Effect of Dreissena polymorpha Pallas on the ecosystem of an eutrophic

ABSTRACT Dreissena polymorpha has been invading fresh waterbodies of eastern and western Europe since the beginning of the 19th century and is still invading. A long history of monitoring and experimental studies conducted in the Former Soviet Union (FSU) has provided us with an understanding of the effects of zebra mussels on waterbodies they invade. However, this work has not been generally available. We review work conducted in the FSU and eastern Europe over the past 60 y on the community effects of this invading species. In freshwater areas, where Dreissena are the only bivalves that attach to hard substrates and have a planktonic larval stage, they can become enormously abundant and, within a short period of time, can obtain a biomass 10 times greater than that of all other native benthic invertebrates. When zebra mussels invade, benthic invertebrate communities change dramatically in terms of total biomass, species composition, and relative abundance of functional groups. Native filter feeders are outcompeted by D. polymorpha and decrease in abundance, while animals feeding on the sediments increase in abundance. Although D. polymorpha can cause a dramatic decline in the abundance of unionids, after initial peaks in zebra mussel abundance, D. polymorpha coexist with unionids. Dreissena are very effective filter feeders and shift materials from the pelagic to the benthos through their filter feeding and deposition of pseudofeces. When zebra mussels invade phytoplankton and zooplankton abundance decreases, the biomass of benthophage fish increases, and a greater percentage of the primary productivity is consumed by higher trophic levels than in systems without zebra mussels