Sinikka Lennartz¹, Andrea Mentges², Bernd Blasius², Curtis A. Deutsch³, David P Keller⁴, Andreas Oschlies⁴, Christoph Feenders² and Thorsten Dittmar⁵, (1)University of Oldenburg, ICBM-MPI Bridging Group for Marine Geochemistry, Institute for Chemistry and Biology of the Marine Environment, Oldenburg, Germany, (2)Carl von Ossietzky University Oldenburg, Institute for Chemistry and Biology of the Marine Environment (ICBM), Oldenburg, Germany, (3)University of Washington Seattle Campus, School of Oceanography, Seattle, WA, United States, (4)GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, (5)University of Oldenburg, Oldenburg, Germany