ENHANCED MICROBIAL METHANE OXIDATION IN WATER FROM A DEEP-SEA HYDROTHERMAL VENT FIELD AT SIMULATED INSITU HYDROSTATIC PRESSURES

Water from a hydrothermal vent field was incubated in the presence of (CH4)-C-14 under conditions of both atmospheric (1 atm) and simulated in situ hydrostatic pressure (approximately 200 atm). Methane oxidation rates measured in samples incubated at elevated pressures were 21-62% higher than those measured in replicate samples incubated at atmospheric pressure. The magnitude of the observed effect was consistent with that predicted to occur from changes in CH4 activity with depth-dependent pressure, suggesting that microbial CH4 oxidation is a functionally barophilic process. The data indicate that methane oxidation, as well as other microbial gas consumption processes, is likely to be affected by moderate increases in hydrostatic pressure and that the rates of these processes in the deep sea, based on measurements at atmospheric pressure, may be underestimated.