PUMPING RATES AND PROJECTED FILTERING IMPACTS OF JUVENILE ZEBRA MUSSELS (DREISSENA-POLYMORPHA) IN WESTERN LAKE ERIE

Small-bodied (2-11 mm), settled zebra mussels (Dreissena polymorpha Pallas) comprise up to 90% of individuals inhabiting reefs in western Lake Erie. We assessed pumping rates of these size classes of D. polymorpha by injecting an inert dye into inhalant filtering currents and monitoring exhalant flows using high-resolution videography. Pumping rates ranged between 0.20 and 4.45 mL.ind-1.h-1 and increased in relation to mussel shell length. Based on 1990 size-frequency distributions for reefs in western Lake Erie and our pumping rate - shell length regression, small settled D. polymorpha were theoretically capable of pumping between 39 and 96% of the water column daily. Small-bodied mussels inhabiting Sunken Chicken Reef were collectively capable of processing between 110 and 400% of the values previously reported for Daphnia. Recent changes in water quality in western Lake Erie could be primarily related to zebra mussel filtering activities, including those of small-bodied individuals.