Starry stonewort, an invasive algae, was found for the first time in Wisconsin, in Little Muskego Lake in Waukesha County. The algae has caused problems for boaters and fishermen in lakes in Michigan. Credit: Scott Brown

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An invasive algae spreading quickly through Michigan inland lakes has been found for the first time in Wisconsin — in Little Muskego Lake in Waukesha County.

The state Department of Natural Resources said that starry stonewort, a native to Europe and Asia, was discovered in the 506-acre lake in September.

It's the latest of more than 30 aquatic invasive species to strike Wisconsin. In some cases, such as zebra mussels, they wreak havoc on state waters. In others cases, these hitchhikers from other parts of the world have had a more limited impact.

Starry stonewort was found near Detroit in 1986 in Lake St. Clair, which is part of the Great Lakes system. The algae is known for growing in dense mats that crowd out native plants and wipe out habitat for young fish.

When it takes hold in a lake, it's bad news for boaters and anglers, and Michigan officials said that Wisconsin's planned eradication approach might not be effective.

Sarah LeSage, a Michigan expert, said some lakes in her state "almost look like an underwater golf course," choking out other native plant life.

In an inland lake, it was first discovered near Flint in eastern Michigan in 2006. Starry stonewort has since been estimated to have infested more than 250 lakes, according to Michigan Lake & Stream Associations Inc.

"It is one we know that is rapidly spreading from lake to lake," said LeSage, aquatic invasive species program coordinator for the Michigan Department of Environmental Quality.

"We're definitely keeping our eye on it and trying to better understand how to manage it."

Starry stonewort is one of six invasive algae and cyanobacteria that are prohibited from introduction to Wisconsin under state invasive species regulations.

It was found in 2 to 5 feet of water in a small patch on the east side of Little Muskego on Sept. 16, according to Heidi Bunk, a DNR lakes biologist.

"We are hopeful it is contained to this area," Bunk said.

It's not known how the algae — similar in appearance to a native species known as chara — got into the lake. But Bunk said aquatic invasive species routinely enter lakes, rivers and streams via boats.

Scott Brown, executive director of Michigan Lake & Stream Associations, said Wisconsin could experience the same problems as his state.

He described starry stonewort as a "connoisseur of clean water," the kind of water quality and water chemistry found in both states, which ironically is in short supply in its native habitat.

"Our level of concern is quite high," Brown said. "So watch out."

The Wisconsin DNR's plan to control starry stonewort is to work with the local lakes association and the Little Muskego Lake Management District to remove known infestations.

Several weed harvesting machines now operate on the lake. One will be dedicated to starry stonewort on the eastern side of the lake, Bunk said.

More signs will be posted on boat launches warning people to clean debris off watercraft. Local officials will mount a public awareness campaign. There also are plans to conduct more monitoring of the lake.

But Michigan officials said Tuesday that the starry stonewort has been difficult to eradicate.

Michigan officials say they don't have data, but it appears that the use of mechanical harvesting equipment spreads infestations, according to Lisa E. Huberty, who works on aquatic invasive species for the Michigan Department of Environmental Quality.

Starry stonewort can regrow from pieces of plants that are chopped off and not harvested.

Chemical treatments have been used with mixed success but can pose problems to other aquatic life.

"Any choice is going to have its strengths and weaknesses," Huberty said.