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Eriksson, A., Wild, B., Hong, W.-L., Holmstrand, H., Nascimento, F. J. A., Bonaglia, S., . . . Gustafsson, Ö. (2026). Enhanced methane cycling across the Laptev Sea signaled by time-integrated biomarkers of aerobic methane oxidation. Biogeosciences, 23(4), 1459-1475
Open this publication in new window or tab >>Enhanced methane cycling across the Laptev Sea signaled by time-integrated biomarkers of aerobic methane oxidation
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2026 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 23, no 4, p. 1459-1475Article in journal (Refereed) Published
Abstract [en]

Elevated methane concentrations in seawater have been reported over extensive areas of the East Siberian Arctic Seas, overlying thawing subsea permafrost. However, observed methane concentrations of the ephemeral seawater are highly variable across both space and time, compromised by both the timing of rare measurements and storm-driven exchanges to the atmosphere. Here, we applied time-integrated signals of the δ13C-composition of specific C30 hopanoids (diploptene, hop-17(21)-ene, neohop-13(18)-ene and diplopterol) in surface sediments to trace aerobic methane oxidation as a proxy for enhanced methane cycling. Interpretations of hopanoids and possible sources were further assessed by 16S-rRNA analyses in the surface sediments. The consistently low δ13C-C30 hopenes signals, ranging between −57.5 ‰ to −37.1 ‰ (n=23) across the Laptev Sea shelf indicated aerobic methane oxidation. This suggests ubiquitous methane cycling with the most pronounced intensities in the outer shelf region, broadly consistent with the observed methane concentrations. Notably, depleted δ13C-C30 hopenes were also found in the mid-shelf region of the Laptev Sea, earlier thought to be an area of comparatively low methane cycling. High methane concentrations were also observed in the vicinity of the Lena River delta, yet the isotopically heavier δ13C-C30 hopenes may here reflect a combination of lower aerobic methane oxidation, a greater relative abundance of type II methanotrophs (lower isotope fractionation during hopanoid production) and isotope dilution from non-methanotrophic sources. While this complicates the biomarker interpretation in the unique setting near the Lena River delta, the δ13C-C30 hopenes were still much lower than δ13C-organic carbon, indicating aerobic methane oxidation and a clear methane cycling signal also in this regime. Taken together, the results unravel the wider cross-shelf patterns of enhanced methane cycling in the Laptev Sea through probing of methane fossilised in membrane lipids of aerobic methanotrophs, with the molecular-isotopic pattern being preserved in the sedimentary archive.

National Category
Physical Geography
Identifiers
urn:nbn:se:su:diva-253052 (URN)10.5194/bg-23-1459-2026 (DOI)001697434100001 ()2-s2.0-105031010387 (Scopus ID)
Available from: 2026-03-09 Created: 2026-03-09 Last updated: 2026-03-09Bibliographically approved
Eriksson, A., Wild, B., Hong, W.-L., Maciute, A., Nascimento, F. & Gustafsson, Ö. (2025). Geospatial Extent of Aerobic Methane Activity in the Laptev Sea Assessed through Geohopanoids in Surface Sediments. In: IMOG 2025: . Paper presented at 32nd International Meeting on Organic Geochemistry (IMOG 2025), Porto, Portugal, 7-11 September, 2025. European Association of Geoscientists and Engineers
Open this publication in new window or tab >>Geospatial Extent of Aerobic Methane Activity in the Laptev Sea Assessed through Geohopanoids in Surface Sediments
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2025 (English)In: IMOG 2025, European Association of Geoscientists and Engineers, 2025Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
European Association of Geoscientists and Engineers, 2025
Series
EAGE Proceedings, ISSN 2214-4609
National Category
Oceanography, Hydrology and Water Resources
Identifiers
urn:nbn:se:su:diva-253468 (URN)10.3997/2214-4609.202533199 (DOI)2-s2.0-105030833747 (Scopus ID)
Conference
32nd International Meeting on Organic Geochemistry (IMOG 2025), Porto, Portugal, 7-11 September, 2025
Available from: 2026-03-13 Created: 2026-03-13 Last updated: 2026-03-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0009-0004-8977-4869

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