Hot weather fuels early algae blooms on Minnesota lakes

When lake temperatures warm, blue-green algae thrives.
A blue-green algae bloom on Peltier Lake, near Lino Lakes, Minn., on July 18, 2017. When lake temperatures warm, blue-green algae thrives, often forming in thick, pea-soup colored blooms that spread out across the surface of lakes.
Dan Kraker | MPR News

Blue-green algae typically doesn’t make its unsightly appearance on Minnesota lakes until August. 

But this summer has been anything but typical. Hot, dry weather to start the month of June has heated up lake water temperatures across much of the state, creating ideal conditions for the potentially harmful blooms to form.

"Algae thrive off of calm, sunny, hot conditions, “ said Pam Anderson, who manages surface water monitoring for the Minnesota Pollution Control Agency. “If there's not any cloud cover or any rain to kind of break the cycle, blooms can really take hold, and persist for quite a while."

Due to a lack of rain and drought conditions across much of Minnesota, water levels in many lakes and rivers are low, which also helps the water heat up faster. 

Surface water temperatures in many lakes are already approaching the 70- and 80-degree range, which usually doesn’t happen until late July or August, Anderson said. She said she's already received reports of blue-green algae as far north as Brainerd and Grand Rapids

 Blue-green algae aren’t really algae, but a type of bacteria called cyanobacteria. Blooms have a thick, cloudy appearance that can look like spilled green paint or pea soup. Some species contain toxins that can sicken humans and be deadly to dogs and other animals.

Anderson advises avoiding swimming or allowing pets in water with blue-green algae, and rinsing off immediately after coming into contact with a bloom. 

Animals can experience symptoms within minutes of exposure, including vomiting, diarrhea, weakness, difficulty breathing and seizures. Pet owners should seek veterinary care right away if they think their pet has been exposed, Anderson said.

People can report sightings of blue-green algal blooms to the MPCA by calling 651-757-2822 or emailing algae.mpca@state.mn.us, she said.

Nutrients such as phosphorus that run off lawns, farm fields and urban areas into storm drains and eventually, lakes and rivers, also can help feed algae blooms, Anderson said.

“Anytime that you see sediment leaving your property, phosphorus attaches itself to that,” she said. “And if it makes it to its local waterways, that's something that eventually ends up with our streams, rivers and lakes.”

Anderson said people can help reduce nutrient runoff by sweeping up grass clippings and leaves, cleaning up after pets and planting rain gardens, which help filter out nutrients.