Exotic flagellates of coastal North Sea waters

Abstract

Flagellate species have been shown to survive transocean passage by ballast water and the large dinoflagellate Gymnodinium catenatum was introduced from Japanese to Tasmanian waters in this way. Gymnodinium mikimotoi - better known as Gyrodinium aureolum - and Fibrocapsa japonica as well as Alexandrium leeii are good candidates to have been introduced recently. Species which seem to have been introduced recently into the North Sea but apparently are transported from adjacent seas by currents into the region are Gymnodinium chlorophorum and Alexandrium minutum. Species reported as introduced due to misidentifications are Gymnodinium catenatum and Lepidodinium viride. Under other names the species Prorocentrum minimum, Prorocentrum redfieldii, and Heterosigma akashiwo have been known for a long time in the North Sea. The recent reports of three Chattonella species may be either due to introduction or they have been overlooked. The reasons why the introduction of flagellates into coastal North Sea waters is difficult to prove will be discussed.