The Baltic Sea — A Field Laboratory for Invasion Biology

Since the early 1800s, about 103 NIS have been recorded in the Baltic Sea. In this brackish sea (salinity range from less than 2 to approximately 20 PSU) horizontal and vertical gradients provide the nonindigenous species of different origin an extended repertoire of hospitable conditions. Several ecological functions of the non-native animals are new (and hence unique) for the species-poor Baltic Sea ecosystem. A review of the research into invasion biology in the Baltic Sea countries reveals a timeline from first records of single new species toward more sophisticated studies in invasion biology.