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The zebra mussel: Twenty years later

This year marks the 20th anniversary of the discovery of the zebra mussel in Lake St. Clair. The mussel was discovered by Bernie Muncaster, then a graduate student at McMaster University. He was performing research when he came across a strange looking mussel attached to a clam.

Unsure of what this strange new mussel was, he contacted Gerry Mackie, a professor at the University of Windsor.

“He brought both specimens to my office and I tentatively called it a zebra mussel but asked him to leave it with me so I could verify my identification,” recalled Mackie.

After a week spent in the library, reviewing descriptions, taxonomic keys, and information about the mussel, Mackie was confident that Muncaster’s discovery was indeed the type of mussel that had been wreaking havoc in Europe.

About one week after the identification, Dr. Joe Leach, with the Ontario Ministry of Natural Resources, found mussels in Lake Erie as well.

With these two discoveries, experts knew that the landscape of the Great Lakes would be changed irrevocably.

“We predicted that the mussel would plug pipelines and intake structures of industries and utilities, alter the ecology of lakes, and affect recreational, sporting and fishing activities,” said Mackie, referring to a 1989 report he was contracted to write for the Ontario Ministry of the Environment.

“ Our predictions were pretty much bang on, although I didn’t think it would reach the Gulf of Mexico as quickly as it did.”

A Continental Problem

The impact of the zebra mussel is one that is being felt across the continent. The 100th Meridian Initiative is a cooperative effort among state, provincial and federal agencies to prevent the spread of the zebra mussel and its close cousin the quagga mussel from crossing the line that divides western North America from the east. The quagga mussel was discovered in the Great Lakes in 1989.

The Initiative took on the daunting task of educating the public and inspecting boats being hauled across the Rocky Mountains for invasive mussels. Initiative partners also regularly monitored popular recreational waters in the west, with a rapid response plan ready should a population of mussels be discovered.

Despite attempts to prevent the spread of invasive mussels, zebra and quagga mussels have been discovered as far west as Nevada and California.

In Nevada, live zebra mussels were first discovered in Lake Mead in 2007, though authorities suspect they were there as early as 2005.

“The big scare for Las Vegas is that about 80 percent of the town’s drinking water comes from Lake Mead,” said Kevin Cabble, president of the Nevada Wildlife Federation.

“Also, the Colorado River goes down into California, and it is likely that the mussels will continue to spread, affecting not only the Las Vegas water supply, but also the water supply of other cities and states.”

In January 2008, California officials confirmed that live zebra mussels had turned up in the San Justo Reservoir in San Benito County. The reservoir is connected to California’s central waterways that feed millions of acres of farmland and provide drinking water.

Similarly, Quagga mussels were first detected in the Colorado River system in January 2007 and were later found in San Diego and Riverside counties by California water agencies.

“Quagga and zebra mussels pose a serious threat to California’s vast fishing and recreational boating opportunities, they threaten the state’s extensive water delivery systems and agriculture, and pose a serious threat to California’s diverse native aquatic resources,” said Susan Ellis, California Statewide Invasive Species Coordinator.

Studying the Devastation

Prior to 1993, the Rideau River that runs through Ottawa was clean of zebra mussels and had a rich diversity and abundance of native freshwater clams. But, it would not take long for the zebra mussel to take hold and spread throughout the river.

For six years André Martel and his team at the Canadian Museum of Nature tracked how the zebra mussel virtually destroyed the native clam population, building huge colonies on the shells of the native clams, effectively starving them.

In only four years the native clam population had disappeared over vast areas of the river and the spread of the zebra mussel was comparable to, if not greater than, the highest spread of the mussel in the Great Lakes. In some downstream areas, densities of zebra mussels exceeded 150,000 individuals per square metre.

“We knew that the ecological impact of the zebra mussel was severe in the Great Lakes region. Here in the Rideau River, we found the first zebra mussels soon after their discovery in Lake St. Clair,” said Martel. “They were on a large steel ship that had made its way up the Rideau Canal to Ottawa after having spent some time sailing in the zebra mussel-ladden Lake Erie.”

Martel and his fellow researchers and volunteer divers were the first to employ SCUBA-diving techniques to quantitatively investigate and document the long-term impacts of the zebra mussel on a small river ecosystem.

“Ironically, the Rideau River and Rideau Canal would become one of Canada’s Heritage Rivers and a UNESCO World Heritage Site. It is unfortunate that the Rideau River-Rideau Canal system had to lose much of its rich native mussel populations before reaching this status simply because of our failure to properly control or prevent the transport of invasive mollusks like the zebra mussels in transoceanic cargo ships bound for Canada.”

Shipping Industry’s the Problem

The zebra mussel has become a poster-child for the havoc international shipping on the Great Lakes is wreaking on the natural habitat of the ecosystem. Since the St. Lawrence Seaway opened to ocean-vessels, 70 per cent of all new aquatic invaders can be traced back to these ships.

Invasive species can hitch a ride on almost any part of the ship, from hulls and anchors to sea chests. However, scientists have been pointing to ballast water as the main problem. Within the ballast tanks of ships crossing the Atlantic lurk the next wave of invasive species. While the U.S. and Canadian governments require ships carrying ballast to exchange this water in the open ocean, regulating ships without ballast on board has moved much slower. Despite being empty of water, invasive species can sit in the mud and grime at the bottom of ballast tanks.

“Our collective federal governments have responded at what can only be described as a glacial pace,” said Francine MacDonald with the Ontario Federation of Anglers and Hunters.

In 2006, the Canadian government required ships without ballast on board to flush their tanks in the open ocean, and in 2008 the St. Lawrence Seaway Corporation followed suit with similar regulations. Despite the Canadian regulations, enforcement has been uncommon.

“The Environment Commissioner in a recent report found that in 2006, only half of the ships that declared no ballast on board actually followed the best management practices. Obviously we need the regulation, but we need the enforcement as well,” said MacDonald.

Added to this, salt water flushing is not guaranteed to kill all invaders. Some species can survive the salt water shock and flushing of tanks doesn’t reach those species hiding on anchors or in sea chests.

“I’ve used the metaphor of Russian roulette to describe the chances we take with a new invader each year that the St. Lawrence Seaway opens,” said Jennifer Nalbone of Great Lake United. “With salt water flushing, we’re still playing with a loaded gun, just using fewer bullets.”

Cleaning up Ballast Water

Though critics argue it’s a couple of decades too late, the U.S. House of Representatives recently passed a bill that would require ocean-vessels to install cleaning technology to treat ballast water before it is discharged to the Great Lakes.

The challenge remains, however, of passing this legislation in the Senate and getting it signed by the President before the fall election.

“We’re running against the clock, “said Nalbone. “The presidential election is on the brink of consuming everyone’s attention. And, unfortunately, as important as the election is, every political division translates into deadlines in the bill being pushed back.”

Once passed in the United States, Canadian authorities have stated that they will work to harmonize with the U.S. standard, which by 2012, or at the absolute latest 2014, will be 100 times stronger than standards developed by the International Maritime Organization for future international regulation.

“The technologies are there. They’re available and they’re proven. The question is will somebody require ocean going vessels to put them on” said Andy Buchsbaum of the National Wildlife Federation.

© 2008 Great Lakes News.