scholarly journals Transport and fate of different components of terrestrial organic matter across the Siberian-Arctic shelves

2020 ◽  
Author(s):  
Örjan Gustafsson ◽  
Igor Semiletov ◽  
Natalia Shakhova ◽  
Oleg Dudarev ◽  
Jorien Vonk ◽  
...  
Keyword(s):  
Organic Matter ◽  
Landscape Heterogeneity ◽  
Oxidation Products ◽  
Terrestrial Organic Matter ◽  
Inverse Approach ◽  
Degradation Rates ◽  
Siberian Arctic ◽  
Global Soil ◽  
Shelf Sea ◽  
Dependent Transport

<p>About one-third to half of the global soil carbon is held in the top 1-3 m of tundra+taiga permafrost PF (~1000 Pg-C) with deeper layers below as Deep-PF (~400 Pg-C) and in Pleistocene Ice Complex Deposit permafrost (ICD-PF, ~400 Pg-C), lining 4000 km of the East Siberian Arctic coast.  In order to overcome the landscape heterogeneity and the stochastic nature of e.g. erosional release processes, we use the East Siberian Arctic Shelf (ESAS) in an inverse approach – as a natural integrator of the TerrOM releases from both the river drainage basins and from the erosion of ICD-containing bluffs. We are exploring how source-dependent transport and translocated degradation affect the released TerrOM.</p><p> </p><p>The sources of released terrOM have been increasingly constrained using great rivers and the ESAS as natural integrators through a combination of biomarkers and δ<sup>13</sup>C/Δ<sup>14</sup>C on bulk-C and on compound level. There are significant gradients in sources both E-W and S-N across each shelf sea and between water column DOM, POM and sedimentary OM. The largest source of OC to ESAS sediments is not rivers or marine plankton – it is coastal erosion of old ICD.  Our initial limited dataset has now been much expanded, as has the end-member database while the statistical source apportionment method has been refined. They combine to show more efficient cross-shelf transport of river-borne “topsoil-PF” compared to ICD-PF and a clear distinction in sources of TerrOM between western and eastern ESAS regimes separated roughly along 165E, consistent with the local oceanography.</p><p>There have been good strides also in understanding degradation of TerrOM exported to ESAS. Studies are demonstrating continuous offshoreward degradation of all TerrOM, yet with large differences between compound classes. Physical association of TerrOM with different sediment components, and sorting of the sediments exert first-order control on TerrOM distribution and degradation. An expanded dataset on specific surface area (SSA) and CuO oxidation products reveals spatial patterns across ESAS. The combination of compound-specific radiocarbon analysis of terrestrial biomarkers with SSA-normalized TerrOM signals constrains the ambient degradation rates and fluxes during the 3-4000 year timescale of cross-shelf transport. The degradation of TerrOM also causes severe ocean acidification of the ESAS.</p><p>Investigations of sources and fate of TerrOM on the ESAS – the World’s largest shelf sea– provides a window to constrain permafrost-C remobilization and to study mechanisms of transport and degradability of different components of released terrestrial organic matter.</p>

scholarly journals Uncovering the gene machinery of the Amazon River microbiome to degrade rainforest organic matter

2019 ◽  
Author(s):  
Célio Dias Santos ◽  
Hugo Sarmento ◽  
Fernando Pellon de Miranda ◽  
Flávio Henrique-Silva ◽  
Ramiro Logares
Keyword(s):  
Organic Matter ◽  
Lignin Degradation ◽  
Amazon River ◽  
Spatial Distributions ◽  
Gene Repertoire ◽  
Terrestrial Organic Matter ◽  
Incubation Experiments ◽  
Degradation Rates ◽  
Redundant Genes ◽  
Gene Functions

ABSTRACTThe Amazon River receives, from the surrounding rainforest, huge amounts of terrestrial organic matter (TeOM), which is typically resistant to microbial degradation. However, only a small fraction of the TeOM ends up in the ocean, indicating that most of it is degraded in the river. So far, the nature of the genes involved in TeOM degradation and their spatial distributions are barely known. Here, we examined the Amazon River microbiome gene repertoire and found that it contains a substantial gene-novelty, compared to other environments (rivers and rainforest soil). We predicted ~3.7 million non-redundant genes, affiliating mostly to bacteria. The gene-functions involved in TeOM degradation revealed that lignin degradation correlated to tricarboxylates and hemicellulose processing, pointing to higher lignin degradation rates under consumption of labile compounds. We describe the biochemical machinery that could be speeding up the decomposition of recalcitrant compounds in Amazonian waters, previously reported only in incubation experiments.

scholarly journals Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf

2016 ◽  
Vol 10 (5) ◽  
pp. 2485-2500 ◽  
Author(s):  
Robert B. Sparkes ◽  
Ayça Doğrul Selver ◽  
Örjan Gustafsson ◽  
Igor P. Semiletov ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Organic Matter ◽  
Coastal Erosion ◽  
Principal Component ◽  
Arctic Shelf ◽  
The Arctic ◽  
Gas Chromatography Mass Spectrometry ◽  
Terrestrial Organic Matter ◽  
Pyrolysis Gas ◽  
Siberian Arctic ◽  
Extractable Organic Matter

Abstract. Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis–gas chromatography–mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r2 = 0.67, p < 0.01, n = 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (14COC) which, when coupled with previous measurements, allows us to produce the most comprehensive 14COC map of the ESAS to date. Combining the 14COC and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river–ocean transects of surface sediments transition from river-dominated to coastal-erosion-dominated to marine-dominated signatures.

scholarly journals Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment

2018 ◽  
Vol 15 (2) ◽  
pp. 471-490 ◽  
Author(s):  
Volker Brüchert ◽  
Lisa Bröder ◽  
Joanna E. Sawicka ◽  
Tommaso Tesi ◽  
Samantha P. Joye ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Mineralization ◽  
Laptev Sea ◽  
East Siberian Sea ◽  
Degradation Rates ◽  
Siberian Arctic ◽  
Sediment Carbon ◽  
The Laptev Sea ◽  
Carbon Contribution

Abstract. The Siberian Arctic Sea shelf and slope is a key region for the degradation of terrestrial organic material transported from the organic-carbon-rich permafrost regions of Siberia. We report on sediment carbon mineralization rates based on O2 microelectrode profiling; intact sediment core incubations; 35S-sulfate tracer experiments; pore-water dissolved inorganic carbon (DIC); δ13CDIC; and iron, manganese, and ammonium concentrations from 20 shelf and slope stations. This data set provides a spatial overview of sediment carbon mineralization rates and pathways over large parts of the outer Laptev and East Siberian Arctic shelf and slope and allows us to assess degradation rates and efficiency of carbon burial in these sediments. Rates of oxygen uptake and iron and manganese reduction were comparable to temperate shelf and slope environments, but bacterial sulfate reduction rates were comparatively low. In the topmost 50 cm of sediment, aerobic carbon mineralization dominated degradation and comprised on average 84 % of the depth-integrated carbon mineralization. Oxygen uptake rates and anaerobic carbon mineralization rates were higher in the eastern East Siberian Sea shelf compared to the Laptev Sea shelf. DIC ∕ NH4+ ratios in pore waters and the stable carbon isotope composition of remineralized DIC indicated that the degraded organic matter on the Siberian shelf and slope was a mixture of marine and terrestrial organic matter. Based on dual end-member calculations, the terrestrial organic carbon contribution varied between 32 and 36 %, with a higher contribution in the Laptev Sea than in the East Siberian Sea. Extrapolation of the measured degradation rates using isotope end-member apportionment over the outer shelf of the Laptev and East Siberian seas suggests that about 16 Tg C yr−1 is respired in the outer shelf seafloor sediment. Of the organic matter buried below the oxygen penetration depth, between 0.6 and 1.3 Tg C yr−1 is degraded by anaerobic processes, with a terrestrial organic carbon contribution ranging between 0.3 and 0.5 Tg yr−1.

scholarly journals Effect of terrestrial organic matter on ocean acidification and CO2 flux in an Arctic shelf sea

2020 ◽  
Vol 185 ◽  
pp. 102319
Author(s):  
David W. Capelle ◽  
Zou Zou A. Kuzyk ◽  
Tim Papakyriakou ◽  
Céline Guéguen ◽  
Lisa A. Miller ◽  
...  
Keyword(s):  
Organic Matter ◽  
Ocean Acidification ◽  
Co2 Flux ◽  
Arctic Shelf ◽  
Terrestrial Organic Matter ◽  
Shelf Sea

Source Constraints and Translocated Degradation of Terrestrial Organic Matter Using Siberian Arctic Shelves as Receptors

2019 ◽  
Author(s):  
Ö. Gustafsson ◽  
I.P. Semiletov ◽  
N. Shakhova ◽  
O. Dudarev ◽  
J. Vonk ◽  
...  
Keyword(s):  
Organic Matter ◽  
Terrestrial Organic Matter ◽  
Siberian Arctic

Multi-proxy evaluation of terrestrial organic matter degradation across the East Siberian Arctic Seas

2021 ◽  
Author(s):  
Felipe Matsubara ◽  
Birgit Wild ◽  
Jannik Martens ◽  
Rickard Wennström ◽  
Oleg Dudarev ◽  
...  
Keyword(s):  
Organic Matter ◽  
Coastal Erosion ◽  
River Discharge ◽  
The Arctic ◽  
Laptev Sea ◽  
Terrestrial Organic Matter ◽  
Arctic Seas ◽  
Transport Pathway ◽  
East Siberian Sea ◽  
Siberian Arctic

&lt;p&gt;&amp;#160; &amp;#160; Ongoing global warming is expected to accelerate the thaw of permafrost on land and to increase the input of terrigenous organic matter (terrOM) into the Arctic Ocean through coastal erosion and river discharge. Large remobilization of terrOM into the East Siberian Arctic Shelf (ESAS) dominates the organic matter in surface sediments over large parts of the shelf and its degradation contributes to ocean acidification. Previous studies have focused on the source apportionment of terrOM and the releases of CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; to the atmosphere from terrOM degradation; this study focuses on its diagenetic state during cross-shelf transport, since degradation is the link between permafrost thawing and greenhouse gases emissions. This study probes the degradation status of different terrOM components across the ESAS using various molecular and isotopic proxies and hence evaluates their differences to infer degradation.&lt;/p&gt;&lt;p&gt;&amp;#160; &amp;#160; High-molecular weight (HMW) lipid compounds and lignin phenols are exclusively produced by terrestrial plants, providing protection, strength and rigidity to the plant structure. Owing to diagenesis, microbial degradation leads to &lt;strong&gt;1)&lt;/strong&gt; &lt;strong&gt;loss of functional groups&lt;/strong&gt;, thus the ratios of HMW n-alkanoic acids, HMW n-alkanols and sterols relative to HMW n-alkanes decrease; &lt;strong&gt;2)&lt;/strong&gt; &lt;strong&gt;reduction of unsaturated to saturated carbons&lt;/strong&gt;, so ratios of stanols relative to stenols increase; &lt;strong&gt;3) a higher formation of carboxylic acids in the lignin polymer&lt;/strong&gt; and hence&lt;strong&gt; &lt;/strong&gt;ratios of acids to aldehydes of vanillyl (Vd and Vl) and syringyl (Sd and Sl) increase.&lt;/p&gt;&lt;p&gt;&amp;#160; &amp;#160; The concentrations of lipid- and lignin-derived products per sediment specific surface area decreased with offshore distance of the samples. During cross-shelf transport, the biomarker degradation proxies showed an increasing degradation for Sd/Sl, Vd/Vl, the &amp;#8220;tannin-like&amp;#8221; compound 3,5-dihydrobenzoic acid to vanillyl (3,5-Bd/V), &amp;#946;-sitostanol/ &amp;#946;-sitostenol and Carbon Preference Index (CPI) of HMW n-alkanes. Some other proxies showed no clear trend from inner to outer shelf and such inconsistent patterns are currently being investigated to better understand both the usefulness/response of different proxies and of the lability of terrOM in the ESAS. While &amp;#946;-sitostanol/&amp;#946;-sitostenol and CPI HMW n-alkane did not show strong differences between the East Siberian Sea and the Laptev Sea, Vd/Vl and Sd/Sl ratios indicated stronger degradation on the outer Laptev Sea and 3,5-Bd/V ratios indicated stronger degradation in the outer eastern East Siberian Sea. Such differences could reflect source properties of terrOM entering the ESAS, such as differences in source vegetation or transport pathway, i.e. coastal erosion or river discharge.&lt;/p&gt;

scholarly journals Carbon mineralization in Laptev and East Siberian Sea shelf and slope sediment

2017 ◽  
Author(s):  
Volker Brüchert ◽  
Lisa Bröder ◽  
Joanna E. Sawicka ◽  
Tommaso Tesi ◽  
Samantha P. Joye ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Mineralization ◽  
East Siberian Sea ◽  
Degradation Rates ◽  
Siberian Arctic ◽  
Sulfate Reduction Rates ◽  
Sediment Carbon ◽  
The Laptev Sea ◽  
Carbon Contribution

Abstract. The Siberian Arctic Sea shelf and slope is a key region for the degradation of terrestrial organic material transported from the organic carbon-rich permafrost regions of Siberia. We report on sediment carbon mineralization rates based on O2 microelectrode profiling, intact sediment core incubations, 35S-sulfate tracer experiments, porewater dissolved inorganic carbon (DIC), δ13CDIC, and iron, manganese, and ammonium concentrations from 20 shelf and slope stations. This data set provides a spatial overview of sediment carbon mineralization rates and pathways over large parts of the outer Laptev and East Siberian Arctic shelf and slope, and allowed us to assess degradation rates and efficiency of carbon burial in these sediments. Rates of oxygen uptake and iron and manganese reduction were comparable to temperate shelf and slope environments, but bacterial sulfate reduction rates were comparatively low. In the topmost 20 to 50 cm of sediment, aerobic carbon mineralization dominated degradation and comprised on average 82 % of the depth-integrated carbon mineralization. Oxygen uptake rates and 35S-sulfate reduction rates were higher in the eastern East Siberian Sea shelf compared to the Laptev Sea shelf. DIC/NH4+ ratios in porewaters and the stable carbon isotope composition of remineralized DIC indicated that the degraded organic matter on the Siberian shelf and slope was a mixture of marine and terrestrial organic matter. Based on dual end member calculations, the terrestrial organic carbon contribution varied between 32 % and 36 %, with a higher contribution in the Laptev Sea than in the East Siberian Sea. Extrapolation of the measured degradation rates using isotope end member apportionment over the outer shelf of the Laptev and East Siberian Sea suggests that about 16 Tg C per year are respired in the outer shelf sea floor sediment. Of the organic matter buried below the oxygen penetration depth, between 0.6 and 1.3 Tg C per year are degraded by anaerobic processes, with a terrestrial organic carbon contribution ranging between 0.3 and 0.5 Tg per year.

scholarly journals Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf

2016 ◽  
Author(s):  
Robert B. Sparkes ◽  
Ayça Dogrul Selver ◽  
Örjan Gustafsson ◽  
Igor P. Semiletov ◽  
Negar Haghipour ◽  
...  
Keyword(s):  
Organic Matter ◽  
Coastal Erosion ◽  
Principal Component ◽  
Arctic Shelf ◽  
The Arctic ◽  
Gas Chromatography Mass Spectrometry ◽  
Terrestrial Organic Matter ◽  
Pyrolysis Gas ◽  
Siberian Arctic ◽  
Extractable Organic Matter

Abstract. Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in Eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport, or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis gas chromatography mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial Phenols, Aromatics, Cyclopentenones to marine Pyridines. There is good agreement between proportion Phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r2 = 0.67, p < 0.01, n = 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (14COC) which, when coupled with previous measurements, allows us to produce the most comprehensive 14COC map of the ESAS to date. Combining the 14COC and py-GCMS data suggests that the Aromatics group of compounds is likely sourced from old, aged terrOC in contrast to the Phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of Phenols and Pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastal erosion-dominated to marine-dominated signatures.

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