Invasive algae forms in dense mats in lakes

The Otter Tail County Aquatic Invasive Species Task Force and the Otter Tail County Coalition of Lake Associations sponsored a bus tour to Lake Koronis to view the Starry Stonewort infestation. 

Representatives from Otter Tail County including watercraft inspectors, county commissioners, and Aquatic Invasive Species (AIS) Specialists listened as a Lake Koronis guide discussed the ecological and economic impacts of starry stonewort on the area. 

“We don’t need this stuff in our (Otter Tail County) lakes,” said Bill Rollie, Otter Tail County Watercraft Inspector.

Starry Stonewort is an invasive algae that forms dense mats on the lake bed, sometimes reaching the surface, choking out native plants, disrupting fish habitat, and interfering with navigation and recreation.

AIS Detectors James Wooton and Kevin Farnum shared the impacts of Starry Stonewort in economic terms.

“We don’t want you dealing with what we are dealing with here,” Farnum said. “Management is costly and it’s constant.” 

Treatment could cost upward of $100,000 per year for managing the algae on one lake. The group visited three sites, the Public Water Access where starry stonewort was first discovered in 2015, a private residence, and a marina. Plant racks were thrown to collect samples where tour attendees could examine the algae up close. 

“See this-it pops in your hands when you squeeze it,” Spencer McGrew, Otter Tail County AIS Specialist said. “This is a key trait in getting a proper ID.”

Commissioner Lee Rogness attended the tour and shared his takeaways at the recent board meeting.

“I came away from the tour with an appreciation for our AIS crew. I think we have a good handle on this and good leadership in the field. This is a reminder for us to be vigilant on AIS in our county,” he said. 

The tour concluded with McGrew providing updated information from the latest AIS research at the University of Minnesota’s Aquatic Invasive Species Research Center. 

“Great work is happening at the U of MN and that is where the long-term management solutions will come from for this and other AIS. We’ve seen success with algicide treatments of starry stonewort and with copper-based treatments of zebra mussel larva. Our knowledge about their biology improves every day. I wouldn’t be doing this work if I didn’t think there was light at the end of the tunnel,” said McGrew.