Different amounts of dust (5 mg and 100 mg) were added to a mixture (30 mL) of artificial seawater and 13C-labeled Spirulina extract (~500 µM). Water samples were taken at multiple time points (0, 10, 24, 48, 72, 120, and 168 hours) and analyzed for DOC. Dust samples were analyzed for TOC and δ13C-TOC before and after the experiments. After 72 hours, water samples were also analyzed for δ13C-DIC using isotope ratio infrared spectrometry (IRIS) with a universal reference interface (URI) (Delta Ray, Thermo Scientific), calibrated to the VPDB standard with a precision of ±0.05‰.