Radiocarbon Data Reveal Contrasting Sources for Carbon Fractions in Thermokarst Lakes and Rivers of Eastern Canada (Nunavik, Quebec)

Moguel, Regina Gonzalez; Bass, Adrian M.; Garnett, Mark H.; Pilote, Martin; Keenan, Benjamin; Matveev, Alex; Douglas, Peter

doi:10.1029/2020jg005938

Cited by 8 publications

(8 citation statements)

References 69 publications

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“…The radiocarbon age of DOC in the water (~ 3800 yr BP) was much older than DIC in the water column and the CO 2 and CH 4 in the bubbles, which is in line with previous peatland thaw lake studies (Gonzalez Moguel et al 2021). The 14 C–DOC age of the lake water closely resembles reported ages of DOC in the pore waters of nearby peat plateau active layers (Tanentzap et al 2021) and had a terrigenous stable carbon isotope (𝛿 13 C) value of −26.9‰ (Karlsson et al 2003), suggesting allochthonous origins.…”

Section: Discussionsupporting

confidence: 90%

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

Kuhn

Schmidt

Heffernan

et al. 2022

Limnology & Oceanography

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Methane (CH4) and carbon dioxide (CO2) emissions from small peatland lakes may be highly sensitive to climate warming and thermokarst expansion caused by permafrost thaw. We studied effects of thermokarst expansion on ebullitive CH4 and CO2 fluxes and diffusive CH4 fluxes from a peatland thaw lake in boreal western Canada. Ebullitive CH4 fluxes from the thaw edge (236 ± 61 mg CH4 m−2 d−1) were double and quadruple that of the stable lake edge and center, respectively. Modeled diffusive CH4 fluxes did not differ between the thawing and stable edges (~ 50 mg CH4 m−2 d−1) but were double that of the center. Radiocarbon (14C) analysis of CH4 and CO2 bubbles from the thaw edge was older (~ 1211 and 1420 14C yr BP) than from the stable edge and the center (modern to ~ 102 and 50 14C yr BP, respectively). Incubations indicated that deep, old peat sediment was more labile along the thaw edge than in the center. While our study suggested increase CH4 emissions partly derived from millennial‐aged carbon along the thaw edge, accounting for these emissions only increased the estimated total lake CH4 emissions by ~ 10%, which is a much smaller contribution than measured from thermokarst lakes in yedoma regions. Our study suggests that it is important to account for landscape history and lake types when studying the processes that govern the sensitivity of lake greenhouse gas emissions to climate change.

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Section: Discussionsupporting

confidence: 90%

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

Kuhn

Schmidt

Heffernan

et al. 2022

Limnology & Oceanography

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“…The SAS valley contains permafrost peatlands, and peatlands in general have higher DOC export and concentrations than mineral soils ( Dillon and Molot, 1997 ). Radiocarbon analysis of DOC in the SAS River during winter has indicated much older carbon than in nearby non-peatland rivers, and thermokarst lakes in the KWK River watershed ( Gonzalez Moguel et al, 2021 ), suggesting the mobilization of old frozen peat deposits. In a study of streams flowing through discontinuous permafrost, higher concentrations of DON, as well as higher DOC and lower DOC quality, were associated with a greater extent of permafrost in the watershed ( Balcarczyk et al, 2009 ).…”

Section: Discussionmentioning

confidence: 99%

“…In the third bacterial group correlated with salinity, Gammaproteobacteria, we identified the OM43 clade, a methylotroph in the Methylophilaceae family (Giovannoni et al, 2008), and the SAR92 clade (family Porticoccaceae), which possess genes for the degradation of complex polysaccharides (Klindworth et al, 2014). These two clades are common in coastal waters (Rappé et al, 1997;Morris et al, 2006;Stingl et al, 2007), and a culture study has shown that their growth is stimulated by high molecular weight organic matter (Sosa et al, 2015).…”

Section: Salinity Effectsmentioning

confidence: 97%

Size-Fractionated Microbiome Structure in Subarctic Rivers and a Coastal Plume Across DOC and Salinity Gradients

et al. 2022

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Little is known about the microbial diversity of rivers that flow across the changing subarctic landscape. Using amplicon sequencing (rRNA and rRNA genes) combined with HPLC pigment analysis and physicochemical measurements, we investigated the diversity of two size fractions of planktonic Bacteria, Archaea and microbial eukaryotes along environmental gradients in the Great Whale River (GWR), Canada. This large subarctic river drains an extensive watershed that includes areas of thawing permafrost, and discharges into southeastern Hudson Bay as an extensive plume that gradually mixes with the coastal marine waters. The microbial communities differed by size-fraction (separated with a 3-μm filter), and clustered into three distinct environmental groups: (1) the GWR sites throughout a 150-km sampling transect; (2) the GWR plume in Hudson Bay; and (3) small rivers that flow through degraded permafrost landscapes. There was a downstream increase in taxonomic richness along the GWR, suggesting that sub-catchment inputs influence microbial community structure in the absence of sharp environmental gradients. Microbial community structure shifted across the salinity gradient within the plume, with changes in taxonomic composition and diversity. Rivers flowing through degraded permafrost had distinct physicochemical and microbiome characteristics, with allochthonous dissolved organic carbon explaining part of the variation in community structure. Finally, our analyses of the core microbiome indicated that while a substantial part of all communities consisted of generalists, most taxa had a more limited environmental range and may therefore be sensitive to ongoing change.

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“…Several studies have used the natural abundance of radiocarbon ( 14 C) to estimate the contribution of permafrost carbon to lake carbon cycling (Zimov et al 1997, Nakagawa et al 2002, Walter et al 2006, Elder et al 2018, Gonzalez Moguel et al 2021. However, most studies focused on thermokarst systems overlying degrading Yedoma deposits, Pleistocene-aged permafrost soils with high ice and organic carbon content, in northern Alaska and Siberia (Matveev et al 2016, Walter Anthony et al 2018, Elder et al 2019, Dean et al 2020, Estop-Aragonés et al 2020, Kuhn et al 2023.…”

Section: Introductionmentioning

confidence: 99%

Arctic-boreal lakes of interior Alaska dominated by contemporary carbon

Garcia-Tigreros,

Elder,

Kurek

et al. 2023

Environ. Res. Lett.

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Northern high-latitude lakes are critical sites for carbon processing and serve as potential conduits for the emission of permafrost-derived carbon and greenhouse gases. However, the fate and emission pathways of permafrost carbon in these systems remain uncertain. Here, we used the natural abundance of radiocarbon to identify and trace the predominant sources of methane, carbon dioxide, dissolved inorganic and organic carbon in nine lakes within the Yukon Flats National Wildlife Refuge in interior Alaska, a discontinuous permafrost region with high landscape heterogeneity and susceptibility to climate, permafrost, and hydrological changes. We find that although Yukon Flats lakes primarily process young carbon (modern to 1290 ± 60 years before present), permafrost-derived carbon is present in some of the sampled lakes and contributes, at most, 30 ± 10% of the dissolved carbon in lake surface waters. Apportionment of young carbon and legacy carbon (carbon with radiocarbon age ⩾5000 years before present) is decoupled among the dissolved inorganic and organic carbon species, with methane showing a stronger legacy signature. Our observations suggest that permafrost-thaw-related transport of carbon through Yukon Flats lacustrine ecosystems and into the atmosphere is small, and likely regulated by surficial sediments, permafrost distribution, wildfire occurrence, or masked by contemporary carbon processes. The heterogeneity of lakes across our study area and northern landscapes more broadly cautions against using any one region (e.g. Yedoma permafrost lakes) to upscale their contribution across the pan-Arctic.

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Radiocarbon Data Reveal Contrasting Sources for Carbon Fractions in Thermokarst Lakes and Rivers of Eastern Canada (Nunavik, Quebec)

Cited by 8 publications

References 69 publications

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

Size-Fractionated Microbiome Structure in Subarctic Rivers and a Coastal Plume Across DOC and Salinity Gradients

Arctic-boreal lakes of interior Alaska dominated by contemporary carbon

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