Pathways and Environmental Requirements for Biogenic Gas Production in the Ocean

Mechalas, Byron J.

doi:10.1007/978-1-4684-2757-8_2

Cited by 40 publications

(11 citation statements)

References 11 publications

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“…Physiological factors presumedly also control the vertical segregation of oxygen, nitrate, iron, and manganese oxide respiration. This mechanistic explanation is pref~rable to the oft~n cited (CLAYPOOL and KAPLAN, 1974;FROELICH et ~/., 1979;ATKINSON and RICH-ARDS, 1967;NISSENBAUM et al, 1972;MECHALAS, 1974) but invalid (McCARTY, 1972) argument that some respiratory processes exclude others because they are more thermodynamically favorable.…”

Section: Resultsmentioning

confidence: 94%

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

Lovley

Klug

1986

Geochimica et Cosmochimica Acta

290

144

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Abstract-A model, based on the in situ physiological characteristics of methanogens and sulfate reducers, was developed to describe the distribution of methanogenesis and sulfate reduction in freshwater sediments. The model predicted the relative importance of methane production and sulfate reduction in lakes of various trophic status and generated profiles of sulfate, acetate, methanogenesis, and sulfate reduction comparable to the profiles that are expected based on field studies. The model indicated that at sulfate concentrations greater than 30 itM a sulfate-reducing zone develops because sulfate reducers maintain acetate concentrations too low for methanogens to grow. At lower sulfate concentrations a methanogenic zone develops because the dual limitations of low sulfate concentrations and acetate consumption by methanogens prevents sulfate reducers from growing. The model and a compilation of previously published field data indicate that, within the reported range of sulfate concentrations, the relative importance of methanogenesis and sulfate reduction in freshwater sediments is primarily dependent upon the rates of o~nic matter decomposition.describe chemical profiles in the sulfate-reducing and methanogenic zones, and iii) to investigate which factors may be important in controlling the relative importance of sulfate reduction and methanogenesis in the decomposition of organic matter in anaerobic freshwater sediments.

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Section: Resultsmentioning

confidence: 94%

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

Lovley

Klug

1986

Geochimica et Cosmochimica Acta

290

144

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“…Thermodynamic calculations (Thauer et al 1977;Claypool and Kaplan 19'74) indicate a progressively lower energy yield for organic matter decomposition coupled to respiration using various potential electron acceptors in the order 0, > NO3 -> MnO, > FeO(OH) > SOG2-> CO*. Although the thermodynamic argument does not fully explain the distribution of microbial activities, and factors such as differential toxicity and substrate specificity and afhnity may be involved, the predicted thermodynamic progression is often observed (Claypool and Kaplan 1974;Mechalas 1974;Fenchel and Blackburn 1979;Froelich et al 19'79). Indeed, there is often a vertical sc-quence of microbial respiration moving into a sediment as the more energetically favorable electron acceptors are used first.…”

Section: Pathways Of Respiration and Carbon Mineralizationmentioning

confidence: 99%

Comparison of microbial dynamics in marine and freshwater sediments: Contrasts in anaerobic carbon catabolism

Capone¹,

KIENE²

1988

Limnol. Oceangr.

386

318

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The microbiota of freshwater and marine sediments serve similar roles in carbon degradation and nutrient regeneration. However, because of differences in the chemical environment between freshwater and marine systems, distinct physiological groups of bacteria dominate terminal carbon catabolism in each system. In general, the distribution and rates of microbial activities within a sediment are determined by availability of electron acceptors for respiration and metabolizable organic substrates.Sulfate ion is a primary factor in the distribution of microbial activities in anoxic sediments. At

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“…Some methanogens can, however, survive exposure to O2 and resume methane production soon after being returned to anaerobic conditions [Zehnder and Wuhrmann, 1977]. Mechalas [1974] described erin production as a two-stage process. A separate heterogeneous group of microorganisms break down complex organic molecules into short-chain alcohols, fatty acids, acetates, formates, H2, and CO. Methanogenic bacteria then use these products to form CHn in reactions such as CO2 + 4H2 --• CH4 + 2H20 and CHaCOOH -• CHn + CO2.…”

mentioning

confidence: 99%

Dissolved hydrogen, carbon monoxide, and methane at the CEPEX site

Bullister¹,

Guinasso²,

Schink³

1982

J. Geophys. Res.

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Concentrations of three trace gases--H2, CO, and CH4--wer•e measured in the upper waters and in the near-surface atmosphere at the Controlled Ecosystem Population Experiment (CEPEX) site in Saanich Inlet, B.C., Canada. The upper 20 m of water contained these reduced gases at concentrations significantly higher than atmospheric equilibrium values in the presence of high levels of dissolved oxygen. Because vertical mixing was quite weak within the CEPEX container, distributions of CO, CH4, and H2 were most strongly influenced by in situ production and consumption. Concentrations of hydrogen and carbon monoxide were generally highest at or near the surface in all containers. Daily cycles of CO concentrations in the CEPEX enclosures and in the water outside the enclosures were observed. A similar, but less pronounced, H 2 cycle was seen only inside the enclosure. In the CEPEX container that received no nutrient additions, a methane maximum was commonly found at depths between 8 and 12 m. Methane concentrations and distributions in this container showed little change over a period of several weeks. Methane distribution did undergo significant change in the nutrientenriched containers. In Saanich Inlet, the CH4 maxima occurred deeper in the water column. No excess of H2 or CO was found in this methane-rich deeper water. Within the containers, changing hydrogen concentrations seem related to phytoplankton abundance, but the hydrogen distribution suggests zooplankton play a role. Carbon monoxide abundance varies with the amount of illumination received by the waters. Probably a variety of factors influence the distribution of each of the gases.Seawater samples collected at the site and incubated in dark containers, at in situ temperature, showed rapid decreases of CO and H2 levels to below air equilibrium. Cai'bon monoxide in these incubated samples reached subequilibrium levels within 12 hours. Shallow and deep water samples that had been briefly exposed to sunlight during sample handling subsequently showed higher levels of dissolved CO than did samples' that were carefully shielded from outside light. Care is needed to avoid such artifacts when studying diurnal variations in dissolved CO. INTRODUCTION Surface waters of the ocean have concentrations of H2 and CO far greater than atmospheric equilibrium solubility would predict [Swinnerton et al., 1968; Williams and Bainbridge, 1973; Seiler, 1978], so the ocean must be a source of these gases to the atmosphere. CO concentrations show substantial daily variations (-2x minimum values) in surface waters. According to Linnenbom et al. [1973], Seller and Schmidt [ 1974], and Conrad and Seiler [1980], the maximum in variations correlate with the intensity, amplitude, and phase of sunlight even at a depth of 100 m. Hydrogen has not been reported as having a regular daily pattern; however, significant variations in surface water concentrations (e.g., 0.18-2.96 nmol/1) have been observed [Herr and Barger, 1978; Seiler and Schmidt, 1974]. The vertical distribution patterns of H2 ...

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Pathways and Environmental Requirements for Biogenic Gas Production in the Ocean

Cited by 40 publications

References 11 publications

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

Comparison of microbial dynamics in marine and freshwater sediments: Contrasts in anaerobic carbon catabolism

Dissolved hydrogen, carbon monoxide, and methane at the CEPEX site

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