Zebra mussels (Dreissena polymorpha) originated in western Russia but have now become widespread in Europe and North America. They are widely known for their conspicuous invasion of rocks and other hard substrates in North American and European watersheds¹. We have found beds of zebra mussels (Fig. 1) directly colonizing sand and mud sediments each year across hundreds of square kilometres of North America's Lake Erie. This transformation of sedimentary habitats into mussel beds represents an unforeseen change in the invasive capacity of this species.

1. Byrd Polar Research Center, Ohio State University, 108 Scott Hall, 1090 Carmack Road, Columbus, Ohio 43210, USA
   e-mail: Email: paul+@osu.edu
2. Ohio Sea Grant College Program, Ohio State University, 1541 Research Center, 1314 Kinnear Road, Columbus, Ohio 43212, USA
3. Biological Resources Division, United States Geological Survey, 1451 Green Road, Ann Arbor, Michigan 48105, USA
4. Division of Geological Survey, Ohio Department of Natural Resources, 1634 Sycamore Line, Sandusky, Ohio 44870, USA