Protists — A Dominant Component of the Ballast-Transported Biota

  • Norbert Hülsmann
  • Bella S. Galil


Ship’s ballast water and sediments serve as a main vector in the transportation and spreading of protists: toxic dinoflagellates, parasitic labyrinthulids and other potentially harmful and harmless unicellular beings. The omnipresence of protists in the sea means that photo- and heterotrophic protists invariably occur in ballast water and sediments. Ballast tanks — especially in container vessels with a high turnover of ballast water — serve as mesocosms supporting rich assemblages of heterotrophic protists. We estimate that more than 250 protist taxa are commonly present in a ballast tank, since their size and diet favour survival in there. As protists form an important part of the marine food web, otherwise harmless protists may be indirectly involved in the successful transport of bioinvaders by increasing the chances of survival of entrained filter-feeding and biofilm-grazing metazoans. Furthermore, we suggest that ballast-transported protists, harmless in their native habit ts, may modify or trigger changes in native assemblages, or may affect them by wholly outcompeting or partially displacing native taxa. Of momentous concern is whether protists, that are harmless in their native habitats, may become toxic after ballast-mediated spreading into the microbial associations of a recipient area, or vice versa, that the introduction of bacteria may start toxin production in formerly harmless eukaryotes.


High Trophie Level Ballast Water Native Assemblage Container Vessel Ballast Tank 
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Copyright information

© Springer Science+Business Media Dordrecht 2002

Authors and Affiliations

  • Norbert Hülsmann
    • 1
  • Bella S. Galil
    • 2
  1. 1.Institute of Zoology/ProtozoologyFree University BerlinBerlinGermany
  2. 2.Israel Oceanographic and Limnological ResearchNational Institute of OceanographyHaifaIsrael

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