MENOMONIE — For the Center of Limnological Research and Rehabilitation (CLRR) at the University of Wisconsin-Stout, Bill James, CLRR founder and director, said their job is something which is typically done one lake at a time.
That lake was Green Lake in the past year, which sits in Green Lake County and stands as one of Wisconsin’s largest and best-known natural inland lakes. It covers 7,600 acres and goes roughly 236 feet, making it also the deepest inland lake as well.
And for those in the limnology department, the lake was the site of a study in 2024 to help diagnose the lake and test its water quality.
As a center in the university which diagnoses freshwater ecosystems and offers management solutions to help with the quality, James explained that the CLRR “started in 2012, and it has been going on for 12 years. We have done a lot of research in Wisconsin, Minnesota and nationally.”
“As a center, we have tried to increase our exposure and advertise our expertise in what we can do, because that is our role,” he said. “We are trying to train students and we’re trying to give them real-world experience, and we are actually trying to improve our 15,000 lakes in the state.”
Locally, one of CLRR’s projects has been Halfmoon Lake in Eau Claire. But for their recent work, CLRR has had to travel out of the Chippewa Valley.
“Green Lake is a very large and unique system, and it is pretty pristine — which is sort of rare these days,” said James. “It is one of the deepest lakes in Wisconsin, and they are really being proactive, and by ‘they’ I mean the Green Lake district. They want to keep the lake pristine.”
But in that effort to keep the lake at a healthy quality, members of the Green Lake Association stressed concerns that excess phosphorus had built up over decades at two inlets on the shore. That concern over phosphorus is certainly not unfounded, as Green Lake faced two beach closures from toxic blue-green algae blooms and an additional bloom in the marsh during summer of last year. Looking for the root of the problem, CLRR’s task was to look at the soil.
“We brought sediment cores into the lab,” said James. “We incubate them and we measure the phosphorus that is accumulating in the overlying water, and this gives us a rate of phosphorus recycling.”
The excess amount of phosphorus is likely a cause for the algae blooms, and determining where it is coming from is another critical step.
The next step is addressing a broader context to figure out what can or should be done to preserve the lake quality. They ask questions, such as: how much phosphorus is the sediment that has accumulated over the years contributing to the lake?
“From there, the district wants to try and develop management to control the sediment in the lake,” said James.
With all that the limnology department at Stout helps with, he continued and said, “It is definitely a process, and it starts with partnerships. We are usually partnered with the lake district and with the state with the Department of Natural Resources (DNR). We all get together and we talk about the problems… We might be monitoring streams, the flow, the nutrient concentrations, and then we monitor the lake itself.”’
With the aforementioned process of bringing sediment cores into the labs, James said they can determine a lot from what concentrations of phosphorus come back. They can also learn a lot from the toxic algae blooms, and hopefully figure out a solution.
“This sort of dictates how we manage the lake,” said James. “We want to manage what is important; we don’t want to spend a million dollars on watershed management when most of the phosphorus is coming from the internal sediment. We tell the clients where the phosphorus is coming from.”
The research on the lake began roughly in July 2024, as concerns for the quality of the lake continued. While agricultural practices may have an impact, warm weather was also a concern as the Green Lakes Association’s Chief Executive Officer Stephanie Prellwitz determined that the few times the lake has failed to freeze over the past years may have given algae an advantage to grow.
“The lake is giving us warning signs,” Prellwitz said in a press release from the university. “For a gem of a lake like Green Lake, it’s important we take the necessary steps to reduce phosphorus sooner rather than later. It’s time to step back and plan how to tackle a challenge of this magnitude.”
Now with the work done over the past year to gather data, James said the next step is to compile it into a report for recommendations of how to manage the lake moving forward. He estimated that time could be March 2025 when the report is submitted.
While it is not often that the limnology department plays a role in managing the lake, James said sometimes it is their responsibility to catalog the lake’s response to management. Until then, the work for them is still ongoing.
“This particular study has been, I would say, very high caliber,” he said. “We really got some outstanding results.”