes were swollen shut,” Newton said. She took him outside to rinse his eyes out, but minutes later, Zeus struggled to walk.

“He started stumbling sideways,” she said. Newton phoned her daughter, telling her to call the veterinarian. Newton called a friend to help her get the dog to the vet.

“Within that time, he barely made it into the house, vomited on the floor, fell to the floor and then appeared to have mild seizures,” she said. “I was absolutely terrified.”

Zeus died on the way to the vet.

“It’s really awful to watch an animal or anything go through what he did. He was struggling to survive and to stand and there was nothing I could do for him,” Newton said.

Her daughter was devastated, Newton said. “That was her baby.”

After Zeus’ death, the veterinarian asked Newton to exhume Petey’s body. The dog’s stomach and parts of his liver and lung were sent for testing. Microcystin, a liver toxin produced by blue-green algae, was in Petey’s system, and the vet said that, given the circumstances, toxic algae likely killed Zeus, too.

MPCA research scientist Steve Heiskary has been investigating reports of blue-green algae exposure in dogs for years.

“I can appreciate what the people are dealing with,” he said. Heiskary has two hunting dogs of his own.

It’s often difficult to determine whether a dog has been poisoned by blue-green algae, even after MPCA staff investigate. And some of the few confirmed cases of toxic algae deaths in dogs have happened in waters where there were no visible signs of a blue-green algae bloom. That’s led the MPCA and other agencies to rethink how they inform dog owners about the possible dangers.

The “when-in-doubt-stay-out” advice that the MPCA and other agencies have given dog owners is not foolproof. MPCA officials recommend people and dogs stay out of water that looks like green paint, but Heiskary notes that toxins can linger even after the scum disappears.

“The bloom collapses. They die, they start to decompose. Toxins are released. Is the water safe to swim in a day later? We don’t know. Two days later? We don’t know,” he said. “As a scientist, you like to be more certain. I’d like to be able to accurately convey a risk.”

To complicate things further, blue-green algae is not always toxic, and it’s impossible to know without testing if an algae bloom contains toxins, Heiskary said.

Captain, a 10-month-old Lab-golden mix, died last June after playing in Red Rock Lake, west of Alexandria.

“The water was 100 percent crystal clear,” Captain’s owner, Dawn Stimmler, said. But the University of Minnesota’s Veterinary Diagnostic Lab later confirmed high levels of anatoxin-a, a neurotoxin found in some blue-green algae, in Captain’s body.

Stimmler, who has two other dogs, was with Captain and Liberty, a German shepherd, the day Captain got sick. Liberty normally loves to swim, but was acting odd that day, she said.

“She kept whining and whining and refused to go in the water,” Stimmler said.

The Minnesota Department of Health has been looking for algae illnesses and deaths in dogs for the past few years.

“Dog cases are becoming more commonly reported,” said Kirk Smith, a veterinarian who oversees the health department’s unit that addresses waterborne illnesses. “Dogs and other animals can be sentinels for human disease.”

Two people who fell ill last summer after swimming in Lake Henry in Alexandria and West Olaf Lake near Pelican Rapids are suspected toxic algae cases. Smith said there are likely more out there that health officials don’t know about.

“For most every disease, what we find out about is the tip of the iceberg,” he said.

The challenge is determining whether toxic algae is the culprit when there is no diagnostic test for it in humans, said Stephanie Gretsch, an epidemiologist who tracks waterborne diseases at the health department.

“These illnesses are generally pretty mild and they’re also non-specific,” she said. “It could be a harmful algal bloom, or it could be something else in the lake, or it could be something they ate while they were at the lake.”


Are Minnesota lakes with legacy phosphorus pollution doomed to a life of pea-green summers and toxic water?

Not necessarily.

Scuba divers nominated Bald Eagle Lake, in the Twin Cities’ northeastern suburbs, as the worst place in the state to scuba dive in a 2007 online community forum.

“My 1,800 lumen light could only cut through about 1-2 feet of scum water,” one diver wrote. “Kept imagining the bottom of an unflushed toilet from all the dark brown water and scum.”

Research showed roughly 40 to 50 percent of the phosphorus in the lake was being stirred up from bottom sediment rather than being added by stormwater runoff, said Matt Kocian, a lake and stream specialist with the Rice Creek Watershed District.

These days, the lake is among the clearest in the metro, thanks to a lake additive called alum. The liquid aluminum sulfate makes a chemical bond with phosphorus on the bottom of the lake, preventing the nutrient from leaching out of the sediment and fueling algae growth.

The alum was added to the lake in two phases: once in 2014, and again last month. The Rice Creek Watershed District, which is overseeing the project, has seen drastic improvements.

“We’ve had the phosphorus concentrations cut nearly in half, similarly for the amount of algae on the lake,” Kocian said.

A barge equipped with tanks applied 247,000 gallons — 59 tanker trucks worth — of alum to the 1,000-acre lake in April.

But the project wasn’t cheap. The watershed district split the cost with the Bald Eagle Area Homeowners Association. Homeowners had voted to tax themselves to pay the nearly $900,000 price tag. They wanted to be able to see their feet when standing in chest-deep water, Kocian said.

While the community is thrilled with the project’s success, Kocian said the alum treatment followed years of study to determine how much was needed to be effective.

“It’s not a tool to be used on every lake,” he said. Shallow lakes, whose sediment gets stirred up by carp and other bottom-feeders or wind storms, aren’t good candidates. Neither are lakes where most of the phosphorus comes from stormwater runoff.

Treating a lake with alum to address phosphorus is not the norm in Minnesota. Usually, the efforts focus on identifying the source of nutrients then working with farmers, cities and industry to reduce inputs.

That could mean upgrading treatment technology for a wastewater treatment plant, planting buffers or cover crops to keep more nutrients on the land, or building wetlands, rain gardens or other means of natural treatment to slow the amount of runoff entering surface waters. There are also projects around the state that have found ways to capture and reuse stormwater and wastewater.


It would cost billions of dollars to get rid of excess phosphorus in Minnesota’s lakes, and there’s still a lot that’s unknown about just how effective that would be in curbing blue-green algae.

And just as the Minnesota Department of Health has heightened its awareness of Lyme disease-carrying ticks, heat illness, allergies and other health concerns expected to worsen with climate change, officials say blue-green algae is worth watching, too.

“It’s kind of hard to communicate the risk when we really don’t have a great sense of the risk ourselves,” said the health department’s Smith. “We’re really kind of in the infancy of studying this whole problem, so we just try to get the facts out there.”

Awareness, at least, seems to be growing among veterinarians and dog owners, said Ahna Brutlag, a veterinarian who specializes in toxicology and works for the Pet Poison Helpline, a fee-based service for pet owners. She said algae calls are much less common than cases of the most common dog poison: chocolate.

When dog owners do call about blue-green algae, often it’s because they let their dogs play in water and then noticed a warning sign afterward, she said.

“They’re calling us because they’re frantic,” she said. “They’re looking for immediate guidance.”

Luckily, most of those dogs turn out to be fine, Brutlag said. Those who aren’t show a range of symptoms: drooling, vomiting, diarrhea, tremors, seizures, refusing to eat, yellow gums.

If the dog has been exposed to microcystin or anatoxin-a, the prognosis is poor. “It’s difficult to get that dog to the clinic fast enough,” she said.

Owners who have lost dogs to blue-green algae say they won’t be taking any chances this summer.

Lisa Newton keeps Flash, her new beagle-basset hound mix, on a leash during walks along Mud River.

Spot, Jack Lundbohm’s new hunting dog, won’t be fetching sticks in late summer on Lake of the Woods.

And for Dawn Stimmler’s dogs, Liberty and Kaiya, swimming at the family cabin is a distant memory.

“They’re forbidden to go in,” she said. “We set up a kiddie pool for them to cool off.”

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Information from: Minnesota Public Radio News.


An AP member exchange story.