This dataset contains diel measurements of alkalinity, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC), d18O values of dissolved oxygen, and calculated partial pressure of CO2 (pCO2), calculated CO2 fluxes, and calculated gas-transfer velocity (k600) from stream-water samples collected at three sites along the Wiesent karst headwater stream in northern Bavaria, Germany, between 21 and 22 August 2023. Measurements were conducted at 4 h intervals over a 24 h period to assess short-term variability in carbon and oxygen cycling and CO2 evasion.