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Lake Erie’s “dead zone”

Image courtesy: Earth Sciences and Image Analysis, NASA - Johnson Space Centre. Mission: STS096; Roll: 701; Frame: 18

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Mapping mussel DNA
By Michael Bardwaj

In a classic Hollywood summer blockbuster, an alien invasion that has threatened to take over the world is stopped when the cigar-chomping hero and his side-kick inject the mother ship with a virus, thus exposing the alien invaders to destruction. In the end, the champions were able to conquer the aliens by first deciphering who these beings were and then finding the weakness within.

Although much less dramatic, a similar approach is being taken by one invasive species researcher who has suggested that controlling and reducing the alien invasion of zebra mussels first requires an understanding of how they function in their native European range.

Using a series of genetic tests, Carol Stepien, director of the Great Lakes environmental genetics laboratory at Cleveland State University, has traced Lake Erie’s zebra mussel populations back to the Netherlands and Poland, where they currently exist as part of the natural aquatic equilibrium.

These original mussels acted as a source population for the Lake Erie invasion, providing the lake with several introductions, more than likely caused by the dumping of ballast water from transatlantic commercial tankers.

Making accurate comparisons between Lake Erie’s mussels to their most closely related northern European cousins helps researchers like Stepien get a better understanding of the nature of the invasive species and a sense of how to conquer the conqueror.

“Invasions have changed over the course of time and we keep getting new ones in,” says Stepien. “We need to know whether we are comparing apples and apples, oranges and oranges, not apples and oranges.”

By pinning down the European origin of North American zebra mussels, Stepien says certain environmental comparisons can be made that might provide clues into how to control if not eliminate these invaders all together.

For example, ecological factors such as water temperature, water chemistry and the matrix of aquatic species may limit the expansion of zebra mussels in the Netherlands and Poland. If these limits were replicated on a smaller, tightly controlled scale in Lake Erie, then North American’s mussel invasion could be halted, if not reversed completely.

“We need to do everything we can to keep them out,” says Stepien. “It is much cheaper to prevent them than to fight them.”

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