Despite lakeshore property owners’ ramped-up investments to keep Green Lake free of zebra mussels, the invasive species has infested the lake near Spicer.

A property owner found a zebra mussel attached to a dock post in about 4 feet of water on July 21, and the Department of Natural Resources later confirmed the specimen, which was dead. DNR personnel conducted additional searches and water samples of the lake, but no other zebra mussels were found, officials announced Monday.

“I’m disappointed,” said Terry Frazee, executive secretary of the Green Lake Property Owners Association. “We’re working with the city of Spicer and Kandiyohi County to do everything we can and still, we found one mussel — one. And I still believe that’s the only one we’re going to find.”

The group is one of the state’s most active lake associations when it comes to fighting aquatic invasive species, said Nicholas Brown, DNR aquatic invasive species specialist. The Green Lake Property Owners Association installed a $18,000 high-pressure boat washer earlier this summer in efforts to deter zebra mussels, which attach to boats, nets, docks and other equipment. In partnership with the city of Spicer, Kandiyohi County and the Middle Fork Crow River Watershed District, the group also kicked in $17,000 to pay inspectors.

Association officials said they believe their group is the only lake association in the state to have purchased a boat washer, and many of the funds come directly from community members. With about 800 property owners, the group asks for annual dues of $100 from each owner.

“We’re always disappointed to find new infestations, especially when we see them on a lake where the lake association and surrounding community has put as much work into keeping the invasive species out,” Brown said.

The department has designated Green Lake as infested with zebra mussels and is expanding its watercraft inspection efforts for the rest of the year, Brown said. It plans to bring more boat washing units and expanded washing hours to Green Lake next year, with the help of $256,000 in state funding. The money is part of a tax bill signed by Gov. Mark Dayton in May, providing $10 million per year to help local governments combat invasive aquatic species.

Jamie Duininck, President of the Green Lake Property Owner’s Association, encouraged all boaters to wash their crafts and equipment as they enter and exit the lake. The boat washing service is available free of charge to anyone — even if they’re not using Green Lake. It is open 11 hours a day, Thursday through Sunday, at the Saulsbury Park boat launch.

“Right now we kind of see it as a call to action for everyone that is concerned about Green Lake or the lakes of [Minnesota],” Duininck said. “Were not blaming anybody … we’re getting things in place.”

Heavy infestations of zebra mussels threaten to kill native mussels and fish populations in Minnesota’s lakes. They feed on the same plankton as many fish, can clog water intakes, and interfere with swimming, as their sharp edges can be quite painful, Brown said.

If no additional zebra mussels are found in Green Lake for the next five years, the DNR may revisit the decision to list the lake as infested. More than 175 Minnesota water bodies are designated as infested with the mussels.

“When they become more numerous, that’s when we really see the problem,” Brown said. “We don’t know what’s going to happen.”

As a precaution, Lake Calhoun in Kandiyohi County also will be designated as infested because it is directly downstream from Green Lake.

Also in Kandiyohi County, a new infestation of Eurasian watermilfoil in Games Lake, east of Sunburg, was reported Monday. A lakeshore owner found the plant near the outlet from Norway Lake, which has been infested with the watermilfoil for more than 10 years, Brown said. Games becomes the fourth lake — including Green Lake — in the county infested with Eurasian watermilfoil.

“It’s not surprising,” Brown said about the Eurasian watermilfoil.“ Given the fact that we hadn’t seen zebra mussels in the region before, I think that’s drawing a lot of our attention right now.”