We conducted a field study including a series of cruises over an isolated offshore zebra mussel reef (7–11 m deep) in Western Lake Erie to examine the effect of zebra mussels ( Dreissena spp.) on the water column. The horizontal currents over the reef were found to be primarily due to the hydraulic flow and surface gravitational seiches. The turbulence generated by these currents was found to be too weak to fully mix the water...