Amphipod Gammarus tigrinus spreads strongly in Helsinki coastal waters

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Gammarus tigrinus, which belongs to the amphipods, an order of animals including more than 7,000 species of small, shrimp-like crustaceans, has spread surprisingly forcefully across the coastal waters of Helsinki.
      Previously only a few individuals of the species have been encountered in the coastal towns of Naantali and Hamina, but in the latest census studies researchers have encountered the species on the Helsinki shores by the hundreds.
     
The small non-indigenous creature, originally from North America, was discovered by the Finnish Institute of Marine Research (FIMR) and the City of Helsinki Environment Centre by accident.
      The newcomer was found when FIMR special researcher Kari Lehtonen and Anna Packalén, who is preparing her dissertation at the City of Helsinki Environment Centre, accidentally ran across hundreds of individuals of Gammarus tigrinus while examining altogether different amphipod species.
      The discovery was verified by the amphipod taxonomy expert Samuli Korpinen from the Baltic Marine Environment Protection Commission, generally known as the Helsinki Commission or HELCOM.
     
The newcomer has presumably arrived in the Helsinki area in the ballast water of ships.
      “It looks like it has been here for some time. It has gained ground quite aggressively”, Lehtonen says.
      In Munkkiniemi and Marjaniemi, Gammarus tigrinus formed over 90 per cent of the collected specimens. A few individuals were also found in Lauttasaari and Korkeasaari.
      The aggressive spread of the species worries Lehtonen, as Gammarus tigrinus seems capable of quickly replacing the area’s native amphipods and thus changing the ecosystem.
     
"At worst, Gammarus tigrinus may increase the Baltic Sea’s eutrophication. The ecosystem may falter if such an omnivorous predator causes species to disappear that only concentrate on certain types of food.”
      “The increased marine traffic brings more and more invasive foreign species into the Baltic Sea, and climate change may make it easier for them to adapt to the new area”, Lehtinen concludes.


Links:
  Gammarus tigrinus
  Finnish Institute of Marine Research: A new invasive species

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