# Greenhouse gases, organic carbon, major and trace elements in ultra-small water bodies (<100 m2) of permafrost peatlands: Assessment across seasons and permafrost gradient

Artem G Lim, Rinat M Manasypov, Ivan V Krickov, Liudmila S Shirokova, Sergey N Vorobeyev, Oleg S Pokrovsky

► To cite this version:

Artem G Lim, Rinat M Manasypov, Ivan V Krickov, Liudmila S Shirokova, Sergey N Vorobeyev, et al.. Greenhouse gases, organic carbon, major and trace elements in ultra-small water bodies (<100 m2) of permafrost peatlands: Assessment across seasons and permafrost gradient. Journal of Hydrology, 2025, 660, pp.133343. 10.1016/j.jhydrol.2025.133343. hal-05527860

HAL Id: hal-05527860

https://hal.science/hal-05527860v1

Submitted on 25 Feb 2026

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons CC BY 4.0 - Attribution - International License
<figure><img src="image_2.png" /></figure>

# Greenhouse gases, organic carbon, major and trace elements in ultra-small water bodies (<100 m²) of permafrost peatlands: Assessment across seasons and permafrost gradient☆

<figure><img src="image_3.png" /></figure>

Artem G. Lim<sup>a</sup>, Rinat M. Manasypov<sup>a</sup>, Ivan V. Krickov<sup>a</sup>, Liudmila S. Shirokova<sup>b</sup>, Sergey N. Vorobyev<sup>a</sup>, Oleg S. Pokrovsky<sup>c, ID</sup>

## ARTICLE INFO

Keywords:

Permafrost
CO₂, CH₄, peatland
Surface water
Trace metals
Thermokarst

## ABSTRACT

Thawing permafrost releases substantial amounts of greenhouse gases (GHGs), organic carbon (OC), nutrients, and trace metals into surface waters including rivers and, eventually, the Arctic Ocean. However, intermediate components linking soil and surface waters—specifically, small and ultra-small puddles and depressions (<10–100 m²) formed after snowmelt in spring and through permafrost thaw in summer—have largely remained outside the scope of research. In this study, we investigated 206 surface waters from small depressions and puddles (1–100 m²) in spring, summer, and autumn across a permafrost gradient, spanning from sporadic to continuous permafrost zones in the Western Siberian Lowlands (WSL). Our findings showed the highest concentrations of carbon dioxide (CO₂) and methane (CH₄) in the sporadic/discontinuous permafrost zones during summer and autumn, likely due to intensive mobilization of organic carbon from peat and GHG generation at the active permafrost thawing front. Across all permafrost zones, the highest concentrations of major and trace solutes were observed during summer and autumn, with the lowest concentrations in spring. This trend likely reflects a progressive increase in connectivity between surface and subsurface waters, which are enriched in GHGs, organic matter (OM) and inorganic components due to leaching from peat and soil minerals. For the two main size ranges of studied small water bodies (SWBs) in the WSL — <10 m² and 10–100 m² — no significant seasonal or spatial differences were observed in CO₂, CH₄, DOC, macro- and micronutrient or metal concentrations. When averaged across all seasons and permafrost zones, SWBs showed concentrations of CH₄ and CO₂ approximately 10 times higher and levels of certain macro- (Si and P) and micronutrients (Fe, Co, Rb and Mn) 3 to 7 times higher when compared to thermokarst lakes. Thus, despite their limited surface area, SWBs may serve as crucial regulators of GHG dynamics and nutrient storage, especially during the understudied transitional seasons of spring and autumn.

## 1. Introduction

The evolution of aquatic ecosystems in the permafrost-affected high latitude regions is at the forefront of scientific research yet the factors controlling aquatic carbon (C) and hydrological responses to permafrost thaw remain poorly understood and available field studies are strongly regionally-biased (Knoblauch et al., 2018; Tank et al., 2020; Walvoord and Striegl, 2021). Although the role of high-latitude inland waters as a persistent source of CO₂ and CH₄ to the atmosphere is well established

(Bastviken et al., 2004; McEnroe et al., 2009; Pelletier et al., 2014; Vonk et al., 2015; Turetsky et al., 2019; Gonzalez Moguel et al., 2021), substantial uncertainties remain regarding the magnitude of these fluxes, largely due to pronounced seasonal and spatial variations in GHG and organic carbon concentrations in lake waters (Tan et al., 2015; Serikova et al., 2019; Tank et al., 2009; Zabelina et al., 2022; Stolpmann et al., 2021, 2024; Taillardat et al., 2024). These uncertainties are particularly evident in regions with abundant thermokarst lakes and thaw ponds, such as permafrost peatlands. Northern wetlands are currently a focal

<footnote><sup>a</sup> BIO-GEO-CLIM Laboratory, Tomsk State University, 36 Lenina Av., Tomsk 634004, Russia</footnote>

<footnote><sup>b</sup> N. Laverov Federal Center for Integrated Arctic Research, Russian Academy of Science, 20 Nikolski Prospekt, Arkhangelsk 163000, Russia</footnote>

<footnote><sup>c</sup> GET UMR 5563 CNRS University of Toulouse, 14 Avenue Edouard Belin, 31400 Toulouse, France</footnote>

<footnote>* This article is part of a special issue entitled: 'Water-Carbon processes' published in Journal of Hydrology.</footnote>

<footnote>* Corresponding author.
E-mail address: oleg.pokrovsky@get.omp.eu (O.S. Pokrovsky).</footnote>
point of environmental research due to their vast carbon stocks (Schuur et al., 2015), hydrological shifts (Vonk et al., 2019), increases in active layer thickness (ALT) (Kaverin et al., 2021), loss of permafrost landforms (Wang et al., 2024), surface vegetation spatial dynamics (Auda et al., 2023), carbon accumulation (McGuire et al., 2009) and related changes in microbial communities that process organic C (McCalley et al., 2014). Altogether, these factors are capable of enhancing C release and greenhouse gas emissions (Lundin et al., 2016; Miner et al., 2022), hence playing a pivotal role in positive retroactive link to climate warming.

In these areas, thawing frozen peat and the generally flat landscapes, especially at watershed divides, create ideal conditions for the persistence of stagnant surface waters. The Western Siberian Lowland (WSL) is an example, where the permafrost-affected region (1.05 million km²) contains numerous lakes and ponds that serve as significant GHG sources and hold large amounts of dissolved organic carbon, nutrients, and metals (Polishchuk et al., 2017, 2018). Lakes in this area, primarily of thermokarst origin, were formed during the thawing of frozen peat bogs and locally, at the watershed divides, can cover up to 40–60 % of the land area (Loiko et al., 2020; Manasypov et al., 2023).

The lentic waters of the WSL have been the focus of biogeochemical studies for over a decade (Audry et al., 2011; Shirokova et al., 2013; Karlsson et al., 2014; Manasypov et al., 2023). Among the various water bodies in permafrost peatlands, lakes and ponds (> 100–1000 m²) have been extensively studied in terms of carbon (C) dynamics within the water column (Pokrovsky et al., 2014; Manasypov et al., 2017; Shirokova et al., 2020), sediment composition (Manasypov et al., 2022; Manasypov et al., 2024), hydrochemistry (Pokrovsky et al., 2011; Manasypov et al., 2014, 2015, 2020) and greenhouse gas (GHG) emissions (Serikova et al., 2019). However, small water bodies (< 100 m²), including temporary puddles in micro-relief depressions and those formed at the onset of permafrost collapse (Loiko et al., 2017), remain largely unstudied. Thus, in the most recent assessment of GHG emissions from high-latitude lakes (Song et al., 2024), ponds smaller than 100 m² were not included in the analysis. These small water bodies (SWB) are of particular interest for two reasons. First, their close connection to organic-rich soils and ground vegetation makes them critical sites for observing biogeochemical processes at the terrestrial-aquatic interface. Second, SWBs may serve as significant hotspots for carbon and nutrient cycling within permafrost peatlands, as concentrations of dissolved organic carbon (DOC), solutes and GHGs can be up to ten times higher in the smallest thaw ponds (100–1000 m²) compared to typical thermokarst lakes (Pokrovsky et al., 2013; Shirokova et al., 2020, 2021; Zabelina et al., 2021). The highest concentrations and emissions of carbon in the smallest ponds are driven by the supply of labile organic matter from permafrost soils and fresh vegetation leachates, their high perimeter-to-volume ratio, and the limited photosynthetic activity in their very thin photic zone. Consequently, the role of SWBs in the carbon and GHG balance of high latitudes, particularly in permafrost peatlands, may be significantly underestimated.

Globally, very small lakes and ponds (< 1000 m²), though comprising less than 10 % of the total water surface area, have been estimated to emit more than 15 % of CO₂ and 40 % of CH₄ (Holgerson and Raymond, 2016). High-resolution remote sensing in northern Siberia suggests that excluding small lakes and ponds from thermokarst lake-related measurements—such as methane emissions—may lead to bias in global estimates (Grosse et al., 2008). In western Siberia, where the quantity and water coverage of small lakes are well documented (Polishchuk et al., 2018), there is still a lack of seasonally resolved, in situ GHG measurements for SWBs, especially those with surface areas under 100 m². In the typical cyclic development of thermokarst lakes in the WSL (Kirpotin et al., 2011; Pokrovsky et al., 2011), similar to other subarctic regions (Czudek and Demek, 1970; Matthews et al., 1997; Jorgenson and Shur, 2007), such small water bodies represent transitional stages. These begin with initial peat thawing and localized permafrost collapse in small depressions, eventually forming small,

stable thaw ponds. This transition is a critical component of the hydrological continuum, linking soil porewaters and suprapermafrost flow with stagnant surface waters.

To enhance our understanding of the biogeochemistry of SWBs in permafrost peatlands, this study examines the spatial and seasonal variability of greenhouse gases (GHGs) and major and trace solutes across three hydrological seasons and a significant permafrost and climate gradient. Our research objectives were to: (i) quantify the concentrations of GHGs in small water bodies across different permafrost zones; (ii) assess the potential influence of SWB size on DOC, GHG and inorganic solute concentrations in the water column; and (iii) identify the key environmental factors controlling the spatial and seasonal variability of solute concentrations in SWBs. We proposed two key hypotheses regarding the temporal and spatial controls on SWB hydrochemistry. First, since the primary source of dissolved carbon, solutes, and greenhouse gases (GHGs) in surface waters is soil water (Raudina et al., 2018; Manasypov et al., 2020), we expect GHG and solute concentrations in SWBs to peak at the end of the season (autumn), when the active (unfrozen) layer (Raudina et al., 2025) and the hydrological connectivity between soil porewaters and surface waters (Ala-aho et al., 2018a) are at their maximum. Second, the highest concentrations of dissolved organic carbon (DOC), CO₂, and CH₄ in SWBs should occur in regions experiencing the most active permafrost thaw, particularly in the sporadic to discontinuous permafrost zone, where the active layer is thickest. This pattern has also been observed in WSL rivers and streams (Krickov et al., 2024). These hypotheses were tested through an extensive field campaign from late May to early October across four major permafrost zones in the WSL.

## 2. Study site description and methods

### 2.1. Study site description and sampling strategy

The Western Siberian Lowland comprises three major biomes of boreal and subarctic zone: taiga, forest-tundra and tundra landscapes. The water bodies such as thermokarst lakes, thaw ponds and depressions are developed in sporadic, discontinuous and continuous permafrost zones. They are typically formed due to thawing of permafrost and start via subsidences of frozen peat as described in details elsewhere (Kirpotin et al., 2009, 2011; Audry et al., 2011; Shirokova et al., 2013; Manasypov et al., 2015). In the present study, we focused on small and ultra-small water bodies (typically less than 100–200 m²) which were chiefly ignored in previous works for this region (Serikova et al., 2019; Manasypov et al., 2014; Manasypov et al., 2015, 2023).

For sampling, we chose four key sites located in four permafrost zones across the WSL (Fig. 1). These key sites represent the permafrost and climate gradient of the Western Siberian Lowland, where extensive studies have been conducted on limnology (Manasypov et al., 2020; Manasypov et al., 2022), hydrobiology (Noskov et al., 2024), river hydrochemistry (Pokrovsky et al., 2020), and soil science (Raudina et al., 2017, 2018). Notably, all areas containing SWBs were within the watersheds of lakes and rivers where previous extensive hydrochemical sampling had been performed. Through numerous ground observations and remote sensing inventories, we ensured that the selected site in each permafrost zone was representative of a typical permafrost peat bog in the Western Siberian Lowland. At each site, we selected an approximately equal number of ultra-small (< 10 m²) and small (10–100 m²) waterbodies, located in close proximity to thermokarst lakes previously studied by our group (Manasypov et al., 2020; Manasypov et al., 2022). The thermokarst lake complexes of the WSL are characterized by relatively uniform peat thickness, a consistent lithological background, and a highly similar dwarf shrub-sphagnum-lichen vegetation community. Therefore, our findings can be generalized to similar permafrost peatland pools in northeastern Europe, such as the Bolschemelskaya Tundra (Zabelina et al., 2021).

The most southern site, Kogalym, is a taiga biome within the isolated
<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Map of the study area in the Western Siberia Lowland, Russia. Color shading represents different permafrost zones of the WSL. Green squares indicate the four studied sites, illustrated in four bottom panels in the isolated (Kogalym), sporadic (Khanymey), discontinuous (Urengoi) and continuous (Tazovsky) permafrost zones. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)</figcaption></figure>

permafrost zone. Further north, the Khanymey site is located in a northern taiga biome on the border between the sporadic and discontinuous permafrost zone. The third site is within the town of Urengoy, where a forest-tundra biome is present over the discontinuous permafrost zone. Finally, the most northern site, Tazovsky, is in a tundra biome of the continuous permafrost zone (Fig. 1). Study sites are located on elevated parts of the Ob, Nadym, Pur and Taz river watersheds and thus not affected by temporary flooding from rivers. Average annual temperatures in the four sites are -4.0, -5.6, -6.4 and -9.1 °C in a south to north transect (Trofimova and Balybina, 2014). During summer

sampling, the average thickness of the active layer ranged from 200–300 cm in the south to 40 cm in the north (Raudina et al., 2018). A more detailed description of climate, soil and vegetation parameters of these study sites is provided in other works (Manasypov et al., 2020; Raudina et al., 2017).

An important feature of chosen settings is that in the first three “southern sites” – Kogalym, Khanymey and Urengoy – the peat thickness is 3 to 1.5 m, which normally exceeded the active layer depth. As a result, in these sites, surface water bodies are located essentially within the peat substrate without the sizable effect of underlying mineral
layers. In contrast, in the most northern Tazovsky site, the typical peat thickness of the psala zone where water samples were taken is only 20 to 50 cm, which is comparable to the active layer thickness (ALT) of 30–40 cm. As a result, small surface water bodies in Tazovsky contact not only with peat but also with the underlying mineral substrate (marine clay deposits), especially at the end of the active season, in autumn, when the active layer is at its maximum.

In 2016, we visited each site during the ice-off event (21 May – 12 June 2016), in the middle of the summer (15–24 August 2016) and before ice-on in autumn (27 September – 8 October 2016). Note that due to the inherently ephemeral nature of small puddles and depressions within psala peat bog complexes, we were unable to sample the exact same water body across seasons. In approximately 30 % of cases, different SWBs—though located within the same test area—were sampled during different seasons. In spring, we started from the south and moved northward along existing road infrastructure, therefore sampling the water bodies at approximately the same period of ice-off. Similarly, in autumn, we moved southward starting from the most northern site, covering a similar early freezing period along the chosen S – N transect of 900 km. During three main hydrological seasons, we studied approximately 50 small water bodies in each permafrost zone (Table 1). The GHG concentrations were measured in 60 SWB of Kogalym (sporadic permafrost zone), 55 SWB of Khanymey (sporadic/ discontinuous zone), 51 of Urengoy (discontinuous zone) and 40 SWB of Tazovsky (continuous zone). For hydrochemical analyses of major and trace solutes, 5 SWB in each site were collected during each season.

The studied SWB are isolated, mostly isometric round or oval shape. We were unable to quantify the area of each sampled SWB with sufficient precision. Consequently, we categorized SWBs into two main size classes, as determined in the field: less than 10 m² and 10–100 m². This classification allowed us to assess the potential impact of SWB surface area on the hydrochemistry of the water column. The SWBs are extremely shallow, with typical depths ranging from 10 to 30 cm. A maximal depth of 50 cm was observed in strong depressions of the relief and it was not connected to the size of the SWB. The SWBs lack any connection to a hydrological network via an inlet or outlet. While their shapes are generally round to oval, some are elongated, with dense

vegetation (mainly mosses) along the shore. The watershed for each WSB could not be precisely quantified but is estimated to be no more than twice the area of the pool itself.

Similar to neighboring thermokarst lakes and thaw ponds, the main source of water for SWB is atmospheric precipitation in the form of snow melt in spring and rain in summer and autumn. Approximately 30 % of SWB almost completely dried out during the summer. However, some water still remained in the central part of the depression. Alternatively, it could be extracted via making 10–20 cm pit in the waterlogged, humid mosses and organic detritus of the dry bottom of depression. Water temperature showed minor variations across different permafrost zones and was primarily influenced by seasonal changes. It ranged from 4–5 °C in spring to 17–19 °C in summer and 2–3 °C in autumn. No chemical or thermal stratification was observed between the surface and bottom water layers of the sampled SWB.

## 2.2. Analyses

In-situ temperature, pH, specific conductivity (S.C.) and dissolved oxygen (DO) were measured using a WTW Multi 3430 m. Water samples were collected from the middle part of the SWB using sterile plastic syringes and vinyl gloves. The water was filtered in situ immediately after sampling through disposable Sartorius syringe driven filter units (0.45 µm). The first 20–50 ml of the filtrate were discarded. One part of the filtrate was collected in polypropylene vials (10 mL) that were pre-washed in a clean room (class A 10,000). It was acidified with ultra-pure nitric acid to pH = 2 for major and trace element analysis. The other, non-acidified, part of the filtrate was used for analyses of DOC, DIC, major anions (Cl and SO₄) and UV absorbance. Immediately after collection, samples were stored in a refrigerator at 4 °C.

Major cations, Si and ~ 40 trace elements were measured by inductively coupled plasma mass spectrometry using an ICP-MS quadrupole (Agilent Technologies 7500 ce), with an In + Re internal standard, and an uncertainty of ± 5 %. International geo-standard SLRS-6 (river water reference material for trace element analysis certified by the National Research Council of Canada) was used to validate the analyses (Yeghicheyan et al., 2019). The agreement of the results with certified

<table><caption>**Table 1**
Median and IQR values of GHG, major and trace solutes in small water bodies across seasons and permafrost zones.</caption><thead><tr><th rowspan="2">Parameters</th><th colspan="3">Kogalym</th><th colspan="3">Khanymey</th><th colspan="3">Urengoi</th><th colspan="3">Tazovsky</th></tr><tr><th>spring<br>n<sub>1</sub> = 6<br>n<sub>2</sub> = 21</th><th>summer<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 19</th><th>autumn<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 20</th><th>spring<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 20</th><th>summer<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 15</th><th>autumn<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 20</th><th>spring<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 17</th><th>summer<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 14</th><th>autumn<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 20</th><th>spring<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 20</th><th>summer<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 33</th><th>autumn<br>n<sub>1</sub> = 5<br>n<sub>2</sub> = 20</th></tr></thead><tbody><tr><td>pH</td><td>3.9±<br>0.1</td><td>3.8±<br>0.05</td><td>3.7±<br>0.2</td><td>3.8<br>4.2±<br>0.1</td><td>3.8±<br>0.1</td><td>3.9±<br>0.09</td><td>4.2±<br>0.5</td><td>4.1±<br>0.7</td><td>4.2±<br>0.05</td><td>4.6±<br>0.6</td><td>ND</td><td>4.6±<br>0.4</td></tr><tr><td>SUVA<sub>254</sub></td><td>4.2±<br>0.9</td><td>4.6±<br>0.05</td><td>4.5±<br>0.3</td><td>4±<br>0.2</td><td>4.6±<br>0.7</td><td>3.8±<br>0.5</td><td>3.1±<br>2.1</td><td>3.9±<br>0.8</td><td>3.9±<br>0.4</td><td>4.7±<br>1.3</td><td>4.5</td><td>4.9±<br>0.3</td></tr><tr><td>E.C.,<br>µS cm<sup>-1</sup></td><td>51±<br>2</td><td>62±<br>3</td><td>75±<br>22</td><td>41<br>4</td><td>55±<br>4</td><td>80±<br>28</td><td>43±<br>6</td><td>26±<br>37</td><td>55±<br>10</td><td>49±<br>22</td><td>ND</td><td>39±<br>11</td></tr><tr><td>CH<sub>4</sub></td><td>3.9±<br>4.3</td><td>114±<br>69</td><td>164±<br>52</td><td>2.6±<br>8.3</td><td>174±<br>168</td><td>109±<br>171</td><td>0.9±<br>0.9</td><td>31±<br>28</td><td>155±<br>81</td><td>0.8±<br>3</td><td>4±<br>28</td><td>25±<br>56</td></tr><tr><td>CO<sub>2</sub>,<br>µmol L<sup>-1</sup></td><td>489±<br>333</td><td>1311±<br>655</td><td>1295±<br>550</td><td>321±<br>201</td><td>1867±<br>285</td><td>2310±<br>1066</td><td>709±<br>197</td><td>620±<br>421</td><td>1600±<br>171</td><td>1036±<br>540</td><td>862±<br>1210</td><td>1355±<br>1209</td></tr><tr><td>Cl<sup>-</sup>,<br>mg L<sup>-1</sup></td><td>0.05±<br>0.08</td><td>0.2±<br>0.2</td><td>0.3±<br>0.02</td><td>0.2±<br>0.06</td><td>0.1±<br>0.04</td><td>0.2±<br>0.06</td><td>0.5±<br>0.1</td><td>0.3±<br>1.2</td><td>0.2±<br>0.1</td><td>0.2±<br>0.2</td><td>ND</td><td>0.1±<br>0.1</td></tr><tr><td>SO<sub>4</sub><sup>2-</sup>,<br>mg L<sup>-1</sup></td><td>0.14±<br>0.2</td><td>0.06±<br>0.03</td><td>0.07±<br>0.01</td><td>0.8±<br>0.3</td><td>0.1±<br>0.02</td><td>0.03±<br>0.003</td><td>0.6±<br>0.4</td><td>0.2±<br>0.3</td><td>0.09±<br>0.04</td><td>0.4±<br>0.4</td><td>ND</td><td>0.7±<br>1.1</td></tr><tr><td>DOC,<br>mg L<sup>-1</sup></td><td>26±<br>6</td><td>42±<br>2.9</td><td>46±<br>11</td><td>29±<br>21</td><td>46±<br>9.5</td><td>66±<br>35</td><td>29±<br>12</td><td>23±<br>35</td><td>45±<br>4.7</td><td>43±<br>17</td><td>21±<br>10</td><td>41±<br>3.6</td></tr><tr><td>DIC,<br>mg L<sup>-1</sup></td><td>0.4±<br>0.3</td><td>1.6±<br>0.3</td><td>0.8±<br>0.2</td><td>0.6±<br>0.3</td><td>0.5±<br>0.3</td><td>1.8±<br>2.8</td><td>0.4±<br>0.2</td><td>0.6±<br>0.3</td><td>0.8±<br>1.4</td><td>0.8±<br>0.2</td><td>2.6±<br>3.1</td><td>1.8±<br>1</td></tr><tr><td>Al,<br>µg L<sup>-1</sup></td><td>16±<br>10</td><td>49±<br>19</td><td>55±<br>6.9</td><td>67±<br>87</td><td>160±<br>59</td><td>219±<br>12</td><td>40±<br>38</td><td>182±<br>115</td><td>123±<br>20</td><td>182±<br>135</td><td>44±<br>58</td><td>138±<br>59</td></tr><tr><td>Si,<br>µg L<sup>-1</sup></td><td>632±<br>825</td><td>1465±<br>470</td><td>1159±<br>29</td><td>221±<br>80</td><td>3468±<br>2651</td><td>1415±<br>3260</td><td>283±<br>186</td><td>2157±<br>745</td><td>1962±<br>403</td><td>1640±<br>1034</td><td>1648±<br>3129</td><td>5103±<br>250</td></tr><tr><td>Fe,<br>µg L<sup>-1</sup></td><td>28±<br>13</td><td>184±<br>121</td><td>193±<br>22</td><td>182±<br>232</td><td>330±<br>267</td><td>366±<br>93</td><td>123±<br>44</td><td>334±<br>16</td><td>573±<br>46</td><td>1324±<br>5613</td><td>507±<br>547</td><td>1728±<br>1210</td></tr></tbody></table>

<footnote>*n₁ – quantity of samples for major and trace solutes, n₂ – quantity of samples for GHG.</footnote>
SLRS-6 values ranged from 10 to 15 % for 40 elements. Non acidified samples were used for determination of 1) DOC (TOC VCSN, Shimadzu), with an accuracy of 3 %, and a detection limit of 0.1 mg L⁻¹; 2) Cl⁻ and SO₄²⁻ by high-performance liquid chromatography using Dionex ICS-2000, with an accuracy of 2 %, and a detection limit of 0.02 mg·L⁻¹; and 3) ultraviolet absorption at 254 nm using a Bruker CARY-50 UV–VIS spectrophotometer and 10-mm quartz cuvette.

For dissolved CO₂ and CH₄ analysis, river water was collected from a depth of approximately 10 cm into 25-mL serum bottles, which were sealed without air bubbles using vinyl stoppers and aluminum caps. To prevent microbial activity, 2 mL of saturated KCl solution was added to each sample immediately after collection. The samples were then wrapped in aluminum foil and stored in a refrigerator for approximately three weeks before gas chromatography analysis of the headspace, as described previously (Serikova et al., 2019; Krickov et al., 2021).

## 2.3. Statistical treatment

The normality of the data on element concentrations was checked using the Shapiro-Wilk test. Nonparametric statistics methods were used for data presentation. Values of the median and interquartile range (median ± IQR, Interquartile Range) were used due to the abnormally distributed data and the presence of outliers. For comparison with literature data on lakes and soil waters, we also used the mean values and standard deviation (mean ± SD). A correlation analysis with

Spearman correlation coefficient (Rs) (p < 0.05) was used to identify the relationship between the major hydrochemical parameters of the water (DOC, Fe and Al), GHG and major and trace elements. Comparisons of DOC, GHG and major and minor solute concentration between different permafrost zones, different seasons, and for the SWB of two main size grid ( < 10 m² and 10 – 100 m²) were conducted using a non-parametric Mann Whitney U test at a significance level of 0.05. The hydrochemical data were also treated via multiparametric statistical approaches, which included a Principal Component Analysis using a variance estimation method. Hierarchical Cluster Analysis (HCA) helped to distinguish groups of inter-connected components, including both major and trace elements, organic carbon and dissolved gases. Statistical treatment was performed using STATISTICA-7 (http://www.statsoft.com).

# 3. Results

## 3.1. Spatial and seasonal dynamics of GHG concentrations and DOC across the SWB size and permafrost gradient

Median values and Inter-Quartile Range (IQR) of GHG, major and trace solutes in small water bodies of western Siberia are listed in Table 1 and Table S1 of the Supplement. The GHG concentrations across seasons and permafrost zones exhibited the following patterns as summarized in Fig. 2 and detailed for each site in Fig. S1 of the Supplement. For all permafrost zones, maximal concentrations of CO₂ and CH₄ were

<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Boxplots of median and IQR range of CH₄ (A), CO₂ (B) concentration, pH (C), Electrical Conductivity (D), DOC (E), SUVA₂₅₄ (F), Cl⁻ (G) and SO₄²⁻ (H) concentrations in small water bodies of western Siberia for each season across 4 permafrost zones. Asterisks represent the difference between seasons as following: * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001 (see Table S2 for Mann-Whitney U test). Shaded zones depict significant differences. Here and below in other figures, Kogalym, Khanymey, Urengoi and Tazovsky represent sporadic, isolated/discontinuous, discontinuous and continuous permafrost zone, respectively.</figcaption></figure>
observed during summer and autumn period and were maximal in the Khanymey site, on the border between the sporadic and discontinuous permafrost zone. Much lower concentrations of GHG were found in spring, when values were rather similar among all sites. The differences in GHG concentrations between spring, summer and autumn were significant at *p* < 0.05 (Table S2). The dissolved CH4 was more than an order of magnitude lower than the CO2 concentration (mean ratio of CO2: CH4 was 224 and the median ratio was 38; Table 1). There was no significant (at *p* < 0.05) difference in GHG concentration in ultra-small (< 10 m²) and small (10 – 100 m²) water bodies studied across all seasons, regardless of the permafrost zone. DOC concentration increased from spring to summer and autumn, being highest in the Khanymey site of the sporadic/discontinuous permafrost zone (Fig. 2). The SUVA254 did not vary across seasons and decreased from south (Kogalym) to north (Urengoi). The SWB were acidic (pH of 3.5 to 5.2) and exhibited a systematic increase (ca. 1.5 unit) from south to north. The waters were humic (20 ≤ [DOC] ≤ 80 mg/L), low mineralized (E.C. from 20 to 100 µS cm⁻¹) and poor in Cl and SO₄ (Fig. 2). The outliers did not sizably affect the median and IQR of CO₂, CH₄ and DOC concentrations, and their inclusion in statistical treatment did not affect the final values. We were unable to determine the cause of outliers for organic carbon, GHG and these inorganic solutes. These outliers were not reproducible from one season to another at the same site and showed no clear association with specific SWB characteristics such as shape, depth, proximity to a lake or river, peat thickness, or dominant vegetation. Detailed analysis of the spatial pattern of dissolved C during autumn, the period of maximal connectivity between soil water and surface waters due to maximal active layer thickness, demonstrated a clear maxima in CO₂ and DOC concentrations in Khanymey, at the most active permafrost thawing front (Fig. S2).

## 3.2. Spatial and seasonal patterns of major and trace elements

Seasonal variations of inorganic solute concentrations across the different permafrost zones demonstrated variable patterns. The concentrations of Al, Si, Mg, Sr, Ba, Ti, Cr, Ni, Y, Zr and Cd increased from spring to autumn (Fig. 3). There were significant (*p* < 0.01) difference in major and trace solute concentrations between spring and summer, but these differences were less pronounced between summer and autumn (Table S2). A few nutrients linked to plant litter leaching (K and Rb) and elements originated from atmospheric deposition in the form of snow-pack (Cs and Pb) exhibited the highest concentrations in spring or were not dependent on season (Sb). Overall, in the northward direction, there was a steady and systematic increase in concentration of alkaline-earth metals (Ca and Sr), transition metals (Fe, Mn, Ni and Co) and trivalent hydrolysates (Y and REEs). During autumn period of maximal connectivity between surface and soil waters, spatial pattern of major and trace elements exhibited distinct difference between two main groups of solutes (Fig. S2). While major salts demonstrated gradual decrease northward (E.C., Na, Cl), other showed an abrupt increase between discontinuous and continuous permafrost zone (Urengoi and Tazovsky, respectively). These included anions (SO₄, Mo, As), Si, alkalis and alkaline-earth metals (Li, Mg, Ca, Sr) but also trace metals and low-mobility trivalent and tetravalent hydrolysates. Among the inorganic solutes, the outliers were pronounced for Si, Al, Cr and Cd solely for the Tazovsky region. Their inclusion did not affect the final values, and, alike for C and GHG, we could not relate them to specific morphological parameters of SWBs and thickness of peat versus mineral deposits.

A pairwise (Spearman) correlation analysis of solute and GHG concentration for the entire data set (Table S3) demonstrated that DOC positively correlated with CO₂, CH₄, Al, P, Ga, Nb, Cd, Cs and Pb (Fig. 4). Because many trace elements in humic waters of peatland exist as organo-Fe, Al colloids (Pokrovsky et al., 2005, 2016; Manasypov et al.,

<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Histograms of median and IQR range of inorganic solutes – Al (A), Si (B), Cr (C), Cd (D), Cs (E) and Sb (F) concentration in SWB of western Siberia across seasons and permafrost zones. Asterisks represent the difference between seasons as following: \* *P* < 0.05, \*\* *P* < 0.01, \*\*\* *P* < 0.001, \*\*\*\* *P* < 0.0001 (see Table S2 for Mann-Whitney *U* test). Shaded zones depict significant differences.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Positive correlations of CO₂ concentration with DOC (A) and negative correlations of CO₂ and CH₄ with O₂ (B, C). (D): Positive correlation of Al and DOC. Examples of other correlations between Fe and TE are provided in Fig. S3 of the Supplement.</figcaption></figure>

2023), we also tested correlations for these major components of col-
loids with other solutes (Table S3). Dissolved Al positively correlated
with lithogenic elements (Ti, V, Cr, Ga, Nb, Th and U) and Cd, whereas

Fe correlated with both soluble labile elements (Li, Mg, Si, P, Ca, Sr, As, Mo and Ba), heavy metals (Cr, Mn, Co, Ni, Cu and Zn) and insoluble trivalent and tetravalent hydrolysates such as Y, Zr, REEs and Hf

<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Ratio of mean GHG and solute concentrations in ultra-small (< 10 m²) to those in small (10–100 m²) water bodies across all permafrost zones in spring (A) and autumn (B).</figcaption></figure>
(Fig. S3).

Further treatment of the data via multi-parametric statistics (PCA) demonstrated the presence of two main factors. However, the explicatory capacity of these factors was quite low (13 and 12 %, respectively; **Fig. S4**). The 1st factor exhibited high loading (eigenvalue > 0.70) on lithogenic low solubility trace elements (Ti, V, Y, Zr, Nb, REEs, Hf, Th and U). The 2nd factor positively acted on CO₂, DOC, anions (Cl, SO₄, As and Mo) and labile cations including some transition metals (Mg, Ca, Mn, Fe, Co, Ni, As, Rb, Sr and Mo). The hierarchical cluster analysis generally confirmed the PCA structure and yielded two significant links between two main groups of components at Euclidean distances < 0.1 (Fig. S5). The first cluster included lithogenic elements such as low mobility trivalent and tetravalent hydrolysates. The second cluster grouped labile Mo, As, Sr, Ca and Mg along with some heavy metals (Mn, Ni, Co and Fe). Another cluster was represented by CO₂, CH₄, DOC, DIC and Electrical Conductivity.

### 3.3. Two main grid sizes of SWB and comparison with lakes and soil waters

Solute concentrations were compared between the two main size classes to evaluate the influence of SWB area on biogeochemical processes. In autumn, the majority of solutes did not demonstrate a sizable, more than a factor of 1.5, difference in mean concentrations between two size grids of SWB < 10 m² and 10–100 m² (Fig. 5). Nevertheless, a Mann-Whitney test applied for the entire data set of SWB averaged across all permafrost zones did not reveal any significant (at p < 0.05) difference in DOC, GHG, major and trace solute concentrations in ultra-small (< 10 m²) and other (10–100 m² area) water bodies (Table S4). The latter finding greatly facilitates upscaling the obtained results to a larger territory of permafrost peatlands: below 100 m² surface area for water bodies, there is no necessity for explicit accounting for GHG and solute concentration change with SWB’s area. Overall, it helps to overcome the cost-prohibitive inventory of organic and inorganic solute pools and GHG fluxes in such territories, given the scarcity of data on carbon, GHG and solute concentration dynamics in ultra-small water bodies.

The hydrological continuum of permafrost peatlands typically includes gravitational soil water and atmospheric precipitates which are first accumulated at the bottom of active (thawed) layer and then transported along this boundary to small water bodies, thaw ponds and thermokarst lakes (Loiko et al., 2017; Raudina et al., 2018). Within the continuum of water flow among major reservoirs (soil water, surface waters, ponds, and lakes), SWBs can be considered distinct compartments within the overall hydrological pathway from soil to river. In this regard, we compared concentrations of GHG and solutes in soil water, SWB, and thermokarst lakes of the WSL averaged across all seasons and study sites (Table S5). This comparison is based on the mean values calculated in this study individually for each site (Kogalym, Khanymey, Urengoi, and Tazovsky) and those reported in previous studies on soil (suprapermafrost) waters (Raudina et al., 2018) and thermokarst lakes (Manasypov et al., 2020) for the same locations. The highest concentrations of GHG are observed in SWB (Fig. 6 A, B). DOC and a number of major and trace elements demonstrated an expected decrease in concentration in the sequence “soil water > SWB > lakes”, with an overall magnitude decrease by a factor of 3 to 5: P, K, Fe, Si, Mo, V, Cr, Ni, Cu, Cd, TE³⁺ and TE⁴⁺ (Fig. 6 C–J). Elements like B, Cl, Na, Mg, Ca, Ba, Zn, Pb, As and Sb, that originated from atmospheric input, were invariant to the type of surface waters or exhibited maximal concentration in thermokarst lakes.

The difference in GHG and solute concentrations between SWB and thermokarst lakes has been inspected via histograms for mean concentration ratios of two main seasons when SWB water coverage was most pronounced – spring and autumn – separately for each permafrost zone (Fig. S6). In spring, the SWB were preferentially enriched in elements which originated from vegetation leachates (K, P and Rb), but also in CO₂ and CH₄ (in two southern sites). In the most northern site (Tazovsky), particular enrichment in Cs could be linked to the effect of mineral substrate (desorption from marine clays). In autumn, the enrichment of SWB relative to lakes was mostly pronounced for GHG, DOC and macronutrients (P and Si).

<figure><img src="image_9.png" /><figcaption>**Fig. 6.** Comparison of GHG (CH₄, A; CO₂, B), DOC (C) and some major and trace solute concentrations (K, D; P, E; Fe, F; Cr, G; Ni, H, Cd, I and La, J) in suprapermafrost soil water (blue circles; Raudina et al., 2019), small water bodies (green squares; this study) and thermokarst lakes (red diamonds; Manasypov et al., 2022). The data are averaged across seasons and 4 main study sites (Kogalym, Khanymey, Urengoi and Tazovsky). Note log Y scale for K, P and Fe. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)</figcaption></figure>
# 4. Discussion

## 4.1. Temporal and spatial GHG and DOC pattern

Comparing the seasonal dynamics of SWB observed in this study with previous findings from thermokarst lakes in Western Siberia's discontinuous permafrost zone (Manasypov et al., 2015) and across a broad permafrost gradient (Manasypov et al., 2020) revealed several key patterns. Based on observations from peatland pools globally (Arsenault et al., 2018; Arsenault et al., 2019; Arsenault et al., 2023), in Canadian permafrost peatlands (Laurion et al., 2010; Bouchard et al., 2014; Bouchard et al., 2017; Bouchard et al., 2018) and Northern Sweden (Kuhn et al., 2018; Karlsson et al., 2010), the primary hydrochemical changes typically occur during the unfrozen ('active') season (Ala-aho et al., 2018a). In these systems, dominant processes are spring dilution from snowfall followed by summer evaporation and autochthonous biological activity when the water body is supplied by suprapermafrost waters (Manasypov et al., 2015; Manasypov et al., 2020; Shirokova et al., 2013, 2020). To some extent, summertime production, respiration, and CO₂ uptake in SWBs may resemble those observed in proglacial lakes of the Canadian High Arctic (St. Pierre et al., 2019). The most intense exchange of solutes between sediments and the water column in the WSL likely takes place in early autumn as freezing begins, when both the active layer and SWB connections to soil water are at their peak. However, in ultra-small, shallow water bodies, the absence of distinct, permanent sediments and limited biological activity—mainly due to the dystrophic nature of the water column—may reduce the expression of these processes on the seasonal and spatial scales observed in this study.

Dissolved CH₄ concentrations in SWBs were 10 to 100 times lower than those of CO₂. Typically, in inland waters of permafrost peatlands, such as thermokarst lakes and rivers, CH₄ concentrations and fluxes account for less than 1 % of those of CO₂ (Serikova et al., 2019; Krickov et al., 2024; Vorobeyev et al., 2022, 2024). The higher CH₄:CO₂ ratios observed in SWBs compared to lakes and rivers suggest pronounced CH₄ generation in bottom layers and a limited methanotrophy in SWBs. This is particularly evident given the very shallow water depth (10–30 cm) and the partially anoxic conditions, with dissolved oxygen saturation ranging from 30 % to 90 %.

The highest pCO₂ levels observed during the summer in the sporadic permafrost zone likely indicate (i) strong connectivity to CO₂-rich soil waters (Raudina et al., 2018) and (ii) CO₂ production via bio- and photodegradation of dissolved and particulate organic matter (OM) within the water column (Turner et al., 2016; Vachon et al., 2016; Chupakov et al., 2024; Xiao et al., 2024). This is supported by the peak summer water temperature (18 ± 1 °C), which promotes both deeper hydrological connectivity and OM degradation. However, since high CO₂ concentrations were also detected in autumn, albeit at much lower water temperatures (2–3 °C), we suggest that lateral CO₂ influx from shallow subsoil and suprapermafrost waters plays a greater role than in-column OM degradation. Similar conclusion has been achieved based on both diel observations of DOC and CO₂ pattern in thermokarst lakes of the region (Shirokova et al., 2020) and mesocosm experiments in permafrost peatlands (Manasypov et al., 2017; Shirokova et al., 2021). Positive correlations between CO₂ and DOC may indicate that both DOM breakdown through photo- and biodegradation in very shallow SWB can be at least partially responsible for CO₂ production in the water column (i.e., Shirokova et al., 2019; Chupakov et al., 2024). More likely, these correlations reflect the inflow of CO₂- and DOC-rich suprapermafrost waters (Raudina et al., 2018). Negative relationships between CO₂ and CH₄ with DO (R<sub>S</sub> = -0.47 and -0.39, respectively; see Fig. 4 B, C) are common in western Siberian peatland waters (Krickov et al., 2023, 2024; Vorobeyev et al., 2024) and may suggest diffusion from partially anoxic sediments or the inflow of suboxic soil waters into surface waters. Based on detailed diel observations of the CO₂ regime in small thermokarst lakes and thaw ponds of western Siberia, Shirokova et al. (2020) ruled out planktonic photosynthetic and heterotrophic activity in

the water column, as well as DOM photolysis, as major drivers of the observed CO₂ variations. Instead, they suggested that the balance between benthic respiration of dissolved and particulate organic matter and the primary productivity of periphyton, aquatic macrophytes, and submerged mosses was responsible for enhanced CO₂ emissions at night and CO₂ uptake or decrease during the day. In this context, small water bodies in permafrost peatlands may exhibit distinct CO₂ regulation mechanisms compared to those observed across a large number of lakes worldwide (e.g., Golub et al., 2023; Xiao et al., 2024).

At the Khanymey site, located at the most active permafrost thaw front (see Fig. S2 in the Supplement), CO₂ and DOC concentrations peak during autumn. This coincides with the period of maximum active layer thickness (ALT), accompanied by a substantial release of biolabile dissolved organic matter (DOM) from thawing peat ice, which can then undergo processing in surface waters (Lim et al., 2021, 2022b; Krickov et al., 2024). Lower SUVA₂₅₄ values in Khanymey's SWB (Fig. 2 F) further suggest the mobilization of optically transparent organic matter from thawing ice. Additionally, dissolved phosphorus, which is highly concentrated in dispersed ice (Lim et al., 2022b; Kuzmina et al., 2023), also reached its highest levels at the Khanymey site (Fig. S2). The connectivity between surface and soil/subsoil waters, likely most pronounced at the end of the season, systematically decreases moving northward, as indicated by water isotope studies (Ala-aho et al., 2018b). In particular, the connectivity between lakes, bogs and rivers is achieved via water movement along the permafrost table in the thawed active layer, in the form of so-called suprapermafrost flow.

As the active layer depth progressively increased during the summer-autumn season, more groundwater began to flow into the surface water bodies. This is proven by water isotope (δ¹⁸O and deuterium excess) analyses (Ala-aho et al., 2018a, b). Therefore, the present study corroborates previous findings by demonstrating that electrical conductivity, which reflects total salt content and the connectivity between SWB and soil waters, increases from spring to autumn and decreases moving northward. (Fig. 2 D). The information obtained on water, dissolved carbon, and GHG patterns in SWBs of western Siberia has provided a better understanding of the dominant sources of other major and trace elements in these aquatic landscapes, as discussed below.

## 4.2. Source of inorganic solutes in SWB

As in the thermokarst lakes and thaw ponds of the Western Siberian Lowland (WSL) (Manasypov et al., 2015, 2023; Shirokova et al., 2021), shallow surface water bodies have three primary solute sources: (i) wave-induced abrasion of coastal peat and leaching of peat particles, (ii) degradation of plant litter with subsequent leachate delivery via surface flow, and (iii) inflow of suprapermafrost waters at the boundary between active and frozen layers. Some atmospherically derived trace metals and metalloids (e.g., Pb, Cd, Zn, Cs, Sb and As) are introduced to surface waters through snowmelt (Krickov et al., 2022), while other macro- and micronutrients (e.g., K, Rb, Mo and SO₄) may leach from litter ash following wildfires, which are common in western Siberian peatlands (Kuzmina et al., 2022). During the open water period from May/June to October, suprapermafrost water, originating from rain and snowmelt, percolates through the moss and lichen layer and thawed peat ice as the active layer thickness (ALT) gradually increases.

The spatial variation in chemical composition of SWB along the south-north gradient sampled in this study was influenced by permafrost coverage and the presence of mineral substrates beneath peat layers. Specifically, a northward increase in concentrations of certain trace metals (Fe, Ni, Mn, Co, C and Cr), alkalis (Li, Rb), alkaline earth metals (Ca and Sr) and lithogenic elements (Y and REEs) in both SWB and thermokarst lakes of western Siberia (see Fig. S2) suggests a closer proximity of marine clays to the peat layer, enhancing interaction with surface waters. This effect was particularly evident in the Tazovky region and is consistent with findings from previous studies on large thermokarst lakes in the northern WSL (Manasypov et al., 2014;
Manasypov et al., 2020). Additionally, the consistently high concentrations of DOC across all lentic waters studied in the WSL (10–60 mg L⁻¹) facilitate the transport of divalent metals and lithogenic trivalent hydrolysates as organic and organo-Fe/Al colloids (Pokrovsky et al., 2016; Manasypov et al., 2023). This is further supported by positive correlations between Al, P and trivalent/tetravalent trace elements with Fe and DOC (Fig. 4 D and Fig. S3). Consequently, in areas with mineral deposits, DOM-driven leaching of trace metals and lithogenic elements from clay minerals occurs via subsurface waters, delivering these solutes to the SWB. This process is especially pronounced in autumn, during the period of maximum connectivity between soil and surface waters and the greatest depth of the active layer. To contextualize the biogeochemistry of SWBs within the broader environmental framework of permafrost peatlands, we compared solute concentrations in SWBs to those in adjacent thermokarst lakes. This comparison aimed to evaluate the relative importance of SWBs in regulating carbon, GHGs, and nutrient dynamics in the inland waters of northern wetlands, as detailed below.

### 4.3. Role of SWB compared to thermokarst lakes in GHG regime, nutrient and trace element storage

It is important to note that when comparing our findings with existing data on lakes and ponds from the WSL territory, we can be confident that the environmental context and the methods of sampling and analysis are largely identical. This is because our study of SWBs was conducted during the same field campaign as that of thermokarst lakes and thaw ponds of the WSL (Manasypov et al., 2020; Serikova et al., 2019). Additionally, we ensured that all studied SWBs were located within the watersheds of large thermokarst lakes and thaw ponds previously examined in our group's earlier studies. A histogram of GHG and solute concentration ratios of SWB: thermokarst lakes, averaged across two seasons and four permafrost zones for the entire western Siberia (Fig. 7) demonstrated that SWB are strongly enriched in CH₄, CO₂, DOC, macro- and micro-nutrients (P, Si, Co, Mo, Rb, Fe and Si), Cs and lithogenic elements (Ti, Nb, Th and REEs). These components were likely delivered in large quantities from partially anoxic soil waters, vegetation litter, and soil mineral layers. In contrast, lakes generally exhibited higher concentrations of B, Na, Zn, and Ba compared to SWB. This difference can be attributed to more pronounced direct atmospheric inputs in larger water bodies, as observed in snowpack studies from this region (Shevchenko et al., 2017; Krickov et al., 2022).

The maximal concentrations of GHGs and redox-sensitive Mn observed in SWB, compared to lakes and soil waters (Fig. 6, Table S5), can be attributed to the specific redox conditions in SWB. These conditions result from a combination of suboxic water influx via supra-permafrost flow and organic matter (OM) processing in sediments and detritus within a very shallow water column. Notably, high concentrations of Mn and Fe were detected in all SWB at the Tazovsky site, located in the continuous permafrost zone (Fig. S2). The enrichment of surface waters with Mn and Fe observed in this study corroborates previous findings on pore water and ice from the Tazovsky region (Ji et al., 2021),

where manganese (Mn) was identified as an effective proxy for the connection between mineral soils and surface waters during the summer-autumn thaw. Taken together, these observations may have implications for the increased export of this metal by mid-sized Arctic rivers in western Siberia (Pokrovsky et al., 2022), which could partially explain the missing Mn source to the Arctic Ocean, as inferred from oceanographic studies (Middag et al., 2011).

Similar to previously studied thermokarst lakes of western Siberia, pH and concentrations of alkaline-earth metals and lithogenic elements increased northward. This increase, however, was not gradual: concentrations of labile, high-solubility elements, trace metals, lithogenic low-mobility hydrolysates and U changed insignificantly from the isolated to the discontinuous permafrost zone, and increased sharply (2 to 5-fold) in the continuous permafrost zone. This pattern, as illustrated in Fig. S2 of the Supplement, was most strongly pronounced during autumn, the period of maximum hydrological connectivity between the soil waters and surface waters of the WSL territory. A possible factor affecting this pattern is shallower peat deposits in the most northern site (Tazovsky) of the tundra zone, where the thawed layer reaches the mineral horizon represented by marine clays containing illite, chlorite and montmorillonite (Lim et al., 2022a). On one hand, labile anions, cations, and Si can be desorbed (leached) from clay minerals or accumulated in ground ice, and subsequently released as the active layer thickens. On the other hand, marine clays can efficiently release low-mobility lithogenic elements in the form of organo-mineral colloids, facilitated by the high concentration of dissolved organic matter (DOM) in surface waters at the Tazovsky site (Fig. 2E). The higher concentrations of lithogenic elements in SWB compared to lakes in this region may be attributed to the effects of cryoturbation in mineral (marine clay) horizons, which are exposed to the surface and interact with surface waters. This enrichment is likely driven by the excavation of subsurface mineral layers through slumping and cryoturbation processes, phenomena that are particularly pronounced in the continuous permafrost zone (Kaiser et al., 2007).

### 4.4. Global significance of small water bodies in the context of climate change and permafrost thaw

Strong enrichment of small water bodies in GHG relative to thaw ponds and thermokarst lakes has a fundamental importance – the role of SWB in CH₄ (and, to a lesser degree, CO₂) emissions may be comparable or higher than that of lakes, even though their surface area is less than 1 % the size of lakes (Polishchuk et al., 2018). However, more precise, seasonally-resolved, inventory of surface coverage by SWB for a larger territory of permafrost peatlands is necessary to confirm this possibility. Rising temperatures and increasing active layer thickness are expected to accelerate the thawing of nutrient- and metal-rich dispersed ground ice, particularly at the permafrost thawing front within sporadic to discontinuous permafrost zones (Lim et al., 2021, 2022b; Kuzmina et al., 2023). This may alter the proportion of the main sources supplying the carbon and inorganic solutes to the surface waters in these regions. Given that SWB demonstrate a stronger connection to surrounding peat

<figure><img src="image_10.png" /><figcaption>**Fig. 7.** The ratio of concentrations of GHG, DOC, macro- and micronutrients in SWB (this study) to that of thermokarst lakes (Manasypov et al., 2022), averaged across 4 permafrost zones of the WSL and 2 seasons.</figcaption></figure>
soils compared to lakes, due to the much higher circumference to volume ratio of the former, the impact of ground ice thaw on SWB hydrochemistry is expected to be most strongly pronounced. Further, the number of small and ultra-small lakes in these permafrost zones is increasing whereas large thermokarst lakes are systematically diminishing (Kirpotin et al., 2009, 2011; Polishchuk and Kupriyanov, 2022). Overall, a general trend of SWB formation and large lake disappearance is pronounced across the entire Arctic and subarctic territory (Marsh et al., 2009; Grosse et al., 2013), especially in the continuous permafrost zone of western Siberia (Smith et al., 2005; Kravtsova and Rodionova, 2016; Polishchuk et al., 2018).

The global significance of these trends is that SWB could become central to carbon, nutrient and GHG mobilization as permafrost thaws in currently frozen peatlands. The connectivity of SWB with the surrounding hydrological network will likely be a critical factor in determining solute transfer from soil and dispersed ice to lakes, rivers and eventually the Arctic coast. Hydrological modeling combined with isotopic tracing would prove especially effective for evaluating this connectivity. In contrast, GHG emissions from SWB will primarily depend on the extent of water coverage and its duration over the active season. High-resolution (≤ 0.5 m) spatial measurements—using remote sensing, LiDAR, or drones—across the open water period and in multiple key sites along the permafrost gradient are essential to capture these dynamics.

## 5. Conclusions

This study investigated greenhouse gas dynamics and chemical compositions of ultra-small (<100 m²) water bodies in the world's largest permafrost peatland across four permafrost zones and three main hydrological open-water periods. Dissolved organic carbon, CO₂, and CH₄ concentrations increased from spring to autumn across all permafrost zones, suggesting progressively greater connectivity between subsurface/soil water and SWB throughout the year. Unlike in nearby lakes and rivers, CH₄ accounted up to 10% of dissolved GHG, indicating that SWB may act as local hotspots for methane emissions. The highest concentrations of carbon and GHG were observed in the sporadic to discontinuous permafrost zones, near the permafrost thaw front, likely due to extensive peat ice thaw and the mobilization of labile organic carbon and nutrients from soil to surface waters. In the northern continuous permafrost zone, where SWB are in contact with underlying clay substrates due to shallow peat and possible cryoturbation, these water bodies displayed the highest levels of labile and lithogenic elements. Analyses of DOC, CO₂, CH₄, and major and trace element concentrations across a wide range of SWB sizes demonstrated that explicit accounting for GHG and solute concentration changes with SWB area is not necessary.

Within the hydrological continuum of 'soil water - SWB - thermokarst lake,' major and trace solutes exhibited a systematic decrease, reflecting the progressive leaching of carbon, metals, and nutrients from peat porewater into suprapermafrost waters, then into SWB, and ultimately into larger lakes where nutrient, DOC, and metal concentrations diminished. Given the strong enrichment of SWB in organic carbon, CO₂, CH₄, and certain nutrients relative to thermokarst lakes, these small water bodies likely play a significant role in carbon and nutrient storage as well as greenhouse gas (GHG) emissions. This role may become even more critical as large lakes continue to disappear and new small water bodies form across the permafrost zone. Overall, SWB act as essential regulators of GHG dynamics and nutrient storage, particularly during the less-studied 'shoulder' seasons of spring and autumn.

### CRediT authorship contribution statement

Artem G. Lim: Writing – original draft, Methodology, Investigation, Formal analysis, Data curation. Rinat M. Manasypov: Writing – review & editing, Investigation, Conceptualization. Ivan V. Krickov: Writing –

review & editing, Methodology, Investigation. Liudmila S. Shirokova: Writing – review & editing, Methodology, Investigation, Data curation. Sergey N. Vorobyev: Writing – review & editing, Validation, Software, Formal analysis. Oleg S. Pokrovsky: Writing – original draft, Validation, Supervision, Resources, Project administration, Funding acquisition, Data curation, Conceptualization.

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgments

Main support for this work was from the RSF project 24-17-00300 "Role of lakes in carbon balance of the boreal zone, western Siberia". Partial support by TSU Programme "Priority-2030" and project PEACE of PEPR FairCarboN ANR-22-PEXF-0011 is also acknowledged.

## Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.jhydrol.2025.133343.

### Data availability

Primary hydrochemical data of sampled sites are available from the Mendeley Data, V1, https://data.mendeley.com/datasets/5gmww5ck5t/1.

### References

Ala-aho, P., Soulsby, C., Pokrovsky, O.S., Kirpotin, S.N., Karlsson, J., Serikova, S., Vorobyev, S.N., Manasypov, R.M., Loiko, S., Tetzlaff, D., 2018a. Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape. J. Hydrology 556, 279-293.

Ala-aho, P., Soulsby, C., Pokrovsky, O.S., Kirpotin, S.N., Karlsson, J., Serikova, S., Manasypov, R.M., Krickov, I., Lim, A., Tetzlaff, D., 2018b. Permafrost and lakes control river isotope composition across a boreal-arctic transect in the western Siberia lowland. Environ. Res. Lett. 13 (3). Art No 034028.

Arsenault, J., Talbot, J., Moore, T.R., 2018. Environmental controls of C, N and P biogeochemistry in peatland pools. Sci. Total Environ. 631-632, 714-722.

Arsenault, J., Talbot, J., Moore, T.R., Beauvais, M.-P., Franssen, J., Roulet, N.T., 2019. The spatial heterogeneity of vegetation, hydrology and water chemistry in a peatland with open-water pools. Ecosystems 22, 1352-1367.

Arsenault, J., Talbot, J., Brown, L.E., Helbig, M., Holden, J., Hoyos-Santillan, J., Jolin, É., Mackenzie, R., Martinez-Cruz, K., Sepulveda-Jauregui, A., Lapierre, J.-F., 2023. Climate-driven spatial and temporal patterns in peatland pool biogeochemistry. Glob. Chang. Biol. 29, 4056-4068. https://doi.org/10.1111/gcb.16748.

Auda, Y., Lundin, E.J., Gustafsson, J., Pokrovsky, O.S., Cazaurang, S., Orgogozo, L., 2023. A new land cover map of two watersheds under long-term environmental monitoring in the Swedish Arctic using Sentinel-2 data. Water (MDPI) 15, 3311. https://doi.org/10.3390/w15183311.

Audry, S., Pokrovsky, O.S., Shirokova, L.S., Kirpotin, S.N., Dupré, B., 2011. Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments. Biogeosciences 8, 3341-3358.

Bastviken, D., Cole, J., Pace, M., Tranvik, L., 2004. Methane emissions from lakes: Dependence of lake characteristics, two regional assessments, and a global estimate. Global Biogeochemical Cycles, 18(4), Art No GB4009. doi:10.1029/2004GB002238.

Bouchard, F., Francus, P., Pienitz, R., Laurion, I., Feyte, S., 2014. Subarctic thermokarst ponds: investigating recent landscape evolution and sediment dynamics in thawed permafrost of Northern Québec (Canada). Arct. Antarct. Alp. Res. 46, 251-271.

Bouchard, F., MacDonald, L.A., Turner, K.W., Thienpont, J.R., Medeiros, A.S., Biskaborn, B.K., Korosi, J., Hall, R.I., Pienitz, R., Wolfe, B.B., 2017. Paleolimnology of thermokarst lakes: a window into permafrost landscape evolution. Arct. Sci. 3, 91-117.

Bouchard, F., Proult, V., Pienitz, R., Antoniades, D., Tremblay, R., Vincent, W.F., 2018. Periphytic diatom community structure in thermokarst ecosystems of Nunavik (Québec, Canada). Arct. Sci. 4, 110-129. https://doi.org/10.1139/as-2016-0020.

Chupakov, A.V., Chupakova, A., Zabelina, S.A., Shirokova, L.S., Pokrovsky, O.S., 2024. Seasonal and spatial pattern of bio- and photodegradation in boreal humic waters. Biogeosciences 21, 5725-5743. https://doi.org/10.5194/bg-21-5725-2024.

Golub, M., Koupaei-Abyazani, N., Vesala, T., Mammarella, I., Ojala, A., Bohrer, G., et al., 2023. Diel, seasonal, and inter-annual variation in carbon dioxide effluxes from lakes
and reservoirs. Environ. Res. Lett. 18 (3), 034046. https://doi.org/10.1088/1748-9326/acb834.

Gonzalez Moguel, R., Bass, A. M., Garnett, M. H., Pilote, M., Keenan, B., Matveev, A., & Douglas, P.M.J., 2021. Radiocarbon data reveal contrasting sources for carbon fractions in thermokarst lakes and rivers of eastern Canada (Nunavik, Quebec). J. Geophysical Research: Biogeosciences, 126, Art No e2020JG005938. doi: 10.1029/2020JG005938.

Grosse, G., Romanovsky, V., Walter, K., Morgenstern, A., Lantuit, H., Zimov, S., 2008. Distribution of thermokarst lakes and ponds at three yedoma sites in Siberia, Proc. of the 9th Int. Conf. on Permafrost (June 29 – July 3, 2008). Fairbanks, Alaska 2008, 551–556.

Grosse, G., Jones, B., Arp, C., 2013. Thermokarst lakes, drainage, and drained basins. In Treatise on Geomorphology, 3rd ed.; Schroder, J., Giardino, R., Harbor, J., Eds.; Academic Press: San Diego, CA, USA, Volume 8, pp. 325–353.

Czudek, T., Demek, J., 1970. Thermokarst in Siberia and its influence on the development of lowland relief. Quat. Res. 1, 103–120.

Holgerson, M.A., Raymond, P.A., 2016. Large contribution to inland water CO₂ and CH₄ emissions from very small ponds. Nat. Geosci. 9 (3), 222–226. https://doi.org/10.1038/ngeo2654.

Ji, X., Abakumov, E., Polyakov, V., Xie, X., 2021. Mobilization of geochemical elements to surface water in the active layer of permafrost in the Russian Siberian. Water Resources Res. 57, e2020WR028269. https://doi.org/10.1029/2020WR028269.

Jorgenson, M.T., Shur, Y., 2007. Evolution of lakes and basins in northern Alaska and discussion of the thaw lake cycle. J. Geophys. Research: Earth Surface 112, F02S17. https://doi.org/10.1029/2006JF000531.

Kaiser, C., Meyer, H., Biasi, C., Rusalimova, O., Barsukov, P., Richter, A., 2007. Conservation of soil organic matter through cryoturbation in Arctic soils in Siberia. J. Geophys. Res. 112 (G2). https://doi.org/10.1029/2006JG000258.

Karlsson, J., Christensen, T.R., Crill, P., Förster, J., Hammarlund, D., Jackowicz-Korczyński, M., Kokfelt, U., Roehm, C., Rosén, P., 2010. Quantifying the relative importance of lake emissions in the carbon budget of a subarctic catchment. J. Geophys. Res. 115, Art No G03006, doi: 10.1029/2010JG001305.

Karlsson, J.M., Lyon, S.W., Destouni, G., 2014. Temporal behavior of lake size-distribution in a thawing permafrost landscape in Northwestern Siberia. Remote Sens. (Basel) 6, 621–636.

Kaverin, D., Malkova, G., Zamolodchikov, D., Shiklomanov, N., Pastukhov, A., Novakovičkiy, A., Sadurtdinov, M., Skvortsov, A., Tsarev, A., Pochikalov, A., Malitsky, S., Kraev, G., 2021. Long-term active layer monitoring at CALM sites in the Russian European North. Polar Geogr. 44, 203–216. https://doi.org/10.1080/1088937X.2021.1981476.

Kirpotin, S., Polishchuk, Y., Bryksina, N., 2009. Abrupt changes of thermokarst lakes in Western Siberia: impacts of climatic warming on permafrost melting. Internat. J. Environ. Stud. 66 (4), 423–431.

Kirpotin, S., Polishchuk, Y., Bryksina, N., Sugaipova, A., Kouraev, A., Pokrovsky, O.S., Shirokova, L., Kolmakova, M., Manasypov, R., et al., 2011. West Siberian palsat peatlands: distribution, typology, cyclic development, present day climate-driven changes, seasonal hydrology and impact on CO₂ cycle. Int. J. Environ. Stud. 68, 603–623.

Knoblauch, C., Beer, C., Liebner, S., et al., 2018. Methane production as key to the greenhouse gas budget of thawing permafrost. Nature Clim. Change 8, 309–312. https://doi.org/10.1038/s41558-018-0095-z.

Kravtsova, V.I., Rodionova, T.V., 2016. Study of the dynamics of the area and number of thermokarst lakes in different areas of the Russian cryolithic zone using satellite images. Cryosph. Earth. 20 (1), 81–89.

Krickov, I.V., Lim, A.G., Shirokova, L.S., Krets, M.A., Pokrovsky, O.S., 2024. Fluvial carbon dioxide emissions peak at the permafrost thawing front in the Western Siberia Lowland. Sci. Total Environ. 936, Art No 173491. doi: 10.1016/j.scitotenv.2024.173491.

Krickov, I.V., Lim, A.G., Vorobyev, S.N., Shevchenko, V.P., Pokrovsky, O.S., 2022. Colloidal associations of major and trace elements in the snow pack across a 2800 km south-north gradient of western Siberia. Chem. Geol. 610, 121090. https://doi.org/10.1016/j.chemgeo.2022.121090.

Krickov, I.V., Lim, A.G., Krets, M., Shirokova, L.S., Karlsson, J., Pokrovsky, O.S., 2023. Environmental controllers for carbon emission and concentration patterns in Siberian rivers during different seasons. Sci. Total Environ. 859, Art No 160202. doi: 10.1016/j.scitotenv.2022.160202.

Krickov, I.V., Lim, A.G., Shirokova, L.S., Krets, M.A., Pokrovsky, O.S., 2024. Fluvial carbon dioxide emissions peak at the permafrost thawing front in the Western Siberia Lowland. Sci. Total Environ. 936, Art No 173491. doi: 10.1016/j.scitotenv.2024.173491.

Kuhn, M., Lundin, E.J., Giesler, R., Johansson, M., Karlsson, J., 2018. Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands. Scientific Rep. 8, Art No 535. doi:10.1038/s41598-018-27770-x.

Kuzmina, D., Lim, A.G., Loiko, S.V., Pokrovsky, O.S., 2022. Experimental assessment of tundra fire impact on element export and storage in permafrost peatlands. Sci. Total Environ. 853, 158701. https://doi.org/10.1016/j.scitotenv.2022.158701.

Kuzmina, D., Lim, A.G., Loiko, S.V., Shirokova, L.S., Julien, F., Rols, J.L., Pokrovsky, O.S., 2023. Dispersed ice of permafrost peatlands represents an important source of labile carboxylic acids, nutrients and metals. Geoderma, 429, Art No 116256. doi: 10.1016/j.geoderma.2022.116256.

Laurin I., Vincent W.F., MacIntyre S., Retamal L., Dupont C., Francis P., Pienitz R., 2010. Variability in greenhouse gas emissions from permafrost thaw ponds. Limnol. Oceanogr. 55(1), 115–133 55. doi: 10.4319/lo.2010.55.1.0115.

Lim, A.G., Loiko, S.V., Kuzmina, D.M., Krickov, I.V., Shirokova, L.S., Kulizhsky, S.P., Pokrovsky, O.S., 2022b. Organic carbon, and major and trace elements reside in labile low-molecular form in the ground ice of permafrost peatlands: a case study of

colloids in peat ice of Western Siberia. Environ. Sci. Process. Impacts. 24, 1443–1459.

Lim, A.G., Loiko, S.V., Kuzmina, D.M., Krickov, I.V., Shirokova, L.S., Kulizhsky, S.P., Vorobyev, S.N., Pokrovsky, O.S., 2021. Dispersed ground ice of permafrost peatlands: Potential unaccounted carbon, nutrient and metal sources. Chemosphere 266, 128953. https://doi.org/10.1016/j.chemosphere.2020.128953.

Lim, A.G., Loiko, S.V., Pokrovsky, O.S., 2022a. Sizeable pool of labile organic carbon in mineral soils of permafrost peatlands: an experimental approach. Geoderma, 409, Art No 115601. doi: 10.1016/j.geoderma.2021.115601.

Loiko, S.V., Pokrovsky, O.S., Raudina, T., Lim, A., Kolesnichenko, L.G., Shirokova, L.S., Vorobyev, S.N., Kirpotin, S.N., 2017. Abrupt permafrost collapse enhances organic carbon, CO₂ nutrient, and metal release into surface waters. Chem. Geol. 471, 153–165.

Loiko, S.V., Klimova, N.V., Kuzmina, D.M., Pokrovsky, O.S., 2020. Lake drainage in permafrost regions produces variable plant communities of high biomass and biological productivity. Plants (MDPI), 9 867. https://doi.org/10.3390/plants9070867.

Lundin, E.J., Klaminder, J., Giesler, R., Persson, A., Olefeldt, D., Heliasz, M., Christensen, T.R., Karlsson, J., 2016. Is the subarctic landscape still a carbon sink? Evidence from a detailed catchment balance. Geophys. Res. Lett. 43, 1988–1995. https://doi.org/10.1002/2015GL066970.

Matthews, J.A., Dahl, S.O., Berrisford, M.S., Nesje, A., 1997. Cyclic development and thermokarstic degradation in the mid-alpine zone at Leirpullan, Crevrefjel, southern Norway. Permafr. Periglac. Process. 8, 107–122.

Manasypov, R.M., Pokrovsky, O.S., Kirpotin, S.N., Shirokova, L.S., 2014. Thermokarst lake waters across the permafrost zones of western Siberia. Cryosphere 8, 1177–1193. https://doi.org/10.5194/tc-8-1177-2014.

Manasypov, R.M., Shirokova, L.S., Pokrovsky, O.S., 2017. Experimental modeling of thaw lake water evolution in discontinuous permafrost zone: Role of peat, lichen leaching and ground fire. Sci. Total Environ. 580, 245–257.

Manasypov, R.M., Fan, L., Lim, A.G., Krickov, I.V., Pokrovsky, O.S., Kuzyakov, Y., Dorodnikov, M., 2024. Size matters: aerobic methane oxidation and CO₂ production in the sediments of West Siberian shallow thermokarst lakes. Global Change Biol. 30, Art No e17120. doi: 10.1111/gcb.17120.

Manasypov, R.M., Lim, A.G., Krickov, I.V., Shirokova, L.S., Shevchenko, V.P., Aliev, R.A., Pokrovsky, O.S., 2022. Carbon storage and burial in thermokarst lakes of permafrost peatlands. Biogeochemistry 159 (1), 69–86. https://doi.org/10.1007/s10533-022-00914-y.

Manasypov, R.M., Lim, A.G., Krickov, I.V., Shirokova, L.S., Vorobyev, S.N., Kirpotin, S. N., Pokrovsky, O.S., 2020. Spatial and seasonal variations of C, nutrient, and metal concentration in thermokarst lakes of Western Siberia across a permafrost gradient. Water. 12 (6), 1830. https://doi.org/10.3390/w12061830.

Manasypov, R.M., Vorobyev, S.N., Loiko, S.V., Kritzkov, I.V., Shirokova, L.S., Shevchenko, V.P., Pokrovsky, O.S., 2015. Seasonal dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost zone of western Siberia. Biogeosciences 12 (10), 3009–3028. https://doi.org/10.5194/bg-12-3009-2015.

Manasypov, R.M., Lim, A.G., Krickov, I.V., Raudina, T.V., Kurashev, D.G., Shirokova, L. S., Pokrovsky, O.S., 2023. Colloids in thermokarst lakes along a permafrost and climate gradient of permafrost peatlands in Western Siberia using in situ dialysis procedure. Water, 15, 1783, doi: 10.3390/w15091783.

Marsh, P., Russell, M., Pohl, S., Haywood, H., Onlin, C., 2009. Changes in thaw lake drainage in the Western Canadian Arctic from 1950 to 2000. Hydrol. Process. 23, 145–158.

McCalley, C.K., Woodcroft, B.J., Hodgkins, S.B., Wehr, R.A., Kim, E.H., Mondav, R., Crill, P.M., Chanton, J.P., Rich, V.I., Tyson, G.W., Saleska, S.R., 2014. Methane dynamics regulated by microbial community response to permafrost thaw. Nature 514, 478–481. https://doi.org/10.1038/nature13798.

McEnroe, N.A., Roulet, N.T., Moore, T.R., Garneau, M., 2009. Do pool surface area and depth control CO₂ and CH₄ fluxes from an ombrotrophic raised bog, James Bay, Canada? J. Geophys. Res. 114 (1), 1–9. https://doi.org/10.1029/2007JG000639.

McGuire, A.D., Anderson, L.G., Christensen, T.R., Scott, D., Laodong, G., Hayes, D.J., Martin, H., Lorenson, T.D., Macdonald, R.W., Nigel, R., 2009. Sensitivity of the carbon cycle in the Arctic to climate change. Ecol. Monogr. 79, 523–555. https://doi.org/10.1890/08-2025.1.

Middag, R., de Baar, H., Laan, P., Klunder, M., 2011. Fluvial and hydrothermal input of manganese into the Arctic Ocean. Geochim. Cosmochim. Acta 75, 2393–2408. doi: 10.1016/j.gca.2011.02.011.

Miner, K.R., Turetsky, M.R., Malina, E., Bartsch, A., Tamminen, J., McGuire, A.D., Fix, A., Sweeney, C., Elder, C.D., Miller, C.E., 2022. Permafrost carbon emissions in a changing Arctic. Nat. Rev. Earth Environ. 3, 55–67. https://doi.org/10.1038/s43017-021-00230-3.

Noskov, Y., Manasypov, R.M., Ermolaeva, N.I., Aantonets, D.V., Shirokova, L.S., Pokrovsky, O.S., 2024. Environmental factors controlling seasonal and spatial variability of zooplankton in thermokarst lakes along a permafrost gradient of Western Siberia. Science Total Environ. 922, Art No 171284. doi: 10.1016/j.scitotenv.2024.171284.

Pelletier, L., Strachan, I.B., Garneau, M., Roulet, N.T., 2014. Carbon release from boreal peatland open water pools: implication for the contemporary C exchange. J. Geophys. Res.: Biogeosciences 119 (3), 2292–2311.

Pokrovsky, O.S., Dupré, B., Schott, J., 2005. Fe-al organic colloids control the speciation of trace elements in peat soil solutions: results of ultrafiltration and dialysis. Aquat. Geochem. 11, 241–278.

Pokrovsky, O.S., Shirokova, L.S., Manasypov, R.M., Kirpotin, S.N., Kulizhsky, S.P., Kolesnichenko, L.G., Loiko, S.V., Vorobyev, S.N., 2014. Thermokarst lakes of
Western Siberia: a complex biogeochemical multidisciplinary approach. Int. J. Environ. Stud. 71, 733-748. https://doi.org/10.1080/00207233.2014.942535.

Pokrovsky, O.S., Shirokova, L.S., Kirpotin, S.N., Audry, S., Viers, J., Dupré, B., 2011. Effect of permafrost thawing on organic carbon and trace element colloidal speciation in the thermokarst lakes of western Siberia. Biogeosciences 8, 565-583.

Pokrovsky, O.S., Shirokova, L.S., Kirpotin, S.N., Kulizhsky, S.P., Vorobiev, S.N., 2013. Impact of Western Siberia heat wave 2012 on greenhouse gases and trace metal concentration in thaw lakes of discontinuous permafrost zone. Biogeosciences 10, 5349-5365.

Pokrovsky, O.S., Manasypov, R.M., Loiko, S.V., Shirokova, L.S., 2016. Organic and organo-mineral colloids in discontinuous permafrost zone. Geochim. Cosmochim. Acta 188, 1-20. https://doi.org/10.1016/j.gca.2016.05.035.

Pokrovsky, O.S., Manasypov, R.M., Kopysov, S.G., Krickov, I.V., Shirokova, L.S., Loiko, S. V., Lim, A.G., Kolesnichenko, L.G., Vorobyev, S.N., Kirpotin, S.N., 2020. Impact of permafrost thaw and climate warming on riverine export fluxes of carbon, nutrients and metals in Western Siberia. Water (MDPI) 12, Art No 1817.

Pokrovsky, O.S., Manasypov, R.M., Chupakov, A.V., Kopysov, S. 2022. Element transport in the Taz River, western Siberia. Chemical Geology 614, Art No 121180. doi: 10.1016/j.chemgeo.2022.121180.

Polishchuk, Y., Bogdanov, A.N., Muratov, I.N., Polishchuk, V., Lim, A., Manasypov, R.M., Pokrovsky, O.S., 2018. Minor contribution of small thaw ponds to the pools of carbon and methane in the inland waters of the permafrost-affected part of the Western Siberian Lowland. Environ. Res. Lett. 13 (4), 045002. https://doi.org/10.1088/1748-9326/aab046.

Polishchuk, Y.M., Bogdanov, A.N., Polishchuk, V.Y., Manasypov, R.M., Shirokova, L.S., Kirpotin, S.N., Pokrovsky, O.S., 2017. Size distribution, surface coverage, water, carbon, and metal storage of thermokarst lakes in the permafrost zone of the Western Siberia Lowland. Water 9, 228. https://doi.org/10.3390/w9030228.

Polishchuk, Y.M., Kupriyanov, M.A., 2022. Study of the dynamics of thermokarst lakes in the West Siberian Arctic based on the analysis of time series of satellite measurements. Bulletin Ugra State University No. 3, 137-144 in Russian.

Raudina, T.V., Loiko, S.V., Lim, A., Manasypov, R.M., Shirokova, L.S., Istigechev, G.I., Kuzmina, D.M., Kulizhsky, S.P., Vorobyev, S.N., Pokrovsky, O.S., 2018. Permafrost thaw and climate warming may decrease the CO₂ carbon, and metal concentration in peat soil waters of the Western Siberia Lowland. Sci. Total Environ. 634, 1004-1023.

Raudina, T.V., Loiko, S.V., Lim, A.G., Krickov, I.V., Shirokova, L.S., Istigechev, G.I., Kuzmina, D.M., Kulizhsky, S.P., Vorobyev, S.N., Pokrovsky, O.S., 2017. Dissolved organic carbon and major and trace elements in peat powerful of sporadic, discontinuous, and continuous permafrost zones of western Siberia. Biogeosciences 14, 3561-3584.

Raudina, T.V., Loiko, S.V., Istigechev, G.I., Kulizhsky, S.P., Orgogozo, L., Pokrovsky, O. S., 2025. Contrasting soil temperature regimes in microlandscapes of the discontinuous permafrost zone (Western Siberia). Geoderma, submitted after revision.

Schuur, E.A.G., McGuire, A.D., Schädel, C., Grosse, G., Harden, J.W., Hayes, D.J., Hugelius, G., Koven, C.D., Kuhry, P., Lawrence, D.M., Natali, S.M., Olefeldt, D., Romanovsky, V.E., Schaefer, K., Turetsky, M.R., Treat, C.C., Vonk, J.E., 2015. Climate change and the permafrost carbon feedback. Nature 520, 171-179. https:// doi.org/10.1038/nature14338.

Serikova, S., Pokrovsky, O.S., Laudon, H., Krickov, I.V., Lim, A.G., Manasypov, R.M., Karlsson, J., 2019. High carbon emissions from thermokarst lakes of Western Siberia. Nature Comm. 10, Art No 1552. DOI: 10.1038/s41467-019-09592-1.

Shevchenko, V.P., Pokrovsky, O.S., Vorobyev, S.N., Krickov, I.V., Manasypov, R.M., Politova, N.V., Kopysov, S.G., Dara, O.M., Auda, Y., Shirokova, L.S., Kolesnichenko, L.G., Zemtsov, V.A., Kirpotin, S.N., 2017. Impact of snow deposition on major and trace element concentrations and elementary fluxes in surface waters of the Western Siberian Lowland across a 1700 km latitudinal gradient. Hydrol. Earth System Sci. 21, 5725-5746. https://doi.org/10.5194/hess-21-5725-2017.

Shirokova, L.S., Pokrovsky, O.S., Kirpotin, S.N., Desmukh, C., Pokrovsky, B.G., Audry, S., Viers, J., 2013. Biogeochemistry of organic carbon, CO₂, CH₄, and trace elements in thermokarst water bodies in discontinuous permafrost zones of Western Siberia. Biogeochemistry 113, 573-593. https://doi.org/10.1007/s10533-012-9790-4.

Shirokova, L.S., Payandi-Rolland, D., Lim, A., Manasypov, R.M., Allen, J., Bénézeth, P., Rols, J.-L., Karlsson, J., Pokrovsky, O.S., 2020. Diurnal cycle of C concentration and emission fluxes in humic thaw ponds of frozen peatlands: application for C balance constraints. Science Total Environ. 737, Art No 139671, doi: 10.1016/j.scitotenv.2020.139671.

Shirokova, L.S., Chupakov, A.V., Ivanova, I.S., Moreva, O.Y., Zabelina, S.A., Shutskiy, N. A., Pokrovsky, O.S., 2021. Lichen, moss and peat control of C, nutrient and trace metal regime in lakes of permafrost peatlands. Sci. Total Env. 782, 146737. https:// doi.org/10.1016/j.scitotenv.2021.146737.

Smith, L.C., Sheng, Y., MacDonald, G.M., Hinzman, L.D., 2005. Disappearing Arctic lakes. Science 308 (3), 111-154.

Song, C., Liu, S., Wang, G., Zhang, L., Rosentreter, J. A., Zhao, G., Sun, X., Yao, Y., Mu, C., Sun, S., Hu, Z., Lin, S., Sun, J., Li, Y., Wang, Y., Li, Y., Raymond, P.A., Karlsson, J., 2024. Inland water greenhouse gas emissions offset the terrestrial carbon sink in the northern cryosphere. Science advances, 10(39), Art No eadp0024. doi: 10.1126/ sciadv.adp0024.

St. Pierre, K A, St. Louis, V. L., Schiff, S.L., Lehnherr, I., Dainard, P.G., Gardner, A.S., Aukes, P.J.K., Sharp, M.J., 2019. Proglacial freshwater emissions are significant and previously unrecognized sinks of atmospheric CO₂. Proc. Natl Acad. Sci. 116 (36), 17690-17695, doi: 10.1073/pnas.1904241116.

Stolpmann, L., Coch, C., Morgenstern, A., Boike, J., Fritz, M., Herzschuh, U., Stoof- Leichsenring, K., Dvornikov, Y., Heim, B., Lenz, J., et al., 2021. First pan-Arctic assessment of dissolved organic carbon in lakes of the permafrost region. Biogeosciences 18, 3917-3936. https://doi.org/10.5194/bg-18-3917-2021.

Stolpmann, L., Nitze, I., Bussmann, I., Jones, B. M., Lenz, J., Meyer, H., Wolter, J., Grosse, G., 2024. Thermokarst lake change and lake hydrochemistry: A snapshot from the Arctic Coastal Plain of Alaska. EGUSphere [preprint]. doi: 10.5194/ egusphere-2024-2822.

Taillardat, P., Linkhorst, A., Deblois, C.P., Prijac, A., Gandois, L., Tremblay, A., Garneau, M., 2024. A carbon source in a carbon sink: Carbon dioxide and methane dynamics in open-water peatland pools. Global Biogeochem. Cycles 38, e2023GB007909. https://doi.org/10.1029/2023GB007909.

Tan, Z., Zhuang, Q., Anthony, K.W., 2015. Modeling methane emissions from arctic lakes: model development and site-level study. J. Adv. Model. Earth Syst. 7, 459-483. https://doi.org/10.1002/2014MS000344.

Tank, S.E., Lesack, L.F.W., Hesslein, R.H., 2009. Northern delta lakes as summertime CO₂ absorbers within the arctic landscape. Ecosystems 12, 144-157. https://doi.org/ 10.1007/s10021-008-9213-5.

Tank, S., Vonk, J., Walvoord, M., McClelland, J., Laurion, I., Abbott, B., 2020. Landscape matters: predicting the biogeochemical effects of permafrost thaw on aquatic networks with a state factor approach. Permafrost Periglacial Proc. 31, 358-370. https://doi.org/10.1002/pppp.2057.

Trofimova, I.E., Balybina, A.S., 2014. Classification of climates and climatic regionalization of the West-Siberian plain. Geogr. Nat. Resour. 35, 114-122. https:// doi.org/10.1134/S1875372814020024.

Turetsky, M.R., Abbott, B.W., Jones, M.C., Anthony, K.W., Olefeldt, D., Schuur, E.A.G., Koven, C., McGuire, A.D., Grosse, G., Kuhry, P., et al., 2019. Permafrost collapse is accelerating carbon release. Nature 569, 32-34.

Turner, T.E., Billett, M.F., Baird, A.J., Chapman, P.J., Dinsmore, K.J., Holden, J., 2016. Regional variation in the biogeochemical and physical characteristics of natural peatland pools. Sci. Total Environment 545-546, 84-94.

Vachon, D., Lapierre, J.-F., del Giorgio, P.A., 2016. Seasonality of photochemical dissolved organic carbon mineralization and its relative contribution to pelagic CO₂ production in northern lakes. J. Geophys. Res. Biogeosci. 121, 864-878.

Vonk, J.E., Tank, S.E., Bowden, W.B., Laurion, I., Vincent, W.F., Alekseychik, P., Amyot, M., Billet, M.F., Canário, J., Cory, R.M., et al., 2015. Reviews and syntheses: effects of permafrost thaw on Arctic aquatic ecosystems. Biogeosciences 12, 7129-7167.

Vonk, J.E., Tank, S.E., Walvoord, M.A., 2019. Integrating hydrology and biogeochemistry across frozen landscapes. Nat. Commun. 10, 5377. https://doi.org/ 10.1038/s41467-019-13361-5.

Vorobyev, S.N., Pokrovsky, O.S., Korets, M., Shirokova, L.S., 2022. A snapshot-assessment of carbon emission and export in a pristine river draining permafrost peatlands (Taz River, Western Siberia). Front. Environ. Sci. 10, Art No 987596. doi: 10.3389/fenvns.2022.987596.

Vorobyev, S.N., Kolesnichenko, Y., Karlsson, J., Pokrovsky, O.S., 2024. Carbon emission from the Lower Ob River floodplain during spring flood. Science Total Environment, 954, Art No 176294. doi: 10.1016/j.scitotenv.2024.176294.

Walvoord, M., Striegl, R., 2021. Complex vulnerabilities of the water and aquatic carbon cycles to permafrost thaw. Front. Clim. 3. Art No 730402.

Xiao, Q., Xu, X., Qi, T., Luo, J., Lee, X., Duan, H., 2024. Lakes shifted from a carbon dioxide source to a sink over past two decades in China. Science Bulletin 69 (12), 1857-1861. https://doi.org/10.1016/j.scib.2024.03.022.

Yeghicheyan, D., Aubert, D., Bouhnik-Le Coz, M., Chmeleff, J., Delpoux, S., Djouraev, I., Granier, G., Lacan, F., Piro, J.-L., Rousseau, T., Cloquet, C., Marquet, A., Menniti, C., Pradoux, C., Freydier, R., Vieira da Silva-Filho, E., Suchorski, K., 2019. A new interlaboratory characterisation of silicon, rare earth elements and twenty-two other trace element concentrations in the natural river water certified reference material SLRS-6 (NRC-CNRC). Geostandards Geoanal. Res. 43, 475-496. https://doi.org/ 10.1111/ggr.12268.

Zabelina, S., Shirokova, L., Klimov, S., Chupakov, A., Lim, A., Polishchuk, Y., Polishchuk, V., Bogdanov, A., Muratov, I., Guerin, F., Karlsson, J., Pokrovsky, O., 2021. Carbon Emission from Thermokarst Lakes in NE European Tundra. Limnol. Oceanogr. 66 (S1), S216-S230. https://doi.org/10.1002/Ino.11560.