Methane production, sulfate reduction and competition for substrates in the sediments of Lake Washington
Abstract
Rates of methane production (both acetate fermentation and CO 2 reduction) and sulfate reduction were directly measured as a function of depth in the sediments of Lake Washington. Although methanogenesis was the primary mode of anaerobic respiration (63%), the major zone of methane prodiction existed only below the sulfate reduction zone (16 cm). Acetate fermentation accounted for 61 to 85% of the total methane production, which is consistent with other low sulfate environments. The observed spatial separation of methane production and sulfate reduction, which has been reported for marine sediments, is attributed to competition between the methane-producing and sulfate-reducing bacterua for acetate and hydrogen. This hypothesis is supported by the strong correlation between the measured distributions of acetate and hydrogen and the rates of methane produced from these two precursors in Lake Washington sediments. Acetate concentrations increased rapidly (from 10-16 μM to 30-40 μM) once the sulfate concentration decreased below 30 μM and methane production via acetate fermentation began. A similar trend was observed for hydrogen concentrations, which increased from 7 to 22 nM up to 40 to 55 nM, at the onset of methanogenesis from CO 2 and H 2 (sulfate concentrations of 35-40 μM). These results show, for the first time in a freshwater lake, the separation of methane production and sulfate reduction and the corresponding changes in acetate and hydrogen concentrations.
- Publication:
-
Geochimica et Cosmochimica Acta
- Pub Date:
- February 1989
- DOI:
- 10.1016/0016-7037(89)90392-X
- Bibcode:
- 1989GeCoA..53..409K