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Pathways of organic carbon oxidation in three continental margin sediments
We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated. We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH+4 and ∑CO2 liberation in sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6–17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mnoxide were found (3–4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.
Microsoft Academic Graph classification: Sediment Mineralogy Oxide chemistry.chemical_compound chemistry Manganese chemistry.chemical_element Sulfate Carbon dioxide Denitrification Geology Environmental chemistry Geologic Sediments Total organic carbon
Carbon, Carbon Dioxide, Denmark, Geologic Sediments, Iron, Manganese, Marine Biology, Nitrates, Norway, Oxidation-Reduction, Oxygen, Quaternary Ammonium Compounds, Sulfates, Water Microbiology, Geochemistry and Petrology, Geology, Oceanography, Carbon, Carbon Dioxide, Denmark, Geologic Sediments, Iron, Manganese, Marine Biology, Nitrates, Norway, Oxidation-Reduction, Oxygen, Quaternary Ammonium Compounds, Sulfates, Water Microbiology
Carbon, Carbon Dioxide, Denmark, Geologic Sediments, Iron, Manganese, Marine Biology, Nitrates, Norway, Oxidation-Reduction, Oxygen, Quaternary Ammonium Compounds, Sulfates, Water Microbiology, Geochemistry and Petrology, Geology, Oceanography, Carbon, Carbon Dioxide, Denmark, Geologic Sediments, Iron, Manganese, Marine Biology, Nitrates, Norway, Oxidation-Reduction, Oxygen, Quaternary Ammonium Compounds, Sulfates, Water Microbiology
Microsoft Academic Graph classification: Sediment Mineralogy Oxide chemistry.chemical_compound chemistry Manganese chemistry.chemical_element Sulfate Carbon dioxide Denitrification Geology Environmental chemistry Geologic Sediments Total organic carbon
- Georgia Institute of Technology United States
- University of Southern Denmark Denmark
- Aarhus University Denmark
- Max Planck Society Germany
- Georgia Institute of Technology United States
- University of Southern Denmark Denmark
- Aarhus University Denmark
- Max Planck Society Germany
We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated. We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH+4 and ∑CO2 liberation in sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6–17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mnoxide were found (3–4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.