Exotic flagellates of coastal North Sea waters

Flagellate species have been shown to survive transocean passage by ballast water and the large dinoflagellate Gymnodinium catenatum was introduced fr om Japanese to Tasmanian waters in this way. Gymnodinium mikimotoi - better known as Gyrodinium aureolum - and Fi brocapsa japonica as well as Alexand rium leeii are good candidates to have been introduced recently. Species wh ich seem to have been introduced recently into the North Sea but apparently are transported from adjacent seas by currents into the region are Gymnodi nium chlorophorum and Alexandrium minutum. Species reported as introduced d ue to misidentifications are Gymnodinium catenaium and Lepidodinium viride. Under other names the species Prorocentrum minimum, Prorocentrum redfieldi i, and Heterosigma akashiwo have been known for a long time in the North Se a. The recent reports of three ChattoneIla species may be either due to int roduction or they have been overlooked. The reasons why the introduction of flagellates into coastal North Sea waters is difficult to prove will be di scussed.