Thomas Kiørboe1, Mridul K Thomas2,3,4. 1. Centre for Ocean Life, DTU Aqua, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark; tk@aqua.dtu.dk. 2. Centre for Ocean Life, DTU Aqua, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark. 3. Department F.-A. Forel for Environmental and Aquatic Sciences, University of Geneva, CH-1211 Geneva, Switzerland. 4. Institute for Environmental Sciences, University of Geneva, CH-1211 Geneva, Switzerland.