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Lake Koronis takes on starry stonewort

PAYNESVILLE -- An aggressive, five-year campaign that is expected to cost over $800,000 is being launched to manage starry stonewort in Lake Koronis.Koronis and adjoining Mud Lake are first waters where the invasive species has been discovered in...

starry stonewort
The starry stonewort grows branchlets and forms thick, dense mats that crowd out native vegetation and smother spawning habitat for fish. (SUBMITTED)
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PAYNESVILLE - An aggressive, five-year campaign that is expected to cost over $800,000 is being launched to manage starry stonewort in Lake Koronis.
Koronis and adjoining Mud Lake are first waters where the invasive species has been discovered in Minnesota. Managing its growth in Koronis is important not only for the lake, but also for reducing the risk of spreading it to other lakes across Minnesota, according to Kevin Farnum with the Koronis Lake Association.
“We’re trying to reduce the risk of export. Let’s just say we don’t want to be the mother lode,’’ he told an audience in the Paynesville High School Auditorium Tuesday evening.
Farnum and John Rodgers, a Clemson University professor and expert on the invasive species, were joined by representatives of the Minnesota Department of Natural Resources in outlining the management plan as well as the threat the plant represents to lakes.
Since its discovery in August, starry stonewort has continued to spread. It covers 250 acres in the 3,000-acre lake. It’s heavily concentrated in the southeast bay near the Minnesota Highway 55 access.
Red and green buoys will be placed next week to create a navigation channel near the access this coming week. A mechanical harvester will be used to remove as much of the starry stonewort as possible in the channel. Scuba divers will assist in its removal. Later in the season, algaecide will be applied. Knocking it down in the channel will reduce the risk of boats chopping up the plant, aiding in its spread or carrying it out of the lake.
The DNR will also station inspectors at the access.
A native of Europe and Asia, starry stonewort creates dense mats that crowd out native vegetation and cover fish spawning habitat. It can grow to be over six-feet tall and in large masses thick enough to choke boat motors.
If left unchecked, the alga can quickly spread throughout the littoral area of a lake. It is already found as deep as 20-feet in Lake Koronis, according to Rodgers.
New populations of starry stonewort often crowd themselves and die-out. The thick mats of decomposing starry stonewort will rob the lake of oxygen, blanket the bottom sediment and kill invertebrates, and release a foul combination of dead fish and rotten egg odors, according to Rodgers.
And just when it seems the die-off means the end of the infestation, “it comes back with a vengeance, worse than ever,’’ he said.
It can be controlled, but here’s the catch. Its vulnerability to algaecides and various treatment strategies varies from lake to lake. The DNR will work with Rodgers and the Clemson laboratory to determine what algaecide is most effective in Lake Koronis.
The initial strategy will focus on a small area of Lake Koronis to determine the most effective strategy. A mechanical harvester, algaecide and scuba divers all will be employed.
Rodgers said effective management plans whittle away at the population. It’s impossible to eradicate it from a lake, but it can be controlled, he said.
He spent two days examining the infestation this week. He discovered that it is already widely distributed in Koronis. And yet he said: “I don’t think it has been there very long.’’
Along with managing it, Rodgers encouraged efforts to monitor boats and educate those using the lake to prevent its spread. Researchers don’t know how long it can live out of water. The University of Minnesota Aquatic Invasive Species Research Center is currently conducting research to determine how long it remains viable out-of-water.
Rodgers said he has tested similar algaes and found they can revive themselves even after several days in the sun.
“I don’t want to be alarmist and I didn’t say this is going to happen, but if I were in an adjacent watershed and I knew what I knew, I’d be getting my plan together. I would not wait until I had it,’’ he said. “And I’d ask these people at Lake Koronis ‘please do what you can to get it under control and keep it out of my watershed.’ ’’
The Minnesota Department of Natural Resources has been examining lakes within a 10- to 20- miles of Koronis. It has not found starry stonewort, according to Chip Welling, aquatic invasive species management coordinator with the DNR. He said the monitoring efforts will be ongoing.
Farnum told the Paynesville audience that the Lake Association has been able to line up $400,000 in grant funds to date, but still needs to raise another $400,000 for the five-year, pilot management program. It’s a lot of money for a small community to raise, but he noted the stakes are large.
“If we make a decision to do nothing, we’re not making the decision just for us. We’re making the decision for every other lake in the state,” he said.
The invasive algae was first discovered in the U.S. in the St. Lawrence seaway in 1978. It has since spread to lakes in Michigan, New York, Pennsylvania, Vermont, Wisconsin and now, Minnesota.

 

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starry stonewort map Lake Koronis
This map shows how widely distributed starry stonewort has become in Paynesville’s Lake Koronis since its discovery last summer. When discovered in August, it covered 55 acres. Today, it covers 250 acres in the 3,000-acre lake. (MINNESOTA DEPARTMENT OF NATURAL RESOURCES | SUBMITTED)

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