Denitrification, Acetylene Reduction, and Methane Metabolism in Lake Sediment Exposed to Acetylene

AUTOR(ES)

Knowles, Roger

RESUMO

Samples of sediment from Lake St. George, Ontario, Canada, were incubated in the laboratory under an initially aerobic gas phase and under anaerobic conditions. In the absence of added nitrate (NO3−) there was O2-dependent production of nitrous oxide (N2O), which was inhibited by acetylene (C2H2) and by nitrapyrin, suggesting that coupled nitrification-denitrification was responsible. Denitrification of added NO3− was almost as rapid under an aerobic gas phase as under anaerobic conditions. The N2O that accumulated persisted in the presence of 0.4 atm of C2H2, but was gradually reduced by some sediment samples at lower C2H2 concentrations. Low rates of C2H2 reduction were observed in the dark, were maximal at 0.2 atm of C2H2, and were decreased in the presence of O2, NO3−, or both. High rates of light-dependent C2H2 reduction occurred under anaerobic conditions. Predictably, methane (CH4) production, which occurred only under anaerobiosis, was delayed by added NO3− and inhibited by C2H2. Consumption of added CH4 occurred only under aerobic conditions and was inhibited by C2H2.

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