Cedar Lake: Blue-green algae bloom update

minneapolis park and recreation

Lakes & Water Quality

Cedar Lake: Blue-green algae bloom update

Blue-green algae can be harmful to humans and animals.

Algae blooms on area lakes are normal and usually not harmful. However, the algae bloom present on Cedar Lake is likely a harmful algae bloom (HAB): blue-green algae.


This type of algae is actually a bacteria that produces cyanotoxins, which can make humans and animals sick. Symptoms can include vomiting, diarrhea, rash, eye irritation, cough, sore throat, and headache. Symptoms generally begin several hours up to 2 days after exposure.


Despite their name, blue-green algae blooms can have a vibrant rust color and may look like spilled paint. They usually form in summer and early fall, but can occur at other times of year under the right conditions.


There is no way to tell if an algae bloom is toxic just by looking at it. Therefore, the Minnesota Department of Health advises the following:

  • Don’t swim if you can’t see your feet in knee-high water (and wash off with fresh water).
  • Don’t let your dog drink or swim in the water. *
  • When in doubt, stay out!

For more infomation on blue-green algae and HABs, visit the MDH website: 



* Note: Dogs are not allowed in Minneapolis water bodies, per ordinances from the Minneapolis Park and Recreation Board (MPRB).


Robin Smothers

Minneapolis Park and Recreation Board

Phone: 612-230-6410

Email: rsmothers@minneapolisparks.org