scholarly journals Acetate turnover and methanogenic pathways in Amazonian lake sediments

2019 ◽  
Author(s):  
Ralf Conrad ◽  
Melanie Klose ◽  
Alex Enrich-Prast
Keyword(s):  
Lake Sediments ◽  
Turnover Rates ◽  
Hydrogenotrophic Methanogenesis ◽  
Ch4 Production ◽  
Relative Contribution ◽  
Acetate Methyl ◽  
Syntrophic Oxidation ◽  
Aceticlastic Methanogenesis ◽  
Respiratory Index ◽  
Amazonian Lake

Abstract. Lake sediments in Amazonia are a significant source of CH4, a potential greenhouse gas. Previous studies of sediments using 13C analysis found that the contribution of hydrogenotrophic versus aceticlastic methanogenesis to CH4 production was relatively high. Here, we determined the methanogenic pathway in the same sediments (n = 6) by applying [14C]bicarbonate or [2-14C]acetate, and confirmed the high relative contribution (50–80 %) of hydrogenotrophic methanogenesis. The respiratory index (RI) of [2-14C]acetate, which is 14CO2 relative to 14CH4 + 14CO2, divided the sediments into two categories, i.e., those with an RI  0.4 showing that a large percentage of the acetate-methyl was oxidized to CO2 rather than reduced to CH4. Hence, part of the acetate was probably converted to CO2 plus H2 via syntrophic oxidation, thus enhancing hydrogenotrophic methanogenesis. This happened despite the presence of potentially aceticlastic Methanosaetaceae in all the sediments. Alternatively, acetate may have been oxidized with a constituent of the sediment organic matter (humic acid) serving as oxidant. Indeed, apparent acetate turnover rates were larger than CH4 production rates except in those sediments with a R 

scholarly journals Acetate turnover and methanogenic pathways in Amazonian lake sediments

2020 ◽  
Vol 17 (4) ◽  
pp. 1063-1069 ◽  
Author(s):  
Ralf Conrad ◽  
Melanie Klose ◽  
Alex Enrich-Prast
Keyword(s):  
Lake Sediments ◽  
Turnover Rates ◽  
Hydrogenotrophic Methanogenesis ◽  
Ch4 Production ◽  
Relative Contribution ◽  
Acetate Methyl ◽  
Syntrophic Oxidation ◽  
Acetoclastic Methanogenesis ◽  
Respiratory Index ◽  
Amazonian Lake

Abstract. Lake sediments in Amazonia are a significant source of CH4, a potential greenhouse gas. Previous studies of sediments using 13C analysis found that the contribution of hydrogenotrophic versus acetoclastic methanogenesis to CH4 production was relatively high. Here, we determined the methanogenic pathway in the same sediments (n=6) by applying 14Cbicarbonate or 2-14Cacetate and confirmed the high relative contribution (50 %–80 %) of hydrogenotrophic methanogenesis. The respiratory index (RI) of 2-14Cacetate, which is 14CO2 relative to 14CH4+14CO2, divided the sediments into two categories, i.e., those with an RI < 0.2 consistent with the operation of acetoclastic methanogenesis and those with an RI > 0.4 showing that a large percentage of the acetate-methyl was oxidized to CO2 rather than reduced to CH4. Hence, part of the acetate was probably converted to CO2 plus H2 via syntrophic oxidation, thus enhancing hydrogenotrophic methanogenesis. This happened despite the presence of potentially acetoclastic Methanosaetaceae in all the sediments. Alternatively, acetate may have been oxidized with a constituent of the sediment organic matter (humic acid) serving as oxidant. Indeed, apparent acetate turnover rates were larger than CH4 production rates except in those sediments with a R<0.2. Our study demonstrates that CH4 production in Amazonian lake sediments was not simply caused by a combination of hydrogenotrophic and acetoclastic methanogenesis but probably involved additional acetate turnover.

Similar evolution in δ 13CH4 and model-predicted relative rate of aceticlastic methanogenesis during mesophilic methanization of municipal solid wastes

2009 ◽  
Vol 60 (12) ◽  
pp. 3173-3179 ◽  
Author(s):  
V. A. Vavilin ◽  
X. Qu ◽  
L. Mazéas ◽  
M. Lemunier ◽  
C. Duquennoi ◽  
...  
Keyword(s):  
Relative Rate ◽  
Stable Carbon Isotope ◽  
Solid Wastes ◽  
Production Volume ◽  
Municipal Solid Wastes ◽  
Methane Generation ◽  
Hydrogenotrophic Methanogenesis ◽  
Relative Contribution ◽  
Partial Pressures ◽  
Aceticlastic Methanogenesis

Similar evolution was obtained for the stable carbon isotope signatures δ 13CH4 and the model-predicted relative rate of aceticlastic methanogenesis during mesophilic methanization of municipal solid wastes. In batch incubations, the importance of aceticlastic and hydrogenotrophic methanogenesis changes in time. Initially, hydrogenotrophic methanogenesis dominated, but increasing population of Methanosarcina sp. enhances aceticlastic methanogenesis. Later, hydrogenotrophic methanogenesis intensified again. A mathematical model was developed to evaluate the relative contribution of hydrogenotrophic and aceticlastic pathways of methane generation during mesophilic batch anaerobic biodegradation of the French and the Chinese Municipal Solid Wastes (FMSW and CMSW). Taking into account molecular biology analysis reported earlier three groups of methanogens including strictly hydrogenotrophic methanogens, strictly aceticlastic methanogens (Methanosaeta sp.) and Methanosarcina sp., consuming both acetate and H2/H2CO3 were considered in the model. The total organic and inorganic carbon concentrations, methane production volume, methane and carbon dioxide partial pressures values were used for the model calibration and validation. Methane isotopic composition (δ 13CH4) evolution during the incubations was used to independently validate the model results. The model demonstrated that only the putrescible solid waste was totally converted to methane.

scholarly journals Straw application in paddy soil enhances methane production also from other carbon sources

2013 ◽  
Vol 10 (8) ◽  
pp. 14169-14193 ◽  
Author(s):  
Q. Yuan ◽  
J. Pump ◽  
R. Conrad
Keyword(s):  
Priming Effect ◽  
Carbon Sources ◽  
Methanogenic Archaea ◽  
Rice Fields ◽  
Soil Environment ◽  
Traditional Management ◽  
Positive Priming ◽  
Hydrogenotrophic Methanogenesis ◽  
Ch4 Production ◽  
Straw Application

Abstract. Flooded rice fields are an important source of the greenhouse gas methane. Methane is produced from rice straw (RS), soil organic matter (SOM), and rice root organic carbon (ROC). Addition of RS is widely used for ameliorating soil fertility. However, this practice provides additional substrate for CH4 production and results in increased CH4 emission. Here, we found that decomposing RS is not only a substrate of CH4 production, but in addition stimulates CH4 production from SOM and ROC. Apart from accelerating the creation of reduced conditions in the soil environment, RS decomposition exerted a positive priming effect on SOM-derived CH4 production. In particular, hydrogenotrophic methanogenesis from SOM-derived CO2 was stimulated, presumably by H2 released from RS decomposition. On the other hand, the positive priming effect of RS on ROC-derived CH4 production was probably caused by the significant increase of the abundance of methanogenic archaea in the RS treatment compared with the untreated control. Our results show that traditional management of rice residues exerts a positive feedback on CH4 production from rice fields, thus exacerbating its effect on the global CH4 budget.

scholarly journals Thermokarst lake methanogenesis along a complete talik profile

2015 ◽  
Vol 12 (14) ◽  
pp. 4317-4331 ◽  
Author(s):  
J. K. Heslop ◽  
K. M. Walter Anthony ◽  
A. Sepulveda-Jauregui ◽  
K. Martinez-Cruz ◽  
A. Bondurant ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Relative Magnitude ◽  
Thermokarst Lake ◽  
Ch4 Production ◽  
Lake Sediment Core ◽  
Permafrost Soils ◽  
Thawing Permafrost ◽  
Top 40 ◽  
Lake Systems

Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD: 5.95 ± 1.67 μg C–CH4 g dw−1 d−1; 125.9 ± 36.2 μg C–CH4 g C−1org d−1). High CH4 production potentials were also observed in recently thawed permafrost (1.18 ± 0.61 μg C–CH4g dw−1 d−1; 59.60± 51.5 μg C–CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawing in the talik for a longer period of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw and shore erosion of yedoma permafrost are important to lake CH4 production.

scholarly journals Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

2011 ◽  
Vol 8 (3) ◽  
pp. 795-814 ◽  
Author(s):  
R. Conrad ◽  
M. Noll ◽  
P. Claus ◽  
M. Klose ◽  
W. R. Bastos ◽  
...  
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Carbon Isotope ◽  
Community Composition ◽  
Isotope Fractionation ◽  
Microbial Community Composition ◽  
Methanogenic Archaea ◽  
Methane Formation ◽  
Large Variability ◽  
Ch4 Production

Abstract. Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is mainly produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sediments in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorgansisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate, CO2, and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of Corg to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

scholarly journals Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

2010 ◽  
Vol 7 (6) ◽  
pp. 8619-8661 ◽  
Author(s):  
R. Conrad ◽  
M. Noll ◽  
P. Claus ◽  
M. Klose ◽  
W. R. Bastos ◽  
...  
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Carbon Isotope ◽  
Community Composition ◽  
Isotope Fractionation ◽  
Microbial Community Composition ◽  
Methanogenic Archaea ◽  
Methane Formation ◽  
Large Variability ◽  
Ch4 Production

Abstract. Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is mainly produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sediments in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorgansisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of Corg to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

scholarly journals Fractionation of stable carbon isotopes during acetate consumption by methanogenic and sulfidogenic microbial communities in rice paddy soils and lake sediments

2021 ◽  
Vol 18 (24) ◽  
pp. 6533-6546
Author(s):  
Ralf Conrad ◽  
Pengfei Liu ◽  
Peter Claus
Keyword(s):  
Microbial Communities ◽  
Lake Sediments ◽  
Lake Sediment ◽  
Stable Carbon Isotopes ◽  
Rice Paddy ◽  
Enrichment Factors ◽  
The Philippines ◽  
Paddy Soils ◽  
Aceticlastic Methanogenesis ◽  
Rice Paddy Soils

Abstract. Acetate is an important intermediate during the degradation of organic matter in anoxic flooded soils and sediments. Acetate is disproportionated to CH4 and CO2 by methanogenic or is oxidized to CO2 by sulfate-reducing microorganisms. These reactions result in carbon isotope fractionation, depending on the microbial species and their particular carbon metabolism. To learn more about the magnitude of the isotopic enrichment factors (ε) involved, acetate conversion to CH4 and CO2 was measured in anoxic paddy soils from Vercelli (Italy) and the International Rice Research Institute (IRRI, the Philippines) and in anoxic lake sediments from the northeastern and the southwestern basins of Lake Fuchskuhle (Germany). Acetate consumption was measured using samples of paddy soil or lake sediment suspended in water or in phosphate buffer (pH 7.0), both in the absence and presence of sulfate (gypsum), and of methyl fluoride (CH3F), an inhibitor of aceticlastic methanogenesis. Under methanogenic conditions, values of εac for acetate consumption were always in a range of −21 ‰ to −17 ‰ but higher in the lake sediment from the southwestern basin (−11 ‰). Under sulfidogenic conditions εac values tended to be slightly lower (−26 ‰ to −19 ‰), especially when aceticlastic methanogenesis was inhibited. Again, εac in the lake sediment of the southwestern basin was higher (−18 ‰ to −14 ‰). Determination of εCH4 from the accumulation of 13C in CH4 resulted in much lower values (−37 ‰ to −27 ‰) than from the depletion of 13C in acetate (−21 ‰ to −17 ‰ ), especially when acetate degradation was measured in buffer suspensions. The microbial communities were characterized by sequencing the bacterial 16S rRNA (ribosomal ribonucleic acid) genes as well as the methanogenic mcrA and sulfidogenic dsrB genes. The microbial communities were quite different between lake sediments and paddy soils but were similar in the sediments of the two lake basins and in the soils from Vercelli and the IRRI, and they were similar after preincubation without and with addition of sulfate (gypsum). The different microbial compositions could hardly serve for the prediction of the magnitude of enrichment factors.

Estimating evolution of δ13CH4 during methanization of municipal solid waste based on chemical reactions, isotope accumulation in products and microbial ecology

2012 ◽  
Vol 65 (2) ◽  
pp. 270-276 ◽  
Author(s):  
V. A. Vavilin
Keyword(s):  
Municipal Solid Waste ◽  
Microbial Ecology ◽  
Solid Waste ◽  
Chemical Reactions ◽  
Final Stage ◽  
Sharp Decrease ◽  
Hydrogenotrophic Methanogenesis ◽  
13C Isotope ◽  
Aceticlastic Methanogenesis ◽  
Thermophilic Conditions

Natural isotopic composition in substrate may be used to reveal the metabolic pathways of substrate transformation by microbial community. In this paper, a change in δ13CH4 during methanization of reconstituted municipal solid waste was described using a mathematical model based on stoichiometric chemical reactions, equation for the 13C isotope accumulation in products at the low natural C13/C12 ratio and microbial ecology. A set of experimental data used in the model was taken from Qu et al. (2009a). According to the model, during mesophilic municipal solid waste methanization initially hydrogenotrophic and further aceticlastic methanogenesis dominated. At the final stage hydrogenotrophic methanogenesis followed by acetate oxidation dominated again. In spite of rather high measured values of δ13C for CO2 above −21‰, a sharp decrease in δ13CH4 from −20‰ to −60‰ at the final stage was explained by a larger fractionation against 13C during methanogenesis from H2/H2CO3 due to a kinetic isotope effect when hydrogenotrophic methanogens preferentially take down light 12C. The model also confirmed that in thermophilic conditions a comparatively stable value of δ13CH4 about −60‰ measured earlier (Qu et al. 2009b) was due to a dominance of hydrogenotrophic methanogenesis during all methanization process of cardboard waste.

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