Composition and fate of terrigenous organic matter along the Arctic land-ocean continuum in East Siberia

Insights from biomarkers and carbon isotopes

Tommaso Tesi, Igor Semiletov, Gustaf Hugelius, Oleg Dudarev, Peter Kuhry, Örjan Gustafsson

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Climate warming is predicted to translocate terrigenous organic carbon (TerrOC) to the Arctic Ocean and affect the marine biogeochemistry at high latitudes. The magnitude of this translocation is currently unknown, so is the climate response. The fate of the remobilized TerrOC across the Arctic shelves represents an unconstrained component of this feedback. The present study investigated the fate of permafrost carbon along the land-ocean continuum by characterizing the TerrOC composition in three different terrestrial carbon pools from Siberian permafrost (surface organic rich horizon, mineral soil active layer, and Ice Complex deposit) and marine sediments collected on the extensive East Siberian Arctic Shelf (ESAS). High levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the Arctic Ocean. In ESAS sediments, comparison of these terrigenous biomarkers with other TerrOC proxies (bulk δ13C/δ14C and HMW lipid biomarkers) highlighted contrasting across-shelf trends. These differences could indicate that TerrOC in the ESAS is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport. In this reactive spectrum, lignin is the most reactive, decreasing up to three orders of magnitude from the inner- to the outer-shelf while the decrease of HMW wax lipid biomarkers was considerably less pronounced. Alternatively, degradation might be negligible while sediment sorting during the across-shelf transport could be the major physical forcing that redistributes different TerrOC pools characterized by different matrix-association.Despite the marked decrease shown by lignin, the fingerprint of lignin phenols such as the acid:aldehyde ratio of vanillyl and syringyl phenols showed a lack of any across-shelf trends and exhibited an extremely wide range of values in all terrestrial samples. By contrast, the 3,5-dihydroxybenzoic:vanillyl phenols ratio exhibited a clear across-shelf trend suggesting either increasing degradation with distance from the coast or TerrOC sorting along the sediment dispersal system. The ratio of syringyl:vanillyl phenols indicated that gymnosperm tissues are more important than angiosperm tissues in surface sediments, in particular off the Lena River mouth, consistent with the vegetation in its watershed. Conversely, the fingerprint of p-hydroxybenzenes suggests lack of substantial input of moss-derived material. Finally, autochthonous lipid- and protein-derived CuO reaction products displayed a strong along-shelf gradient likely reflecting the inflow of nutrient-rich Pacific waters from the Bering Strait that stimulate primary productivity in the eastern ESAS. In particular short-chain fatty acids showed a clear frontal/transition zone between Pacific-influenced and river-influenced waters approximately along the 160°E longitude. Considering the labile nature of phytoplankton, priming and co-metabolism processes might stimulate degradation of TerrOC in the easternmost region of the Siberian shelf. This study demonstrated the need to consider multiple TerrOC proxies at isotopic/molecular levels to differentiate the fate for different allocthonous components in Arctic sediments and the need to assess how these TerrOC pools are distributed in different density, size, and settling fractions to better discriminate between the extent of hydrodynamic sorting versus degradation.

Original languageEnglish
Pages (from-to)235-256
Number of pages22
JournalGeochimica et Cosmochimica Acta
Volume133
DOIs
Publication statusPublished - 15 May 2014
Externally publishedYes

Fingerprint

Carbon Isotopes
Biomarkers
Organic carbon
Biological materials
carbon isotope
biomarker
organic carbon
organic matter
Phenols
ocean
Chemical analysis
Sediments
Lignin
phenol
lignin
Sorting
sorting
Degradation
Permafrost
degradation

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Composition and fate of terrigenous organic matter along the Arctic land-ocean continuum in East Siberia : Insights from biomarkers and carbon isotopes. / Tesi, Tommaso; Semiletov, Igor; Hugelius, Gustaf; Dudarev, Oleg; Kuhry, Peter; Gustafsson, Örjan.

In: Geochimica et Cosmochimica Acta, Vol. 133, 15.05.2014, p. 235-256.

Research output: Contribution to journalArticle

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T1 - Composition and fate of terrigenous organic matter along the Arctic land-ocean continuum in East Siberia

T2 - Insights from biomarkers and carbon isotopes

AU - Tesi, Tommaso

AU - Semiletov, Igor

AU - Hugelius, Gustaf

AU - Dudarev, Oleg

AU - Kuhry, Peter

AU - Gustafsson, Örjan

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N2 - Climate warming is predicted to translocate terrigenous organic carbon (TerrOC) to the Arctic Ocean and affect the marine biogeochemistry at high latitudes. The magnitude of this translocation is currently unknown, so is the climate response. The fate of the remobilized TerrOC across the Arctic shelves represents an unconstrained component of this feedback. The present study investigated the fate of permafrost carbon along the land-ocean continuum by characterizing the TerrOC composition in three different terrestrial carbon pools from Siberian permafrost (surface organic rich horizon, mineral soil active layer, and Ice Complex deposit) and marine sediments collected on the extensive East Siberian Arctic Shelf (ESAS). High levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the Arctic Ocean. In ESAS sediments, comparison of these terrigenous biomarkers with other TerrOC proxies (bulk δ13C/δ14C and HMW lipid biomarkers) highlighted contrasting across-shelf trends. These differences could indicate that TerrOC in the ESAS is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport. In this reactive spectrum, lignin is the most reactive, decreasing up to three orders of magnitude from the inner- to the outer-shelf while the decrease of HMW wax lipid biomarkers was considerably less pronounced. Alternatively, degradation might be negligible while sediment sorting during the across-shelf transport could be the major physical forcing that redistributes different TerrOC pools characterized by different matrix-association.Despite the marked decrease shown by lignin, the fingerprint of lignin phenols such as the acid:aldehyde ratio of vanillyl and syringyl phenols showed a lack of any across-shelf trends and exhibited an extremely wide range of values in all terrestrial samples. By contrast, the 3,5-dihydroxybenzoic:vanillyl phenols ratio exhibited a clear across-shelf trend suggesting either increasing degradation with distance from the coast or TerrOC sorting along the sediment dispersal system. The ratio of syringyl:vanillyl phenols indicated that gymnosperm tissues are more important than angiosperm tissues in surface sediments, in particular off the Lena River mouth, consistent with the vegetation in its watershed. Conversely, the fingerprint of p-hydroxybenzenes suggests lack of substantial input of moss-derived material. Finally, autochthonous lipid- and protein-derived CuO reaction products displayed a strong along-shelf gradient likely reflecting the inflow of nutrient-rich Pacific waters from the Bering Strait that stimulate primary productivity in the eastern ESAS. In particular short-chain fatty acids showed a clear frontal/transition zone between Pacific-influenced and river-influenced waters approximately along the 160°E longitude. Considering the labile nature of phytoplankton, priming and co-metabolism processes might stimulate degradation of TerrOC in the easternmost region of the Siberian shelf. This study demonstrated the need to consider multiple TerrOC proxies at isotopic/molecular levels to differentiate the fate for different allocthonous components in Arctic sediments and the need to assess how these TerrOC pools are distributed in different density, size, and settling fractions to better discriminate between the extent of hydrodynamic sorting versus degradation.

AB - Climate warming is predicted to translocate terrigenous organic carbon (TerrOC) to the Arctic Ocean and affect the marine biogeochemistry at high latitudes. The magnitude of this translocation is currently unknown, so is the climate response. The fate of the remobilized TerrOC across the Arctic shelves represents an unconstrained component of this feedback. The present study investigated the fate of permafrost carbon along the land-ocean continuum by characterizing the TerrOC composition in three different terrestrial carbon pools from Siberian permafrost (surface organic rich horizon, mineral soil active layer, and Ice Complex deposit) and marine sediments collected on the extensive East Siberian Arctic Shelf (ESAS). High levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the Arctic Ocean. In ESAS sediments, comparison of these terrigenous biomarkers with other TerrOC proxies (bulk δ13C/δ14C and HMW lipid biomarkers) highlighted contrasting across-shelf trends. These differences could indicate that TerrOC in the ESAS is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport. In this reactive spectrum, lignin is the most reactive, decreasing up to three orders of magnitude from the inner- to the outer-shelf while the decrease of HMW wax lipid biomarkers was considerably less pronounced. Alternatively, degradation might be negligible while sediment sorting during the across-shelf transport could be the major physical forcing that redistributes different TerrOC pools characterized by different matrix-association.Despite the marked decrease shown by lignin, the fingerprint of lignin phenols such as the acid:aldehyde ratio of vanillyl and syringyl phenols showed a lack of any across-shelf trends and exhibited an extremely wide range of values in all terrestrial samples. By contrast, the 3,5-dihydroxybenzoic:vanillyl phenols ratio exhibited a clear across-shelf trend suggesting either increasing degradation with distance from the coast or TerrOC sorting along the sediment dispersal system. The ratio of syringyl:vanillyl phenols indicated that gymnosperm tissues are more important than angiosperm tissues in surface sediments, in particular off the Lena River mouth, consistent with the vegetation in its watershed. Conversely, the fingerprint of p-hydroxybenzenes suggests lack of substantial input of moss-derived material. Finally, autochthonous lipid- and protein-derived CuO reaction products displayed a strong along-shelf gradient likely reflecting the inflow of nutrient-rich Pacific waters from the Bering Strait that stimulate primary productivity in the eastern ESAS. In particular short-chain fatty acids showed a clear frontal/transition zone between Pacific-influenced and river-influenced waters approximately along the 160°E longitude. Considering the labile nature of phytoplankton, priming and co-metabolism processes might stimulate degradation of TerrOC in the easternmost region of the Siberian shelf. This study demonstrated the need to consider multiple TerrOC proxies at isotopic/molecular levels to differentiate the fate for different allocthonous components in Arctic sediments and the need to assess how these TerrOC pools are distributed in different density, size, and settling fractions to better discriminate between the extent of hydrodynamic sorting versus degradation.

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