Increases in temperature and nutrient availability positively affect methane‐cycling microorganisms in Arctic thermokarst lake sediments

Abstract. This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m−2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions was suggested. This shift was likely promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

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Organic carbon characteristics in yedoma and thermokarst deposits on Baldwin Peninsula, West-Alaska

10.5194/bg-2018-151 ◽

2018 ◽

Author(s):

Loeka L. Jongejans ◽

Jens Strauss ◽

Josefine Lenz ◽

Francien Peterse ◽

Kai Mangelsdorf ◽

...

Keyword(s):

Organic Carbon ◽

Lake Sediments ◽

Lake Basin ◽

Study Region ◽

Thermokarst Lake ◽

Discontinuous Permafrost ◽

Lipid Biomarker ◽

Biomarker Analysis ◽

Thawing Permafrost

Abstract. As Arctic warming continues and permafrost thaws, more soil and sedimentary organic carbon (OC) will be decomposed in northern high latitudes. Still, uncertainties remain in the quantity and quality of OC stored in different deposit types of permafrost landscapes. This study presents OC data from deep permafrost and lake deposits on the Baldwin Peninsula which is located in the southern portion of the continuous permafrost zone in West Alaska. Sediment samples from yedoma and drained thermokarst lake basin (DTLB) deposits as well as thermokarst lake sediments were analyzed for cryostratigraphical and biogeochemical parameters and their lipid biomarker composition to identify the size and quality of belowground OC pools in ice-rich permafrost on Baldwin Peninsula. We provide the first detailed characterization of yedoma deposits on Baldwin Peninsula. We show that three quarters of soil organic carbon in the frozen deposits of the study region (total of 68 Mt) is stored in DTLB deposits (52 Mt) and one quarter in the frozen yedoma deposits (16 Mt). The lake sediments contain a relatively small OC pool (4 Mt), but have the highest volumetric OC content (93 kg/m3) compared to the DTLB (35 kg/m3) and yedoma deposits (8 kg/m3), largely due to differences in the ground ice content. The biomarker analysis indicates that the OC in both yedoma and DTLB deposits is mainly of terrestrial origin. Nevertheless, the relatively high carbon preference index of plant leaf waxes in combination with a lack of degradation trend with depth in the yedoma deposits indicates that OC stored in yedoma is less degraded than that stored in DTLB deposits. This suggests that OC in yedoma has a higher potential for decomposition upon thaw, despite the relatively small size of this pool. These findings highlight the importance of molecular OC analysis for determining the potential future greenhouse gas emissions from thawing permafrost, especially because this area close to the discontinuous permafrost boundary is projected to thaw substantially within the 21st century.

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Thermokarst lake methanogenesis along a complete talik profile

Biogeosciences ◽

10.5194/bg-12-4317-2015 ◽

2015 ◽

Vol 12 (14) ◽

pp. 4317-4331 ◽

Cited By ~ 21

Author(s):

J. K. Heslop ◽

K. M. Walter Anthony ◽

A. Sepulveda-Jauregui ◽

K. Martinez-Cruz ◽

A. Bondurant ◽

...

Keyword(s):

Lake Sediments ◽

Relative Magnitude ◽

Thermokarst Lake ◽

Ch4 Production ◽

Lake Sediment Core ◽

Permafrost Soils ◽

Thawing Permafrost ◽

Top 40 ◽

Lake Systems

Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD: 5.95 ± 1.67 μg C–CH4 g dw−1 d−1; 125.9 ± 36.2 μg C–CH4 g C−1org d−1). High CH4 production potentials were also observed in recently thawed permafrost (1.18 ± 0.61 μg C–CH4g dw−1 d−1; 59.60± 51.5 μg C–CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawing in the talik for a longer period of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw and shore erosion of yedoma permafrost are important to lake CH4 production.

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Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska

Geobiology ◽

10.1111/gbi.12124 ◽

2015 ◽

Vol 13 (2) ◽

pp. 181-197 ◽

Cited By ~ 15

Author(s):

P. B. Matheus Carnevali ◽

M. Rohrssen ◽

M. R. Williams ◽

A. B. Michaud ◽

H. Adams ◽

...

Keyword(s):

Lake Sediments ◽

North Slope ◽

Thermokarst Lake ◽

The North ◽

North Slope Of Alaska

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Rapid climatic events as recorded in Middle Weichselian thermokarst lake sediments

Quaternary Science Reviews ◽

10.1016/j.quascirev.2007.09.017 ◽

2008 ◽

Vol 27 (1-2) ◽

pp. 162-174 ◽

Cited By ~ 23

Author(s):

S.J.P. Bohncke ◽

J.A.A. Bos ◽

S. Engels ◽

O. Heiri ◽

C. Kasse

Keyword(s):

Lake Sediments ◽

Thermokarst Lake

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Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

Biogeosciences Discussions ◽

10.5194/bgd-8-8845-2011 ◽

2011 ◽

Vol 8 (4) ◽

pp. 8845-8894

Author(s):

S. Audry ◽

O. S. Pokrovsky ◽

L. S. Shirokova ◽

S. N. Kirpotin ◽

B. Dupré

Keyword(s):

Trace Elements ◽

Organic Matter ◽

Organic Carbon ◽

Lake Sediments ◽

Water Column ◽

Western Siberia ◽

Ecosystem Development ◽

Thermokarst Lake ◽

Fe And Mn ◽

The Impact

Abstract. This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m−2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways was evidenced from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions. This shift was promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

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Organic matter characteristics in yedoma and thermokarst deposits on Baldwin Peninsula, west Alaska

Biogeosciences ◽

10.5194/bg-15-6033-2018 ◽

2018 ◽

Vol 15 (20) ◽

pp. 6033-6048 ◽

Cited By ~ 11

Author(s):

Loeka L. Jongejans ◽

Jens Strauss ◽

Josefine Lenz ◽

Francien Peterse ◽

Kai Mangelsdorf ◽

...

Keyword(s):

Organic Matter ◽

Lake Sediments ◽

Lake Basin ◽

Study Region ◽

Thermokarst Lake ◽

Discontinuous Permafrost ◽

Lipid Biomarker ◽

Biomarker Analysis ◽

Thawing Permafrost

Abstract. As Arctic warming continues and permafrost thaws, more soil and sedimentary organic matter (OM) will be decomposed in northern high latitudes. Still, uncertainties remain in the quality of the OM and the size of the organic carbon (OC) pools stored in different deposit types of permafrost landscapes. This study presents OM data from deep permafrost and lake deposits on the Baldwin Peninsula which is located in the southern portion of the continuous permafrost zone in west Alaska. Sediment samples from yedoma and drained thermokarst lake basin (DTLB) deposits as well as thermokarst lake sediments were analyzed for cryostratigraphical and biogeochemical parameters and their lipid biomarker composition to identify the belowground OC pool size and OM quality of ice-rich permafrost on the Baldwin Peninsula. We provide the first detailed characterization of yedoma deposits on Baldwin Peninsula. We show that three-quarters of soil OC in the frozen deposits of the study region (total of 68 Mt) is stored in DTLB deposits (52 Mt) and one-quarter in the frozen yedoma deposits (16 Mt). The lake sediments contain a relatively small OC pool (4 Mt), but have the highest volumetric OC content (93 kg m−3) compared to the DTLB (35 kg m−3) and yedoma deposits (8 kg m−3), largely due to differences in the ground ice content. The biomarker analysis indicates that the OM in both yedoma and DTLB deposits is mainly of terrestrial origin. Nevertheless, the relatively high carbon preference index of plant leaf waxes in combination with a lack of a degradation trend with depth in the yedoma deposits indicates that OM stored in yedoma is less degraded than that stored in DTLB deposits. This suggests that OM in yedoma has a higher potential for decomposition upon thaw, despite the relatively small size of this pool. These findings show that the use of lipid biomarker analysis is valuable in the assessment of the potential future greenhouse gas emissions from thawing permafrost, especially because this area, close to the discontinuous permafrost boundary, is projected to thaw substantially within the 21st century.

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