Harmful algal blooms, like this one photographed in Blue Earth County, are a valid concern due to weather conditions as of late. 

The Minnesota Pollution Control Agency is now predicting more new algal blooms in time for the upcoming July 4 weekend. These can be harmful or even fatal to pets like cats or dogs or other house pets, as they are more likely than people to get sick or even die after contact with harmful algae blooms — in part because they are smaller.

The MPCA says that in most people, symptoms may include vomiting, diarrhea, rash, eye irritation, cough, sore throat and headache.

According to a release from the MPCA, nutrients in run-off from spring rainstorms combined with the current heat wave could potentially trigger algal blooms that can and are harmful to people and pets.

The agency states that recent reports of blooms already spotted across the state have led to swimming advisories. And with temperatures just now hitting the 90s and above, MPCA predicts that several more blooms could develop in time for the July 4 holiday weekend.

The MPCA is advising people to stay out of lakes and streams if the water looks green and slimy, especially if it has a blue-green tint. The algae could contain toxic bacteria that can sicken people and kill dogs, livestock and other animals within hours of contact.

The agency says there is no way to tell if a blue-green algal bloom is toxic just by looking at it, with some toxins persisting in the water after a bloom.

They warn that signs of a recent bloom include green scum on the shoreline.

“If in doubt, stay out,” says Lee Engel, surface water monitoring supervisor for the MPCA. “Excess nutrients such as phosphorus and warm water temps are ideal for growing algae and causing nuisance blooms. Holiday weekends typically see more people out on Minnesota lakes to boat, fish and swim — and due to this year’s conditions, we need everyone to remain vigilant in looking for potentially harmful algae.”

Higher temperatures due to climate change have led to warmer lakes, too. The MPCA states they have documented increased reports of potentially harmful algal blooms in more places that persist throughout the season.

Some activities that present the highest risk include drinking (incidental or intentional), swimming, diving, water skiing, windsurfing, tubing and paddle boarding. These present the highest potential for health consequences of coming into contact with an algal bloom

The agency is so concerned this year that they are encouraging residents statewide to report suspected harmful algal blooms to

More information is available online at MPCA’s blue-green algae and harmful algal blooms web page at

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