McMahon pointed out that the name “algae” is a bit of a misnomer as the organism is not an algae at all, rather, it is a type of bacteria called cyanobacteria. From an evolutionary standpoint, blue-green algae is more similar to humans than it is true algae. Distinguishing it from true algae is important when one considers how blue-green algae functions in the ecosystem. Unlike true algae, blue-green algae does not play a major role in establishing the aquatic food chain. It produces toxins, reduces light penetration, causes foul odors, and contributes to harmful dissolved oxygen depletion in our lakes.
Some cyanobacteria species are native to Wisconsin and blooms have occurred for centuries in our lakes. In recent years however, the frequency and magnitude of blooms has grown at an alarming rate. Most scientists point to the influx of phosphorus into open water systems and McMahon detailed how the nutrient serves as a limiting factor which regulates cyanobacteria population size. Changes in agricultural techniques, land use, and soil disturbance have all contributed to increased levels of phosphorus in our lakes, creating a situation in which blue-green algae can flourish.
Dr. McMahon’s fascinating presentation catalyzed a bright discussion with many of the attendees sharing their experiences and insights into the not-well-understood phenomenon of blue-green algae blooms. Among the many problems associated with the frequent blooms in our lakes is how their occurrences could affect our perception of Madison lakes. Dr. McMahon poignantly remarked that if people are afraid to be in or around the lakes, they’ll use them less. If Madison residents stop interacting with our lakes, they might give up on the them, making it much harder to solve the problems that require our help.
After Dr. McMahon’s presentation, Dea Larsen Converse, from the Clean Lakes Alliance (CLA), discussed the CLA’s mission, the importance of their Water Quality Monitoring Program, and how individuals can assist in reducing nutrient pollution and improve the cleanliness of Lake Mendota water.
Arlene Koziol, Friend of the Lakeshore Nature Preserve and Clean Lakes Alliance Water Quality Monitor, explained the role of a CLA Water Quality Monitor while Jeff Koziol demonstrated how to use a turbidity tube to assess water clarity. See Arlene's account of the 2018 Cyanobacteria blooms on Lake Mendota. Steve Sentoff of the Friends has formed a team of volunteers who will monitor water quality following the Clean Lake Alliance protocol along University Bay boating pier.
Seth McGee was the Friends' host for the event. He provided this summary and photos.