Stable Isotopes and Global Budgets

Whiticar, Michael J.

doi:10.1007/978-3-642-84605-2_8

Cited by 38 publications

(4 citation statements)

References 34 publications

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“…Overall, isotopic enrichment of up to 16‰ associated with an enrichment factor (51) of 1.016 at seeps and with an enrichment factor of only 1.008 at off-seep sites has been observed below and in the chemocline. Previous studies also documented that microbial methane oxidation is the only plausible explanation for pronounced isotope frac- (2,51). In comparison, mixing processes could not lead to this enrichment due to the missing heavy ( 13 C-enriched) methane source at these relatively shallow depths (Fig.…”

Section: Resultsmentioning

confidence: 65%

Evidence of Intense Archaeal and Bacterial Methanotrophic Activity in the Black Sea Water Column

Durisch-Kaiser

Klauser

Wehrli

et al. 2005

Appl Environ Microbiol

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In the northwestern Black Sea, methane oxidation rates reveal that above shallow and deep gas seeps methane is removed from the water column as efficiently as it is at sites located off seeps. Hence, seeps should not have a significant impact on the estimated annual flux of ϳ4.1 ؋ 10 9 mol methane to the atmosphere [W. S. Reeburgh, B. B. Ward, S. C. Wahlen, K. A. Sandbeck, K. A. Kilatrick, and L. J. Kerkhof, Deep-Sea Res. 38(Suppl. 2):S1189-S1210, 1991]. Both the stable carbon isotopic composition of dissolved methane and the microbial community structure analyzed by fluorescent in situ hybridization provide strong evidence that microbially mediated methane oxidation occurs. At the shelf, strong isotope fractionation was observed above high-intensity seeps. This effect was attributed to bacterial type I and II methanotrophs, which on average accounted for 2.5% of the DAPI (4,6-diamidino-2-phenylindole)-stained cells in the whole oxic water column. At deep sites, in the oxic-anoxic transition zone, strong isotopic fractionation of methane overlapped with an increased abundance of Archaea and Bacteria, indicating that these organisms are involved in the oxidation of methane. In underlying anoxic water, we successfully identified the archaeal methanotrophs ANME-1 and ANME-2, each of which accounted for 3 to 4% of the total cell counts. ANME-1 and ANME-2 appear as single cells in anoxic water, compared to the sediment, where they may form cell aggregates with sulfate-reducing bacteria

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Section: Resultsmentioning

confidence: 65%

Evidence of Intense Archaeal and Bacterial Methanotrophic Activity in the Black Sea Water Column

Durisch-Kaiser

Klauser

Wehrli

et al. 2005

Appl Environ Microbiol

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“…The mean δD in methane from various sources has been estimated (wetlands: −380‰ [ Whiticar , 1993], −320 ± 20‰ [ Quay et al , 1999], −322 ± 30‰ [ Snover et al , 2000]) by simply averaging previously reported isotope data and applying this to the global methane budget. It is clear, however, that latitudinal variation in δD in methane should be taken into account for accurate estimation.…”

Section: Discussionmentioning

confidence: 99%

Production of methane from alasses in eastern Siberia: Implications from its ¹⁴C and stable isotopic compositions

Nakagawa

Yoshida

Nojiri

et al. 2002

Global Biogeochemical Cycles

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The radiocarbon (14C) and stable isotopic (13C and D) compositions of methane and carbon dioxide from alasses (typical landforms in permafrost terrain, consisting of lakes and wetlands) were measured around Yakutsk, eastern Siberia, where few isotope studies have been done. The carbon isotopic compositions of methane and carbon dioxide were used to study the pathways of methane formation in alasses. The mean value of methane and of carbon dioxide in each alass ranged from −63.9 to −58.2‰ and from −16.7 to −0.6‰, respectively. In small alasses, where the supply of fresh organic matter from surrounding wetland ecosystems is large, methane was produced almost equally from acetate fermentation and CO2 reduction pathways. In larger alasses the CO2 reduction pathway slightly dominates over acetate fermentation, owing to a smaller supply of labile organic matter. The 13C enrichment in CO2 in large lakes indicates depletion of methane precursors. Gas‐bubble methane is depleted in deuterium (the mean δD value from lakes is −360 ± 14‰ and from shores is −380 ± 20‰), which reflects the deuterium‐depleted environmental water (from −136 to −117‰) of alasses. Lake methane relatively enriched in D is interpreted to be the result of depletion in the hydrogen pool in lake sediments. Methane in shallow lakes is somewhat enriched in 14C relative to modern biogenic methane and is produced from fresh, recently fixed organic matter. The 14C content of methane from deeper lakes is 10–20% less than that of shallow lake methane, indicating a greater contribution from older methane derived from deeper parts of the sediment. The mean 13C, D, and 14C of methane from the alasses in general are estimated to be −61.1 ± 4.4‰, −363 ± 20‰, and 104 ± 6 pMC, respectively. This corresponds to the reported mean isotopic composition of methane from wetlands for δ13C, but shows lower value for δD and 14C content.

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“…The sensitivity of the model to this assumption depends on the initial amount of isotopic enrichment and the extent of isotopic dilution that occurs during the incubation. We have assumed the δ 13 C of methane produced by methanogens to be −60‰ (1.05 atom percent 13 C), a commonly observed, intermediate value within the observed range of −50 to −100‰ [ Whiticar , 1993]. At high enrichment levels, deviation from the assumed value within the observed range generates an error of approximately the same size as analytical error and is thus not important.…”

Section: Assumptions and Sensitivity Analysismentioning

confidence: 99%

Separating methane production and consumption with a field‐based isotope pool dilution technique

Fischer

Hedin

2002

Global Biogeochemical Cycles

137

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[1] Despite the importance of methane for climate, it has remained difficult to measure gross rates of methane production and consumption without inducing artifacts. To remedy this, we have developed, tested, and applied a field-based 13 CH 4 pool dilution technique. Laboratory tests, sensitivity analyses, and field data indicate that this technique is robust for measuring gross rates of methane production and consumption. In our analyses of 130 soil cores from 17 field sites of differing environmental conditions, we encountered a wide range of gross methane production rates (0.04-930 mg CH 4 -C m À2 day À1 ), but encountered a narrower range of consumption rates (0.1-9.2 mg CH 4 -C m À2 day À1 ). Unexpectedly, we found that gross production of methane was common (mean = 0.15 mg CH 4 -C m À2 day À1 ) even in dry, oxic soils where average soil conditions cannot support methane producers. Through improved measurement of methane turnover in soils, this technique can offer a more fine-grained understanding of how productive and consumptive processes are linked to soil-atmosphere trace gas balances.

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Stable Isotopes and Global Budgets

Cited by 38 publications

References 34 publications

Evidence of Intense Archaeal and Bacterial Methanotrophic Activity in the Black Sea Water Column

Evidence of Intense Archaeal and Bacterial Methanotrophic Activity in the Black Sea Water Column

Production of methane from alasses in eastern Siberia: Implications from its ¹⁴C and stable isotopic compositions

Separating methane production and consumption with a field‐based isotope pool dilution technique

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Stable Isotopes and Global Budgets

Cited by 38 publications

References 34 publications

Evidence of Intense Archaeal and Bacterial Methanotrophic Activity in the Black Sea Water Column

Evidence of Intense Archaeal and Bacterial Methanotrophic Activity in the Black Sea Water Column

Production of methane from alasses in eastern Siberia: Implications from its 14C and stable isotopic compositions

Separating methane production and consumption with a field‐based isotope pool dilution technique

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Product

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Production of methane from alasses in eastern Siberia: Implications from its ¹⁴C and stable isotopic compositions