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Zebra mussel lessons: Garfield Lake residents addressing infestation; genetics tracking AIS spread

The major pattern of zebra mussel spread in Minnesota is "clustered invasions in lake-rich regions, due to dispersal from outside region (red arrows), followed by local spread (shaded colors). (Graphic by Minnesota Aquaitic Invasive Species Research Center)

Ignorance is bliss, Ron Ray told Hubbard County Coalition of Lake Association (COLA) members.

In late September, an independent laboratory confirmed zebra mussel larvae in Garfield Lake, where Ray lives.

He provided an update on the situation during COLA's Sept. 28 board meeting.

Garfield Lake does not have a lake association, but a small group of lakeshore owners formed Friends of Garfield Lake, Ray explained.

"We're trying to educate landowners as to good stewardship of the lake," he said.

With help from COLA, they began lake water quality testing last spring.

Their first zebra mussel veliger test discovered two larvae in the water sample.

"With that unfortunate news, the issue is 'Where do you go from here?' I come from a background of I'd rather know about it than not," he said. "I've probably gotten about 30 phone calls."

Property owners are being trained about what to look for "when they pull their docks out, their boats out," Ray said. "The macro is we're doing everything we can we know about."

There may be an opportunity for the Minnesota Department of Natural Resources' to utilize one of its zebra mussel-sniffing dogs to walk around the lake. Permission is needed from property owners first, Ray said.

Modern genetic tools assisting in AIS fight

Dr. Michael McCartney is a zebra mussel biologist at the Minnesota Aquatic Invasive Species Research Center. He also spoke to COLA last week.

Using modern genetic markers, his laboratory has been tracking the "transfer pathways" of zebra mussel spread in Minnesota for the past three-and-a-half years.

The goal of his research is to help AIS managers around the state direct their efforts toward those vectors that carry the highest risks of invasion.

"It's really a story of bad luck that we have these in North America and also bad luck that they have the traits that they do. They have these traits because they evolved from marine ancestors. They are very similar to clams," said McCartney, a marine biologist by training.

Zebra mussels are able to produce offspring quickly.

"Females cast into the water somewhere around a half-a-million eggs," he said. "These things have an enormous capacity to reproduce."

Mille Lacs Lake has roughly three trillion zebra mussels in it, he said.

The larvae, called veligers, can spread long distances "because the larvae spend so much time in the water developing, on average three weeks. So they have this ability to disperse very broadly."

They produce long threads to attach to any hard surface — boats, lifts, docks, plant materials, rocks, sand, one another, McCartney explained.

Dense zebra mussel populations remove half to three-quarters of the plankton mass from lakes and rivers.

"So they can have dramatic effects. Biologists working on impacts are just beginning to struggle with what this means," he said.

The North American invasion of zebra mussels began in the late 80s.

Minnesota's rate of new, inland invasion is now among the highest in the U.S., McCartney said. "What we're seeing is what other states saw 10, 15 years ago."

While the state's larger lakes are infested, there are many smaller lakes to protect, he said.

His laboratory first tested the "super-spreader lake" theory — the idea that Mille Lacs, for example, served as the hub for invasion throughout the rest of the state.

Using genetic markers, they were able to distinguish the zebra mussels from Mille Lacs with those in any other infested lake in the U.S.

After testing 35 lakes, they found "dramatically high" genetic diversity among adult zebra mussels.

"Not a single time does Mille Lacs turn out to be the source," he said. "It was a total surprise."

The pattern appears to be "clustered invasions in lake regions." An initial mussel invasion arrives from an unknown, outside source, then rapidly spreads through interconnected waterways or overland through recreational boating.

"Each is a separate genetic cluster which is unique and not found anywhere else," he explained.

McCartney's lab suspects the highest risk for transfer of zebra mussels is through infested plant matter on a trailered boat.

He emphasized the importance of surveillance in slowing spread of AIS.

"We can't relax the watercraft inspection program," he said.

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