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MILWAUKEE, WI – Volunteers with the River Alliance of Wisconsin say they’ve found two new instances of starry stonewort – an invasive algae that has been known to clog waterways. If confirmed, their findings would bring the number of total locations from 17 to 19 in the state.

On Aug. 17, 170 volunteers from the River Alliance of Wisconsin waded in or trekked along the shorelines of more than 100 bodies of water across the state—embarking on a search for aquatic invasive species. Volunteers met at their Training Sites, received a brief training on species identification and monitoring protocols, were equipped with the tools needed to find them, and traveled to their assigned sites for their”scavenger hunt.”

Data is still rolling in and potential finds are being confirmed, organizers say. Organizers say a volunteer found an unusual specimen on Pewaukee Lake. This turned out to be Starry Stonewort, a submerged macro alga that has recently made its way into several southeast Wisconsin lakes.

A few days later the same volunteer found a specimen in Lower Nemahbin Lake — a 239-acre lake in Waukesha County. The Wisconsin Department of Natural Resources and partners are working to determine the full impacts of this prohibited species with concerns over its potential to reduce the diversity of native plants and impair fish spawning, as it forms dense mats in affected waterways.

“This is a different kind of success and one which shows how important our volunteers are. While finding a prohibited species may seem like bad news, this early detection will allow for management and prevention efforts, before a population further establishes,” Natalie Dutack, River Alliance of Wisconsin’s Aquatic Invasive Species and Watershed Groups Manager, said.

Starry Stonewort Confirmed Sites in Wisconsin


Little Muskego Lake


Big Muskego Lake

Long Lake

Pike Lake

Silver Lake


Channel around High Cliff Park (Sturgeon Bay, WI)

Ellison Bay/Lake Michigan

Fish Creek (Green Bay)

Green Lake

Lake Michigan – Rowleys Bay Access

Little Sturgeon Bay

Sister Bay/Green Bay Access

Sturgeon Bay


Wind Lake


Geneva Lake

Little Cedar Lake


Okauchee Lake

Source: Wisconsin DNR

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