1. Section for Marine Botany, Department of Biology, University of Oslo, P.O. Box 1069 Blindern, N-0316 Oslo, Norway
2. Electron Microscope Unit, University of Plymouth, Plymouth PL4 8AA, UK
3. Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, ME 04575, USA
4. Station biologique, Centre National de la Research Scientifique et Université Pierre et Marie Curie, BP 74 29682 Roscoff Cx, France
5. Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, Germany