Dataset accompanying the paper "Connecting the N Isotopic Composition of Planktic Foraminifer Tissue to Surface Ocean Nutrient Cycling: A Case Study in the Northern South China Sea", (Bieler et al., submitted to Geochemistry, Geophysics, Geosystems, 2025). This dataset contains data files on the nitrogen isotope composition of planktic foraminifer tissue from vertical net tows and seawater nitrate as well as accompanying foraminifer population dynamics collected aboard RV Sonne during cruise SO269 in the northern South China Sea in summer 2019. Methods and analytical procedures are described in the paper mentioned above; please refer to the paper when using this dataset. Individual files are in CSV format and contain descriptive headers.