EFFECTS OF ZEBRA MUSSELS (DREISSENA-POLYMORPHA) ON SESTON LEVELS AND SEDIMENT DEPOSITION IN WESTERN LAKE ERIE

The establishment of high densities of the zebra mussel (Dreissena pol ymorpha) in western Lake Erie has resulted in a substantial increase i n the flux of particulate matter from the water column to the benthos. Effects of D. polymorpha on seston levels were determined in field-st ation experiments with flow-through Lake Erie water, while sedimentati on rates were determined in the same experimental design and in field experiments with mussels on sedimentation traps. At mussel densities r eflective of natural conditions, biodeposition exceeded normal sedimen tation by about 50%. Extremely high biodeposition rates (averaging 28 mg . cm(-2). day(-1) at a mussel density of 1180 individuals/m(2)) wer e measured at high-turbidity sites near the mouth of the Maumee River. Suspended matter concentrations were substantially reduced in the pre sence of the mussels. Calculations combining biodeposition estimates w ith measured suspended matter levels predict that zebra mussels in wes tern Lake Erie may remove between 7 and 30% of the total suspended mat ter per day. Biodeposition by zebra mussels may also result in an incr ease in sediment organic content.