Avoiding harmful algae in the park

Cyanobacteria, also known as blue-green algae, can multiply and “bloom” rapidly in lakes in response to sunlight, increased nutrients, and warming temperatures. These blooms can produce toxins that have been linked with acute poisoning of humans, pets, and wildlife, and are often referred to as harmful algal blooms (HABs). Harmful algal blooms often look like pea soup, green paint, or floating mats of scum and sometimes have a bad smell.

There are HABs nearly every summer in Voyageurs National Park. Visitors enjoying the park’s amazing lakes should take appropriate precautions to stay safe.  Exposure to freshwater cyanotoxins occurs most frequently through the ingestion of water, either by drinking or during recreational activities where water is swallowed.  Dogs are particularly susceptible to ingesting cyanotoxins when they lick their fur to clean themselves after exiting a bloom site. If you encounter a bloom and you’re not sure if the water is safe, it’s best for people and pets to stay out of the water.  Make sure to bring your own drinking water or follow the Department of Health/MN Pollution Control Agency guidance for filtering.  Boiling lake water can actually increase toxin levels.

For more information click here to access a fact sheet about HABs created by the Minnesota Pollution Control Agency.