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Blue-Green Algae

As the weather warms, be wary of blue-green algae

Cyanobacteria, commonly known as blue-green algae, were seen all across the state of Minnesota last year. When blooming, these organisms produce toxins that can cause harm to humans and animals. Blooms normally begin to occur in July and the warm weather of this year, along with ample rainfall, create conditions that have already allowed blooms to form and prosper.

Harm caused by blue-green algae

Most of the time, blue-green algae has a particular look and smell that deters people from going into the water. Swimming isn’t the only way blue-green algae can cause harm to humans and pets, though. Humans have become sick from accidentally ingesting water droplets that splash up into boats. Of course, that means humans and animals may fall ill from drinking the water. Blue-green algae can also cause skin irritation.

Dogs are more at risk for harm from blue-green algae because of the amount of water they swallow while swimming, especially if they are retrieving a toy from the water. They also may lick algae from their fur, which can cause harm, as well. Dogs may experience vomiting, diarrhea, rash, difficulty breathing, general weakness, liver failure, and seizures if exposed to blue-green algae. If you believe your dog may have been exposed, seek veterinary help immediately. In extreme cases, blue-green algae exposure may cause death.

Protecting yourself

Harmful blooms are often described as looking like green paint, pea soup, or “a floating mat of scum”. A harmful bloom may or may not have an unpleasant smell. Sometimes, though, a harmful algal bloom may be present with no obvious signs. Enter water with caution: check the edge of the water for algae (an indicator that a bloom may have recently occurred and that the water may contain toxins) before you, your pets, or your children dive right in. Remember the recommendation when it comes to blue-green algae: if in doubt, stay out!

If you believe you or your pet may have accidentally come into contact (through skin or ingestion) with a harmful algal bloom (HAB), immediately wash off with fresh water, paying special attention to those areas that were covered with a swim suit or clothing. Symptoms such as vomiting, diarrhea, eye irritation, skin rash, sore throat, cough, headache, or seizures may occur anywhere from two hours to two days after exposure. If symptoms do occur, contact your doctor or veterinarian as soon as possible.

More information on blue-green algae, including how to report a possible human or animal illness, is available on the Minnesota Department of Health Harmful Algal Blooms web page.

Reducing algal blooms

For an algal bloom to be exterminated, the weather must disrupt its growth. There is no short-term solution to the issue. There are things that can be done to reduce algal blooms in the future.

To solve problems with HABs, water quality must be improved. Algal blooms are caused in large part by high concentrations of phosphorus in a body of water. Phosphorus naturally is present in organic material, and it increases plant growth. To produce algal blooms, phosphorus must be present in excess. Excess phosphorus can find its way to lakes through runoff from urban and agricultural land that is treated with fertilizer. Reducing fertilizer use, along with keeping yard and pet wastes off of pavement, can help reduce the amount of phosphorus in lakes, thereby improving water quality and reducing the number of algal blooms.