Anaerobic dihydrogen consumption of nutrient-limited aquifer sediment microbial communities examined by stable isotope analysis

ABSTRACT

The biogeochemical consequences of dihydrogen (H₂) underground storage in porous aquifers are poorly understood. Here, the effects of nutrient limitations on anaerobic H₂ oxidation of an aquifer microbial community in sediment microcosms were determined in order to evaluate possible responses to high H₂ partial pressures. Hydrogen isotope analyses of H₂ yielded isotope depletion in all biotic setups indicating microbial H₂ consumption. Carbon isotope analyses of carbon dioxide (CO₂) showed isotope enrichment in all H₂-supplemented biotic setups indicating H₂-dependent consumption of CO₂ by methanogens or homoacetogens. Homoacetogenesis was indicated by the detection of acetate and formate. Consumption of CO₂ and H₂ varied along the differently nutrient-amended setups, as did the onset of methane production. Plotting carbon against hydrogen isotope signatures of CH₄ indicated that CH₄ was produced hydrogenotrophically and fermentatively. The putative hydrogenotrophic Methanobacterium sp. was the dominant methanogen. Most abundant phylotypes belonged to typical ferric iron reducers, indicating that besides CO₂, Fe(III) was an important electron acceptor. In summary, our study provides evidence for the adaptability of subsurface microbial communities under different nutrient-deficient conditions to elevated H₂ partial pressures.

KEYWORDS:

• Anaerobic H₂ consumption
• aquifer microbial communities
• carbon-13
• carbon dioxide
• hydrogen-2
• stable isotope analysis
• methanogenesis

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by Bundesministerium für Bildung und Forschung 03G0875B and Bundesministerium für Wirtschaft und Klimaschutz 03ET6122B.