Minn. DNR continues fight against invasive species

Eurasian water milfoil, zebra mussels
Eurasian water milfoil and zebra mussels are two invasive species that threaten Minnesota and other U.S. waterways.
Images courtesy of Army Corps of Engineers and Wikimedia under GNU license

The Minnesota DNR is stepping up enforcement efforts to slow the spread of invasive species in lakes.

But state officials say protecting Minnesota lakes from invasive species like Eurasian water milfoil or zebra mussels will ultimately depend on citizen cooperation.

The wind is keeping most boaters off of Lake Le Homme Dieu near Alexandria, there are only a couple of empty trailers in the parking lot.

"They can pick up a lot of debris when they're launching," said conservation officer Mike Shelden. You can see what I mean when you just eyeball these things."

The trailer has carpeted supports, or bunks, for the boat to rest on. Shelden said it's a great place for invasive species to attach and often one of the places boaters forget to check.

Brandon Randt was test driving his recently-repaired pontoon boat on the lake. Randt said, even when he's only on the lake for a few minutes, he follows the same routine.

"I always check the trailer to make sure there's no weeds or vegetation hanging on it," he said. "I also pull the plug at the landing and make sure everything is drained out. Then make sure the boat doesn't have any weeds hanging on it."

Signs posted at public lake access points are part of the DNR effort to educate boaters about invasive species. The DNR says the primary focus is education, but people who violate the law can face fines of up to $500.
MPR Photo/Dan Gunderson

That's exactly what conservation officer Mike Shelden hopes will become a habit for everyone boating on Minnesota Lakes.

"If everybody takes responsibility for themselves and pulls their boat out and takes the precautions that we're telling them, we can prevent the spread of this," Shelden said.

Zebra mussels are the invasive species getting a lot of attention right now. They were recently found in Lake Le Homme Dieu. As a result six other connected lakes are now considered infested as well. The mussels were also recently found in Lake Mille Lacs, one of the most popular fishing spots in the state.

There's currently no effective way to kill zebra mussels in a lake.

Daniel Molloy, director of Cambridge Field Research Laboratory for the New York State Museum, said he's found a way to kill zebra mussels with natural bacteria, but his method hasn't been tested in open water such as a lake.

"It's a bacteria that is one of the most common in the environment," Molloy said. "Its job is living in soil and protecting plant roots from mildew. Just by serendipity we isolated a strain that when fed to zebra mussels, kills them."

Boat trailer
DNR inspectors say preventing the spread of invasive species requires more than a cursory check of boat and trailer. These carpeted boat supports or bunks can easily hide tiny zebra mussels or fragments of an invasive plant.
MPR Photo/Dan Gunderson

Molloy said the bacteria have been successfully tested on zebra mussels clogging the water intakes at power plants. He said EPA approval is expected in about a year and the bacterial treatment will then be tested on lakes.

Zebra mussels filter algae and zooplankton from the water, which makes the water much clearer. Sunlight penetrates deeper into the clear water causing plant growth to explode, choking the lake with vegetation over time and harming fish habitat.

There are also other unwanted species making a slow march across the state. The spiny water flea also consumes the algae and zooplankton that are a critical part of the food chain in a lake.

Eurasian water milfoil, curly leaf pondweed and flowering rush are all plants that can choke out native species and make boating and swimming difficult.

Minnesota spends nearly $4 million a year on its aquatic invasive species program.

Luke Skinner runs that program at the DNR. Skinner thinks the program is working, and he offers the zebra mussel as an example. He said Michigan, Wisconsin and Minnesota had about the same number of lakes infested with zebra mussels 20 years ago.

Invasive species alert
Zebra mussels were recently found in Lake Le Homme Dieu near Alexandria, Minn. There are enhanced penalties for boaters who don't remove vegetation and drain water after using a lake infested with invasive plants or animals.
MPR Photo/Dan Gunderson

"Today we have ten confirmed lakes with zebra mussels," Skinner said. "Michigan has 250 and Wisconsin has 130 or so. We think we've really been able to slow the spread in the state."

Still there are those who think the state could do more. Minnesota Lakes Association President Paul Isensee said the state should be spending more money to combat invasive species. He said lake association members donate thousands of dollars a year to pay for herbicide applications to control invasive plants.

"I mean, if it is public water why isn't the public taxpayer giving us the money to administer the application of this stuff to keep the lakes nice and clean," Isensee said.

Isensee said the state could also improve efficiency by giving lake associations more control over local invasive species control programs.

State Invasive Species Program Manager Luke Skinner said there's always more that can be done, but with a limited budget, the state has to be pragmatic. He said a focus on education seems more effective than heavy enforcement.

"It's always a challenge to know if you're doing enough," Skinner said. "In some western states they're now requiring inspections going on to some lakes like Lake Tahoe. It's a big lake, but it's only one lake in the area and the boating traffic is a fraction of what we have in Minnesota.

"Minnesota, land of 10,000 lakes, and it's just so many lakes and accesses it's very difficult. How do you inspect everybody?"

On Lake Le Homme Dieu, conservation officer Mike Shelden pondered the same question. He is responsible for enforcing regulations on more than 50 lakes, and that's just part of his job.

He said it's not practical to think invasive species can be stopped.

"It just takes one bad apple that completely disregards what we're trying to get them to do and that's how you transfer it from one lake to another," he said.

But he said if every boater does their part, the inevitable march of invasive species can be slowed.

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