They are small clam-like creatures that seem to spread in the blink of an eye and squeeze the life out of the rivers and lakes they inhabit.
This summer, those who grapple with zebra mussels will be watching Manitoba, where officials are trying to stop an invasion with a unique experiment.
Once the winter ice recedes on Lake Winnipeg, a silk curtain will be lowered to the lake floor to seal off four infested harbours. Liquid potash will then be pumped into the water until it reaches a lethal concentration for the mussels and clogs their gills.
The technique has been tried in a closed quarry, but this is believed to be the first time liquid potash has been used in open water.
Scientists who study the mussels say Manitoba presents a “golden opportunity” to find a way to prevent their proliferation in waterways around the world.
The postash plan will cost $500,000, but many say it could save millions down the road if it works.
“There is only one guarantee and that is, if nothing is done, then the situation will certainly get worse,” said Manitoba Conservation Minister Gord Mackintosh. “The impact of zebra mussels in areas where they have infested waterways is quite profound.”
The invasive mussels, which are already in the Great Lakes and have spread throughout parts of the United States, were found for the first time in the province last October.
The tiny mussels reproduce rapidly. One female can produce up to one million eggs a year. The waterborne, microscopic larvae can be carried unwittingly from lake to lake in buckets and in the live wells of boats.
Once hatched, the mussels can attach to virtually any hard surface, including other native mussels and crayfish. They clog up pipes and hydro dams. They threaten fish by interfering with the food chain and have been linked to increases in toxic blue-green algae.
“Where zebra mussels have established, they have a significant ecological and economic impact,” said Laureen Janusz, fisheries biologist with Manitoba Conservation. “There are annual maintenance costs to having zebra mussels that just never go away.”
The Manitoba government was presented with a series of options once the mussels were discovered. Although liquid potash had never been tried in open water, it was unanimously agreed upon, Janusz said. Liquid potash is lethal for zebra mussels, but doesn’t appear to hurt any other aquatic life aside from native mussels, she said.
“Everyone is still trying to find a control that has no effect on anything else.”
Those who depend on the lake for their livelihoods are concerned about the experiment and the impact it could have on the short fishing season.
Jocelyn Burzuik with the Gimli Harbour Authority said Lake Winnipeg is no ordinary lake. It is so huge, it has its own wind tides making it unpredictable and dangerous.
“It’s going to be very tricky,” Burzuik said.
Complicating matters further, Burzuik said, both commercial fishermen and those injecting the water with liquid potash need access to the harbour when the water temperature rises to between 10 and 12 C. The two groups are working together to figure out how the experiment can go ahead without devastating the fishery, she said.
“It’s not that we don’t want them to treat zebra mussels. We know exactly what they can do to a fishery,” she said. “The cure cannot kill the community.”
Many are watching the outcome.
Hugh MacIsaac, director of the Canadian Aquatic Invasive Species Network, said scientist are very interested in finding effective ways to kill zebra mussels before they take hold.
“Given that this animal is in the early stages of its invasion in Manitoba, I think it’s important to try to eradicate it,” said MacIsaac, a professor at the University of Windsor.
“Sometimes it doesn’t work, but this is a golden opportunity to try to knock them out. If it succeeds then great.”