Constructed and restored wetland soils play a key role in the cycling and retention of nutrients from polluted surface waters. Elevated SO42-loading from irrigated agriculture, however, has been shown to affect boThthe availability and mobility of P in wetland soils. This study investigated the biogeochemical cycling of Fe, S, and P in wetland pore waters and surface soils, to determine the role of sulfides in inducing mobilization of P in a constructed wetland in the Central Valley of California (CVC). Water column, pore-water, and solid-phase soil chemistry were measured at three sites, representing a range in wetland environmental conditions (i.e., sediment and nutrient loading, redox environment, and Fe-S-P geochemistry). High SO 42-concentration and active SO42-reduction in wetland pore waters contributed to elevated pore water PO43-concentration (0.42 -1.29 mg L-1) via SO 42-induced P mobilization. Although high concentrations of acid volatile sulfide (AVS) were present in the surface (0-5 cm) layer ( x : 6.5-10.3 $\mu$mol g-1), only ∼8\% of the labile Fe pool was S2-bound, leaving sufficient Fe to buffer S2-. Additionally, surface soils experienced a three-to four-fold increase in P sorption index (PSI) under anaerobic versus aerobic conditions. Results from solid-phase chemical extractions and chemical equilibrium modeling showed that this higher PSI may be due to the conversion of crystalline Fe(III) oxides to poorly crystalline forms, the preservation of Fe(III) oxides due to kinetic constraints on microbial Fe reduction, and the formation of Fe(II) oxides. This study demonstrates that mineral dominated wetlands withsufficient Fe to buffer boThdissolved sulfide and PO43-concentrations, can limit the effects of high SO42-loading and SO42-reduction on the mobilization and flux of soil PO43-to the wetland water column. \textcopyright Soil Science Society of America.