Chemical Speciation of Phosphorus, Iron, and Manganese in Arctic Sediments of Baffin Bay: A Microbial Community Perspective

The chemical speciation of phosphorus (P), iron (Fe), and manganese (Mn) in Arctic marine sediments is critical for evaluating nutrient availability, redox dynamics, and carbon preservation in rapidly changing polar environments. In Baffin Bay, intensifying climate-driven changes in sea-ice cover, primary productivity, and terrestrial inputs have increased the significance of microorganisms in mediating mineral transformations and diagenetic pathways that control the mobility of these elements. This study examines the relationship between microbial community composition and the speciation of P, Fe, and Mn in sediment cores collected along a depth gradient from shallow coastal zones to deep basins. Through the integration of solid-phase extractions, porewater chemistry, sediment geophysical properties, and microbial community profiling, microbially driven redox transitions that regulate elemental release, retention, and burial are identified. The results demonstrate that distinct microbial assemblages, particularly iron-reducing, sulfate-reducing, and manganese-oxidizing taxa, are associated with zones of intensified elemental cycling, thereby influencing the distribution of reactive and mineral-bound P, Fe, and Mn. These findings emphasize the role of microbially mediated geochemical processes in controlling nutrient cycling and sedimentary stability in Baffin Bay and offer a framework for predicting future biogeochemical responses to ongoing Arctic environmental change.