Dave's Blog

When the Army Corps of Engineers explored the potential benefits of expanding the St. Lawrence Seaway a few years back, the agency pooh-poohed worries that more overseas ships carrying more unwanted hitchhiking organisms would, logically, lead to more ecological trouble for the Great Lakes.

The Corps did acknowledge that opening the once-isolated lakes to overseas ships already had resulted in the arrival of some troublesome species. But it told the public not to fret the environmental consequences of a Seaway expansion.

"The most dramatic impacts to the ecosystem have likely already occurred," the Corps concluded in a more than 400-page report, released in June 2002.

What, after all, could cause more havoc than the zebra mussel?

Meet the quagga mussel.

Less than four years after that reassuring report, quagga mussels have gone from a rare find on the bottom of Lake Michigan to its dominant invasive mussel. Along the way, they have done what many invasion biologists thought would be impossible: They have nearly annihilated Lake Michigan's zebra mussel population.