As a result of their filter feeding, Dreissena populations shift suspended matter from the water column to the benthos (Lyakhnovich et al. 1988, Reeders et al. 1993, Karatayev et al. 1997, Strayer et al. 1999). As a result, zebra mussels have been associated with increases in water transparency (Hebert et al. 1991, Holland 1993, Leach 1993, Fahnenstiel et al. 1995b); decreases in turbidity (Skubinna et al. 1995); and decreases in chlorophyll, phytoplankton abundance, and production (Leach 1993, Nichols and Hopkins 1993, Fahnenstiel et al. 1995a, Fahnenstiel et al. 1995b; Strayer et al. 1999).
These pelagic impacts have also been documented in the former Soviet Union and other European freshwaters (Karatayev et al. 1997). After the invasion of Dreissena in Lukomskoe Lake (Belarus), water transparency increased from 1.8 to 4 m, and seston concentrations decreased threefold (Lyakhnovich et al. 1988, Karatayev and Burlakova 1995b). Dissolved organic mater in the water column also decreased. Subsequent to the invasion of Dreissena, the biomass of phytoplankton and zooplankton declined more than tenfold. Similar results were obtained in Narochanskie lakes in Belarus (Karatayev et al. 1997).
The suppression of zooplankton populations due to zebra mussel filtration is thought to affect the feeding of some fish. This reduction of zooplankton in the water column may affect the growth of fish that are planktivorous at some point in their development (MacIsaac 1996).