Abstract
The role of acetate in the biogeochemical cycling of organic matter in contemporary marine anoxic sediments of Skan Bay, Alaska was investigated with inhibition and quasi in situ turnover experiments. The turnover time for acetate oxidation in the upper 30 cm of the sediment column is ca. 1 hr. A molybdate inhibition experiment indicated that sulfate reducing bacteria were responsible for more than 95% of acetate oxidation. However, measured acetate oxidation rates exceeded sulfate reduction rates indicating that acetate oxidation rates are overestimated. Values for acetate concentration calculated from sulfate reduction rates (0.3–3.4 μM) were considerably lower than directly measured acetate concentrations (3.1–10.8 μM). Much of the chemically measured acetate may be microbially unavailable, perhaps in the form of a soluble or colloidal complex. A sorption experiment indicates that 10% to 40% of added acetate associates with Skan Bay sediment particles. Production of methane from acetate was detected only at 2 m depth.
Highlights
Sulfate reduction generally appears to be preferred when sulfate is available, the factors whichORGANICMATTERis recycled in marine sediments to control the relative importance of these pathways in carbon dioxide and other simple molecules by a anoxic marine sediments are not yet fully understood.complex and incompletely understood set of biogeo-We have sought to determine the rates at which chemical processes
Acetate is consumed by sulfate reducing bacteria and these processes are selective, indirect and incomplete. by methanogens in order to establish the relative
The complexity of carbon remineralization in an- In the course of this work we found a discrepancy in oxic marine sediments is reflected in the diverse the measured sedimentary redox budget which sugmicrobial communities that reside there
Summary
Geochlmlco rr Cosmoehimica Acva Vol 48, pp. 1819-1825 8 PcrgamonPIUS Ltd. 1984.Printed in U.S.A. Abstract-The role of acetate in the biogeochemical cycling of organic matter in contemporary marine anoxic sediments of Skan Bay, Alaska was investigated with inhibition and quasi in situ turnover experiments. The turnover time for acetate oxidation in the upper 30 cm of the sediment column is cu. A molybdate inhibition experiment indicated that sulfate reducing bacteria were responsible for more than 95% of acetate oxidation. Measured acetate oxidation rates exceeded sulfate reduction rates indicating that acetate oxidation rates are overestimated. Values for acetate concentration calculated from sulfate reduction rates (0.3-3.4 PM) were considerably lower than directly measured acetate concentrations Much of the chemically measured acetate may be microbiahy unavailable, perhaps in the form of a soluble or colloidal complex. A sorption experiment indicates that 10% to 40% of added acetate associates with Skan Bay sediment particles. Production of methane from acetate was detected only at 2 m depth
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