1. Institute of Chemistry and Biology of the Marine Environment; University of Oldenburg; Schleusenstrasse 1 Wilhelmshaven 26382 Germany
2. Oceanlab; University of Aberdeen; Main Street Newburgh AB41 6AA UK
3. Department of Biology; Section of Protistology and Aquatic Ecology; University of Ghent; Krijgslaan 281 S8 Ghent 9000 Belgium
4. Institute of Biological Sciences, Applied Ecology & Phycology; University of Rostock; Albert-Einstein-Strasse 3 Rostock 18059 Germany