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Out-musseling the mussels: Researcher hopeful of new tactic against invasive species

Zebra mussels are an aquatic invasive species. 1 / 2
Mike McCartney2 / 2

A researcher with the University of Minnesota is out to make zebra mussels their own worst enemy.

Mike McCartney, a zebra mussels expert in the aquatic invasive species department at the University of Minnesota, gave a presentation at this year's Lake L'Homme Dieu Association meeting on how communities such as Alexandria can limit and prevent the spread of zebra mussel invasion in the lakes, and perhaps use genetic engineering to combat them.

The new research his department is conducting deals with what they call genetic biocontrol of zebra mussels, an invasive species that can harm lakes by eating up nutrients needed to support native fish. Zebra mussels reproduce rapidly and cause other problems from clogging pipes to cutting the feet of swimmers with their sharp-edged shells.

"It's the attempt to reduce the population of a pest," McCartney said Saturday, July 13. "You use a genetic approach, which actually goes into, in this case, the genome of the animal and makes changes."

The hope for this idea is to modify the genes to create a mussel that can't survive, and then release it into infested lakes to breed with the existing population with the hope of passing along that gene and killing it off.

"You could create a lethal gene that causes the mussels to die while they're developing as larvae," McCartney said. "That would work pretty much like a pesticide, because you could release it on an area and those animals in that area wouldn't be able to successfully reproduce."

Easy enough, right? Just go in and mess with the genome sequencing of the species and put it out in the lakes to kill them all.

Not quite. The U of M AIS department still has a lot of work to do, and some of what they aim to do isn't allowed by law yet. When asked at the end of the presentation how long it might be until this can be put into practice, McCartney said his best guess was around 10 years, and a groan went through the crowd.

"I was hoping he was going to say three to five, because you're tapping into some known technology with the oysters and some other ways this has been done," Steve Henry, president of the Lake L'Homme Dieu Association said. "I hope (McCartney is) right — if the powers in Washington start to say, 'Hey this is exciting, this is favorable,' maybe we can move along. But I just think whenever you hear 'genetically modified,' you get a lot of pushback from a lot of non-scientific people, and somewhat rightfully so. It's scary."

In Lake L'Homme Dieu, zebra mussels and other invasive species aren't yet an emergency, but the association hopes the people who use the lake will help to keep it from becoming one.

Henry cited research being done at the University of Wisconsin-Madison showing how zebra mussels, which actually make the water clearer, can affect lakes.

"The zebra mussel excrement makes such wonderful fertilizer that we're seeing increased weeds already just because of the water clarity and the sun getting down there," Henry said. "But they're having huge weed problems in lakes in Wisconsin."

Henry reached out to the university to hear about promising new research.

"I contacted the AIS department down there because we've had the local folks come and talk, and I thought it would be nice to go a little higher and see what's on the cutting edge," Henry said. "Between the Eurasian milfoil spreading and the zebra mussels and just the general weeds getting worse, that's the path that I fear."

Eurasian watermilfoil is another pesky invasive species that Lake L'Homme Dieu suffers from. Native to Europe, Asia and Northern Africa, the fast-reproducing weed was introduced to the United States in the 1940s and poses an annoying obstacle for swimmers and boaters.

Checking the spread

McCartney also discussed the spread of zebra mussels which usually occurs between neighboring lakes within small regions. "In each of these regions that we've worked on — around Brainerd, around Alexandria, around Detroit Lakes — each of those individually is a place where they're spreading really fast, really short distances," he said. "The message there is that there are ways that that's happening that need to be better interrupted (with) better surveillance and better prevention."

The easiest and most obvious way is for lake users to be mindful of what waters are infested and what equipment is a potential vehicle for transporting mussels to uninfested waters.

Researchers can determine where a specific mussel came from by exploring its DNA. The Alexandria Chain of Lakes has three clusters of zebra mussels, McCartney said. Knowing which cluster a mussel is from helps determine how that lake became infested and what measures will help to prevent further spread.

Another method that works in some situations is copper sulfate treatment. During his presentation, McCartney referenced an attempt in 2012 that worked nearly perfectly when a man brought a boat lift from Lake Lizzie, a known infested lake in Otter Tail County, to Rose Lake, which is not infested.

"If you saw how many mussels are in (Lake Lizzie), you wouldn't believe it," said McCartney. "It's a terrible thing that he did, but he brought it into that lake, and the DNR finds zebra mussels on hard surfaces nearby and on lake bottom."

The Minnesota DNR treated the area around the lift with copper sulfate three times to kill all the mussels. That fall, they found six mussels, but when they went back in the following years, they didn't find any mussels anywhere in the entire lake.

The problem with copper sulfate treatment is that it only works in small areas. If an entire lake is infested, copper sulfate would not work. .

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