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Foul water for waterfowl

City will drag park pond to reduce amount of duckweed

By: Carol Sanders

Posted: 07/29/2010 1:00 AM | Comments: 0 (including replies)

Ducks and geese swim through the duckweed that covers the pond at St. Vital Park.

Ducks with scummy green bills waded across what looked like a pond of pea soup in St. Vital Park Wednesday as onlookers marvelled.

"It doesn't bother me, but it might bother the ducks," said Jodie Jephcote, watching the birds trudge through the scum covering the surface of the city park's duck pond.

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(MIKE.DEAL@FREEPRESS.MB.CA )

"It looks like Astroturf," said Marie-Lynn Hamilton.

But it isn't. It's duckweed.

"It's a small, tiny plant that floats around and will prevent algal blooms," said Pascal Badiou, a research scientist at Ducks Unlimited Canada.

Duckweed is often spread by birds and grows quickly in clusters when there's adequate food, sunlight and shelter from wind.

The city is going to drag the pond to remove the duckweed over the next few days, it said in a statement.

Badiou isn't sure why.

"I find it a little strange that the city thinks it necessary to drag the pond to remove duckweed," he said.

"The duckweed is absorbing a lot of nutrients and prevents light from penetrating the water column. By doing this, the duckweed prevents algal blooms from occurring, which are just as, if not more, unsightly than duckweed and can also cause odour issues."

The duckweed coating doesn't stink, and hasn't ruined the view -- it has just made the pond look a little strange, Hamilton said.

"It looks like you can walk on it," she said.

Maria Reimer, who moved to Winnipeg two years ago from Belize, where mountain-fed streams flow with crystal clear water, said she looks for the best in her new environment. "It's a beautiful park."

Others don't think so.

"This really isn't pretty, is it?" said Anne Brown, sitting on a park bench by the pond with two other women. "I think it is," said Allison Staff, who was next to her.

A family of ducks dined on the duckweed at the edge of the pond. A flock of geese was feeding, too, close to sidewalks smeared with goose poop.

The third woman on the bench said the duck and goose populations have gotten out of hand.

"It's too much," Lolita Ledda said.

The rising goose population around ponds all over the city has increased the level of nutrients in the water, the city said. That helps accelerate the growth of duckweed, which acts as a filter to remove the nutrients.

Ledda said a practical solution to the water fouled by waterfowl would be to let people catch ducks and geese.

"Let people cook them," Ledda said. Many people would be happy to dine on duck and goose, and would have no problem harvesting them, she said.

People may be part of a stew of probable causes for the scum, said scientist Badiou.

"It's probably a combination of a lot of ducks on the pond and the nutrient addition through their feces. It has been quite hot and people are often feeding them."

The city said it is working on the problem this year so it's not as bad next summer. New aerators were recently installed that should reduce the duckweed, it said.

carol.sanders@freepress.mb.ca

Republished from the Winnipeg Free Press print edition July 29, 2010 A3

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