Fig. 3: Output of our S-cycling box-model.

Driven forces: changes in a coefficient k_msr of MSR (microbial sulfate reduction) flux in the water-column, b fraction of H₂S-reoxidized during the MSR, c proportion of aerobic oxidation during H₂S reoxidation, and d added sulfate flux from oxidation of the pre-existing sulfur pool. Model results: e seawater sulfate δ³⁴S, f seawater sulfate δ¹⁸O, g seawater sulfate ∆′¹⁷O, and h seawater sulfate concentration. The initial steady states with sulfate concentration of 0.5 mM (SS4-2, see Supplementary Table 3) and 1.1 mM (SS8-2) were adopted as suggested^72,73.