Invasive Species Threaten Great Lakes

by David Schaper

NPR.org, July 7, 2008 · The blue-green waters of the Great Lakes seem cleaner and clearer than ever before — but while cleaner is good, clearer isn't necessarily so.

"It's a bad thing because the water looks clean because it's becoming sterile," says Cameron Davis, president of the Alliance for the Great Lakes, at a recent visit to a beach in Evanston, Ill.

He says zebra mussels and other invasive species that have worked their way into the Great Lakes filter out the food, making the water clear. At the same time, he says, "it's really stripping the food base out of the food web, such that we're really in danger of unraveling the food chain we have in this region."

Zebra mussels first invaded the Great Lakes through the ballast water of ships from Europe about 20 years ago. Colonies accumulate on the water intake and discharge pipes of power plants, municipal water plants, irrigation systems and even on boat hulls and motors, causing frequent problems. But they wreak havoc on ecosystems because they consume huge amounts of phytoplankton, like algae, effectively starving populations of native fish and other water wildlife.

And now scientists say that another invasive mussel has arrived that might even be doing worse damage to the lakes.

The thumbnail-sized quagga mussel, also carried in ballast water, is native to the Russian area of the Black Sea and first began appearing in the Great Lakes about a decade ago. Quagga populations tripled between 2005 and 2007 to a quadrillion, according to National Oceanic and Atmospheric Administration estimates. Quaggas now carpet the bottom of Lake Michigan and parts of the other Great Lakes. To some extent, they are even crowding out the zebra mussels.

"It's the same problem, times 10," Joel Brammeier of the Alliance for the Great Lakes, recently told the Chicago Sun-Times. As a result, commercial and sports fishermen and women are seeing fewer and thinner fish.

Another species that threatens to invade the Great Lakes is the Asian carp. The carp is working its way up the Illinois River system and edging closer to Lake Michigan. Federal officials hope to stop its migration with an electric fence-like barrier installed on a canal that connects the Chicago River to the Des Plaines River, and ultimately, links the Great Lakes to the Mississippi.

The most frightening invasive species is actually a virus known as viral hemorrhagic septicemia, or VHS. This Ebola-like virus doesn't threaten humans, but it could be a huge threat to the Great Lakes' $4 billion commercial and sport fishing industry. The infection causes fish to hemorrhage and die by the thousands — and unlike other viruses, it seems to attack all species.

"A new invasive species comes into the Great Lakes on average every six to eight months," says Davis. "Prevention is really the name of the game. Once these species get in, it's very hard to get them back out. That's why we need Congress to act to get invasive species controls in place now, and it's been very slow going."

Davis and others hope the attention given to the compact prohibiting large-scale water diversions from the Great Lakes also spurs Congress to pass legislation preventing ballast water from being dumped into the Great Lakes.

The lakes "look big, it looks like you can't hurt it," says Davis, "but in fact, these Great Lakes are incredibly delicate and fragile."