Methane leakage through the sulfate–methane transition zone of the Baltic seabed

Anaerobic oxidation of methane at the sulfate–methane transition in marine sediments is generally considered to be a near-perfect barrier against methane release from the seabed, but the mechanisms involved are not well understood. On the basis of a survey of Baltic Sea sediments we show that a high...

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Bibliographic Details
Published in:Nature geoscience 2024-12, Vol.17 (12), p.1277-1283
Main Authors: Lapham, Laura L., Lloyd, Karen G., Fossing, Henrik, Flury, Sabine, Jensen, Jørn Bo, Alperin, Marc J., Rehder, Gregor, Holzhueter, Wanda, Ferdelman, Timothy, Jørgensen, Bo Barker
Format: Article
Language:English
Subjects:
704/106
704/47/4113
704/829/827
Cores
Earth and Environmental Science
Earth Sciences
Earth System Sciences
Geochemistry
Geology
Geophysics/Geodesy
Leakage
Marine sediments
Methane
Mineralization
Ocean bottom
Ocean floor
Organic matter
Oxidation
Sediment
Sediment analysis
Sediments
Sulfates
Transition zone
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Summary:Anaerobic oxidation of methane at the sulfate–methane transition in marine sediments is generally considered to be a near-perfect barrier against methane release from the seabed, but the mechanisms involved are not well understood. On the basis of a survey of Baltic Sea sediments we show that a highly variable amount (0–100%) of subseafloor methane leaks through the sulfate–methane transition. The diffusive methane flux to the sediment–water interface is often high, reaching over 2 mmol m −2  d −1 . Even though anaerobic methane oxidation is thermodynamically and kinetically favoured where methane fluxes are high, there is no evidence of methane oxidation in concentration, isotope and modelling results. Cores that lacked anaerobic methane oxidation had high modelled organic matter mineralization rates, suggesting that a possible mechanism could be high electron donor availability due to elevated H 2 concentrations, as has been predicted by laboratory studies. We show that methane leakage across the sulfate–methane transition is widespread in organic-rich marine sediments. Inhibition of anaerobic methane oxidation in organic-rich marine sediments causes widespread methane leakage from the seabed, according to an analysis of sediment cores from the Baltic Sea.
ISSN:1752-0894
1752-0908
DOI:10.1038/s41561-024-01594-z