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Donald E Canfield - One of the best experts on this subject based on the ideXlab platform.
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pathways of Carbon Oxidation in continental margin sediments off central chile
Limnology and Oceanography, 1996Co-Authors: Bo Thamdrup, Donald E CanfieldAbstract:Rates and oxidative pathways of organic Carbon mineralization were determined in sediments at six stations on the shelf and slope off Conception Bay at 36.5”s. The depth distribution of C Oxidation rates was determined to 10 cm from accumulation of dissolved inorganic C in l-5-d incubations. Pathways of C Oxidation were inferred from the depth distributions of the potential oxidants (0,, N03-, and oxides of Mn and Fe) and from directly determined rates of SOd2- reduction. The study area is characterized by intense seasonal upwelling, and during sampling in late summer the bottom water over the shelf was rich in NO,- and depleted of OZ. Sediments at the four shelf stations were covered by mats of filamentous bacteria of the genera Thioploca and Beggiatoa. Carbon Oxidation rates at these sites were extremely high near the sediment surface (> 3 pmol cmm3 d-l) and decreased exponentially with depth. The process was entirely coupled to SOd2reduction. At the two slope stations where bottom-water O2 was > 100 PM, C Oxidation rates were lo-fold lower and varied less with depth; C Oxidation coupled to the reduction of 02, N03-, and Mn oxides combined to yield an estimated 15% of the total C Oxidation between 0 and 10 cm. Carbon Oxidation through Fe . reduction contributed a further 12-29% of the depth-integrated rate, while the remainder of C Oxidation was through SOd2- reduction. The depth distribution of Fe reduction agreed well with the distribution of poorly crystalline Fe oxides, and as this pool decreased with depth, the importance of SOd2- reduction increased. The results point to a general importance of Fe reduction in C Oxidation in continental margin sediments. At the shelf stations, Fe reduction was mainly coupled to Oxidation of reduced S. These sediments were generally H,S-free despite high SOd2- reduction rates, and precipitation of Fe sulfides dominated H,S scavenging during the incubations. A large NO,- pool was associated with the Thioploca, and the shelf sediments were thus enriched in N03- relative to the bottom water, with maximum concentrations of 3 pmol cm-3. The NO,- was consumed during our sediment incubations, but no effects on either C or S cycles could be discerned.
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the anaerobic degradation of organic matter in danish coastal sediments iron reduction manganese reduction and sulfate reduction
Geochimica et Cosmochimica Acta, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler HansenAbstract:Abstract We used a combination of porewater and solid phase analysis, as well as a series of sediment incubations, to quantify organic Carbon Oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). In the deep portion of the basin, surface Mn enrichments reached 3.5 wt%, and Mn reduction was the only important anaerobic Carbon Oxidation process in the upper 10 cm of the sediment. In the less Mnrich sediments from intermediate depths in the basin, Fe reduction ranged from somewhat less, to far more important than sulfate reduction. Most of the Mn reduction in these sediments may have been coupled to the Oxidation of acid volatile sulfides (AVS), rather than to dissimilatory reduction. High rates of metal oxide reduction at all sites were driven by active recycling of both Fe and Mn, encouraged by bioturbation. Recycling was so rapid that the residence time of Fe and Mn oxides, with respect to reduction, ranged from 70–250 days. These results require that, on average, an atom of Fe or Mn is oxidized and reduced between 100–300 times before ultimate burial into the sediment. We observed that dissolved Mn 2+ was completely removed onto fully oxidized Mn oxides until the Oxidation level of the oxides was reduced to about 3.8, presumably reflecting the saturation by Mn 2+ of highly reactive surface adsorption sites. Fully oxidized Mn oxides in sediments, then, may act as a cap preventing Mn 2+ escape. We speculate that in shallow sediments of the Skagerrak, surface Mn oxides are present in a somewhat reduced Oxidation level ( 2+ to escape, and perhaps providing the Mn 2+ which enriches sediments of the deep basin.
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biogeochemical cycles of Carbon sulfur and free oxygen in a microbial mat
Geochimica et Cosmochimica Acta, 1993Co-Authors: Donald E Canfield, David Des J MaraisAbstract:Complete budgets for Carbon and oxygen have been constructed for cyanobacterial mats dominated by Microcoleus chthonoplastes from the evaporating ponds of a salt works located in Guerrero Negro, Baja California Sur, Mexico. Included in the budget are measured rates of O2 production, sulfate reduction, and elemental exchange across the mat/brine interface, day and night, at various temperatures and times of the year. We infer from this data the various sinks for O2, as well as the sources of Carbon for primary production. To summarize, although seasonal variability exists, a major percentage of the O2 produced during the day did not diffuse out of the mat but was used within the mat to oxidize both organic Carbon and the sulfide produced by sulfate reduction. At night, most of the O2 that diffused into the mat was used to oxidize sulfide, with O2 respiration of minor importance. During the day, the internal mat processes of sulfate reduction and O2 respiration generated as much or more inorganic Carbon (DIC) for primary production as diffusion into the mat. Also, oxygenic photosynthesis was the most important process of Carbon fixation, although anoxygenic photosynthesis may have been important at low light levels during some times of the year. At night, the DIC lost from the mat was mostly from sulfate reduction. Elemental fluxes across the mat/brine interface indicated that Carbon with an Oxidation state of greater than zero was taken up by the mat during the day and liberated from the mat at night. Overall, Carbon with an average Oxidation state of near zero accumulated in the mat. Both Carbon fixation and Carbon Oxidation rates varied with temperature by a similar amount. These mats are thus closely coupled systems where rapid rates of photosynthesis both require and fuel rapid rates of heterotrophic Carbon Oxidation.
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pathways of organic Carbon Oxidation in three continental margin sediments
Marine Geology, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler Hansen, Bo Barker Jorgensen, Henrik Fossing, Ronnie N Glud, Jens K Gundersen, Niels B Ramsing, Lars Peter Nielsen, Per O J HallAbstract:We have combined several different methodologies to quantify rates of organic Carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic Carbon Oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major Carbon Oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic Carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic Carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.
Bo Thamdrup - One of the best experts on this subject based on the ideXlab platform.
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pathways of Carbon Oxidation in continental margin sediments off central chile
Limnology and Oceanography, 1996Co-Authors: Bo Thamdrup, Donald E CanfieldAbstract:Rates and oxidative pathways of organic Carbon mineralization were determined in sediments at six stations on the shelf and slope off Conception Bay at 36.5”s. The depth distribution of C Oxidation rates was determined to 10 cm from accumulation of dissolved inorganic C in l-5-d incubations. Pathways of C Oxidation were inferred from the depth distributions of the potential oxidants (0,, N03-, and oxides of Mn and Fe) and from directly determined rates of SOd2- reduction. The study area is characterized by intense seasonal upwelling, and during sampling in late summer the bottom water over the shelf was rich in NO,- and depleted of OZ. Sediments at the four shelf stations were covered by mats of filamentous bacteria of the genera Thioploca and Beggiatoa. Carbon Oxidation rates at these sites were extremely high near the sediment surface (> 3 pmol cmm3 d-l) and decreased exponentially with depth. The process was entirely coupled to SOd2reduction. At the two slope stations where bottom-water O2 was > 100 PM, C Oxidation rates were lo-fold lower and varied less with depth; C Oxidation coupled to the reduction of 02, N03-, and Mn oxides combined to yield an estimated 15% of the total C Oxidation between 0 and 10 cm. Carbon Oxidation through Fe . reduction contributed a further 12-29% of the depth-integrated rate, while the remainder of C Oxidation was through SOd2- reduction. The depth distribution of Fe reduction agreed well with the distribution of poorly crystalline Fe oxides, and as this pool decreased with depth, the importance of SOd2- reduction increased. The results point to a general importance of Fe reduction in C Oxidation in continental margin sediments. At the shelf stations, Fe reduction was mainly coupled to Oxidation of reduced S. These sediments were generally H,S-free despite high SOd2- reduction rates, and precipitation of Fe sulfides dominated H,S scavenging during the incubations. A large NO,- pool was associated with the Thioploca, and the shelf sediments were thus enriched in N03- relative to the bottom water, with maximum concentrations of 3 pmol cm-3. The NO,- was consumed during our sediment incubations, but no effects on either C or S cycles could be discerned.
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the anaerobic degradation of organic matter in danish coastal sediments iron reduction manganese reduction and sulfate reduction
Geochimica et Cosmochimica Acta, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler HansenAbstract:Abstract We used a combination of porewater and solid phase analysis, as well as a series of sediment incubations, to quantify organic Carbon Oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). In the deep portion of the basin, surface Mn enrichments reached 3.5 wt%, and Mn reduction was the only important anaerobic Carbon Oxidation process in the upper 10 cm of the sediment. In the less Mnrich sediments from intermediate depths in the basin, Fe reduction ranged from somewhat less, to far more important than sulfate reduction. Most of the Mn reduction in these sediments may have been coupled to the Oxidation of acid volatile sulfides (AVS), rather than to dissimilatory reduction. High rates of metal oxide reduction at all sites were driven by active recycling of both Fe and Mn, encouraged by bioturbation. Recycling was so rapid that the residence time of Fe and Mn oxides, with respect to reduction, ranged from 70–250 days. These results require that, on average, an atom of Fe or Mn is oxidized and reduced between 100–300 times before ultimate burial into the sediment. We observed that dissolved Mn 2+ was completely removed onto fully oxidized Mn oxides until the Oxidation level of the oxides was reduced to about 3.8, presumably reflecting the saturation by Mn 2+ of highly reactive surface adsorption sites. Fully oxidized Mn oxides in sediments, then, may act as a cap preventing Mn 2+ escape. We speculate that in shallow sediments of the Skagerrak, surface Mn oxides are present in a somewhat reduced Oxidation level ( 2+ to escape, and perhaps providing the Mn 2+ which enriches sediments of the deep basin.
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pathways of organic Carbon Oxidation in three continental margin sediments
Marine Geology, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler Hansen, Bo Barker Jorgensen, Henrik Fossing, Ronnie N Glud, Jens K Gundersen, Niels B Ramsing, Lars Peter Nielsen, Per O J HallAbstract:We have combined several different methodologies to quantify rates of organic Carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic Carbon Oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major Carbon Oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic Carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic Carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.
Bo Barker Jorgensen - One of the best experts on this subject based on the ideXlab platform.
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pathways of Carbon Oxidation in an arctic fjord sediment svalbard and isolation of psychrophilic and psychrotolerant fe iii reducing bacteria
Marine Ecology Progress Series, 2006Co-Authors: Verona Vandieken, Niko Finke, Bo Barker JorgensenAbstract:The main mineralization pathways were determined in permanently cold fjord sediment on the west coast of Svalbard. In whole core incubations, the total oxygen uptake rate was 4.2 ± 0.4 mmol m -2 d -1 and the sulfate reduction rate 2.6 ± 0.6 mmol m -2 d -1 at 0 to 20 cm depth. Sulfate reduction was the most important anaerobic mineralization process, accounting for 57% of anaerobic organic Carbon Oxidation in anoxic bag incubations of the top 5 cm of the sediment. The remaining 43% Oxidation was attributed to microbial Fe(III) reduction. Both processes occurred con- currently in the uppermost 2 cm, and the Fe-reducing community appeared to be limited mainly by the availability of Fe(III). Below 2 cm, sulfate reduction was the dominant electron-accepting process. Calculations for the uppermost 10 cm of the sediment yielded the following contribution of the differ- ent respiratory pathways to total Carbon Oxidation: aerobic respiration 53%, sulfate reduction 34%, Fe(III) reduction 13%. In situ, the importance of Fe(III) reduction may vary through competition for substrate with oxygen- and nitrate-reducing bacteria in the surface sediment. Fe(III)-reducing bacte- ria belonging to the genera Desulfuromonas, Desulfuromusa, Shewanella and Desulfovibrio were isolated from enrichment cultures of 2 fjord sediments from Svalbard. Strains related to Desulfovib- rio reduced Fe(III) without energy generation for growth. All isolates were psychrophilic or psychro- tolerant and grew at -2°C, the freezing point of sea water, indicating adaptation to permanently cold temperatures. Besides Fe(III), the strains reduced other electron acceptors such as oxygen, man- ganese, elemental sulfur and sulfate.
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pathways of organic Carbon Oxidation in three continental margin sediments
Marine Geology, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler Hansen, Bo Barker Jorgensen, Henrik Fossing, Ronnie N Glud, Jens K Gundersen, Niels B Ramsing, Lars Peter Nielsen, Per O J HallAbstract:We have combined several different methodologies to quantify rates of organic Carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic Carbon Oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major Carbon Oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic Carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic Carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.
Jens Wurgler Hansen - One of the best experts on this subject based on the ideXlab platform.
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the anaerobic degradation of organic matter in danish coastal sediments iron reduction manganese reduction and sulfate reduction
Geochimica et Cosmochimica Acta, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler HansenAbstract:Abstract We used a combination of porewater and solid phase analysis, as well as a series of sediment incubations, to quantify organic Carbon Oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). In the deep portion of the basin, surface Mn enrichments reached 3.5 wt%, and Mn reduction was the only important anaerobic Carbon Oxidation process in the upper 10 cm of the sediment. In the less Mnrich sediments from intermediate depths in the basin, Fe reduction ranged from somewhat less, to far more important than sulfate reduction. Most of the Mn reduction in these sediments may have been coupled to the Oxidation of acid volatile sulfides (AVS), rather than to dissimilatory reduction. High rates of metal oxide reduction at all sites were driven by active recycling of both Fe and Mn, encouraged by bioturbation. Recycling was so rapid that the residence time of Fe and Mn oxides, with respect to reduction, ranged from 70–250 days. These results require that, on average, an atom of Fe or Mn is oxidized and reduced between 100–300 times before ultimate burial into the sediment. We observed that dissolved Mn 2+ was completely removed onto fully oxidized Mn oxides until the Oxidation level of the oxides was reduced to about 3.8, presumably reflecting the saturation by Mn 2+ of highly reactive surface adsorption sites. Fully oxidized Mn oxides in sediments, then, may act as a cap preventing Mn 2+ escape. We speculate that in shallow sediments of the Skagerrak, surface Mn oxides are present in a somewhat reduced Oxidation level ( 2+ to escape, and perhaps providing the Mn 2+ which enriches sediments of the deep basin.
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pathways of organic Carbon Oxidation in three continental margin sediments
Marine Geology, 1993Co-Authors: Donald E Canfield, Bo Thamdrup, Jens Wurgler Hansen, Bo Barker Jorgensen, Henrik Fossing, Ronnie N Glud, Jens K Gundersen, Niels B Ramsing, Lars Peter Nielsen, Per O J HallAbstract:We have combined several different methodologies to quantify rates of organic Carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic Carbon Oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major Carbon Oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic Carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic Carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.
Anhuai Lu - One of the best experts on this subject based on the ideXlab platform.
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Changes in Carbon Oxidation State of Metagenomes Along Geochemical Redox Gradients
Frontiers in Microbiology, 2019Co-Authors: Jeffrey M Dick, Jingqiang Tan, Miao Yu, Anhuai LuAbstract:There is widespread interest in how geochemistry affects the genomic makeup of microbial communities, but the possible impacts of Oxidation-reduction (redox) conditions on the chemical composition of biomacromolecules remain largely unexplored. Here we document systematic changes in the Carbon Oxidation state, a metric derived from the chemical formulas of biomacromolecular sequences, using published metagenomic and metatranscriptomic datasets from 18 studies representing different marine and terrestrial environments. We find that the Carbon Oxidation states of DNA, as well as proteins inferred from coding sequences, follow geochemical redox gradients associated with mixing and cooling of hot spring fluids in Yellowstone National Park (USA) and submarine hydrothermal fluids. Thermodynamic calculations provide independent predictions for the environmental shaping of the gene and protein composition of microbial communities in these systems. On the other hand, the Carbon Oxidation state of DNA is negatively correlated with oxygen concentration in marine oxygen minimum zones. In this case, a thermodynamic model is not viable, but the low Carbon Oxidation state of DNA near the ocean surface reflects a low GC content, which can be attributed to genome reduction in organisms adapted to low-nutrient conditions. We also present evidence for a depth-dependent increase of Oxidation state at the species level, which might be associated with alteration of DNA through horizontal gene transfer and/or selective degradation of relatively reduced (AT-rich) extracellular DNA by heterotrophic bacteria. Sediments exhibit even more complex behavior, where Carbon Oxidation state minimizes near the sulfate-methane transition zone and rises again at depth; markedly higher Oxidation states are also associated with older freshwater-dominated sediments in the Baltic Sea that are enriched in iron oxides and have low organic Carbon. This geobiochemical study of Carbon Oxidation state reveals a new aspect of environmental information in metagenomic sequences, and provides a reference frame for future studies that may use ancient DNA sequences as a paleoredox indicator.