1. School of Biological Sciences/Institute for Global Food Security; Queen's University of Belfast; Belfast BT9 7BL United Kingdom
2. Phycology Research Group; Ghent University; 9000 Gent Belgium
3. 1 Impasse des Mouettes; F 56000 Vannes France
4. Mediterranean Institute of Oceanography, Aix-Marseille University; F 13288 Marseille cedex 9 France