During the research cruises BE03/2016 (08.03.2016), BE10/2016 (19.10.2016), BE10/2018 (23.10.2018), BE03/2019 (15.03.2019), L23-13 (13.09.2023 - 15.09.2023), Sagitta24-1 (16.09.2024), Sagitta24-2 (23.09.2024), Hai24VE2 (24.09.2024), L25-2b (09.02.2025 - 17.02.2025) and EMB374 (04.09.2025 - 13.09.2025), CTDs were deployed and sediment corers were retrieved at 131 stations in Kiel Bight in the southwestern Baltic Sea. Water column oxygen concentrations, temperature and salinity were determined using oxygen and CTD sensors. At selected water depths, water samples were collected with Niskin bottles for the analysis of nitrate concentrations using an autoanalyzer. Short sediment cores (<50cm) were recovered using a Multicorer (MUC), Minicorer (MIC) or Rumohrlot (RL). Bottom waters were sampled from the supernatant water in the sediment cores. Solid phase sediment samples were analyzed for total organic carbon using an element analyzer. Porewater was extracted from the sediment cores uzing rhizones and analyzed for total alkalinity (titration), ammonium (photometer), sulfate (ion chromatography), hydrogen sulfide (photometer), dissolved iron (ICP-OES) and dissolved manganese (ICP-OES). The collected data will be used to (i) determine the spatial and temporal variability of hydrogen sulfide in bottom waters of the Kiel Bight, (ii) identify the controlling factors governing the accumulation of hydrogen sulfide at the seafloor, and (iii) establish an early warning system of sulfidic conditions for regional stakeholders in the Baltic Sea.