10. Non-native Crustaceans

The ubiquitous process of globalization is reflected in and affects not only the human economy, but has also given rise to unprecedented environmental changes. The appearance of alien crustaceans is a phenomenon that is very hard to define unequivocally. Newly colonized areas are often inhabited by just a small number of native species, which are susceptible to the effects of human activities. Among invertebrates it is crustaceans that most frequently colonize new water bodies; indeed, freshwater crustaceans are thought to be the most effective invasive non-native species. Species new to the Baltic are often given the negative prefix “xeno” (from the Greek: xenon—foreign), as disruptors of life in that sea. While it is true that most non-indigenous crustaceans have an adverse impact on the newly-colonized environment and that their colonization is invasive, some of them eventually become a regular feature of the ecosystem and an important element of the food web, while others are economically important but with a potential yet to be fully realised. Most new crustacean species are not limited to a specific region but spread very quickly and inhabit further water bodies.