Green, smelly algae is back in MN lakes – and it's harmful to humans and dogs


If you're thinking about jumping in a lake this Memorial Day weekend, look out for blue-green algae.

Last year, two people got sick and several dogs died after being exposed to the toxic algae, the Minnesota Department of Health said in a news release.

They warn Minnesotans about the nasty substance pretty much every year during this time, when warm weather creates the ideal conditions for blue-green algae – which is not actually an algae, but something called cyanobacteria – to grow.

The algae "blooms" usually show up in June when it heats up. But since we've had a mild spring, some Minnesota lakes may already be affected, the release said.

How do you know if a lake has blue-green algae?


Harmful blooms kind of look like pea soup, green paint, or floating patches of scum, the department says. It also usually has a bad smell.

They also said that not all blue-green algae is toxic, but there's no way to tell if the algae you see is the harmful stuff or not – so "when in doubt, stay out."

“If you’re not sure, it’s best for people and pets to stay out of the water," Pam Anderson, MPCA Water Quality Monitoring Supervisor said in the release.

What happens if I am exposed?

Try to wash yourself and your pets off immediately if you think you've been exposed to blue-green algae, the release said.

You could get sick if it touches your skin, is accidentally swallowed, or is breathed in through tiny water droplets. Most people experience mild symptoms like vomiting, diarrhea, rash, cough, eye irritation, sore throat and headache, the department said.


What about dogs?

Dogs are especially at risk, because they will go in areas of the water that humans avoid, the department warns. They might also swallow lake water while swimming or retrieving toys, and they tend to lick their coats after getting out, potentially ingesting the stuff.

At least 18 dogs are suspected of getting blue-green algae poisoning since the Minnesota Pollution Control Agency started tracking the issue about 10 years ago, MPR said.

The department recommends seeking veterinary treatment immediately if a dog displays vomiting, diarrhea, rash, difficulty breathing, general weakness, liver failure or seizures after visiting a lake.

Why don't they just clean it out of the lakes?

Phosphorus is largely responsible for promoting algae growth – it's a nutrient present in soil and plants, as well as runoff from urban and agricultural land.

Once a bloom occurs, the only thing that can make it go away is a change in weather.

So really, there are no short-term solutions, the department said.

But they say there are things that people can do to help improve the overall water quality of lakes: limiting use of fertilizers that contain phosphorus, sweeping up lawn clippings and soil off sidewalks and pavement, and cleaning up after pets, so that rain doesn't wash their waste into nearby lakes and rivers.

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