scholarly journals The Formation of Authigenic Carbonates at a Methane Seep Site in the Northern Part of the Laptev Sea

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 948
Author(s):  
Alexey Ruban ◽  
Maxim Rudmin ◽  
Oleg Dudarev ◽  
Alexey Mazurov
Keyword(s):  
Seawater Temperature ◽  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Laptev Sea ◽  
Cold Seeps ◽  
Authigenic Carbonates ◽  
Oxidation Of Methane ◽  
Major Oxide ◽  
Mg Content ◽  
The Laptev Sea

Authigenic carbonates from cold seeps are unique archives for studying environmental conditions, including biogeochemical processes associated with methane-rich fluid migration through the sediment column. The aim of this research was to study major oxide, mineralogical, and stable isotopic compositions of cold-seep authigenic carbonates collected in the northern part of the Laptev Sea. These carbonates are represented by Mg-calcite with an Mg content of 2% to 8%. The δ13C values range from −27.5‰ to −28.2‰ Vienna Peedee belemnite (VPDB) and indicate that carbonates formed due to anaerobic oxidation of methane, most likely thermogenic in origin. The authigenic pyrite in Mg-calcite is evidence of sulfate reduction during carbonate precipitation. The δ18O values of carbonates vary from 3.5‰ to 3.8‰ VPDB. The calculated δ18Ofluid values show that pore water temperature for precipitated Mg-calcite was comparable to bottom seawater temperature. The presence of authigenic carbonate in the upper horizons of sediments suggests that the sulfate–methane transition zone is shallowly below the sediment–water interface.

scholarly journals Phosphorus Species in Deep-Sea Carbonate Deposits: Implications for Phosphorus Cycling in Cold Seep Environments

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 645
Author(s):  
Junlie Zhou ◽  
Mengran Du ◽  
Jiwei Li ◽  
Hengchao Xu ◽  
Kaiwen Ta ◽  
...  
Keyword(s):  
Deep Sea ◽  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Organic P ◽  
Anaerobic Oxidation ◽  
Phosphorus Species ◽  
China Sea ◽  
Oxidation Of Methane ◽  
Deep Sediments

Phosphorus (P) is an important nutrient for biological communities in cold seeps. However, our knowledge on the source, species, and cycling of P in cold seep environments is limited. In this study, the concentration, species, and micro to nanometer scale distribution of P in seep carbonates were examined at three deep-sea cold seeps in the South China Sea and East China Sea. The Ca-P accounts for the largest proportion of P—followed by detrital-P, Fe-P, organic-P, and exchangeable-P. The distribution patterns of Ca-P, detrital-P, and organic-P in the seep carbonates differ from one another, as shown by elemental mapping with NanoSIMS and scanning electron microscopy. The covariation of P with Ca and C reveals that Ca-P co-precipitates with Ca-carbonate, which is linked to the process of sulfate-driven anaerobic oxidation of methane. Organic-P is also observed within biofilm-like organic carbon aggregates, revealing the microbial enrichment of P by fluids in the process of anaerobic oxidation of methane. P with a granulated morphology was identified as detrital-P derived from deep sediments. Most importantly, it is evident that Ca-P is positively correlated to the Fe content in all the seep carbonates. This indicates the likelihood that the dissolved P in cold-seep fluids is released primarily from Fe oxides through Fe-driven anaerobic oxidation of methane in deep sediments. These processes associated with different species of P may have significant implications for P geochemical cycling and anaerobic oxidation of methane impelled by Fe and sulfate reduction in cold seep environments.

scholarly journals Evidence for an expanded repertoire of electron acceptors for the anaerobic oxidation of methane in authigenic carbonates in the Atlantic and Pacific Ocean

2020 ◽  
Author(s):  
Sabrina Beckmann ◽  
Ibrahim F. Farag ◽  
Rui Zhao ◽  
Glenn D Christman ◽  
Nancy G Prouty ◽  
...  
Keyword(s):  
Electron Acceptors ◽  
Nitrogen Compounds ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Authigenic Carbonates ◽  
Sulfate Reducing ◽  
Oxidation Of Methane ◽  
The Pacific ◽  
Pacific Margin ◽  
Sulfur And Nitrogen Compounds

AbstractAuthigenic carbonates represent a significant microbial sink for methane, yet little is known about the microbiome responsible for the methane removal. We identify carbonate microbiomes distributed over 21 locations hosted by 7 different cold seeps in the Pacific and Atlantic Oceans by carrying out a gene-based survey using 16S rRNA- and mcrA gene sequencing coupled with metagenomic analyses. These sites were dominated by bacteria affiliated to the Firmicutes, Alpha- and Gammaproteobacteria. ANME-1 and −2 clades were abundant in the carbonates yet their typical syntrophic partners, sulfate reducing bacteria, were not significantly present. Our analysis indicated that methane oxidizers affiliated to the ANME-1 and −2 as well as to the Candidatus Methanoperedens clades, are capable of performing complete methane- and potentially short-chain alkane oxidations independently using oxidized sulfur and nitrogen compounds as terminal electron acceptors. Gammaproteobacteria are hypothetically capable of utilizing oxidized nitrogen compounds in potential syntrophy with methane oxidizing archaea. Carbonate structures represent a window for a more diverse utilization of electron acceptors for anaerobic methane oxidation along the Atlantic and Pacific Margin.

scholarly journals An experimental study on short-term changes in the anaerobic oxidation of methane in response to varying methane and sulfate fluxes

2009 ◽  
Vol 6 (5) ◽  
pp. 867-876 ◽  
Author(s):  
G. Wegener ◽  
A. Boetius
Keyword(s):  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Anaerobic Oxidation ◽  
Short Term ◽  
Sulfate Reducing ◽  
Oxidation Of Methane ◽  
Column System ◽  
Methane Fluxes ◽  
Anaerobic Methanotrophs

Abstract. A major role in regulation of global methane fluxes has been attributed to the process of anaerobic oxidation of methane (AOM), which is performed by consortia of methanotrophic archaea and sulfate reducing bacteria. An important question remains how these energy limited, slow growing microorganisms with generation times of 3–7 months respond to rapid natural variations in methane fluxes at cold seeps. We used an experimental flow-through column system filled with cold seep sediments naturally enriched in methanotrophic communities, to test their responses to short-term variations in methane and sulfate fluxes. At stable methane and sulfate concentrations of ~2 mM and 28 mM, respectively, we measured constant rates of AOM and sulfate reduction (SR) for up to 160 days of incubation. When percolated with methane-free medium, the anaerobic methanotrophs ceased to produce sulfide. After a starvation phase of 40 days, the addition of methane restored former AOM and SR rates immediately. At methane concentrations between 0–2.3 mM we measured a linear correlation between methane availability, AOM and SR. At constant fluid flow velocities of 30 m yr−1, ca. 50% of the methane was consumed by the anaerobic methanotrophic (ANME) population at all concentrations tested. Reducing the sulfate concentration from 28 to 1 mM, a decrease in AOM and SR by 50% was observed, and 45% of the methane was consumed. Hence, the marine anaerobic methanotrophs (ANME) are capable of oxidizing substantial amounts of methane over a wide and variable range of fluxes of the reaction educts.

scholarly journals Microbial activity and carbonate isotope signatures as a tool for identification of spatial differences in methane advection: a case study at the Pacific Costa Rican margin

2014 ◽  
Vol 11 (2) ◽  
pp. 507-523 ◽  
Author(s):  
S. Krause ◽  
P. Steeb ◽  
C. Hensen ◽  
V. Liebetrau ◽  
A. W. Dale ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Microbial Activity ◽  
Methane Flux ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Authigenic Carbonates ◽  
Biogenic Methane ◽  
Oxygen And Carbon Isotope ◽  
Oxidation Of Methane ◽  
Methane Fluxes

Abstract. The forearc of the convergent margin offshore Costa Rica is a region characterized by strong advection of methane-charged fluids causing the formation of ubiquitous cold seeps (mounds). Presented here are the first measurements of microbial anaerobic oxidation of methane (AOM) and sulfate reduction (SR) rates in sediments from two mounds (11 and 12), applying radiotracer techniques in combination with numerical modelling. In addition, analysis of microbial, methane-dependent carbonate δ18O, δ13C, and 87Sr / 86Sr signatures constrained the origin of the carbonate-precipitating fluid. Average rates of microbial activities differed by a factor of ~5 to 6 between Mound 11 (AOM 140.71 (±40.84 SD) mmol m−2 d−1, SR 117.25 (±82.06 SD) mmol m−2 d−1) and Mound 12 (AOM 22.37 (±0.85 SD) mmol m−2 d−1, SR 23.99 (±5.79 SD) mmol m−2 d−1). Modelling results yielded upward fluid advection velocities of 200 cm yr−1 at Mound 11 and 15 cm yr−1 at Mound 12. Analysis of oxygen and carbon isotope variations of authigenic carbonates from the two locations revealed more enriched values for Mound 11 (δ18O : 3.18 to 6.15‰; δ13C: −14.14 to −29.56‰) compared to Mound 12 (δ18O : 3.09 to 4.48‰; δ13C : −39.53 to −48.98‰). The variation of carbonate 87Sr / 86Sr indicated considerable admixture of deep-source fluid at Mound 11, while seawater 87Sr / 86Sr characteristics prevailed at Mound 12 during precipitation. The present study is in accordance with previous work supporting considerable differences of methane flux between the two mounds. It also strengthens the hypothesis of a dominant deep fluid source with thermogenic methane at Mound 11 versus a shallow source of biogenic methane at Mound 12. The results demonstrate that measurements of methane-driven microbial activity in combination with numerical modelling are a valid tool for constraining recent methane fluxes in the study area. In addition, the analysis of methane-derived authigenic carbonates provides an independent line of evidence for long-term fluid contribution to the porewater chemistry of shallow sediments in the study area.

scholarly journals Short-term changes in anaerobic oxidation of methane in response to varying methane and sulfate fluxes

2008 ◽  
Vol 5 (4) ◽  
pp. 3069-3090 ◽  
Author(s):  
G. Wegener ◽  
A. Boetius
Keyword(s):  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
Anaerobic Oxidation ◽  
Short Term ◽  
Oxidation Of Methane ◽  
Column System ◽  
Wide Range ◽  
Methane Fluxes ◽  
Anaerobic Methanotrophs

Abstract. A major role in global methane fluxes has been attributed to the process of anaerobic oxidation of methane, which is performed by consortia of methanotrophic archaea and sulfate reducing bacteria. An important question remains how these very slow growing microorganisms with generation times of 3–7 months respond to natural variations in methane fluxes at cold seeps. Here, we used an experimental flow-through column system filled with cold seep sediments naturally enriched in methanotrophic communities, to test their response to short-term variations in methane and sulfate fluxes. At stable methane and sulfate concentrations of ~2 mM and 28 mM, respectively, we measured constant rates of anaerobic oxidation of methane (AOM) and sulfide production (SR) for up to 160 days of incubation. When percolated with methane-free medium, the anaerobic methanotrophs ceased to oxidize methane and to produce sulfide. After a starvation phase of 40 days, the addition of methane restored former AOM and SR rates immediately. At methane concentrations between 0–2.3 mM we measured a linear correlation between methane availability, AOM and SR. At constant fluid flow rates of 30 m yr−1, ca. 50% of the methane was consumed by the ANME population at all concentrations tested. Reducing the sulfate concentration from 28 to 1 mM, a decrease in AOM and SR by 35% was observed. Hence, the marine anaerobic methanotrophs (ANME) are capable to consume substantial amounts of methane rising from the subsurface seabed to the hydrosphere over a wide range of fluxes of methane and sulfate.

scholarly journals Anaerobic oxidation of methane in hypersaline cold seep sediments

2012 ◽  
Vol 83 (1) ◽  
pp. 214-231 ◽  
Author(s):  
Loïs Maignien ◽  
R. John Parkes ◽  
Barry Cragg ◽  
Helge Niemann ◽  
Katrin Knittel ◽  
...  
Keyword(s):  
Cold Seep ◽  
Anaerobic Oxidation Of Methane ◽  
Anaerobic Oxidation ◽  
Oxidation Of Methane

scholarly journals Miniaturized biosignature analysis reveals implications for the formation of cold seep carbonates at Hydrate Ridge (off Oregon, USA)

2007 ◽  
Vol 4 (6) ◽  
pp. 4443-4458 ◽  
Author(s):  
T. Leefmann ◽  
J. Bauermeister ◽  
A. Kronz ◽  
V. Liebetrau ◽  
J. Reitner ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Cold Seep ◽  
Chemical Compositions ◽  
Anaerobic Oxidation Of Methane ◽  
Oxidation Of Methane ◽  
Hydrate Ridge ◽  
The Individual ◽  
A Minor ◽  
Relationship Of ◽  
The Relationship

Abstract. Methane-related carbonates from Hydrate Ridge typically show several macroscopically distinguishable phases, namely whitish aragonite, lucent aragonite, and gray micrite. The relationship of these phases to particular microorganisms or biogeochemical processes is as yet unclear. We used a miniaturized biomarker technique on mg samples, combined with factor analysis and subsequent electron microprobe analysis, to study lipid biomarkers and chemical compositions of the individual phases. This allows us to identify particular mechanisms involved in the formation of the different carbonate precipitates. Our combined analysis of biomarkers and petrographic traits shows that most of the lipids related to the anaerobic oxidation of methane (>90% by weight) are concentrated within only a minor compartment (~20% by volume) of the Hydrate Ridge carbonates (whitish aragonite). The patterns indicate that the whitish aragonite represents fossilized biofilms of methanotrophic consortia, whereas the precipitation of the lucent aragonite does not seem to be directly controlled by microorganisms. The gray micrite shows a partly Mg-calcitic mineralogy, higher pyrite contents, and a much higher proportion of allochthonous biomarkers. The formation of these precipitates is interpreted to reflect periodic methane-rich fluid pulses that disrupted the sediments and promoted the growth of the respective methanotrophic consortia along fluid pathways.

scholarly journals Methane emission and consumption at a North Sea gas seep (Tommeliten area)

2005 ◽  
Vol 2 (4) ◽  
pp. 1197-1241 ◽  
Author(s):  
H. Niemann ◽  
M. Elvert ◽  
M. Hovland ◽  
B. Orcutt ◽  
A. Judd ◽  
...  
Keyword(s):  
North Sea ◽  
Oil And Gas ◽  
Salt Diapir ◽  
Anaerobic Oxidation Of Methane ◽  
Cold Seeps ◽  
The North ◽  
Oxidation Of Methane ◽  
Phylogenetic Cluster ◽  
Carbonate Formation ◽  
Gas Seepage

Abstract. The North Sea hosts large coal, oil and gas reservoirs of commercial value. Natural leakage pathways of subsurface gas to the hydrosphere have been recognized during geological surveys (Hovland and Judd, 1988). The Tommeliten seepage area is part of the Greater Ekofisk area, which is situated above the Tommeliten Delta salt diapir in the central North Sea. In this study, we report of an active seep site (56°29.90'N, 2°59.80'E) located in the Tommeliten area, Norwegian Block 1/9, at 75 m water depth. Here, cracks in a buried marl horizon allow methane to migrate into overlying clay-silt and sandy sediments. Hydroacoustic sediment echosounding showed several venting spots coinciding with the apex of marl domes where methane is released into the water column and potentially to the atmosphere during deep mixing situations. In the vicinity of the gas seeps, sea floor observations showed small mats of giant sulphide-oxidizing bacteria above patches of black sediments and carbonate crusts, which are exposed 10 to 50 cm above seafloor forming small reefs. These Methane-Derived Authigenic Carbonates (MDACs) contain 13C-depleted, archaeal lipids indicating previous gas seepage and AOM activity. High amounts of sn2-hydroxyarchaeol relative to archaeol and low abundances of biphytanes in the crusts give evidence that ANaerobic MEthane-oxidising archaea (ANME) of the phylogenetic cluster ANME-2 were the potential mediators of Anaerobic Oxidation of Methane (AOM) at the time of carbonate formation. Small pieces of MDACs were also found subsurface at about 1.7 m sediment depth, associated with the Sulphate-Methane Transition Zone (SMTZ). The SMTZ of Tommeliten is characterized by elevated AOM and Sulphate Reduction (SR) rates, increased concentrations of 13C-depleted tetraether derived biphytanes, and specific bacterial Fatty Acids (FA). Further biomarker and 16S rDNA based analyses give evidence that AOM at the Tommeliten SMTZ is mediated by archaea belonging to the ANME-1b group and Sulphate Reducing Bacteria (SRB) most likely belonging to the Seep-SRB1 cluster. The zone of active methane consumption was restricted to a distinct horizon of about 20 cm. Concentrations of 13C-depleted lipid biomarkers (e.g. 500 ng g-dw-1 biphythanes, 140 ng g-dw-1 fatty acid ai-C15:0), cell numbers (1.5x108 cells cm-3), AOM and SR rates (3 nmol cm-3 d-1 in the SMTZ are 2-3 orders of magnitude lower compared to AOM zones of highly active cold seeps such as Hydrate Ridge or the Gulf of Mexico.

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