En-route investigations of plankton in ballast water on a ship's voyage from the Baltic to the open Atlantic coast of Europe

Abstract

Ballast water of ships has been recognized as a major vector for the unintentional transfer of exotic aquatic organisms between and within many parts of the world. Studies in several European ports have shown that most of the ballast water discharged originates from nearby sea areas indicating the importance of secondary introductions. However, the patterns of interregional transfer of exotic species within Europe remain largely unknown. The present study examined the transfer of phyto- and zooplankton organisms in the ballast water to assess the potential for the transport of invasive aquatic species between the Baltic Sea and the open Atlantic coast of Europe. Six potentially toxic phytoplankton species were found in the ballast water examined. In four ballast water sampling trials no significant changes in abundance of both phyto- and zooplankton organisms were observed during first 3–4 days of experiment. Even in the end of the longest sampling trial (15 days) millions of plankton organisms were found. The results obtained indicate the importance of interregional European shipping in the dispersal of exotic plankton organisms