Blue-green algae blooms
“When in doubt, best keep out”
Have you come across a lake that looks like it has spilled green paint on it or has a split pea-soup appearance? If so, it is possible the lake has 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.
Hot days like what we have been experiencing in Minnesota this June are prime conditions for blue-green algae blooms. These blooms typically occur later in summer, but the abnormally early hot weather this year adds to the possibility of earlier blooms.
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?
In general, if you suspect a blue-green algae bloom contact the Minnesota Pollution Control Agency (MPCA) or the Minnesota Department of Health (MDH).
- MPCA lake monitoring staff track reports of potential harmful algae blooms. You can email pictures of the suspected bloom to email@example.com, call 651-757-2822 or 800-657-3864, or visit the MPCA’s Blue-Green Algae and Harmful Algal Bloom web page.
- 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 webpage.