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Take Care to Avoid Contact

Based on recent news reports about blue-green algae sightings on Lake Mendota, as well as several beach closing notices, it is safe to assume that this year´s blue-green algae season has begun.  
Blue-green algae are actually not algae, but photosynthetic bacteria known as cyanobacteria.  They occur naturally in lakes, streams and ponds and have been around for millions of years.  They only become a problem for us when they grow enough to produce large scummy mats on the surface of lakes and rivers. They tend to be green to blue-green in color, but can also be reddish-purple, or brown sometimes looking like paint. 
Some of these blooms are capable of producing toxins.  Exposure to these toxins can produce a range of reactions, from rashes and lip blistering to harmful effects on the liver and nervous system.  Other reactions can include sore throats, headaches, muscular and joint pain and asthmatic and gastro-intestinal symptoms.  If you believe you have been exposed, contact your doctor right away.
When you see blue-green algae bloom keep yourself, your children, and your pets out of the water and avoid all contact.  Dogs swimming in or drinking water covered with a bloom can suffer near fatal or fatal consequences. The only benefit to its disgusting appearance and smell is that it tends to keep people away.
Blue-green algae blooms occur frequently throughout the summer season. Spells of hot weather and heavy rains carrying nutrients can create conditions that increase the possibility for increased blue-green algae blooms though they are hard to predict.  Since the lakes are always in motion, the wind and waves that bring a bloom to a beach are just as capable of blowing it away.  Blooms can linger for a few hours or days depending on weather conditions. 
There are no quick chemical fixes that we can use to make these blooms go away.  We have discovered that if we use herbicides or algaecides, we may succeed in killing the bloom, but as the bacteria die, they will release their toxins into the water and thus create a potentially bigger problem.  One long-term strategy includes reducing the amount of phosphorous and nitrogen applied to our yards and fields that runs off into the lakes. This would help reduce the growth of algae.
PHMDC (Public Health-Madison and Dane County) regularly monitors water quality at many Madison area beaches including routine, weekly testing for bacteria and blue-green algae. If test results show that beach conditions are not safe, the beach will be closed for swimming. Follow-up testing is done every day until the problem clears up.   You can report the appearance of a bloom or illness possibly related to blue-green algae by calling PHMDC at (608) 266-4821.   You can also call the Wisconsin Poison Control Center at 1-800-222-1222.

 Click here for Up-to-date beach conditions are always available online
 Click here For more detailed information on blue-green algae from the DNR’s website



  • Jeff Golden, Public Health Madison Dane County, (608) 243-0302
Health & Safety