Tvärminne Zoological Station (TZS) was established in 1902 and belongs to the Faculty of Biological and Environmental Sciences of the University of Helsinki (UH), which is the Finnish partner in ASSEMBLE Plus. TZS is located at the entrance to the Gulf of Finland in the Baltic Sea. It provides good background data for studying long-term environmental change. One of the weather stations of the Finnish Meteorological Institute is located at TZS. TZS serves as a centre for a variety of high-quality biological research, carries out environmental monitoring, and offers facilities for visiting scientists, field courses and seminars. Marine research at TZS focuses on the biodiversity and functioning of the Baltic Sea ecosystem and the anthropogenic stressors affecting the system. The research covers ecology, ecophysiology, ecotoxicology, taxonomy, and behavioural and evolutionary biology.


  • Baltic Sea ecosystems (brackish water ecosystems characterised by vast archipelagos with high habitat complexity)


Ecosystem access

  • Coastal research vessels (On-site service)
    • Sampling at Northern Baltic, Tvarmine, coastal areas
    • R/V Augusta (18 m catamaran) and R/V J.A. Palmén (10.3 m)
    • Smaller boats for coastal sampling
    • Hovercraft for winter sampling
  • Scuba diving facilities (On-site service)
    • For sampling in the Northern Baltic, Tvarmine, coastal areas
  • Sampling equipment (On-site service)
    • Standard sampling equipment such as water samplers, plankton nets, sediment corers and grabs, dredges and trawls, and handheld probes (CTD, oxygen)


Biological resources

  • Culture collections (On-site and remote service)
    • SYKE-MRC Collection, Baltic Sea, Plankton


Experimental facilities

  • Aquaria and tanks (On-site service)
    • Aquaria of different sizes up to 100 L, in temperature- and light-controlled rooms, with flow-through seawater
  • Dry labs (On-site service)
    • Laboratory space for sample preparation, analyses and microscopy
    • Access to analytical equipment, balances, centrifuges, drying ovens, fridges and freezers
  • Wet labs (On-site service)​​​​​​​
    • Temperature- and light-controlled rooms, with flow-through seawater, available for aquarium experiments


Technology platforms 

  • Imaging (On-site service)​​​​​​​
    • Light, inverted, epifluorescence microscopes
  • Structural and chemical analysis (On-site service)​​​​​​​
    • Water chemistry analyses (e.g. nutrients, chlorophyll)



  • Data sets (On-site and remote service)​​​​​​​
    • Long-term monitoring data (temperature, salinity, nutrients, chlorophyll, zooplankton and benthic macrofauna). Note: the monitoring data base is still under development and cannot yet be searched, however data can be provided upon specific request.


Supporting facilities

  • Library services (On-site service)​​​​​​​
  • In-house lodging (On-site service)​​​​​​​
  • In-house catering (On-site service)​​​​​​​


The station is operational all year around. TZS offers accommodation for more than 80 people at a time. 


J.A. Palmenin tie 260
10900 Hanko
Liaison officer: Joanna Norkko ( ), cc to:

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