State warns people and pets to stay away from blue-green algae

Warmer weather, lakes and phosphorus pollution can lead to the dangerous algae

This MPCA photo from 2016 shows harmful algae blooms in Steele County's Beaver Lake
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With hot water approaching, the Minnesota Pollution Control Agency is advising people to avoid lakes and streams with potentially toxic green or blue-green algae.

The agency is also suggesting ways farmers and landowners can prevent the pollution that leads to algae.

Algae blooms have already been spotted across the state and have led to swimming advisories this year, the agency said. It predicts several more blooms in time for the July 4 holiday weekend, and says it is receiving more reports of potentially harmful algal blooms that persist throughout the season.

People and animals should stay out of waters that look green and slimy, especially if it has a blue-green tint, the agency says. If it contains toxic bacteria, it can sicken people and kill dogs, livestock and other animals within hours of contact.

In 2015, a child was hospitalized after coming into contact with blue-green algae on Lake Henry in Alexandria. That same year, two dogs were sickened and one later died after swimming in Red Rock Lake in Douglas County northeast of Hoffman.


Those who are exposed to algae should rinse off with clean water. Dogs should be hosed off immediately and preventing from drinking the water or licking their coats. In humans, exposure can cause skin, throat, eye, and nose irritation and nausea.

The primary culprit in algae growth is a pollutant called phosphorus, and the agency says that one-quarter of Minnesota lakes have too much phosphorus and algae, making them unfit for swimming.

Another culprit is climate change that has led to warmer lakes, the agency says; warmer water also promotes algae growth.

Steps to reduce phosphorus in lakes, according to the agency:

  • Rain gardens, rain barrels, and less earth covered with pavement or other surfaces that don't allow storm water to drain.
  • Phosphorus-free lawn fertilizer, grass clippings and other yard waste kept out of storm drains, and proper disposal of pet waste.
  • Cover crops on farms, more organic matter, and less tillage.
  • Deep-rooted native plants along ditches, lakes, and streams to slow down and filter runoff.
  • Keeping manure out of lakes and streams.
  • Healthy septic systems.

To report suspected harmful algal blooms, email photos to For more information, visit the MPCA’s Blue-green algae and harmful algal blooms web page.

Reporter Karen Tolkkinen grew up in Plymouth, Minnesota, graduated from the University of Minnesota with a journalism degree in 1994, and was driven by curiosity to work her way around the United States.
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