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SPEAKER 1: Continue our series of reports on water here on MPR News with a look at how climate change is likely to make more of our lakes toxic literally. Scientists say global warming could fuel the growth of more blue green algae, which can sicken and even kill. Elizabeth Dunbar reports.

ELIZABETH DUNBAR: This is a story about dogs and water. You might expect to hear barking, panting, splashing around, right? But PD, Sadie, Layla, Captain, Copper, and Zeus aren't around to do that anymore. They and another dozen Minnesota dogs have all died of suspected blue green algae poisoning in the last decade or so.

JACK LUNDBOHM: I had no idea it was that vicious.

ELIZABETH DUNBAR: Jack Lundbohm's four-year-old springer spaniel Layla died suddenly after a swim at the family's cabin on Lake of the Woods on the Canadian border. It happened last August when Lundbohm's five-year-old grandson Gus was visiting.

JACK LUNDBOHM: And he and that dog have grown up together and were just inseparable.

ELIZABETH DUNBAR: Gus was on the beach throwing tennis balls and sticks into the lake for Layla to fetch.

JACK LUNDBOHM: Gus came in to change and have a snack. He went back out and within 20 minutes, not only was the dog dead, but she was as stiff as a statue.

ELIZABETH DUNBAR: Lundbohm says poor little Gus just didn't understand.

JACK LUNDBOHM: First, he said, no, she's just sleeping. No, she's dead. We got a box, and squeezed her into it, and buried her. And the thing he said was-- he said, she was my best friend.

ELIZABETH DUNBAR: The experts agreed toxic algae likely killed Layla. What happened to her is rare, but the lake conditions that sealed her fate are becoming more common. Blue green algae has been blooming like never before on Lake of the Woods and places as pristine as the lakes of Isle Royale on Lake Superior.

MARK EDLUND: Wilderness lakes are having blue green algal blooms in them that we have no record of them ever having those before.

ELIZABETH DUNBAR: Mark Edlund is a biologist at the Saint Croix Watershed Research Station, which belongs to the Science Museum of Minnesota.

MARK EDLUND: The fingers do start pointing to climate change and how that is changing how our lakes are behaving to produce blue green algal blooms in them.

ELIZABETH DUNBAR: I walk with Edlund to the backwaters of the Saint Croix River.

MARK EDLUND: I just was going to go grab some algae.

[LAUGHS]

ELIZABETH DUNBAR: Blue green algae blooms here most summers just as it does in most lakes in Southern Minnesota's farm country. Today, Edlund finds some slimy green stuff.

MARK EDLUND: It's got a cool name. It's called spirogyra.

ELIZABETH DUNBAR: But it's not blue green algae or what scientists call cyanobacteria. The name evokes cyanide, but they're not chemically related. I came to see cyanobacteria so back at his lab, Edlund puts them under the microscope.

MARK EDLUND: And so they don't have any cellular structures, nothing.

ELIZABETH DUNBAR: The cyanobacteria are just light green round blobs, but it turns out these blobs are pretty important. Cyanobacteria were the first forms of life on Earth.

WAYNE CARMICHAEL: We have to thank them for the oxygen in our atmosphere.

ELIZABETH DUNBAR: Wayne Carmichael has studied cyanobacteria and their toxins for 45 years. He's a professor emeritus from Wright State University in Dayton, Ohio.

WAYNE CARMICHAEL: We can find them anywhere. We can find them on rocky outlets, at high alpine altitudes. They're the green mats that you see in hot springs in Yellowstone. They grow on the sides of buildings.

ELIZABETH DUNBAR: Having survived billions of years, blue green algae are extremely resilient. And they like global warming. That concerns people like Kirk Smith, the Minnesota Health Department's lead tracker of waterborne diseases.

KIRK SMITH: Summers get longer and water temperatures are higher for a longer level of time, well, it just stands to reason that we're going to have more harmful algal blooms.

ELIZABETH DUNBAR: Smith isn't just concerned about dogs. Last summer, the health department recorded Minnesota's first two known cases of suspected human illness from toxic algae, a swimmer on West Olaf Lake near Pelican Rapids and another on Lake Henry in Alexandria in which a child was hospitalized. Scientists are still trying to understand how and when blue green algae turned toxic. Sometimes they're harmless so how do you know when the water is dangerous?

STEVE HEISKARY: Good question.

ELIZABETH DUNBAR: Steve Heiskary is a research scientist at the Minnesota Pollution Control Agency. He's been tracking harmful algal blooms for a little over a decade. The early cases were pretty clear, stories of dogs dying after entering lakes that looked like green pea soup.

But several recent cases, Layla, Captain, Petey, Zeus are especially troubling. The water didn't have the smelly, green ooze typical of a blue green algal bloom. The blooms had passed and the water was clear at the time the dogs died.

STEVE HEISKARY: The bloom collapses, they die. They start to decompose, toxins are released. Is the water safe to swim a day later?

We don't know. Two days later? As a scientist, you like to be more certain.

ELIZABETH DUNBAR: The experts wish they could warn people of the risk. Lisa Newton lost not one but two dogs in two days because she didn't know there was a danger. Petey, her beagle died suddenly after drinking water from the mud river in Grygla in Northwestern Minnesota. Newton thought he'd just died of old age, but the very next day Zeus got sick after a walk along the same river.

LISA NEWTON: And I went downstairs and put laundry in. And when I came back up, I looked at him and his eyes were swollen shut.

ELIZABETH DUNBAR: Zeus's symptoms got worse. He started stumbling sideways, he vomited, he fell to the floor, and had seizures.

LISA NEWTON: I was absolutely terrified. And 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.

ELIZABETH DUNBAR: Zeus died on the way to the vet. For researcher Mark Edlund, the hunt for answers leads to mud. Why are you interested in this mud? Because it really just looks like mad to me.

Back at the Saint Croix Watershed Research Station, we're looking at a gray brown cylinder pulled from the bottom of a lake with a specialized tube. The scientists will carefully cut the slab of mud crosswise like slices of cheese. They'll use radioisotopes to date the sediments and analyze everything trapped in there. Sometimes they go back 10,000 years to when the glaciers left.

MARK EDLUND: It will tell you what that lake was like.

ELIZABETH DUNBAR: Fossilized blue green algae show up in the mud. The more algae, the worse the water quality was at the time, like when paper mills flushed waste rich in phosphorus into the river flowing into Lake of the Woods. The algae situation improved when the Clean Water Act clamped down on that in the 1970s. But in the last 20 to 30 years, it's getting worse again. And Edlund says the reasons are still a mystery.

MARK EDLUND: We have not been studying lakes long enough to understand lakes.

ELIZABETH DUNBAR: Edlund's colleague Adam Heathcote says they think old phosphorus on the bottom of Lake of the Woods is leaking out, a condition called internal loading. It happens in other Minnesota lakes too contributing to excessive nutrient pollution or eutrophication.

ADAM HEATHCOTE: So there's enough nutrients in the sediments of the cleanest lakes in Minnesota to instantly drive them eutrophic if it was all released at the same time.

ELIZABETH DUNBAR: Eutrophication is on the rise globally and is one of the most challenging pollution problems on the planet. Climate change is apparently contributing to the nutrient loads in lakes. In some, later freezes and earlier ice outs allow more phosphorus to leach from sediment.

Rainstorms are increasingly intense. More rainfall is running off the land into lakes and streams carrying soil, leaves, and fertilizer. So there's more food for blue-green algae, warmer conditions the bacteria like, and a longer growing season.

ADAM HEATHCOTE: The reason we're seeing blooms we didn't see before is because everything has changed and they've taken advantage of that.

ELIZABETH DUNBAR: What's at risk? Possibly entire ecosystems and other things we care about swimming in a lake or--

[DOG BARKS]

--hanging out with our best friends.

SPEAKER 2: Monty!

ELIZABETH DUNBAR: This two-year-old standard poodle named Monty is making everyone smile here at Minnehaha Dog Park in Minneapolis. A poof of black hair on his head bobs as he plays and leads to an invitation for a selfie with this guy.

SPEAKER 3: Monty, come here. Oh, my gosh, he's so-- we got the same hair.

[LAUGHS]

ELIZABETH DUNBAR: Reporting on the environment, Elizabeth Dunbar, Minnesota Public Radio News.