Carbon isotope fractionation during microbial methane oxidation

Barker, James; Fritz, P.

doi:10.1038/293289a0

Cited by 349 publications

(184 citation statements)

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“…These calculations enabled us to then determine the rates of methanogenesis at each depth by inserting these rates into the DI 12 C equation. The rates were constrained using the best fit of the d 13 C DIC profile and a fractionation factor for methanogenesis of 60% (after Nü sslein et al 2001) and one for methanotrophy of 10% (after Barker and Fritz 1981;Alperin et al 1988). Two scenarios were examined in the model: only methanogenesis throughout the sediments, and methanogenesis in the upper sediment section and methanotrophy in the lower sediment section.…”

Section: Methodsmentioning

confidence: 99%

Quantifying rates of methanogenesis and methanotrophy in Lake Kinneret sediments (Israel) using pore‐water profiles

Adler

Eckert

Sivan

2011

Limnology & Oceanography

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Full seasonal sets of chemical and isotope profiles from the pore water of Lake Kinneret (Sea of Galilee, Israel) were produced to study methanogenesis and methanotrophy processes and the couplings between methane (CH 4 ), sulfur, and iron. Sulfate is depleted within the upper 10 cm of the sediment mainly by traditional bacterial sulfate reduction by organic matter. Maximum sulfate reduction rates calculated from sulfate concentration profiles are found at the water-sediment interface (0-1 cm 2 1.4 3 10 212 6 0.2 3 10 212 mol cm 23 s 21 ). CH 4 concentrations and modeling of dissolved inorganic carbon (DIC) and its stable carbon isotope (d 13 C DIC ) suggest that maximum methanogenesis rates of 2.5 3 10 213 6 1.5 3 10 213 mol cm 23 s 21 occur at 5-12-cm depth in the sediments, and that it ends at 20 cm. Of the produced CH 4 , 50-75% is converted to gas bubbles of CH 4 before it reaches the bottom water. Model results suggest the occurrence of anaerobic oxidation of CH 4 (AOM) in the deep sediments of the lake below the zone of methanogenesis.

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Section: Methodsmentioning

confidence: 99%

Quantifying rates of methanogenesis and methanotrophy in Lake Kinneret sediments (Israel) using pore‐water profiles

Adler

Eckert

Sivan

2011

Limnology & Oceanography

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“…2C; Alperin et al 1988;Whiticar 1999). Methanogenesis and AOM have opposite effects on d 13 CH 4 because 12 CH 4 is preferentially formed and consumed, and the fractionation against the heavier isotope has been demonstrated for both aerobic (Barker and Fritz 1981) and anaerobic oxidation (Holler et al 2009). The isotopic composition of CH 4 in the zone of methanogenesis in Lake Ørn was , 54% and 72% lighter than d 13 C of organic C and DIC, respectively (Table 1; Fig.…”

Section: Discussionmentioning

confidence: 99%

Anaerobic oxidation of methane in an iron‐rich Danish freshwater lake sediment

Nordi

Thamdrup

Schubert

2013

Limnology & Oceanography

148

123

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Freshwater systems are identified as one of the main natural methane sources, but little is known about the importance of anaerobic oxidation of methane (AOM) in these systems. We investigated AOM in a lake sediment characterized by a high reactive iron content, normal sulfate concentrations in the bottom water (, 250 mmol L 21 ), and a relatively deep sulfate penetration of , 14 cm, which facilitated the spatial resolution of the zones of methane production and consumption. Methane concentrations, d 13 C methane profiles, and directly measured and modeled AOM rates all consistently demonstrated methane consumption throughout the anoxic, nitrate-free, Fe(III)-and sulfate-containing zone, oxidizing , 90% of the diffusive methane flux. Thus, the concentration gradient of methane was steepest at the base of the Fe(III) and sulfate zone and decreased strongly toward the sediment surface; while d 13 CH 4 increased from , 280% in the methanogenic zone to 248% in the surface sediment. Direct measurements demonstrated AOM activity throughout the Fe(III) and sulfate zone. AOM rates peaked at sulfate concentrations below 3 mmol L 21 , which suggests a possible coupling of AOM to the reduction of more crystalline Fe(III) oxides. Alternatively, AOM could be coupled to sulfate reduction, which was in turn supported by a cryptic sulfur cycle coupled to Fe(III) reduction. Our results show that AOM can substantially reduce methane emission from freshwater sediments, and the finding of AOM at sulfate concentrations , 3 mmol L 21 suggests that AOM could be of greater importance in freshwater systems, and in ancient low-sulfate oceans, than was previously appreciated.

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“…Accordingly, the two precursors of methane, namely acetate and CO2/H2, yield methane with markedly different δ 13 C values; methane from acetate is relatively enriched in 13 C. Average minimum in the carbon isotopic composition of CH4 (-61.4 ‰) occurred deeper in sediments (60 cm) while average maximum in δ 13 C-CH4 occured in the lower sediment depth of 30 cm. Enrichment of 13 C in CH4 probably reflects aerobic CH4 oxidation because oxidation would result in residual CH4 with δ 13 C-CH4 values less negative than the source CH4 (Barker & Fritz 1981;Chanton et al 2004). However, this effect has been observed only at the study site IV.…”

Section: Stable Carbon Isotopesmentioning

confidence: 99%