A couple weeks ago, local angler Robert Kurczek alerted the Green Lake Association (GLA) to a change in the water in Beyer’s Cove. He specifically raised concern over its milky white coloring and the presence of a few small, dead fish floating in the water.
“Naturally, we were very concerned,” Executive Director Stephanie Prellwitz said. “Whenever there’s something unusual happening in the water, we want to act quickly — both for the sake of the lake and just in case there’s a human health risk involved.”
Individuals from the Wisconsin DNR, GLA board, Green Lake Sanitary District, Green Lake Land Conservation Department and University of Wisconsin-Oshkosh came together via email to discuss the potential cause and next steps.
There was speculation that what was happening was a natural and non-dangerous lake phenomenon called a “whiting event.”
To confirm, GLA staff member Kristen Rasmussen collected a water sample from Beyer’s Cove for analysis by GLA board member Bob Wallace, a retired Ripon College biology professor. Wallace confirmed that the substance causing the water to be cloudy was calcium carbonate, and this was indeed a whiting event.
A whiting event is a naturally occurring process that happens when calcium carbonate precipitates, or becomes solid in the water.
Calcium carbonate is abundantly found in nature (it is the main mineral in limestone) and is often highly concentrated in lakes with hard water, such as Green Lake.
Eventually the calcium carbonate that is precipitated in the water, causing the milky color, sinks to the lake bottom where it dissolves or forms a soft rock called “marl.”
“The warming surface waters reached a temperature at which calcium carbonate (CaCO3) precipitated out into little white crystals,” Wallace said of the cause of the phenomenon. “These events happen to lakes all over the world that have very hard water.”
He also added that there is no human health risk associated with the event.
Another factor that may have contributed to the event was the presence of filamentous algae, a native and non-harmful plant that naturally grows in the lake.
Gina LaLiberte, a water quality expert with the Wisconsin DNR, noted “If there’s a lot of filamentous algae present, which is common in springtime, the plant’s photosynthesis and respiration could cause large swings in pH, which could have induced the whiting event.”
She also explained that this also could have reduced the amount of dissolved oxygen in the water, therefore leading to the fish deaths.
This is not the first time Green Lake has seen a whiting event. Green Lake Sanitary District’s Lisa Reas noted that this happened in the same location in 2019.
“The GLA’s main focus is the lake’s water quality, but we can’t be everywhere all the time. It’s so wonderful when community members contact us about what they are seeing out on the water. That enables us to jump in, assess the situation and alert our partners and the community if there’s a safety concern,” Prellwitz said.
The GLA encourages everyone to help be their eyes on and around Big Green Lake. If anyone should see anything unusual when it comes to Green Lake’s water quality, email the GLA at email@example.com or message the association on Facebook at: facebook.com/GreenLakeAssociation/.