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Regional patterns of iron (Fe) and manganese (Mn) reduction rates across the shelf and slope of the southeastern Bering Sea, as well as the relative importance of these pathways in sedimentary organic matter remineralization, were investigated during the spring and summer of 2009. Reduction rates of Fe and Mn were calculated using depth pro! les of solid-phase iron and manganese oxide concentrations and bioturbation coef! cients, Db, determined from pro! les of excess 234 Th. Iron reduction was found to be a signi! cant pathway for carbon mineralization across the shelf, with an average rate of 1.74 mmol m ! 2 d ! 1 . However, Fe reduction rates higher than 6 mmol m ! 2 d ! 1 were calculated, and a signi! cant regional pattern was observed, with highest rates found on the northern shelf, and dropping toward the south and offshore. Conversely, Mn oxide reduction was found to be of minor signi! cance, with low reduction rates in all regions, averaging only 0.09 mmol m ! 2 d ! 1 across the shelf, and accounting for no more than 5% of total carbon oxidation in any region. These results indicate that Fe oxide reduction is a signi! cant pathway for carbon remineralization in the northern and middle-shelf regions, where organic matter deposition rates and benthic biomass are high. Additionally, this work provides insight into the potential role of sedimentary iron reduction as a source of bioavailable Fe in this region. |
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