Hot, calm weather creates the perfect conditions for algae growth in Minnesota lakes. Blue-green algae “blooms” have a thick, cloudy appearance that can look like green paint, pea soup, or floating mats of scum. Some, but not all, species of blue-green algae contain potent toxins that can be deadly to dogs, livestock, and other animals within hours of contact. The toxins can even also sicken humans.
In recent years, we've received multiple reports of dog deaths where exposure to blue-green algae was the likely cause. Be sure to check water conditions when your dog is playing near lakes or slow-flowing streams. If possible, keep your pets away from algae-laden water entirely. If your dog does go into water with heavy algae growth, hose it off right away, before it has a chance to lick itself clean. Animals become ill when they ingest the toxins, so preventing them from drinking affected water or licking toxins from their coat is key to preventing illness.
If you are concerned that your pet has been exposed to harmful blue-green algae, take the animal to a veterinarian immediately.
What causes blue-green algae?
Blue-green algae blooms can occur anytime during the summer, though they are normally associated with warm weather and low rainfall. Algae are a natural part of the ecosystem, but under certain conditions, algae populations can “bloom” with dramatic growth. Most blue-green algae are not toxic, but there is no way to visually identify whether a particular bloom contains toxins that are harmful to people or animals. Once an algae bloom has developed, there is no way to correct it. Blooms often come and go quickly, so the best option is to stay away from the water until rainfall, wind shifts, or cooler temperatures disrupt the algae’s growth.
Algal blooms develop when lakes contain excessive levels of nutrients such as phosphorus. The best way to prevent them over the long term is to reduce the amount of nutrient runoff into lakes from fertilizers and organic materials like leaves and yard waste. Preventing excess nutrients in lakes and rivers is a long-term goal that will involve changing agricultural practices, properly managing municipal stormwater, using in-lake treatments, reinforcing shorelines, and much more.
Blue-green algae's unpleasant odor and appearance tend to keep people out of the water. But people who do come into contact with toxic blue-green algae can experience skin irritation, nausea, and eye, nose, and throat irritation. People should not swim in water if they suspect it has a blue-green algae bloom. If you come in contact with algae, rinse off with clean water afterwards.
Learn more on the Blue green algae and harmful algal blooms page.