Blue-green algae blooms in several District lakes: “when in doubt, best keep out”

Image of Blue-Green Algae
Blue-green algae bloom_Photo by Barr Engineering

Blue-green algae blooms

“When in doubt, best keep out”

Have you come across a lake with a swampy odor or split pea-soup appearance? If so, it is possible the lake had a blue-green algae bloom. Blue-green algae, also known as cyanobacteria, are a natural part of our freshwater systems, but these algae blooms can become harmful to people and pets.

During a blue-green algae bloom, the water may look like it has spilled green paint on the surface. Not all blue-green algae blooms are harmful, however, when conditions are right, these blooms can secrete toxins that are harmful to people and pets. Harmful algae blooms are most likely to occur during warm weather in shallow, nutrient-rich lakes. You and your pets can become sick if you have contact with, inhale airborne water, or swallow water that contains blue-green algal toxins. So, it is best to avoid contact with lakes with potential blue-green algae blooms. Always remember, when in doubt, best keep out.

What if I suspect a blue-green algae bloom?

If you suspect a blue-green algae bloom email pictures of the suspected bloom to For more information on harmful algae blooms, you can also call the Minnesota Pollution Control Agency at 651-757-2822 or 800-657-3864. In addition, report human health effects to the Minnesota Department of Health (MDH) Foodborne and Waterborne Illness Hotline at 1-877-366-3455. For health questions, citizens can contact MDH’s Waterborne Diseases Unit at 651-201-5414 or visit the MDH’s Harmful Algal Bloom web page.

How you can help!

Family cleans out stormdrain
Cleaning up around storm drains keeps pollutants our of our lakes. Photo by: Clean Water MN

To help prevent algae blooms, limit the amount of nutrients entering your lake. Pollutants like grass clippings, leaves, and fertilizer can enter lakes through storm drains or direct runoff and fuel algae blooms. Keeping these pollutants off the street and cleaning around storm drains can help prevent algae blooms. If you live on a lake, make sure you don’t mow to the edge of the lake and consider installing a shoreline buffer. This will help reduce runoff and pollutants from entering the waterbody. You can even get a grant from the District to help install a shoreline buffer! Learn more about the importance of keeping storm drains clean, and adopt a drain near your home, at

Learn more about blue-green algae

Blue Green Algae Fact Sheet