We studied dissolved organic matter (DOM) dynamics in the sea surface microlayer (SML) during a multidisciplinary mesocosm study at the Sea sURface Facility (SURF) of the Institute for Chemistry and Biology of the Marine Environment (ICBM) in Wilhelmshaven, Germany (53.5148 °N, 8.1463 °E). The study was conducted from 18 May to 16 June 2023 as part of the BASS research unit (Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer). This dataset contains environmental data, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and DOM molecular indices (MLBwL, Ibio, Iphoto, IDEG) calculated from ultrahigh-resolution mass spectrometry data (Fourier-transform ion cyclotron resonance mass spectrometer, FT-ICR-MS). Furthermore, we present attenuated total reflectance Fourier Transform Infrared (ATR-FTIR) data from representative samples for each bloom phase. General metadata from the multidisciplinary mesocosm study, including temperature, salinity and chlorophyll a, are provided in Bibi et al. on PANGAEA at the following link: doi:10.1594/PANGAEA.984101.