Tassiana Serafim¹, Ralf Zimmermann², Christopher P Rüger², Heike Simon³, Jutta Niggemann³, Joanna J Waniek¹ and Helena Osterholz⁴, (1)Leibniz Institute for Baltic Sea Research, Rostock, Germany, (2)Joint Mass Spectrometry Centre (JMSC), University of Rostock, Department Life, Light & Matter, Rostock, Germany, (3)Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany, (4)Leibniz Institute for Baltic Sea Research, Marine Chemistry, Rostock, Germany