Feb 11, 2004 — For decades, aquatic invaders have been plaguing the Great Lakes. They've changed the way the ecosystems work and affected the balance of life in the lakes. Most of them didn't just wander in. They hitchhiked a ride into the Lakes in the ballast water of ships from across the Atlantic. The Great Lakes Radio Consortium's Carolyn Gramling reports, the combination of these invasive species is causing changes that concern scientists.