'Substantial' number of zebra mussel larvae found along U.S. shore of Lake of the Woods

Zebra mussel larvae have been found in large numbers inanother large Canadian body of water Lake of the Woods, the world's 30th-largest freshwater lake.

The Minnesota Department of Natural Resources announced Friday it confirmed the presence of the invasive species at three locations along the U.S. shore of Lake of the Woods, an international body of water with basins in Ontario, Minnesota and Manitoba.

Only the larvae, known as veligers, were found.

"While no adult or juvenile zebra mussels have been reported, the number of larvae is substantial," the department said in statement.

Zebra mussels are an invasive species that has colonized the Great Lakes, as well asthe Red River/Lake Winnipeg drainage system.

• Invasive zebra mussel larva found in lake that supplies Winnipeg drinking water

The bivalvescoat surfaces and can clog water pipes. They also have choked out native species in some places, and their shells litter beaches.

The spread of zebra mussels into Lake of the Woods could have huge ramifications for homeowners, cottagers, fishing and tourism in the area. In addition to potential environmental effects, theinvasive species also competes with native mussels for food, growing space and calcium.

"This is a wake-up call to Ontario, in particular, and to all those who love Lake of the Woods,"saidTodd Sellers, the director oftheLake of the Woods Water Sustainability Foundation.

"This is very unfortunate news," he said, though he added the Minnesota natural resources department's findings aren't entirely unexpected, since the basin is near other lakes infested with the mussels.

Thediscovery of zebra mussels will, though, "kick in a whole suite of enhanced regulations in Minnesota," he said.

All jurisdictions need to be more vigilant and ramp up their efforts to prevent the invasive species from spreading, Sellers said.

His group works closely with the states and provinces that share the Lake of the Woods bodies of water.

He said the different parties are trying to find a common response to the issue of zebra musselsthrough theInternational Multi-Agency Arrangement which involvesseveral organizations co-operating to research and manage the basinand the International Joint Commission, a bi-national organization that works to preventand resolvewater disputes between the neighbouring countries.

The next step is to watch for evidence of larvae developing into adults and attaching to docks and rocks, he said.

Zebra mussels can change water quality by sucking nutrients out of the main body of water and redistributing them to areas near shorelines, which reduces potential for oxygen and walleye egg survival.

But scientists are not certain the species can survive in the lake.

Natural defence

Compared to Lake Winnipeg, which has been infested with zebra mussels since 2013, Lake of the Woods could be less hospitable to the species.

All the lakes in the Canadian Shield typically have lowcalcium concentrations and zebra mussels need calcium to build their shells.

"We don't know if the lake's water chemistry is conducive to zebra mussel survival,"research scientist Gary Montzsaid in the Minnesota department of natural resources statement. "It is possible that calcium levels or other factors might prevent propagation."

Lake of the Woods flows through the Winnipeg River into Lake Winnipeg. The lake's Minnesota waters are shallower and less rocky than the Canadian portions of the lake. The Canadian Lake of the Woods areaincludes the city of Kenora and most of the lake's developed cottage areas.

A single zebra mussel veliger was found in 2018 in Shoal Lake, a bay of Lake of the Woods that serves as the source of Winnipeg's drinking water.

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Unlike sandy Lake Winnipeg, Shoal Lake and Lake of the Woods have a lot of exposed granite that could serve as zebra mussel habitat.

The City of Winnipeg has been preparing for the prospect of zebra mussels in Shoal Lake since the 1990s. Zebra mussels can grow on screens, fittings and pipes at the aqueduct intake, Winnipeg water services manager Tim Shanks said in 2018.

The city has taken steps to protect its water supply and has set aside $1.2 million to protect the Winnipeg aqueduct intake pipe and other aspects of its facility at Indian Bay on Shoal Lake, a city engineer told council in 2017.

The city could add chlorine to the aqueduct intake to prevent mussels from growing in the pipe and it also has plans to scrape out the mollusks if need be, he said.

An owner of a cabin on Lake of the Woods said the evidence of larvaeis concerning for him.

Jol Marcouxsaidthe sharp shells of zebra mussels would pose a hazard for families walking along the shorelines, and the mussels would also pose a danger to the lake's biodiversity.

"It's an unfortunate discovery," Marcoux said.

"Whatwill happen to the walleye that I'm such a fan of fishing for?"