Blue-green algae are normally present in lakes throughout Minnesota. This type of algae – which is actually a bacteria called cyanobacteria – thrives in warm, shallow, nutrient-rich lakes. When conditions are right, blue-green algae can grow quickly and form “blooms” that can be toxic to people and animals, causing a variety of symptoms.
Minneapolis Park and Recreation Board staff monitor for blue-green algae weekly by conducting cyanotoxin testing and a visual monitoring index. An advisory is posted on the Lake Water Quality Map if Minnesota Pollution Control Agency (MPCA) guidelines are exceeded or when blooms blow into the beach area. When at the beach, look for informational signs on blooms or yellow advisory signs. See Beach Water Resources for more information on MPRB beach monitoring.
Long-term stormwater management is one key to keeping lake water quality suitable for recreation and for sustaining plants and wildlife. MPRB is seeking dedicated funding to invest in stormwater management and protect Minneapolis lakes.
Blue-green algae blooms are often described as looking like pea soup or spilled green paint. They can also appear as a brown or rust color in the water. See images of actual blue-green algae blooms at the bottom of this page.
However, blooms are not always large and dense and can sometimes cover small portions of the lake with little visible algae present. Blooms can also produce a swampy odor when the cells break down.
Blue green algae can sometimes produce cyanotoxins, which can make humans and animals sick, particularly if ingested. You can become sick if you swallow, have skin contact with, or breathe in airborne water droplets while swimming or boating in water that has harmful algal toxins. According to the Minnesota Department of Health (MDH), symptoms of illness from blue-green algae can include vomiting, diarrhea, rash, eye irritation, cough, sore throat, and headache. Symptoms generally begin from several hours to up to two days after exposure.
Dogs that come into contact with blue-green algae blooms can get sick, and sometimes die because their bodies are smaller, and they tend to swallow a lot of water.
If your dog has been in the water near a blue-green algae bloom and seems sick, call your vet. For more information about protecting your pets visit MDH: Harmful Algal Bloom-Related Illness in Animals.
Adults, children, and animals should avoid contact with water with blue-green algae. There is no way to tell if an algae bloom is toxic just by looking at it. Therefore, the MDH advises the following:
The MDH provides more information about minimizing the risk of exposure to blue-green algae and harmful algae blooms from swimming, boating, or consuming fish.
You can help reduce nutrients in lakes by:
Decreasing nutrients will help to decrease the frequency and intensity of blue-green algae blooms. These actions may take time and a lot of community involvement to effectively change the impacts of blue-green algae blooms in Minneapolis lakes.
There are no announcements at this time. Please check back soon.
