1. Department of Microbial Ecology, Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Biologische Anstalt Helgoland, Kurpromenade 201, 27498 Helgoland, Germany
2. Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering and Institute of Science, Technology and Policy, Swiss Federal Institute of Technology, ETH Zurich, Universitätsstrasse 41, 8092 Zurich, Switzerland