scholarly journals Sulfate reduction and methane oxidation activity below the sulfate-methane transition zone in Alaskan Beaufort Sea continental margin sediments: Implications for deep sulfur cycling

2014 ◽  
Vol 144 ◽  
pp. 217-237 ◽  
Author(s):  
Tina Treude ◽  
Stefan Krause ◽  
Johanna Maltby ◽  
Andrew W. Dale ◽  
Richard Coffin ◽  
...  
Keyword(s):  
Sulfate Reduction ◽  
Transition Zone ◽  
Methane Oxidation ◽  
Continental Margin ◽  
Beaufort Sea ◽  
Sulfur Cycling ◽  
Oxidation Activity

STRUCTURE OF THE BEAUFORT SEA CONTINENTAL MARGIN

Geophysics ◽  
1970 ◽  
Vol 35 (5) ◽  
pp. 849-861 ◽  
Author(s):  
R. J. Wold ◽  
T. L. Woodzick ◽  
N. A. Ostenso
Keyword(s):  
Transition Zone ◽  
Continental Margin ◽  
Gravity Data ◽  
Beaufort Sea ◽  
Continental Margins ◽  
Banks Island ◽  
Basement Rocks ◽  
Area North ◽  
Free Air Anomaly ◽  
Gravity Map

An airlifted gravity survey was conducted in 1968 in the Beaufort Sea between Barter Island and Banks Island, south into the Mackenzie River Delta area and northward to about 74° latitude. The 1968 gravity data were combined with data from previous airlifted surveys and ice island T‐3. The major feature of the free‐air anomaly gravity map of this area is a more or less continuous 100 mgal high paralleling the coast from Barrow, Alaska, to the edge of the survey area north of Banks Island. The gravity high is explained by a thinning of the crust and a ridge in the basement rocks at about the 200 m isobath. This linear anomaly is broken by saddles off the Colville, Mackenzie, and Bernard Rivers, which are interpreted to reflect sedimentary fans built by the discharge of these rivers. Two‐dimensional crustal models constructed from gravity profiles indicate a narrow transition zone from ocean to continental crustal thickness, 55 km to 100 km shoreward of the 2000 m isobath. In a review of continental margin structure, Worzel (1968) found the transition zone to be centered under the 2000 m isobath. The departure from “normal” in the Beaufort Sea area may be explained by a greater accumulation of sediments seaward of the “structural” continental margins. This accumulation implies a faster rate of sedimentation and/or a greater age for the Beaufort Sea continental margins than for those analyzed by Worzel.

Ocean Subduction Dynamics in the Alps

Elements ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 9-16
Author(s):  
Philippe Agard ◽  
Mark R. Handy
Keyword(s):  
Transition Zone ◽  
Continental Margin ◽  
North Atlantic ◽  
Subduction Zones ◽  
Mantle Transition Zone ◽  
Continental Subduction ◽  
The Alps ◽  
Slow Spreading ◽  
Selective Preservation

The Alps preserve abundant oceanic blueschists and eclogites that exemplify the selective preservation of fragments of relatively short-lived, small, slow-spreading North Atlantic–type ocean basins whose subducting slabs reach down to the Mantle Transition Zone at most. Whereas no subducted fragments were returned during the first half of the subduction history, those exhumed afterwards experienced conditions typical of mature subduction zones worldwide. Sedimentary-dominated units were under-plated intermittently, mostly at ~30–40 km depth. Some mafic–ultramafic-dominated units formed close to the continent were subducted to ~80 km and offscraped from the slab only a few million years before continental subduction. Spatiotemporal contrasts in burial and preservation of the fragments reveal how along-strike segmentation of the continental margin affects ocean subduction dynamics.

scholarly journals Anaerobic oxidation of methane in grassland soils used for cattle husbandry

2012 ◽  
Vol 9 (10) ◽  
pp. 3891-3899 ◽  
Author(s):  
A. Bannert ◽  
C. Bogen ◽  
J. Esperschütz ◽  
A. Koubová ◽  
F. Buegger ◽  
...  
Keyword(s):  
Methane Oxidation ◽  
Enrichment Culture ◽  
Anaerobic Oxidation Of Methane ◽  
Anaerobic Oxidation ◽  
Incubation Experiment ◽  
Nutrient Source ◽  
Oxidation Activity ◽  
Oxidation Of Methane ◽  
Cattle Husbandry

Abstract. While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore, anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using 13C-labelled methane. We were able to detect a high microbial activity utilizing CH4 as nutrient source shown by the respiration of 13CO2. Measurements of possible terminal electron acceptors for anaerobic oxidation of methane were carried out. Soil sulfate concentrations were too low to explain the oxidation of the amount of methane added, but enough nitrate and iron(III) were detected. However, only nitrate was consumed during the experiment. 13C-PLFA analyses clearly showed the utilization of CH4 as nutrient source mainly by organisms harbouring 16:1ω7 PLFAs. These lipids were also found as most 13C-enriched fatty acids by Raghoebarsing et al. (2006) after addition of 13CH4 to an enrichment culture coupling denitrification of nitrate to anaerobic oxidation of methane. This might be an indication for anaerobic oxidation of methane by relatives of "Candidatus Methylomirabilis oxyfera" in the investigated grassland soil under the conditions of the incubation experiment.

scholarly journals Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments

2019 ◽  
Vol 85 (14) ◽  
Author(s):  
J. Buongiorno ◽  
L. C. Herbert ◽  
L. M. Wehrmann ◽  
A. B. Michaud ◽  
K. Laufer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Sulfate Reduction ◽  
The Arctic ◽  
Sulfur Cycling ◽  
Glacial Retreat ◽  
Sulfate Reducing ◽  
Glacial Runoff ◽  
Sulfate Reduction Rates ◽  
Fjord Sediments

ABSTRACTGlacial retreat is changing biogeochemical cycling in the Arctic, where glacial runoff contributes iron for oceanic shelf primary production. We hypothesize that in Svalbard fjords, microbes catalyze intense iron and sulfur cycling in low-organic-matter sediments. This is because low organic matter limits sulfide generation, allowing iron mobility to the water column instead of precipitation as iron monosulfides. In this study, we tested this with high-depth-resolution 16S rRNA gene libraries in the upper 20 cm at two sites in Van Keulenfjorden, Svalbard. At the site closer to the glaciers, iron-reducingDesulfuromonadales, iron-oxidizingGallionellaandMariprofundus, and sulfur-oxidizingThiotrichalesandEpsilonproteobacteriawere abundant above a 12-cm depth. Below this depth, the relative abundances of sequences for sulfate-reducingDesulfobacteraceaeandDesulfobulbaceaeincreased. At the outer station, the switch from iron-cycling clades to sulfate reducers occurred at shallower depths (∼5 cm), corresponding to higher sulfate reduction rates. Relatively labile organic matter (shown by δ13C and C/N ratios) was more abundant at this outer site, and ordination analysis suggested that this affected microbial community structure in surface sediments. Network analysis revealed more correlations between predicted iron- and sulfur-cycling taxa and with uncultured clades proximal to the glacier. Together, these results suggest that complex microbial communities catalyze redox cycling of iron and sulfur, especially closer to the glacier, where sulfate reduction is limited due to low availability of organic matter. Diminished sulfate reduction in upper sediments enables iron to flux into the overlying water, where it may be transported to the shelf.IMPORTANCEGlacial runoff is a key source of iron for primary production in the Arctic. In the fjords of the Svalbard archipelago, glacial retreat is predicted to stimulate phytoplankton blooms that were previously restricted to outer margins. Decreased sediment delivery and enhanced primary production have been hypothesized to alter sediment biogeochemistry, wherein any free reduced iron that could potentially be delivered to the shelf will instead become buried with sulfide generated through microbial sulfate reduction. We support this hypothesis with sequencing data that showed increases in the relative abundance of sulfate reducing taxa and sulfate reduction rates with increasing distance from the glaciers in Van Keulenfjorden, Svalbard. Community structure was driven by organic geochemistry, suggesting that enhanced input of organic material will stimulate sulfate reduction in interior fjord sediments as glaciers continue to recede.

scholarly journals Trace methane oxidation and the methane dependency of sulfate reduction in anaerobic granular sludge

2010 ◽  
Vol 72 (2) ◽  
pp. 261-271 ◽  
Author(s):  
Roel J.W. Meulepas ◽  
Christian G. Jagersma ◽  
Yu Zhang ◽  
Michele Petrillo ◽  
Hengzhe Cai ◽  
...  
Keyword(s):  
Sulfate Reduction ◽  
Methane Oxidation ◽  
Granular Sludge ◽  
Anaerobic Granular Sludge

scholarly journals Contrasting Pathways for Anaerobic Methane Oxidation in Gulf of Mexico Cold Seep Sediments

mSystems ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Adrien Vigneron ◽  
Eric B. Alsop ◽  
Perrine Cruaud ◽  
Gwenaelle Philibert ◽  
Benjamin King ◽  
...  
Keyword(s):  
Gene Expression ◽  
Electron Transfer ◽  
Gulf Of Mexico ◽  
Microbial Communities ◽  
Sulfate Reduction ◽  
Methane Oxidation ◽  
Sulfur Cycle ◽  
Anaerobic Methane Oxidation ◽  
Cold Seep ◽  
Biogenic Methane

ABSTRACTGulf of Mexico sediments harbor numerous hydrocarbon seeps associated with high sedimentation rates and thermal maturation of organic matter. These ecosystems host abundant and diverse microbial communities that directly or indirectly metabolize components of the emitted fluid. To investigate microbial function and activities in these ecosystems, metabolic potential (metagenomic) and gene expression (metatranscriptomic) analyses of two cold seep areas of the Gulf of Mexico were carried out. Seeps emitting biogenic methane harbored microbial communities dominated by archaeal anaerobic methane oxidizers of phylogenetic group 1 (ANME-1), whereas seeps producing fluids containing a complex mixture of thermogenic hydrocarbons were dominated by ANME-2 lineages. Metatranscriptome measurements in both communities indicated high levels of expression of genes for methane metabolism despite their distinct microbial communities and hydrocarbon composition. In contrast, the transcription level of sulfur cycle genes was quite different. In the thermogenic seep community, high levels of transcripts indicative of syntrophic anaerobic oxidation of methane (AOM) coupled to sulfate reduction were detected. This syntrophic partnership between the dominant ANME-2 and sulfate reducers potentially involves direct electron transfer through multiheme cytochromes. In the biogenic methane seep, genes from an ANME-1 lineage that are potentially involved in polysulfide reduction were highly expressed, suggesting a novel bacterium-independent anaerobic methane oxidation pathway coupled to polysulfide reduction. The observed divergence in AOM activities provides a new model for bacterium-independent AOM and emphasizes the variation that exists in AOM pathways between different ANME lineages.IMPORTANCECold seep sediments are complex and widespread marine ecosystems emitting large amounts of methane, a potent greenhouse gas, and other hydrocarbons. Within these sediments, microbial communities play crucial roles in production and degradation of hydrocarbons, modulating oil and gas emissions to seawater. Despite this ecological importance, our understanding of microbial functions and methane oxidation pathways in cold seep ecosystems is poor. Based on gene expression profiling of environmental seep sediment samples, the present work showed that (i) the composition of the emitted fluids shapes the microbial community in general and the anaerobic methanotroph community specifically and (ii) AOM by ANME-2 in this seep may be coupled to sulfate reduction byDeltaproteobacteriaby electron transfer through multiheme cytochromes, whereas AOM by ANME-1 lineages in this seep may involve a different, bacterium-independent pathway, coupling methane oxidation to elemental sulfur/polysulfide reduction.

Sign in / Sign up

Export Citation Format

Share Document