Investigating the Bioavailability of Phosphorus in the Presence of Iron Under Fluctuating Redox Conditions in Arctic Soils04/15/2020
Northern latitudes are rapidly warming. As permafrost thaws, soil carbon (C) stocks are at risk of being released into the atmosphere, transitioning arctic systems from C sinks to sources. Soil microbial C metabolism is constrained by temperature, water and nutrients. Nutrients such as phosphate (PO43-), are in turn regulated by iron (Fe) geochemistry, but these interactions vary across redox conditions in arctic soils. Where present, poorly crystalline Fe (oxyhydr)oxides sorb PO43-, limiting its bioavailability. To assess microbial PO43- acquisition in the presence of Fe, we examined phosphorus (P) uptake by the microbial community in arctic soils in Abisko, Sweden. Mesh bags were filled with Fe-rich soil that was either saturated with PO43- or not saturated. Bags were incubated for one week along a thaw gradient representing different redox conditions. Preliminary results show that PO43- concentrations in microbial biomass are low, suggesting that microbes are acclimated to low P conditions and/or may be limited by nutrients other than P in arctic soils resulting in limited uptake of P molecules. Alternatively, PO43- liberated from microbial biomass by chloroform fumigation may have re-sorbed to soil Fe oxides, resisting detection. Continued analysis of soil Fe and P will further elucidate P storage pools.