Ulrich Sommer is an ecologist with ample research experience in freshwater and marine ecology. He started his career at the Institute of Plant Physiology at the University of Vienna (Austria) where he received his doctorate in 1977. From 1979 to 1985 he was Assistant Professor at the Limnological Institute at the University of Constance, Germany. From 1985 to 1991 he worked as Senior Scientist at the Max-Planck-Institute of Limnology at Plön, Germany. In 1991 to 1994 he held a chair of Microbiology of Geological Processes at the Institute for Chemistry and Biology of Marine Systems (ICBM) at the University of Oldenburg. The move from Plön to Oldenburg was connected with a shift of his main focus from limnology to biological oceanography. In 1994 he became full professor of Marine Biology at the University of Kiel and the Institute for Marine Research (IFM) which later became part of the GEOMAR Helmholtz Centre for Ocean Research. He is author of ca. 250 peer-reviewed articles in international journals and several books: Plankton Ecology: Succession in Plankton Communities (1989), Planktologie (1994), Biologische Meereskunde (1st ed. 1998, 2nd ed. 2005) and together with Winfried Lampert Limnoecology (1st ed. 1997, 2nd ed. 2007) and together with Boris Worm Competition and Coexistence (2002). He is Editor-in-Chief of the international journal Marine Biology and Associate Editor of Oecologia and Aquatic Sciences.