When the zebra mussel invades, the development of a large population of effective filter feeders results in a radical shift in the benthic trophic structure (Lvova-Kachanova and Izvekova 1978, Stewart et al. 1998, Strayer et al. 1999). Native filter feeders are outcompeted by the zebra mussel and decrease in abundance, whereas animals feeding on sediments increase in abundance (Karatayev and Burlakova 1992, Karatayev et al. 1997).
In the European study done by Karatayev and Burlakova (1992), the effects of the zebra mussel on the trophic structure of the zoobenthos were examined in detail. They found that before the appearance of the zebra mussel in Lukomskoe Lake (Belarus), the littoral zone was dominated by detritus gatherers and detritus filterers, mainly snails and bivalves. Other trophic groups were not a significant part of the community. The trophic structure of the profundal zone was more complex and included predators-active grabbers (larval chironomids, Procladius choreus, and Chaoborus), deposit feeders, and detritus filterers-gatherers (mainly Chironomus plumosus). For the whole lake, the most important groups were the detritus gatherers and the detritus filterers. After the invasion of zebra mussels, detritus gatherers in the littoral zone generally increased because of the expansion in their food supply, i.e., organic matter deposited by zebra mussels. The number of predators-active grabbers and omnivorous gatherers/grabbers also increased. The proportion of native detritus filterers decreased. In the profundal zone, the dominant groups of benthic animals were detritus gatherers and deposit feeders. The biomass of detritus filterers/gatherers, detritus filterers, and predator-active grabbers decreased relative to preinvasion communities. Except for zebra mussels, animals using food from sediments dominated the community. If Dreissena is considered with the rest of the benthic community, the trophic structure of the benthic community is characterized by an extremely high dominance of one trophic group - detritus filterers, which accounts for 95-percent of the total biomass of benthic invertebrates. Similar patterns have been observed in four other water bodies across the former Soviet Union (Karatayev et al. 1994).