Lack of Snow Could Spur Growth of Minnesota Lake Invader

Curly-leaf pondweed.Courtesy of Michael Verhoeven, University of Minnesota

This year’s lack of snow cover on many Minnesota lakes could boost the growth of a nuisance aquatic plant, a University of Minnesota researcher predicts.

Curly-leaf pondweed is an invasive species that’s been found in Minnesota for more than a century. It’s known to be present in more than 750 water bodies in the state.

It grows in the early spring and can create dense mats on the surface that interfere with recreation.

“It can be hard to use any motorized Jet Ski, boat with a propeller, etcetera, because there’s so much vegetation that it essentially clogs up your propulsion system,” said Michael Verhoeven, a research scientist at the university’s fisheries system ecology lab.

Curly-leaf pondweed. Courtesy of the University of Minnesota Minnesota Aquatic Invasive Species Research Center

That problem could be worse this summer. Verhoeven has studied curly-leaf pondweed and found its growth patterns are closely tied to the amount of snow on the ice that covers lakes.

Snow cover prevents light from reaching plants at the bottom of the lake where curly-leaf pondweed grows during the winter, Verhoeven said. But this year, many Minnesota lakes have had less ice than normal, and little to no snow cover.

“The general consensus from the data that we used in our work is that winters like this will be really good for curly leaf pondweed,” he said. “It’s going to be a happy plant when the ice comes out.”

It’s the snow cover, not the ice, that matters to the invasive plant, Verhoeven said.

“Essentially, if the light is getting through the ice, the curly-leaf doesn’t really care whether or not there’s ice,” he said. “It’s a plant that’s well adapted to grow in cold conditions under the ice.”

Curly-leaf typically dies off by early summer, releasing nutrients into the water that can spur algae growth and contribute to poorer water quality. That cycle is exacerbated in smaller lakes or those where curly-leaf grows abundantly, Verhoeven said. It also can outcompete native plants, reducing a lake’s biodiversity.

Some lakes control problematic curly-leaf pondweed with herbicide or mechanical harvesting.

Curly-leaf pondweed is spread mainly by humans moving boats from one lake to another. The Minnesota Department of Natural Resources advises boaters to clean their watercraft of all aquatic plants and remove drain plugs before transporting their boat.

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