Zebra mussels plague region's waterways

Since the first zebra mussel larvae were sucked into the ballast tanks of a freighter on the Caspian Sea, then jumped ship into the Great Lakes in the 1980s, the small mollusk has wreaked havoc on the inland waters of the United States.

In Kosciusko County, the mussels have been discovered in 19 lakes, including Syracuse, Webster, Winona and Big Barbee. In LaGrange County, they are in nine lakes. In Allen County, they are in the St. Joseph River and the Cedarville Reservoir.

In 2010 the city of Fort Wayne was aware of the mussels. The city has intakes for the water system located in the reservoir and river. Mary Jane Slaton, spokeswoman for City Utilities, said so far the mussels have not caused a problem, although this fall they will be diving to check intake entrances.

The plankton-eating mollusks clear the water and reproduce quickly. One female can lay a million eggs in a single breeding season. The result has been the clogging of city water systems up and down the Great Lakes, and massive blooms of blue-green algae. High concentrations of certain species of blue-green algae can be toxic. Since their appearance in the Great Lakes, zebra mussels have spread all the way to California.

By wiping out plankton, mussels have affected the food chain enough that sport-fishing in the Great Lakes has dropped off as the smaller fish that rely on plankton for food have declined.

Author Jeff Alexander has documented this transformation of the Great Lakes in his book, “Pandora's Locks: The Opening of the Great Lakes-St. Lawrence Seaway,” which traces the ecological disaster invasive species have caused since the St. Lawrence Seaway opened in 1959.

The decline in game fish in the Great Lakes cannot be totally blamed on the zebra mussels or their bigger cousin, the quagga mussel. There have been other invasive species of fish, like the Eurasian ruffe and the tubenose and round goby. Sea lampreys first discovered in 1921 in Lake Erie began the destruction. By the 1950s the lampreys had decimated the lake trout fisheries in lakes Michigan, Huron and Superior. Northern Indiana lakes have yet to see any of these fish species, but the first zebra mussels appeared in Lake Wawasee in 1991.

Old Invaders

Fall 2008

The New Zealand mud snail will have to wait its turn.

The tiny mollusk, native only to New Zealand, was discovered in Lake Michigan in 2008, and now resides in all the Great Lakes but Lake Huron. Scientists fear the snail’s rapid reproduction and lack of native predators could mean trouble.

New invasive species in the Great Lakes are particularly worrisome because scientists like those at Michigan State University are still learning about exotic pests that have been around for decades.

The zebra mussel is celebrating its 20th year in the Great Lakes after hitching a ride from its native Russia in the ballast water of transoceanic ships. Zebra mussels have been implicated in the decline of Great Lakes species like native clams. A single zebra mussel can filter up to a quart of water in a day, removing microscopic plants and animals usually eaten by native mussels and larval fish. Large zebra mussel populations can filter enough plankton from the water to turn once murky lakes clear.

Zebra mussel impacts, however, aren’t always felt by declining populations of other organisms.

Microcystis, a toxin-producing photosynthetic bacterium, thrives in lakes with high phosphorus levels. If a lake doesn’t have a lot of phosphorous, it probably doesn’t have much microcystis unless, said Orlando Sarnelle, an MSU associate professor of fisheries and wildlife, the lake also has zebra mussels.

In 1998, CNN interviewed Sarnelle about a possible link between zebra mussels and rising levels of microcystis in low-nutrient lakes. The problem was, Sarnelle had just begun the research. He hadn’t done any experiments. He had no data. And to make matters worse, he caught guff from a colleague for representing MSU in the national media while wearing a University of California sweatshirt.

Now that he’s done the research, the old invasives that once grabbed national attention just aren’t that sexy anymore.

“That was the end of the story,” said Sarnelle recently, wearing a Spartan-green shirt with an MSU logo in his office in the school’s natural resources building.

“There’s never been another interest by the national media.”

Since the premature CNN interview, Sarnelle has led several rounds of experiments and lake surveys, funded primarily by the Michigan Sea Grant College Program and the Environmental Protection Agency. He has published a number of articles that confirm the link between zebra mussel invasion and rising levels of microcystis in low-phosphorus lakes.

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