Plants remove carbon dioxide (CO2) from the atmosphere and can mitigate climate change, but require nutrients like phosphorus (P) to increase primary productivity and build biomass. P can become limiting to plant growth as changes in the water table alter soil redox conditions. These anoxic-oxic changes can influence geochemical sorption of phosphate (PO43-) to iron (oxyhydr)oxides, modifying P bioavailability. Vernal ponds are one such system that experience seasonal hydrologic changes that result in redox fluctuations. Release of iron-bound phosphorus through microbial mechanisms could increase P bioavailability for plants to grow and in turn take up more CO2. To assess how microbes affect the availability of P in iron-bound PO43-, we examined P uptake by the microbial community in vernal pond soils in Northeast Ohio. Mesh bags were filled with organic material and three types of synthetic iron oxides (ferrihydrite, goethite, and hematite). Iron oxides were either saturated in a PO43- solution or not sorbed with PO43-. Bags were incubated in both lowland (pond) and adjacent upland environments and removed during flooded conditions and after the pond had dried. Preliminary results show that bags in both environments that contained iron-bound PO43- had higher mass following incubation than those without PO43-, suggesting biomass accumulation. Release of iron-bound PO43- could supply plants with vital nutrients needed to grow, resulting in greater uptake of atmospheric CO2.