After missing early signs, DNR working to hit new lake invader hard
The Minnesota Department of Natural Resources is aggressively trying to stop the spread of a new aquatic invasive species, but the plan may already have been slowed by missed opportunities to identify the fast growing algae.
Starry stonewort has been found in three northern lakes this month, a year after it was first discovered in a lake near Alexandria, Minn.
Relatively little research has been done on the grasslike algae, but it could cause big problems in Minnesota lakes.
Stonewort grows rapidly and is very difficult to eradicate. In fact, DNR officials say it has never been eradicated from a lake in the U.S.
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Starry stonewort arrived in the U.S. in 1978, likely in ship ballast water. It's now found in eight states around the Great Lakes.
But the stakes might be especially high in a region that depends on boating, fishing and other water recreation.
Starry stonewort overtakes native vegetation and gets so thick it can block boat traffic and cover fish spawning habitat in shallow water.
It looks a lot like a native algae called chara, so much so that even the experts missed the invasive plants arrival in Minnesota.
"In hindsight we saw it last year," said Beltrami County aquatic invasive species lake technician Bruce Anspach, referring to the Big Turtle lake infestation. "But it wasn't nearly as thick as it is this year. So, we kind of should have got it last year but we didn't know what it looks like."
Once he knew what to look for, Anspach quickly found two more starry stonewort infestations. "From what we've seen so far with three, I'm thinking it might be in more waterbodies. I'm just hoping that it's like this one it's gonna be in a confined location," Anspach said.
The Minnesota Aquatic Invasive Species Research Center at the University of Minnesota has started investigating to understand which lakes are most at risk of a starry stonewort infestation, and the best control methods.
This week, the DNR closed the public access at Big Turtle Lake, just north of Bemidji, and it started cleaning the lake bottom to remove the patch of starry stonewort discovered earlier this month.
One recent day, a small pontoon boat with what looks like a big snowblower attached to the front slowly chewed up plants and one to two feet of muck in the bottom of the lake. It's all pumped ashore into a huge filter bag.
"We capture the muck and the weeds and all the nastiness in the bag," said Tim Smith of Winsted-based Aquatic Restoration Services. "The clean water comes out of the bag and goes right back into the lake."
After the starry stonewort patch — roughly half the size of a football field in size — is sucked off the lake bottom, an herbicide will be applied to kill any remaining plants.
"There's a lot of wild rice here, which kind of makes me a little depressed that we're going to suck it all up," said Anspach as he watched the machine work.
Anspach helped identify this infestation and two others found recently in Upper Red Lake and Cass Lake. He says the risk of starry stonewort spreading justifies clearing all the vegetation near this access.
"If we succeed at getting rid of the starry stonewort in here it's a very small price to pay," he said.
Success is probably a long shot.
Starry stonewort first showed up in Minnesota last year in Lake Koronis near Alexandria. DNR district manager Barry Stratton says that infestation also escaped detection.
"We looked through the notes and someone had called in a few years earlier noticing a dense growth of plants in a couple different locations in the lake. Staff from DNR responded and misidentified it as native chara which it does look roughly similar to," said Stratton.
DNR regional watercraft inspection supervisor Mike Bolinski says anyone who suspects an infestation should call the DNR.
The best way to identify starry stonewort is to look at the roots.
"It almost looks like fishing line when you pull up your weeds and it's got the little stars on him that's the easiest thing to look for with this guy," explained Bolinski. "It looks like a monofilament and then they've got little white knots on them that look just like stars."
By last year the Lake Koronis infestation reached 250 acres, roughly 200 football fields. The lake covers about 3,000 acres.
Kevin Farnum, a Koronis Lake Association board member, says it's a mess.
"I talked with a lady yesterday morning and she said, 'We can't even get our pontoon boat out because we get our motor so fouled up in starry stonewort that it's just impossible to get out,'" Farnum recalled.
Farnum says herbicide treatments failed to control the invasive algae. In a pilot project, the lake association is using a machine to pull all the starry stonewort from the lake in a small area and then treat any remnants with herbicide.
If successful, the lake association wants to attack the entire infestation next summer. That project would cost an estimated $800,000 with no guarantee of long-term success. But Farnum sees no other option.
"Certainly people in in the Paynesville area and around Lake Koronis and I don't think anywhere in the state will say we want to give up one single lake. We want to keep trying," said Farnum.
The DNR seems to agree. Officials are meeting this week to decide how to attack the starry stonewort infestations in Upper Red Lake and Cass lake.
One official promised "an incredibly aggressive approach".
