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Potash used to treat zebra mussel infestation in west metro lake

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A small lake in Hennepin County is the first in Minnesota to be treated with potash as a way to eliminate zebra mussels.

The Department of Natural Resources is experimenting with this new treatment to see if it can help contain the explosion of zebra mussels, which have invaded more than 200 bodies of water in Minnesota in recent years.

Technicians from the department spent several hours Friday pumping 1,000 pounds of potash, a naturally occurring salt compound commonly used in fertilizers, through the ice into an area of Christmas Lake in Shorewood where an isolated infestation of zebra mussels was found in August, the St. Paul Pioneer Press reports.

The chemical interferes with the mussels' respiratory system, so they essentially suffocate. But it doesn't harm fish or other living things in the lake, according to the DNR.

Since the zebra mussels were detected early on and seem to be confined to a small area, the DNR is using Christmas Lake as a test site of sorts to see which treatment methods might work the best against them.

The potash treatment is the third one that's been applied to the lake, the DNR says.

The first treatment was with Zequanox, a substance made up of dead bacteria, which seemed to work well. The next one was a copper-based chemical. Researchers said shortly afterward that it appeared all the mussels inside the test area were killed.

But in parts of Christmas Lake outside the closed-off test area, divers found more zebra mussels. officials said. So they turned to potash, which has been used in just two other locations in the U.S. so far against zebra mussels.

“We’re trying all available options at Christmas Lake as the zebra mussel infestation was isolated to a small area of the lake,” said Keegan Lund, an invasive species specialist for the DNR. “We’re learning a lot about new treatment methods for zebra mussels that have not been used before in lakes.”

A potash treatment may also be tried next spring on Lake Independence in the west metro area, where zebra mussels were found in October at the boat launch. Both lakes will continue to be monitored to determine if the treatments were successful.

The potash treatment should be effective on isolated infestations, but the DNR says it would be too expensive to try it on larger lakes where the zebra mussels are more widespread.

In addition, it would also wipe out any native mollusks in a given lake. Since potash is a fertilizer, it would bring "ecological ramifications" to any lake where it's introduced on a wide scale, according to the DNR's Lund.

Zebra mussels are an invasive species that can crowd out native mussels and compete for food sources with other aquatic animals. They attach to boat hulls and other water-related equipment and can create a hazard for swimmers due to their sharp shells.

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