Submarine groundwater discharge (SGD) is an important pathway of dissolved matter transport to coastal ecosystems, yet its identification in methane seep environments remains challenging because chemical signals are modified by sedimentary biogeochemical processes. This study evaluated hydrochemical tracers of SGD in methane seep sites, bacterial mat areas, and background sediments along the southern coast of Crimea (Black Sea). The studied settings exhibited distinct water chemical characteristics. Chloride concentrations decreased from 10.6 to 11.2 g L−1 in background waters, to 8.7–9.3 g L−1 in bacterial mat pore waters and to 7.7 g L−1 in sediment–water interface waters, indicating the presence of a low-salinity water component. Dissolved silica increased by approximately one order of magnitude relative to background values at methane-associated sites. Methane concentrations ranged from 0.025 to 1058 μM, with the highest values occurring in bacterial mat areas. These zones were further characterized by sulfate depletion (down to 0.9 g L−1), elevated normalized alkalinity, ammonium concentrations reaching 8000 μg L−1, high sulfide contents, and low dissolved Fe concentrations consistent with iron sulfide precipitation. The results demonstrate that no single hydrochemical parameter is sufficient to identify SGD in methane-affected coastal sediments. Instead, the combined use of conservative tracers (Cl− and DSi) and reactive constituents (SO42−, alkalinity, NH4+, HS−, TDFe, and Mn2+) provides a robust hydrochemical framework for recognizing groundwater influence and evaluating associated biogeochemical transformations.

This study presents the first comprehensive comparison of core sediments (0–155 сm) from an active methane seepage and a background (undisturbed) site on the northern Black Sea shelf (near Cape Martyan). Methods included grain-size analysis, toral organic (TOC) and inorganic carbon (TIC) analysis, gas chromatography–mass spectrometry (GC-MS) based biomarker analysis of non-polar and polar organic matter fractions, pyrolysis-GC-MS (Py-GC-MS) and mineralogical analysis by X-Ray diffraction (XRD) and scanning electron microscopy with energy dispersive-ray analysis (SEM/EDX).,Principal differences have been identified in depositional and early diagenesis. Background sediments are characterized by a diffusion-production methane profile, homogeneous silt-like composition, and stable molecular signatures. Meanwhile, methane seepage is marked by the dominance of an advective methane flow, grain-size heterogeneity, and early pyrite and glauconite formation. The content of TOC and total lipid extract in the seepage column is on average half that of the background, while TIC is 15% higher. Py-GC-MS and biomarker analysis results indicate an increased production of autochthonous organic matter in the seep, but this effect is offset by intensive microbial mineralization during the anaerobic oxidation of methane (AOM). It is shown that even a low-flow methane seep significantly transforms the mineral composition and organic matter of sediments. Results are important for reconstructing palaeoconditions, assessing biogeochemical carbon cycles, and predicting the impact of methane releases under climate change.

The organic material in water and peat collected in March 2021 from the extensive Ob Fen in Western Siberia was analysed using gas chromatography - mass spectrometry (GC-MS). It was shown that the process of formation and subsequent transformation of peat is characterised by the entry into the environment of large amounts of organic substances, whose genesis is currently insufficiently studied. A variety of organic compounds were identified including alkanes, fatty acids, terpenoids, alcohols and aromatics. The concentration of most contaminants decreased significantly with increasing depth of peat deposit. Compounds identified in the water were also found in the peat, indicating active exchange processes in the water-peat system. Recommendations for further study and ecological monitoring of Siberian peatlands are presented.

We present data on the composition and distribution of three significant components of peat organic matter (terpenoids, steroids and tocopherols) from two boreholes (H2 and H3) in the Ob Fen in Western Siberia. H2 is located closer to the edge of the peatland than H3. For borehole H2 it is shown that terpenoids and steroids are unevenly distributed along the borehole (up to 6 m depth) and their concentrations reach maxima at 0.50–0.75 m and 0.25–0.50 m, respectively. The spectrum of terpenoid and steroid components becomes broader with increasing sampling depth. The concentration of tocopherols is lower than the content of terpenoids and steroids. An uneven distribution of these components is also evident at different depths within borehole H3 (up to 5.0 m). These components generally decrease significantly in concentration with increasing depth, particularly below 2.75 m. The peat formation regime and organic matter composition differ between H2 and H3.

Arctic soils store 49 Gg mercury (Hg) - an extremely toxic heavy metal, whereas soil Hg can be released to the atmosphere by wildfires. For the first time we investigated the effects of wildfires on the fate of soil Hg in NorthWestern (NW) Siberia based on GIS maps of areas burned during the last 38 years and a field paired comparison of unburned and burned areas in tundra (mosses, lichens, some grasses, and shrubs) and forest-tundra (multi- layered canopy of larch trees, shrubs, mosses, and lichens). These field surveys were deepened by soil controlled burning to assess the Hg losses from organic horizon and mineral soil. The soil Hg stocks in the organic horizon and in the top 10 cm of the mineral soil were 3.3 f 0.6 and 16 f 3 mg Hg m- 2 for unburned tundra and forest- tundra, respectively. After the burning by wildfires, the soil Hg stocks decreased to 2.4 f 0.1 and 6.6 f 0.2 mg Hg m symbolscript 2 for tundra and forest-tundra, respectively. By the averages annual burned areas in NW Siberia 527 km2, 2 , wildfires in tundra and forest-tundra released 0.19 and 2.9 Mg soil Hg per year, respectively, corresponding to 28 % and 59 % of the initial soil Hg stocks. These direct effects of wildfires on Hg volatilization are raised by indirect post-pyrogenic consequences on Hg fate triggered by the vegetation succession and adsorption of at- mospheric Hg on the surface of charred biomass. Charred lichens and trees accumulated 4-16 times more Hg compared to the living biomass. Blackened burned vegetation and soil reduced surface albedo and slowly increased soil temperatures in Arctic after wildfires. This created favorable conditions for seeding grasses and shrubs after wildfire and transformed burned high-latitude ecosystems into greener areas, increasing their ca- pacity to trap atmospheric Hg by vegetation, which partly compensate the burning losses of soil Hg.

Relevance. Dictated by the need to assess functioning of the biogeochemical regime of the Arctic region by studying geochemical properties of organic matter of bottom sediments on the example of the Chaunskaya Bay (East-Siberian Sea). Aim. To study the spatial variability of geochemical parameters of organic matter of bottom sediments of the Chaunskaya Bay using the Rock-Eval method, as well as to identify a possible relationship between the parameter TOC and the pelite fraction. Objects. Samples of bottom sediments of the Chaunskaya Bay (East Siberian Sea). Sampling took place in stages from three horizons (upper 0–2 cm, intermediate 2–5 cm, lower 5–10 cm) during a comprehensive scientific expedition to the R/V "Academician Oparin" in September–October 2020. Methods. Granulometric composition of bottom sediments was determined using the Analysette 22 NanoTec particle analyzer (Fritsch, Germany). The analysis of hydrocarbon compounds of organic matter was performed using pyrolytic analysis on the device (Rock Eval 6 Turbo of Vinci Technologies, France). Results. The results of pyrolytic analysis considered by the authors have shown that such factors as the primary productivity of the waters of the studied water area and the processes of erosion of the coastal zone play a decisive role in the formation of the composition of the TOC in bottom sediments of the Chaunskaya Bay. We also do not exclude the contribution of river runoff to the composition of the TOC in bottom sediments; however, we consider it small due to the insignificant inflow of river sediments into the waters of the studied area. The pyrolytic data obtained by us indicate that both the marine component (primary productivity) and the terrigenous component (erosion of the coastal complex) are present in the composition of the TOC in bottom sediments of the studied area.

Relevance. Gas flares or seeps consisting of bubbles continuously rising from the seabed have been recorded throughout the World Ocean at depths ranging from several meters to three kilometers or more. Measurements of the gas composition of the rising bubbles shown that they are dominated by methane (CH4). The East Siberian Arctic Shelf contains more than 30% of the world CH4 and carbon dioxide reserves, preserved in bottom sediments by underwater permafrost. In the shallow seas of the East Siberian Arctic Shelf, the main mechanism for transporting CH4 from bottom sediments into water is bubble transport. Therefore, it is extremely important to estimate the amount of CH4 transported by rising bubbles from bottom sediments into the water column and the atmosphere. Aim. Estimation of CH4 quantity transported by chains of rising bubbles from the seabed to the atmospheric surface layers. Methods. The manuscript presents a study of the mechanism of gas exchange between rising bubbles and a liquid column, carried out using a specially designed stand that allows simulating local upwelling. Results and conclusions. The paper shows that chains of bubbles coming from the seabed with intensities of ~40 ml∙min–1 and ~110 ml∙min–1, taking into account the hydrostatic pressure, deliver 206 mg∙min–1 and 616 mg∙min–1 of CH4 to the bottom layer of the water column, respectively. The results obtained during laboratory studies allowed us to specify the flux of CH4 from bottom sediments to the atmospheric surface layers. Taking into account the quantity of gas exchange and local upwelling, the amount of methane delivered to the atmospheric surface layers was 69 mg∙min–1 and 286 mg∙min–1. The paper presents an acoustic estimate of the amount of CH4 transported by the seep, which includes the considered chains of rising bubbles. According to calculations, the flux of CH4 into water from this area in 2012 was ~40 g∙min–1. At the same time, the amount of CH4 transported by this seep into the atmospheric surface layers, taking into account local upwelling and gas exchange occurring between the rising bubbles and the liquid column, is ~24.5 kg per day or ~9 tons per year.

Relevance. The lack of elemental speciation data in the bottom sediments of the Laptev Sea, as well as the absence of its quantitative changes in occurrence forms in response to methane emissions. Aim. To assess changes in the elemental speciation in areas where methane-containing fluids are discharged. Objects. Nine samples of bottom sediments taken from three horizons of one “cold seep” and two background stations of the outer shelf-continental slope of the Laptev Sea during the AMK-82 expedition aboard R/V “Academician M.V. Keldysh” in autumn 2020. Methods. Sequential extraction BCR (the European Community Bureau of Reference) was performed to determine the elemental speciation in surface sediments; the residual fraction was determined by dissolving in nitric acid. The obtained fraction solutions were analyzed by ICP-MS (NexIon 300D, Perkin Elmer, Waltham, MA, USA), Pyrolysis (Rock-Eval 6 Turbo, Vinci Technologies). Results. The trend towards an increase in element mobility has been identified as a result of a shift in geochemical conditions that is presumably caused by the authigenic carbonate and sulfide formation. Moreover, the increase in the recoverable fraction (associated only with Fe oxides/hydroxides) is highlighted. We assume that the process of unloading methane-containing fluids plays a significant role in enrichment of authigenic carbonates U, Ni, Zn Co, oxides Fe – Sn and V, authigenic sulfides – Co, Mn and W. We also assume the potential formation of chalcopyrite as an authigenic sulfide in methane discharge areas.

This study presents new data on concentration of dissolved trace elements (DTE) in the Lena River-Laptev Sea mixing zone. Mean concentrations of some dissolved heavy metals in the mixing zone of fresh waters of the Lena River and sea waters of the Laptev Sea on the middle shelf and on the outer shelves are: 0.7 +/- 0.05 mu & Mcy; and 0.5 +/- 0.04 mu & Mcy; for Fe, 0.06 +/- 0.01 mu & Mcy; and 0.07 +/- 0.01 mu & Mcy; for Ni, 0.01 +/- 0.003 mu & Mcy; and 0.003 +/- 0.002 mu & Mcy; for Zn, 59.2 +/- 7.4 n & Mcy; and 73.4 +/- 12.8 n & Mcy; for Cu, respectively. Two major groups of DTE distribution were revealed according to their spatial behavior. The Li, V, As, Rb, Sr, Mo, U concentrations increase towards the outer shelf with increasing salinity. In contrast, mean concentrations of Al, Ti, Mn, Fe, Co decrease with increasing distance from the coast. The identified transport of freshwaters to a distance of 400 km is reflected in the distribution of DTE, which suggests that these elements are able to reach to the Central Arctic Ocean.

Approximately 220 million hectares of former croplands are abandoned worldwide, with a quarter of this area located in Russia. In these areas, natural zonal vegetation is developing, and the soils, including soil carbon (C) stocks, are recovering. Accumulated organic C serves as a structural and energetic source for soil microorganisms. Postagricultural soil restoration affects organic matter stability, microbial organic carbon decomposition, and C cycling. We studied a chronosequence of abandoned croplands in the Eastern Siberian forest steppe zone (Haplic Luvisol) to assess the effects of cropland natural restoration on the stability of soil organic matter (SOM) and energy stocks. The energy content and thermal stability of C in the bulk soil, in free and occluded particulate organic matter (fPOM and oPOM), and in mineral-associated organic matter (MAOM) were analysed by thermogravimetry and differential scanning calorimetry as proxies for C available for microbial decomposition. The soils sequestered 0.85 Mg C ha(-1) y(-1) (0-30 cm) during the first 25 years after abandonment. In abandoned soils, thermally labile C with an activation energy of 69+0.6 kJ.mol(-1) accumulated 2.8 times faster than did stable C with a higher energy barrier to combustion (80+0.5 kJ.mol(-1)). This increased energy availability and microbial activity led to faster C and nutrient cycling in the abandoned soils than in soils of current croplands. MAOM stored 1.7 times more energy per unit of C (42 kJ.g(-1) C) than did the free and occluded POM fractions (25 kJ.g(-1) C). fPOM was the dominant energy pool for labile C in the restored soil and increased microbial activity. Due to the preferential accumulation of C with lower thermal stability and with greater susceptibility to microbial decomposition in the restored soils, greater CO2 release could occur if these lands are tilled again. The content of thermally stable C also increased in abandoned soils; therefore, we must account for the ecological balance between C sequestration and release after the natural restoration of croplands.

The East Siberian Arctic shelf is renowned for its active methane-rich fluid seeps, confirmed by numerous gas flares in the water column and direct observations of methane release from the seafloor. These cold-seep sites serve as natural laboratories for studying the impact of methane seepage on early diagenesis, authigenic mineral formation, and the geochemical cycles of carbon, sulfur, and other elements. This study examines the grain size and chemical composition of two sediment types from the Laptev Sea shelf: cold-seep sediments influenced by sulfate-driven anaerobic methane oxidation, and unaffected "seep-free" sediments (i.e., control site). High methane concentrations (up to 649 mu M/L) in the surface layer of sediments indicate that the sulfate-methane transition zone is found close to the sediment-water interface approximately 5-6 cm below the seabed. At the cold-seep site, thin layers containing up to 40% sand fraction were discovered among the fine-grained sediments. We infer that upward-migrating fluids may contribute to the remobilization of the fine fraction, resulting in concentration of coarse particles. Cold-seep sediments are characterized by molybdenum (Mo) enrichment compared to the lithological background, although one "seep-free" core exhibits evidence of authigenic Mo deposition. The Mo concentration (up to 16.8 ppm) indicates that enrichment occurs under sulfidic conditions restricted to pore water, which are caused by anaerobic methane oxidation. The high Mo concentration in one "seep-free" core likely implies past cold-seep activity. A general Mo-U covariation indicates that the molybdenum enrichment in cold-seep sediments from the Laptev Sea outer shelf is controlled by a weak particulate shuttle process.

The relevance of the study is determined by the need to assess the regional characteristics of transport and transformation of or-ganic matter in various sedimentation and biogeochemical environments on the East Siberian Arctic Shelf, in particular in theless studied and remoted East Siberian Sea.The main aim of the study is to determine the composition and sources of organic matter of bottom sediments of the Chaunskaya Bay (East Siberian Sea).Objects: 25 surface bottom sediments sampled along the transect from the coastal zone of the Chaunskaya Bay to the inner part of the East Siberian Sea shelf during the marine expedition on the R/V 'Academician Oparin >> in September-October 2020.Methods. Rock-Eval pyrolytic analysis was used to analyze groups of hydrocarbon compounds in organic matter from bottom sedi-ments; the n-alkanes distribution was estimated based on the results of gas chromatography-mass-spectrometry. Grain size analy-sis was performed on a laser particle analyzer.Results. The composition of sedimentary material in the Chaunskaya Bay is mainly determined by the features of the underwater relief and gravity flows of the incoming terrigenous material-products of local thermal abrasion of the coastal zone (Ayon Island) and river al-luvium in the southeastern part of the bay. A certain role in the formation of the sedimentary appearance of the bay is presumably played by the processes of cryosol thawing as a result of the destruction of fast ice areas. Pyrolysis data and analysis of the distribution of n-alkanes for surface sediments indicate a mixed genesis of organic matter in surface sediments with a dominant contribution ofter-restrial organic matter of a high degree of transformation and a high content of hardly decomposable humic substances and fulvic acids. The presence of autochthonous organic matter reflects the high productivity of the Chaunskaya Bay waters

Ссылка для цитирования: Особенности состава органического вещества донных осадков Чаунской губы (Восточно-Сибирское море) / Н.А. Полтавская, Е.В. Гершелис, И.А. Оберемок, А.А. Гринько, А.Н. Чаркин, Е.И. Ярощук, О.В. Дударев, Н.А. Смирнова, Н.В. Гусева, И.П. Семилетов // Известия Томского политехнического университета. Инжиниринг георесурсов. – 2023. – Т. 334. – № 2. – С. 130-146. Актуальность исследования определяется необходимостью оценки региональных особенностей транспорта и преобразования органического вещества в различных седиментационных и биогеохимических обстановках, действующих на Восточно-Сибирском арктическом шельфе, в том числе в Восточно-Сибирском море – наиболее ледовитом и наименее изученном море Российской Арктики. Цель исследования заключается в определении состава и источников органического вещества донных осадков Чаунской губы (Восточно-Сибирское море). Объекты: 25 проб поверхностных донных осадков, отобранных по профилю от прибрежной зоны Чаунской губы до внутренней части шельфа Восточно-Сибирского моря в ходе комплексной научно-исследовательской морской экспедиции на борту НИС «Академик Опарин» в сентябре–октябре 2020 г. Методы. Для анализа групп углеводородных соединений ОВ донных осадков был применен пиролитический анализ по методу Rock-Eval; оценка распределения н-алканов проводилась на основе результатов газовой хромато-масс-спектрометрии. Гранулометрический анализ осадков выполнялся на лазерном анализаторе частиц. Результаты. Состав осадочного материала в Чаунской губе преимущественно определяется особенностями подводного рельефа и гравитационными потоками поступающего терригенного материала – продуктов локальной термоабразии береговой зоны (о. Айон) и речного аллювия в юго-восточной части губы. Определенную роль в формировании седиментационного облика губы, предположительно, играют процессы вытаивания криозоля в результате разрушения областей припайного льда. Данные пиролиза и анализ распределения н-алканов для поверхностных осадков указывают на смешанный генезис органического вещества в поверхностных осадках с доминирующим вкладом наземного органического вещества высокой степени преобразованности и высокое содержание трудноразлагаемых гуминовых веществ и фульвокислот. Присутствие автохтонного органического вещества отражает высокую продуктивность вод Чаунской губы.

Ссылка для цитирования: Органическое вещество донных осадков моря Лаптевых и Восточно-Сибирского моря: обзор результатов пиролиза / Е.В. Гершелис, А.С. Рубан, Д.В. Черных, Н.А. Полтавская, И.П. Семилетов // Известия Томского политехнического университета. Инжиниринг георесурсов. – 2023. – Т. 334. – № 4. – С.149-162. Актуальность исследования обусловлена необходимостью изучения механизмов трансформации и накопления терригенного органического углерода, высвобождаемого из мерзлотных толщ, на шельфе арктических морей. При переносе в системе «суша–море» он может в дальнейшем накапливаться в донных осадках в шельфовой или глубоководной зоне и подвергаться деградации и реминерализации, что приводит к критическим экологическим последствиям. Цель: установление источников и степени диагенетической преобразованности терригенного органического вещества в поверхностных осадках морей Восточной Арктики. Объектом исследования послужили пробы донных осадков, взятые с поверхностного горизонта (0–10 см). Отбор проб проводился в морских исследовательских экспедициях 2011–2019 гг. Результаты. Латеральная выдержанность значений водородного индекса в современных осадках в море Лаптевых связана с вкладом гетерогенного наземного органического вещества, характеризующегося относительной биогеохимической доступностью: водородонасыщенное наземное органическое вещество сменяется морским с сохранением величины водородного индекса. Это отличает море Лаптевых от других арктических акваторий, где по мере удаления от берега отмечался устойчивый рост значения водородного индекса в связи с усилением вклада автохтонного органического вещества. В соотношении параметров δ13C и HI/OI наблюдаются значительные отклонения от линейной зависимости, характерной для консервативного геохимического режима морских акваторий: терригенный материал в осадках губы Буор-Хая характеризуется легким изотопным составом δ13C и повышенными отношением HI/OI, нетипичным для наземного генезиса. Для органического вещества, накопленного в глубоководных осадках континентального склона, напротив, отмечается низкое содержание водорода и высокая доля кислородсодержащих соединений, свидетельствующих о значительной степени диагенетической преобразованности органического вещества.

Ongoing global warming accelerates release of relict terrigenous organic carbon from permafrost onto the Arctic shelf waters. When trans-ported in the land-sea system, it can further be accumulated in bottom sediments in the shelf or deep-sea zone and undergo degradation and remineralization, which leads to critical environmental consequences. This study aims at assessing the sources and degradation de-gree of terrigenous organic matter in the surface sediments of the Eastern Arctic seas. Within this study, marine bottom sediments taken from the surface horizon (0-10 cm) were investigated. Sampling was carried out during the 2011-2019 marine research expeditions. La-teral consistency of hydrogen index values in modern marine sediments on the Eastern Arctic shelf (mainly in the Laptev Sea) is associat-ed with the great contribution of heterogeneous biolabile terrestrial organic matter, in contrast to other Arctic waters, where growing hydro-gen index values are associated with the consistently growing contribution of autochthonous organic matter with increasing distance from the coast. While considering the d13C and HI/OI correlation, there are also significant deviations from the linear dependence which usually indicates a conservative marine geochemical regime. Sediments of the Buor-Khaya Bay are characterized by an increased HI/OI values in contrast to the deep-water sediments of the continental slope which shows lower hydrogen content and a higher proportion of oxygen -containing compounds, indicating a strong transformation of organic matter. These findings confirm a key role of terrigenous supply in spe-cific biogeochemical conditions in the studied area and reveal that geochemical indicators of immature organic matter sources in the East-ern Arctic seas should be interpreted differently from other Arctic continental margins.

This paper presents the results of an acoustic survey carried out from the fast ice in the shallow waters of the East Siberian Arctic Shelf (ESAS) using a single beam echosounder. The aim of this paper is to demonstrate an improved approach to study seafloor seepages in the Arctic coastal zone with an echosounder calibrated on site. During wintertime field observations of natural rising gas bubbles, we recorded three periods of their increased activity with a total of 63 short-term ejections of bubbles from the seabed. This study presents quantitative estimates of the methane (CH4) flux obtained in wintertime at two levels of the water column: (1) at the bottom/water interface and (2) at the water/sea ice interface. In winter, the flux of CH4 transported by rising bubbles to the bottom water in the shallow part of the ESAS was estimated at ~19 g·m−2 per day, while the flux reaching the water/sea ice interface was calculated as ~15 g·m−2 per day taking into account the diffusion of CH4 in the surrounding water and the enrichment of rising bubbles with nitrogen and oxygen. We suggest that this bubble-transported CH4 flux reaching the water /sea ice interface can be emitted into the atmosphere through numerous ice trenches, leads, and polynyas. This CH4 ebullition value detected at the water/sea ice interface is in the mid high range of CH4 ebullition value estimated for the entire ESAS, and two orders higher than the upper range of CH4 ebullition from the northern thermocarst lakes, which are considered as a significant source to the atmospheric methane budget.

The East Siberian Sea (ESS) is the largest, shallowest and most icebound Arctic marginal sea. It receives sub-stantial input of terrigenous material and climate-vulnerable old organic carbon from both coastal erosion and rivers draining the extensive permafrost-covered watersheds. This study focuses on the interannual variability and spatial distribution of suspended particulate matter (SPM) in the surface and bottom waters of the ESS during the ice-free period in 2000, 2003, 2004, 2005 and 2008. We report on the composition and variability of par-ticulate organic carbon (POC), total nitrogen (TN), POC/TN ratios, carbon and nitrogen isotopes (delta 13C, delta 15N) and provide estimates of the contribution of terrestrial organic carbon (terrOC) based on the delta 13C isotopic values.The results show that interannual SPM distribution and elemental-isotopic characteristics of POC differ significantly between the western biogeochemical province (WBP; West of 165oE) and the eastern biogeo-chemical province (EBP; East of 165oE) of the ESS. The SPM mean concentration in the WBP is almost an order of magnitude higher than in the EBP. From west-to-east of the ESS, SPM tends to become more depleted in delta 15N, while the delta 13C becomes isotopically heavier. This trend can be explained by a shift in organic matter sources from terrigenous origin (erosion of the coastal ice complex and riverine POC) to becoming dominantly from marine plankton.The maximum contribution of terrOC to POC reached 99% in parts of the WBP, but accounts for as low as 1% in parts of the EBP. At the same time, the type of atmospheric circulation and its associated regime of both water circulation and ice transport control a displacement of the semi-stable biogeochemical border between WBP and EBP to the east or to the west if compared to its long-term average position near 165oE. Our multi-year inves-tigation provides a robust observational basis for better understanding of the transport and fate of terrigenous material upon entering the ESS shelf waters. Our results also provide deeper insights into the interaction in the land-shelf sea system of the largest shelf sea system of the World Ocean, the East Siberian Arctic Shelf system.