Last summer severe algal blooms covered several lakes in central and southern Minnesota. From April through August 2007, Minnesota Pollution Control Agency staff had almost 50 calls from citizens wondering if the algal blooms on their lakes were toxic. Some callers reported dog deaths. Some reported sickness of animals or fish kills. Some described unpleasant odors.
Algae occur in all waters in Minnesota, but their concentration can vary considerably throughout the year and from lake to lake. Of the numerous forms of algae, one variety -- blue-green algae known as cyanobacteria -- can produce toxins that affect humans and animals.
Blue-green algal blooms often make the water appear cloudy or scummy with a green, yellow, or bluish-green cast. Lakes may develop a swampy odor as the algae accumulate in floating mats and decompose. Last year wasn't the first time that blue-green algae has been a problem in Minnesota. From 2004 through 2007, the MPCA received reports from concerned citizens and veterinarians of eight blue-green algae-related dog deaths.
Steve Heiskary, a lake specialist at the MPCA, said blue-green algae can produce several types of toxins that are among the most powerful natural poisons on earth.
"Blue-green algal blooms may or may not become toxic. However, it's not possible to predict which blooms are toxic and which are not," Heiskary said. "People just need to use a little common sense. If they come across thick mats of unpleasant smelling algae, it's best to stay out of it."
Swimming in or ingesting water with a harmful bloom can cause a variety of symptoms in humans and animals, including rashes, vomiting, muscle pain, and diarrhea. In the worst cases, it can result in paralysis, convulsions, respiratory failure, or even death.
The Minnesota Department of Health recommends the following -- do not ingest, swim, or wade in water with blue-green algae; if contact does occur, thoroughly wash off with clean water and soap, paying special attention to the swimsuit area. If your pet comes in contact with a bloom, wash off your pet to prevent ingestion of the algae. For more information visit the Minnesota Pollution Control Agency.
Jennifer Maleitzke, public information officer Minnesota Pollution Control Agency