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Once aquarium plant, now threat to lakes

Weed found in water body shared with N. Dakota

By: Bill Redekop

Posted: 11/2/2009 8:11 AM | Comments: 0 (including replies)

An invasive species introduced to North America in the 1980s as an aquarium plant has surfaced in a Manitoba lake and threatens to choke off that lake and others.

The curly-leaf pondweed has been discovered on the North Dakota side of Lake Metigoshe, which straddles the Manitoba border.

Its innocent-sounding name belies its aggressive nature, said Cheryl Heming, co-ordinator with the Invasive Species Council.
"This thing has the capacity to take over the entire lake" by choking out other plants and reducing biodiversity, she said.

The weed can clog swimming areas, and large mats can prevent boating or clog outboard motor propellers. Curly-leaf pondweed also contributes to high levels of phosphorus, leading to algal blooms that can kill fish.

Lake Metigoshe, just west of Turtle Mountain Provincial Park, is a recreational lake with several hundred cottages. Heming, originally from Deloraine just north of the lake, spent many of her childhood years at Lake Metigoshe.

Although the weed was found on the U.S. side of the lake, it is only a matter of time before it reaches Manitoba’s side. "This weed will fill the lake with vegetation," Heming said.

"We believe, based on its spread through the United States, it would spread into our shallower prairie lakes and into the Interlake region," including lakes Winnipeg and Manitoba, said Heming, a former City of Winnipeg naturalist. "In my opinion, our larger lakes could be susceptible."

Lake Metigoshe has no river or creeks flowing north, so the only way the weed would spread is by boats. The challenge is to get boaters in Lake Metigoshe to remove any fragments stuck to their vessels before they launch in another lake.

Once curly-leaf pondweed has taken root, control is very difficult. Cottage owners would have to regularly cut and rake the vegetation.

The plant grows underwater. It can grow in low light, low temperatures, and prefers water with a lot of nutrients.
What to look for:

❚ The weed’s flowers are tiny, whitish and have four petal-like lobes found on spikes that stick out above the water.

❚ Its leaves are reddish-green and curly with jagged edges. Older leaves can look like lasagna noodles.

❚ Its stems are up to one metre long and flattened.

If you see something you think is curly-leaf pondweed, report it to either info@invasivespeciesmanitoba.com or phone 232-6021.

bill.redekop@freepress.mb.ca

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