Bacterial Number and Genetic Diversity in a Permafrost Peatland (Western Siberia): Testing a Link with Organic Matter Quality and Elementary Composition of a Peat Soil Profile

Abstract

Permafrost peatlands, containing a sizable amount of soil organic carbon (OC), play a pivotal role in soil (peat) OC transformation into soluble and volatile forms and greatly contribute to overall natural CO2 and CH4 emissions to the atmosphere under ongoing permafrost thaw and soil OC degradation. Peat microorganisms are largely responsible for the processing of this OC, yet coupled studies of chemical and bacterial parameters in permafrost peatlands are rather limited and geographically biased. Towards testing the possible impact of peat and peat pore water chemical composition on microbial population and diversity, here we present results of a preliminary study of the western Siberia permafrost peatland discontinuous permafrost zone. The quantitative evaluation of microorganisms and determination of microbial diversity along a 100 cm thick peat soil column, which included thawed and frozen peat and bottom mineral horizon, was performed by RT-PCR and 16S rRNA gene-based metagenomic analysis, respectively. Bacteria (mainly Proteobacteria, Acidobacteria, Actinobacteria) strongly dominated the microbial diversity (99% sequences), with a negligible proportion of archaea (0.3–0.5%). There was a systematic evolution of main taxa according to depth, with a maximum of 65% (Acidobacteria) encountered in the active layer, or permafrost boundary (50–60 cm). We also measured C, N, nutrients and ~50 major and trace elements in peat (19 samples) as well as its pore water and dispersed ice (10 samples), sampled over the same core, and we analyzed organic matter quality in six organic and one mineral horizon of this core. Using multiparametric statistics (PCA), we tested the links between the total microbial number and 16S rRNA diversity and chemical composition of both the solid and fluid phase harboring the microorganisms. Under climate warming and permafrost thaw, one can expect a downward movement of the layer of maximal genetic diversity following the active layer thickening. Given a one to two orders of magnitude higher microbial number in the upper (thawed) layers compared to bottom (frozen) layers, an additional 50 cm of peat thawing in western Siberia may sizably increase the total microbial population and biodiversity of active cells.

Diversity and Distribution Characteristics of Soil Microbes across Forest–Peatland Ecotones in the Permafrost Regions

“…Actinomycetota, Proteobacteria, Firmicutes, Chloroflexota, and Acidobacteriota were the predominant soil bacterial taxa in our study, which was consistent with a number of other comprehensive studies on peatlands [ 38 , 39 ]. We would like to emphasize that Actinomycetota detected in this region were not strongly influenced by environmental variables, as the differences observed between soil samples were not significant.…”

Vertical distribution of bacterial community diversity in the Greater Khingan Mountain permafrost region

“…In the high‐latitude permafrost region of the Greater Khingan Mountain, there was an extremely high amount of litter input on the soil surface derived from the Larix gmelinii forest, and plant roots were concentrated at 0–80 cm. The soil nutrient increased and sustained microbial growth in the active layer, whereas microbial abundance was suppressed by low‐quality substrates in the permafrost layer (Aksenov et al, 2021).…”

“…Most current studies on soil microbial communities in permafrost regions have been conducted in the circumpolar Arctic, Siberia, Alaska, and the Qinghai-Tibet Plateau (Aksenov et al, 2021;Singh et al, 2017;Tripathi et al, 2018;Wu et al, 2017)…”

“…Therefore, both of these environments are likely inhabited by different microbial flora (Mackelprang et al, 2011). Most current studies on soil microbial communities in permafrost regions have been conducted in the circumpolar Arctic, Siberia, Alaska, and the Qinghai‐Tibet Plateau (Aksenov et al, 2021; Singh et al, 2017; Tripathi et al, 2018; Wu et al, 2017), whereas much less attention has been given to the permafrost regions of the Greater Khingan Mountain, an area affected by both the effects of climate change and intense human activities, which limits our knowledge of the spatiotemporal variation trends and potential carbon feedback of permafrost under global warming conditions. The aim of this study was to (1) determine the vertical distribution patterns of soil bacterial community structures; (2) identify the key environmental factors driving the distribution of the bacterial community; and (3) reveal the soil bacterial predicted metabolic functions in the active and permafrost layers of the Larix gmelinii forest located in the Greater Khingan Mountain permafrost region based on Illumina Miseq high‐throughput sequencing.…”

Partitioning of Dissolved Organic Carbon, Major Elements, and Trace Metals during Laboratory Freezing of Organic Leachates from Permafrost Peatlands

“…The dominant vegetation on the mound is mosses and lichens, with some dwarf shrubs. The detailed description of the environmental context of the sampling sites is provided elsewhere (for Bolshezemelskaya Tundra [47,48] and for Western Siberia [49,50]).…”