scholarly journals Biotic and abiotic controls on co-occurring nitrogen cycling processes in shallow Arctic shelf sediments

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
N. D. McTigue ◽  
W. S. Gardner ◽  
K. H. Dunton ◽  
A. K. Hardison
Keyword(s):  
Nitrogen Cycling ◽  
Arctic Shelf ◽  
Shelf Sediments ◽  
Abiotic Controls

Summer and winter denitrification rates in western Arctic shelf sediments

1997 ◽  
Vol 17 (9) ◽  
pp. 1029-1050 ◽  
Author(s):  
Allan H Devol ◽  
Louis A Codispoti ◽  
John P Christensen
Keyword(s):  
Arctic Shelf ◽  
Shelf Sediments ◽  
Western Arctic

scholarly journals Microbial Community Diversity Associated with Carbon and Nitrogen Cycling in Permeable Shelf Sediments

2006 ◽  
Vol 72 (9) ◽  
pp. 5689-5701 ◽  
Author(s):  
Evan M. Hunter ◽  
Heath J. Mills ◽  
Joel E. Kostka
Keyword(s):  
Organic Matter ◽  
Nitrogen Cycling ◽  
Rrna Genes ◽  
Column Experiments ◽  
Ssu Rrna ◽  
Carbon And Nitrogen ◽  
Carbon And Nitrogen Cycling ◽  
In Situ Conditions ◽  
Shelf Sediments

ABSTRACT Though a large fraction of primary production and organic matter cycling in the oceans occurs on continental shelves dominated by sandy deposits, the microbial communities associated with permeable shelf sediments remain poorly characterized. Therefore, in this study, we provide the first detailed characterization of microbial diversity in marine sands of the South Atlantic Bight through parallel analyses of small-subunit (SSU) rRNA gene (Bacteria), nosZ (denitrifying bacteria), and amoA (ammonia-oxidizing bacteria) sequences. Communities were analyzed by parallel DNA extractions and clone library construction from both sediment core material and manipulated sediment within column experiments designed for geochemical rate determinations. Rapid organic-matter degradation and coupled nitrification-denitrification were observed in column experiments at flow rates resembling in situ conditions over a range of oxygen concentrations. Numerous SSU rRNA phylotypes were affiliated with the phyla Proteobacteria (classes Alpha-, Delta-, and Gammaproteobacteria), Planctomycetes, Cyanobacteria, Chloroflexi, and Bacteroidetes. Detectable sequence diversity of nosZ and SSU rRNA genes increased in stratified redox-stabilized columns compared to in situ sediments, with the Alphaproteobacteria comprising the most frequently detected group. Alternatively, nitrifier communities showed a relatively low and stable diversity that did not covary with the other gene targets. Our results elucidate predominant phylotypes that are likely to catalyze carbon and nitrogen cycling in marine sands. Although overall diversity increased in response to redox stabilization and stratification in column experiments, the major phylotypes remained the same in all of our libraries, indicating that the columns sufficiently mimic in situ conditions.

scholarly journals Assessing the potential for non-turbulent methane escape from the East Siberian Arctic Shelf

2019 ◽  
Author(s):  
Matteo Puglini ◽  
Victor Brovkin ◽  
Pierre Regnier ◽  
Sandra Arndt
Keyword(s):  
Gas Hydrate ◽  
Environmental Conditions ◽  
Arctic Shelf ◽  
Water Interface ◽  
Ch4 Flux ◽  
Methane Gas ◽  
Wide Range ◽  
Siberian Arctic ◽  
Shelf Sediments ◽  
Methane Efflux

Abstract. East Siberian Arctic Shelf (ESAS) hosts large, yet poorly quantified reservoirs of subsea permafrost and associated gas hydrates. It has been suggested the global-warming induced thawing and dissociation of these reservoirs is currently releasing methane to the shallow shelf ocean and ultimately the atmosphere. However, the exact contribution of permafrost thaw and methane gas hydrate destabilization to benthic methane efflux from the warming shelf and ultimately methane-climate feedbacks remains controversial. A major unknown is the fate of permafrost and/or gas hydrate-derived methane as it migrates towards the sediment-water interface. In marine sediments, (an)aerobic oxidation reactions generally act as extremely efficient biofilters that often consume close to 100 % of the upward migrating methane. However, it has been shown that a number of environmental conditions can reduce the efficiency of this biofilter, thus allowing methane to escape to the overlying ocean. Here, we used a reaction-transport model to assess the efficiency of the benthic methane filter and, thus, the potential for permafrost and/or gas hydrate derived methane to escape shelf sediments under a wide range of environmental conditions encountered on East Siberian Arctic Shelf. Results of an extensive sensitivity analysis show that, under steady state conditions, anaerobic oxidation of methane (AOM) acts as an efficient biofilter that prevents the escape of dissolved methane from shelf sediments for a wide range of environmental conditions. Yet, high CH4 escape comparable to fluxes reported from mud-volcanoes is simulated for rapidly accumulating (sedimentation rate > 0.7 cm yr−1) and/or active (active fluid flow > 6 cm yr−1) sediments and can be further enhanced by mid-range organic matter reactivity and/or intense local transport processes, such as bioirrigation. In active settings, high non-turbulent methane escape of up to 19 μmolCH4 cm−2 yr−1 can also occur during a transient, multi-decadal period following the sudden onset of CH4 flux triggered by, for instance, permafrost thaw or hydrate destabilization. This window of opportunity arises due to the time needed by the microbial community to build up an efficient AOM biofilter. In contrast, seasonal variations in environmental conditions (e.g. bottom water SO42−, CH4 flux) exert a negligible effect on CH4 efflux through the sediment-water interface. Our results indicate that present and future methane efflux from ESAS sediments is mainly supported by methane gas and non-turbulent CH4 efflux from rapidly accumulating and/or active sediments (e.g. coastal settings, portions close to river mouths or submarine slumps). In particular active sites on the ESAS may release methane in response to the onset or increase of permafrost thawing or CH4 gas hydrate destabilization rates. Model results also reveal that AOM generally acts as an efficient biofilter for upward migrating CH4 under environmental conditions that are representative for the present-day ESAS with potentially important, yet unquantified implications for the Arctic ocean's alkalinity budget and, thus, CO2 fluxes. The results of the model sensitivity study are used as a quantitative framework to derive first-order estimates of non-turbulent, benthic methane efflux from the Laptev Sea. We find that, under present day conditions, AOM is an efficient biofilter and non-turbulent methane efflux from Laptev Sea sediments does not exceed 1 GgCH4 yr−1. As a consequence, we state that previously published estimates of fluxes from ESAS water into atmosphere cannot be supported by non-turbulent methane escape from the sediments, but require the build-up and preferential escape of benthic methane gas from the sediments to the atmosphere that matches or even exceeds such estimated fluxes.

scholarly journals Fate of Terrigenous Nitrogen in East Siberian Arctic Shelf Sediments

2019 ◽  
Author(s):  
E. Burns ◽  
G. Wolff ◽  
R. Jeffreys ◽  
R. Sparkes ◽  
Ӧ. Gustafsson ◽  
...  
Keyword(s):  
Arctic Shelf ◽  
Siberian Arctic ◽  
Shelf Sediments

Anthropogenic Impact on Quantitative Differentiation of Nitrogen Cycling Bacteria in Waters of the Drwęca River

2008 ◽  
Vol 23 (3) ◽  
pp. 667-680 ◽  
Author(s):  
Iwona Gołaś ◽  
Izabella Zmysłowska ◽  
Monika Harnisz ◽  
Karol Korzekwa ◽  
Agnieszka Skowrońska ◽  
...  
Keyword(s):  
Nitrogen Cycling ◽  
Anthropogenic Impact

GEOINFORMATION SUPPORT OF HYDROCARBONS TRANSPORT FROM ARCTIC SHELF

2017 ◽  
Vol 12 ◽  
pp. 14-20
Author(s):  
S.S. Kubrin ◽  
◽  
S.N. Reshetnyak ◽  
A.A. Aleshin ◽  
◽  
...  
Keyword(s):  
Arctic Shelf

РRINCIPLES OF ONSHORE FACILITIES DESIGN FOR THE OBJECTS OF OIL AND GAS COMPLEX IN THE ARCTIC SHELF

2018 ◽  
pp. 62-68
Author(s):  
M.A. Magomedgadzhieva ◽  
◽  
G.S. Oganov ◽  
I.B. Mitrofanov ◽  
A.M. Karpov ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Arctic Shelf ◽  
The Arctic ◽  
Facilities Design
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