Thanks to early detection on the part of the Washington Conservation District, Bone Lake in Scandia will become one of only lakes in the state to be treated in an attempt to eradicate a zebra mussel infestation.
According to Minnesota Department of Natural Resources invasive species specialist Keegan Lund, the Washington County agency has an early detection program for invasive species, which is why surveyors discovered six juvenile zebra mussels in the lake on May 28. On June 11, the DNR held an internal meeting to discuss an application from the Comfort Lake-Forest Lake Watershed District to treat the portion of the lake where the mussels were found (near the public access) with copper sulfate.
“It’s just a matter of ‘What are the chances of success and what are the potential risks to the lake?’” Lund said.
The DNR was ultimately supportive of the application, though Lund said on June 12 there were a few logistics to figure out. One of the logistics was obtaining the proper permission from the U.S. Fish and Wildlife Service to close the access, but late last week, the Comfort Lake-Forest Lake Watershed District announced that the access was cleared for temporary closure. It will be closed from June 17 through June 26 while a half-acre of the lake is treated, with appropriate equipment in place to keep the chemical from spreading beyond the designated area.
Zebra mussels are an invasive species (with no local natural predator) that cling to hard underwater surfaces and filter lake water, potentially contributing to increased lake weed growth. Most of the time, when zebra mussels are found in a body of water, they are adults and have already reproduced. At this point, getting rid of the mussels is considered impossible or at least infeasible without damaging the rest of the body of water’s ecosystem.
However, since the mussels found were all juveniles, it’s possible that the species’ incursion into the lake is recent enough that no adult mussels are in the lake. Thus, it’s possible that a limited treatment of the area where the mussels were found would eradicate the species from the lake before it spreads.
“Your chances go up if you find them early and you’re looking for them,” Lund said, praising the conservation district’s program. He noted that finding mussels in a lake before they mature is rare – so rare, in fact, that only seven lakes in the state have been treated to kill off mussels before they spread.
As the treatment initiative moves forward, Lund said the work will be a collaboration between the DNR, the watershed district, the conservation district, and other state and local partners. The groups have already been working together, as they spearheaded multiple searches for mussels around the lake in the days after the initial discovery, not turning up any additional finds.
By the time treatment begins, there will have been a few weeks between the initial discovery of the mussels and the treatment. Lund said that’s not enough time for any remaining mussels in the lake to grow and propagate, but the creatures could have “hitchhiked” on other surfaces or floated further into the lake in that time. With that in mind, the area to be treated has been expanded a distance beyond the initial area of the mussels’ discovery in an attempt to compensate for potential mussel migration.
Though Lund said the DNR has seen success with lake treatments for mussels in the past, it’s somewhat difficult to judge the effectiveness of the work when new mussels could be introduced by a boater who didn’t take the precaution of cleaning and draining their boats and throwing away their old bait before entering the lake.
“Bone Lake is very near to Forest Lake, which is plumb full of zebra mussels,” he pointed out.