Publications: Peer-reviewed journal articles (by staff)

Biological invasions

  •  Olenin S, Gollasch S, Lehtiniemi M, Sapota M,
  • and Zaiko A
5 April, 2017

Olenin S, Gollasch S, Lehtiniemi M, Sapota M, Zaiko A 2017. Biological invasions. In: Snoeijs-Leijonmalm P, Schubert H, Radziejewska T ed. Biological Oceanography of the Baltic Sea, Springer. Pp. 193-232.


  1. The term “non-indigenous species” (NIS) represents a biogeographical category, which indicates human involvement in the introduction of a certain species to a particular ecosystem and has nothing to do with putting “good” or “bad” tags on these species.
  2. A biological invasion is the spread of a NIS or a cryptogenic species (of uncertain or unknown origin) to an area where it did not previously occur.
  3. About 130 NIS and cryptogenic species have been introduced to the Baltic Sea Area by anthropogenic activities.
  4. Most NIS have arrived to the Baltic Sea during recent decades due to intensification of global trade, human mobility and removal of custom barriers, although the first introductions are thought to have taken place already centuries ago.
  5. The NIS in the Baltic Sea mainly originate from the coastal waters of three source areas (the North American east coast, the Ponto-Caspian region and East Asia), which are connected to the Baltic Sea by a number of introduction pathways, such as shipping and human-made canals.
  6. In the Baltic Sea, NIS are represented by many taxonomic groups, from unicellular plankton organisms to crustaceans, molluscs, fish, waterbirds and mammals.
  7. Many of the NIS in the Baltic Sea have increased functional diversity, bringing new and unusual functions to the species-poor Baltic Sea ecosystem.
  8. Some NIS may spread, highly increase in abundance and cause an adverse impact on biological diversity, ecosystem functioning, socio-economic values and/or human health. These NIS are called “invasive alien species”.
  9. As it cannot be predicted which NIS will become invasive and cause harm in a particular ecosystem, a precautionary approach, preventing the arrival of new NIS in general, is advisable.