Zebra mussels invade Lake Erie muds

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.Figure 1Invading zebra mussels (Dreissena polymorpha) on fine-grain sand sediments at 14 m depth in western Lake Erie in 1994.Adult mussels (10-30 mm in length) are seen extending 2-3 m across and up to 10 cm above the sediment surface. The presence of erect macrophytes at this depth demonstrates the increased water clarity resulting from extremely high filtration rates by mussels.R. RATTNER[graphic not available: see fulltext]