Effects of simulated spring thaw of permafrost from mineral cryosol on CO2 emissions and atmospheric CH4 uptake. Issue 9 (11th September 2015)

• Record Type: Journal Article
• Authors: Stackhouse, Brandon T.; Vishnivetskaya, Tatiana A.; Layton, Alice; Chauhan, Archana; Pfiffner, Susan; Mykytczuk, Nadia C.; Sanders, Rebecca; Whyte, Lyle G.; Hedin, Lars; Saad, Nabil; Myneni, Satish; Onstott, Tullis C.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 9(2015:Nov.)
• Page Start: 1764
• Page End: 1784
• Publication Date: 2015-09-11
• Subjects: Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1002/2015JG003004
• Languages: English
• ISSNs: 2169-8953

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Previous studies investigating organic‐rich tundra have reported that increasing biodegradation of Arctic tundra soil organic carbon (SOC) under warming climate regimes will cause increasing CO<sub>2</sub> and CH<sub>4</sub> emissions. Organic‐poor, mineral cryosols, which comprise 87% of Arctic tundra, are not as well characterized. This study examined biogeochemical processes of 1 m long intact mineral cryosol cores (1–6% SOC) collected in the Canadian high Arctic. Vertical profiles of gaseous and aqueous chemistry and microbial composition were related to surface CO<sub>2</sub> and CH<sub>4</sub> fluxes during a simulated spring/summer thaw under light versus dark and in situ versus water saturated treatments. CO<sub>2</sub> fluxes attained 0.8 ± 0.4 mmol CO<sub>2</sub> m<sup>−2</sup> h<sup>−1</sup> for in situ treatments, of which 85 ± 11% was produced by aerobic SOC oxidation, consistent with field observations and metagenomic analyses indicating aerobic heterotrophs were the dominant phylotypes. The Q<sub>10</sub> values of CO<sub>2</sub> emissions ranged from 2 to 4 over the course of thawing. CH<sub>4</sub> degassing occurred during initial thaw; however, all cores were CH<sub>4</sub> sinks at atmospheric concentration CH<sub>4</sub>. Atmospheric CH<sub>4</sub> uptake rates ranged from −126 ± 77 to −207 ± 7 nmol CH<sub>4</sub> m<sup>−2</sup> h<sup>−1</sup> with CH<sub>4</sub> consumed between 0 and 35 cm depth. Metagenomic and gas chemistry analyses revealed that high‐affinity Type II methanotrophic sequence abundance and activity were highest between 0 and 35 cm depth. Microbial sulfate reduction dominated the anaerobic processes, outcompeting methanogenesis for H<sub>2</sub> and acetate. Fluxes, microbial community composition, and biogeochemical rates indicate that mineral cryosols of Axel Heiberg Island act as net CO<sub>2</sub> sources and atmospheric CH<sub>4</sub> sinks during summertime thaw under both in situ and water saturated states.</p> </abstract>