MEPS 322:15-27 (2006) - doi:10.3354/meps322015
Carbon mineralization in Arctic sediments northeast of Svalbard: Mn(IV) and Fe(III) reduction as principal anaerobic respiratory pathways
Verona Vandieken1,2,*, Maren Nickel1, Bo Barker Jørgensen1
ABSTRACT: Carbon oxidation rates and pathways were determined in 3 sediments at latitude 79° to 81° N in the Barents Sea, where the ice cover restricts primary production to a few months of the year. Oxygen uptake (1.5 to 3.5 mmol m2 d1) and sulfate reduction (<0.1 to 0.22 mmol m2 d1 over 0 to 10 cm depth) rates were measured by whole core incubation. Pathways of anaerobic carbon oxidation were determined by combining results of anoxic sediment bag incubations with pore water and solid phase analyses of the sediments. In accordance with the high contents of solid Mn (≥60 µmol cm3) and Fe(III) (≥108 µmol cm3), dissimilatory Mn(IV) and Fe(III) reduction contributed between 69 and ≥90% to anaerobic carbon mineralization in the upper 10 cm of the sediments. At 2 of the 3 stations, sulfate reduction rates were below our detection limit of 1 nmol cm3 d1. Solid Mn and Fe(III) were abundant from the surface to 10 cm sediment depth and were apparently the only important anaerobic electron acceptors. At the third station, vertical zonation of anaerobic mineralization was observed, with Mn(IV) reduction at 0 to 3 cm followed by concurrent Fe(III) and sulfate reduction at 3 to 5 cm and sulfate reduction at 5 to 10 cm. Rates of microbial carbon oxidation were low compared to those in fjords on the west and south coasts of Svalbard. This is in accordance with the limited organic carbon supply by primary and secondary productivity caused by long periods of ice coverage.
KEY WORDS: Microbial Mn(IV) · Fe(III) reduction · Carbon mineralization · Arctic sediments · Barents Sea · Sediment incubations
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