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Attempt to rid lake of menace
May 08, 2014
When zebra mussels were first found in North America 25 years ago, it was already too late, since no one at the time really knew the threat posed to the ecosystem by the tiny alien invader. While it is too late to remove the mussels from the ecosystems they penetrated since they were first found to foul Canadian and U.S. waters, Manitoba still may have a chance to rid itself of the environmental menace.
Last fall, zebra mussels were, for the first time, found in Lake Winnipeg at the harbours at Gimli, Willow Point, Boundary Creek Marina/Winnipeg Beach and Balsam Bay. The tiny filter-feeders were discovered clinging to the hull of a private boat and a dock at Winnipeg Beach, and on some fishing boats dry docked at Gimli.
To combat the invasive species, the province announced it will take decisive action by investing $500,000 on eradication efforts using liquid potash at four of the affected sites requiring intensive action. Leading scientists have recommended liquid potash treatment, which will be more effective when there is no ice cover.  During the temporary closure of the affected harbours, alternate harbour access will be made available during the estimated three- to four-week treatment period. The eradication program will begin when the water temperature approaches 10°C.
“Our first priority is to make sure fishers continue to fish and protect the health of our commercial fishery industry and of Lake Winnipeg,” said Manitoba Conservation Minister Gord Mackintosh.  “Failure to take immediate action would severely impact Manitoba’s local commercial- and sport-fishing tourism industries and threaten waters downstream.” 
If left unaddressed, the zebra mussel
invasion could affect the water supply of municipalities, First Nation communities and parks along the shores of the lake by clogging water intakes and increasing toxic algal blooms, the minister said.
“We all want to prevent what we have seen from other jurisdictions is the zebra mussel can devastate livelihoods, the fishing industry, communities and destroy fish and other aquatic populations,” said Mackintosh.  
“While we deal with this important issue, boaters, fishers and water enthusiasts will still be able to access the lake. It is open for business and recreation. You may have to travel down the road to launch your boat or to do some fishing but we want all Manitobans to know, we are trying to minimize any disruption while we conduct ‘operation mussel out’.”
It was just a couple of years ago that
zebra mussels, a tiny and deadly invasive species, were reported to be just across the international border in North Dakota.
Earlier, the mussels were found by a local resident at Pelican Lake, Minnesota, about 800 kilometres south of the border. Then zebra mussel larvae were reported to have progressed from Minnesota to North Dakota into the Red River at Wahpeton, where the river begins its northward journey to Lake Winnipeg. It was a mere 635-kilometre leisurely drift on river currents for the larvae to reach Emerson at the U.S.-Canada border.
How the mussels actually made their way into Lake Winnipeg is still a matter of speculation. Since adult zebra mussels can survive out of water for several days or weeks if the temperature is low and humidity is high, they could have been transported on a boat’s hull after it was used in mussel-infected waters, or the larvae could have drifted into Manitoba. Whatever the scenario, they’re here, they’re alive and they’re an extremely serious threat to the lake.
Zebra mussels, a species native to southern Russia, was first noticed in North America in Lake St. Claire, near Detroit, Michigan, in 1988. It is believed mussel larvae hitched a ride in the ballast water of a transoceanic ship. Having gone down the St. Lawrence River and through the manmade locks to the Great Lakes, a ship emptied its ballast, discharging the microscopic larvae and forever changed the freshwater ecosystem of the region. Since that fateful discharge, zebra mussels have rapidly spread across North America.
A female mussel can spawn one-million larvae (called veligers) each year. The prolific and plankton-devouring mussel  uses a special byssal gland to secrete highly-adhesive threads that attach it to rocks, debris, water pipes, fishing nets, boat hulls and
native mussel species. The attachment ability of the mussels results in bio-fouling — masses of mussels clogging pipes and choking off oxygen and the food supply of other organisms.
The residents of Munroe, Michigan, on December 14, 1989, were the first to witness the threat posed by the fingernail-size mussels when the creatures, combined with icy conditions, blocked off the city’s Lake Erie water intake. Schools, restaurants and factories were forced to close down and residents had to boil drinking water until the normal flow was restored a few days later.
Researchers from the Great Lakes Environmental Laboratory in Ann Arbor, Michigan, documented basic changes in the food-chain in the zebra-mussel-infested waters of Lake Huron’s Saginaw Bay.
According to the research by the U.S. National Oceanic and Atmospheric Administration-run laboratory (NOAA), Saginaw Bay’s energy base is no longer dominated by phytoplankton because the microscopic free-floating plant cells are the choice food for zebra mussels, which are able to selectively filter the cells out of the water. 
Zebra mussels may also release nutrients that encourage algae growth, especially toxic blue-green algae, according to the NOAA lab. In Lake Winnipeg,
hundreds of square kilometres of gooey blue-green algae blooms have been noted in the north and south basins in recent years. While the toxins secreted by the
algae stress native species of mussels, a study has found that zebra mussels are
unaffected; thus, they have a free rein to outcompete their competition.
The disruption of the food-chain by zebra mussels has the potential to destroy Lake Winnipeg’s commercial and recreational fishing industries. Commercial fishing, which is primarily based in Lake Winnipeg, provides an income and a way of life for nearly 3,500 Manitobans, representing  nearly $25 million a year in economy benefit. Another potential blow to the local economy is that the mussels can foul recreational beaches.
As an invasive species, zebra mussels have no native predators other than small- and large-mouth bass and crayfish, which cannot eat enough mussels to make a
significant dent in their numbers. 
As yet, no one can predict the exact outcome of the invasion on Manitoba’s lakes and rivers, but the experience in other jurisdictions has shown ecological changes that are bad for commercial and recreational fishing as well as tourism, which is a strong reason to hope that the eradication effort is successful in our freshwater-rich province.