10.18453/rosdok_id00004726 Umbricht, Jacqueline Jacqueline Umbricht http://d-nb.info/gnd/1347161163 Universität Rostock 2023 570 Life science 2023 en https://purl.uni-rostock.de/rosdok/id00004726 urn:nbn:de:gbv:28-rosdok_id00004726-2 It is still unclear, how global primary production in the ocean will respond to climate change. In this thesis, the future and importance of dinitrogen fixation in relation to other nitrogen assimilation processes in a changing ocean was studied in a multi-stressor (pH and temperature) laboratory experiment with the two globally significant N2 fixers Crocosphaera watsonii and Trichodesmium sp. and during a cruise to the Amazon River plume. Results from this thesis can help to improve global models on the future of primary production and CO2 fixation in the ocean.