Lake Koronis projects augment starry stonewort research

Ann Wessel, St. Cloud, MN – Tens of thousands of dollars and hours are aimed at stopping the spread of starry stonewort. Minnesota's first infestation was confirmed last August in Lake Koronis.

Tens of thousands of dollars in grant money and hours of research are funneling into Lake Koronis as the Minnesota Department of Natural Resources ramps up boat inspections, the lake association prepares to launch an $828,600 pilot project and University of Minnesota researchers plot lab experiments — all in response to the state’s first confirmed starry stonewort infestation.

An aquatic invasive species specialist with the Minnesota Department of Natural Resources, uses a double-sided rake on a rope to collect samples of starry stonewort on Lake Koronis near Paynesville. The DNR is monitoring plant growth to determine the best time to apply a chemical treatment.

An aquatic invasive species specialist with the Minnesota Department of Natural Resources, uses a double-sided rake on a rope to collect samples of starry stonewort on Lake Koronis near Paynesville. The DNR is monitoring plant growth to determine the best time to apply a chemical treatment.

The DNR confirmed the presence of the macro algae in August.  The aquatic invasive species, native to Asia and Europe, is known to form dense mats, engulf fish spawning habitat and clog boat motors.

What comes of this season’s work could have applications far beyond the lake near Paynesville on the Stearns-Meeker county line.  Starry stonewort has been confirmed in New York, Michigan, Indiana and Wisconsin.

On Lake Koronis, starry stonewort occupies about 250 acres, most of it concentrated in the bay off the DNR’s Minnesota Highway 55 access.  The rest is in scattered spots throughout the lake.

The size of the infestation prompted the DNR to focus on management, not eradication.  The Koronis Lake Association is taking a more aggressive approach.  Its plans include mechanical and hand removal followed by herbicide.  University researchers plan to grow starry stonewort in the lab, and then experiment to see how it spreads and what herbicides are most effective.

At the launch

The DNR will provide a watercraft inspector at the Highway 55 access eight hours a day, seven days a week, confirmed Evan Freeman, the DNR’s Sauk Rapids-based watercraft inspection supervisor.

For the 15 weeks between Memorial Day and Labor Day, the DNR has allocated 840 hours and $8,400.  (On-site time could increase to as much as 10 hours per day if inspectors live closer to the site; travel time is figured in.)

A DNR decontamination unit will be at the access for 11 days through July 31. Freeman said it's a pilot project to see if the unit works on starry stonewort. If successful, more days could be added.

"Our goal is to intercept all incoming and outgoing watercraft," Freeman said.  "If we can get that person back into compliance, they're allowed to launch."

The Koronis Lake Association will augment DNR inspections, providing 3,205 hours over 30 weeks with DNR-trained inspectors, according to Kevin Farnum.  Farnum serves on the Koronis Lake Association board, the Stearns County Coalition of Lake Associations and the Stearns County AIS Committee.

The KLA and the North Fork of the Crow River Watershed District allocated $51,280 for Lake Koronis inspections.  (Some of that money came from a $35,000 Stearns County AIS Prevention Fund grant to the North Fork Crow River Watershed District; the rest came from lake associations and local governments.)  The KLA will put inspectors at other accesses on Lake Koronis, too.

“(Our) focus is on stopping the spread,” Farnum said.  “We don’t want it to come out of Koronis. We don’t want to be the mother lode of starry stonewort for the state.”

Water access

On Monday, Farnum joined a DNR crew that got onto Lake Koronis for the first time since ice-out.  They raked in clumps of the grasslike algae, monitoring its growth in the bay and at a couple of sites on the lake.

“The plant is still somewhat dormant,” said Chris Jurek, Sauk Rapids-based DNR aquatic invasive species specialist.  The plants were mostly blackish-brown, showing little green.

The DNR plans to treat the 4-acre site at the Highway 55 launch with Komeen Crystal herbicide to reduce the biomass.  Knocking it back could require three to five more applications.

“With treatments, you typically only see reduction of 60 to 80 percent in the biomass.  People need to understand the plant is going to be in the lake.  It’s not going to be eradicated,” Jurek said.  “There’s not a silver bullet for controlling starry stonewort. People’s expectations shouldn’t be high that a miracle’s going to happen.”

Jurek said this would be the first use of the crystal aquatic herbicide in Minnesota outside of trials.  The idea: Crystals will drop through the pillowy mass, exposing more of it to the chemical.  Treatments are most effective when the plants are actively growing.

“Based on our observations, I think we need to wait until the water temperatures warm and the plant—a macro algae—starts to grow,” Jurek said.

So the DNR plans to return in a couple of weeks.

“We don’t want the treatment to interfere with the (May 14) fishing opener,” Jurek said.

If the water doesn't warm up soon enough, treatment will be scheduled later in the summer.  The tentative plan, subject to change, calls for closing the access for 24 hours during treatment—for safety reasons and so the DNR can effectively monitor the treatment.

In the bay

Boats that launch at Highway 55 motor through the inlet bay and a narrow channel before they reach the southeast bay with the bulk of the 250-acre infestation, and continue on to the rest of the 2,968-acre lake.

In an attempt to curb starry stonewort’s spread, the KLA proposed cutting a 20-foot-wide, buoy-lined channel through the mass for boats to pass through. It's dependent on DNR permits.

“It’s kind of like we’re trying to create a path for the boats to travel in and out of the lake,” Farnum said.

A $9,600 Stearns County AIS Prevention Fund grant and in-kind lake association work covers the cost.  A mechanical puller would make five passes.  Farnum described it as a pontoon boat with a boom that lowers into the water.  Rollers gather the plant and heap it into the pontoon.  Scuba divers would then pull remaining plants by hand.  A chemical treatment would follow if money were left over.

Using a mechanical puller, scuba divers and herbicide requires DNR permits. Application has been made; Farnum is awaiting a ruling.

“The idea is that starry stonewort has no roots.  It’s all netted and meshed together.  What we’re worried about is once you start pulling on this pile, am I also pulling from piles 10 or 20 feet away?” Farnum said.  That would fill up the boat immediately.

But pulling is preferable to cutting, which can cause bits and bulbils (the white, star-shaped growths that give the plant its name) to break off and spread.  The strategy: Remove the biomass, allow some regrowth, and then hit it with a chemical treatment when it's more susceptible.

In the lake

The $828,600 pilot project proposed by the KLAis a two-parter, meant to reduce the biomass.

It would start with a two-year intensive, 4-acre treatment at one of the infested sites on the lake.  Cost: $49,700. If successful, for the next three years, the KLA would tackle the 250-acre infestation. Cost: $778,900.

The work, dependent on that same DNR permit, would take place bit by bit within a fine mesh net meant to catch dislodged segments or bulbils.  The mechanical puller would be followed by scuba divers' hand picking.  Herbicide would be applied to regrowth.  A third party would assess effectiveness.

“No one has done this as an integrated approach.  It is truly an integrated approach. It is taking the best of several different things and putting them together.  The pulling, the diving, the seining, and then you’re using the chemical treatment,” Farnum said.

An $11,000 grant made available through the Stearns County AIS Prevention Fund, plus $4,000 and in-kind labor from the KLA, would cover the two-year pilot.

The rest depends upon approval of a $410,000 grant request to the Initiative Foundation.  Because of the amount, it must be approved by the Lessard-Sams Outdoor Heritage Council, which helps fund the foundation.  The KLA would need to come up with matching funds.

“Our ultimate goal is to determine a way to help the rest of the lakes in the state, possibly the nation, to help handle starry stonewort,” Farnum said.

Beyond the lake

The DNR plans to survey boat accesses within 10 to 30 miles of Lake Koronis. Wisconsin DNR surveys showed that most lakes infested by starry stonewort contained the invasive near the access.

Last season, the DNR surveyed lakes within 10 miles of Koronis.

“I think we’re going to learn a lot this summer between what the DNR is doing and what the lake association is doing,” Jurek said.

The Minnesota Aquatic Invasive Species Research Center will collect starry stonewort samples from Lake Koronis, possibly as early as this month, to start lab experiments in the University of Minnesota facility.

Daniel Larken, a faculty member and MAISRC researcher, said staff will grow cultures in the lab, and then start experiments to address the spread risk.

“Boater movement is likely to be a major factor in this species,” Larken said.

What researchers want to know is how long starry stonewort stays viable, particularly if it’s picked up by a boat that travels to another lake.  So far, its movement has been traced to people.

The lab will also test different herbicides.

“The goal of all of this is to come up with scientific findings that can then be translated on the ground, that can lead to solutions to control,” Larken said.

Meanwhile, an ecological niche monitoring study, which took a broad look at where starry stonewort occurs globally, is out for peer review.  It considered factors such as the temperature, weather patterns and environmental conditions defining its fundamental habitat.

Once it’s been published in a journal, results will be shared with the DNR and lake associations.  Those results will help predict where the invasive is most likely to spread.

Next, Larken said a more finely tuned risk assessment would consider where in Minnesota starry stonewort is most likely to spread.

“The goal of all of this is to come up with scientific findings that can then be translated on the ground that can lead to solutions to control," Larkin said.