10.18453/rosdok_id00002774 Weber, Sarah Catherine Sarah Catherine Weber http://d-nb.info/gnd/1219100854 Universität Rostock 2020 570 Life science 2020 en http://purl.uni-rostock.de/rosdok/id00002774 urn:nbn:de:gbv:28-rosdok_id00002774-9 Nitrogen fixation (diazotrophy) is an important input pathway of nitrogen to surface oceans. Diazotrophy can occur in physicochemically complex waters, requiring new tools for assessing diazotroph biogeography and influence. I present a simple method for delineating habitats and pair it with a multi-scale ecosystem assessment of diazotroph impacts in the South China Sea (SCS). This strategy identified clear habitat-specific trends in diazotroph influence across the plankton food web, indicating that diazotrophy is more prevalent in the SCS than previously thought.