The global scale of alien species invasions is becoming more and more evident in the beginning ofthe new millennium. Though the problem ofbiological invasions became a rapidly growing research area, there are large gaps still, both geographically and the matically, to be filled in the near future. This book is the first attempt to provide an overall picture of aquatic species invasions in Europe. Its geographical scope stretches from Irish waters in the west to Volga River and the Caspian Sea in the east, and from Mediterranean in the south up to the Arctic coast of Europe. Not all parts of the continent could be equally covered, as in some countries species invasions are not studied yet. The book tends to represent the array of all major European aquatic systems on the broadest geographical and ecological scope possible from fully saline seas, semi-enclosed brackish water bodies and coastallagoons to freshwater lakes, major river systems and waterways. The key objectives include the present status and impacts caused by non-native aquatic species in European waters. Please note that lengthy species lists submitted for publication and additional informa tion were put on the Internet, as the electronical version of these tables benefits from computer assisted search for data (http: //www. ku. lt/nemo/EuroAquaInvaders. htm). Altogether more than 100 scientists from 24 countries have joined to synthesize the available information on bioinvasions. However, the book does not claim to be fully comprehensive."

Animals are a major link between the water column (pelagic) and the bottom (benthic) habitats in most shallow systems. This coupling is dominated by active processes such as suspension-feeding in which the organism actively uses energy to pump water that is then filtered to remove suspended particles that are consumed while undigested remains are deposited on the bottom. As a result of this feeding on and metabolism of particles, the animals excrete dissolved inorganic and organic waste back into the water column, and thus, become major components in the cycling and feedback of essential elements. With relatively high weight specific filtration rates of 1- 10 liters/hour/gram dry tissue and a propensity to form large aggregated populations (beds, reefs, schools and swarms), these organisms can play an important role in regulating water column processes Although estuarine bivalve molluscs such as oysters and mussels dominate the suspension-feeder literature, other groups including plankton and nekton that are found in estuarine as well as other aquatic systems are also potentially important removers of suspended particles. Thus, a significant part of the NATO Advanced Research Workshop focused on suspension-feeders as controllers of plankton abundance, biomass and diversity, system metabolism, nutrient cycling and scale dependency. Systems dominated by suspension-feeders are typically impacted by human activities including recreation, aquaculture, human and industrial pollution, and bilge water from shipping. Suspension-feeders are often impacted by fisheries and over-exploitation. These impacts commonly result in changes in ecosystem structure either through the food chain concentration of harmful substances or diseases, the introduction of alien species of suspension-feeders, or the instability of suspension-feeders systems through species displacement or phase shifts in the dominance between different suspension-feeding components such as nekton or zooplankton. These issues were addressed near the close of the workshop along with conclusions and syntheses developed by the working groups.

Animals are a major link between the water column (pelagic) and the bottom (benthic) habitats in most shallow systems. This coupling is dominated by active processes such as suspension-feeding in which the organism actively uses energy to pump water that is then filtered to remove suspended particles that are consumed while undigested remains are deposited on the bottom. As a result of this feeding on and metabolism of particles, the animals excrete dissolved inorganic and organic waste back into the water column, and thus, become major components in the cycling and feedback of essential elements. With relatively high weight specific filtration rates of 1a" 10 liters/hour/gram dry tissue and a propensity to form large aggregated populations (beds, reefs, schools and swarms), these organisms can play an important role in regulating water column processes.

Although estuarine bivalve molluscs such as oysters and mussels dominate the suspension-feeder literature, other groups including plankton and nekton that are found in estuarine as well as other aquatic systems are also potentially important removers of suspended particles. Thus, a significant part of the NATO Advanced Research Workshop focused on suspension-feeders as controllers of plankton abundance, biomass and diversity, system metabolism, nutrient cycling and scale dependency.

Systems dominated by suspension-feeders are typically impacted by human activities including recreation, aquaculture, human and industrial pollution, and bilge water from shipping. Suspension-feeders are often impacted by fisheries and over-exploitation. These impacts commonly result in changes in ecosystem structure either through the food chainconcentration of harmful substances or diseases, the introduction of alien species of suspension-feeders, or the instability of suspension-feeders systems through species displacement or phase shifts in the dominance between different suspension-feeding components such as nekton or zooplankton. These issues were addressed near the close of the workshop along with conclusions and syntheses developed by the working groups.

The global scale of alien species invasions is becoming more and more evident in the beginning ofthe new millennium. Though the problem ofbiological invasions became a rapidly growing research area, there are large gaps still, both geographically and the matically, to be filled in the near future. This book is the first attempt to provide an overall picture of aquatic species invasions in Europe. Its geographical scope stretches from Irish waters in the west to Volga River and the Caspian Sea in the east, and from Mediterranean in the south up to the Arctic coast of Europe. Not all parts of the continent could be equally covered, as in some countries species invasions are not studied yet. The book tends to represent the array of all major European aquatic systems on the broadest geographical and ecological scope possible from fully saline seas, semi-enclosed brackish water bodies and coastallagoons to freshwater lakes, major river systems and waterways. The key objectives include the present status and impacts caused by non-native aquatic species in European waters. Please note that lengthy species lists submitted for publication and additional informa tion were put on the Internet, as the electronical version of these tables benefits from computer assisted search for data (http: //www. ku. lt/nemo/EuroAquaInvaders. htm). Altogether more than 100 scientists from 24 countries have joined to synthesize the available information on bioinvasions. However, the book does not claim to be fully comprehensive."