There is a significant potential for the introduction of legumes into the Arctic regions of Russia. The ability of legumes to form a nitrogen-fixing symbiosis with nodule bacteria is one of their most important characteristics. The article studies the genetic diversity of the 24 bacterial strains isolated from root nodules from wild populations of legumes Oxytropis putoranica M. Ivanova, O. mertensiana Turcz., Astragalus norvegicus Grauer, and A. tugarinovii Basil. collected on the Putorana Plateau (Krasnoyarsk region, Arctic Russia). The microbial strains were isolated using yeast broth made with a standard method using YMA mannitol. Genomic DNA was isolated from pure cultures and the primary identification of the strains was carried out by PCR followed by sequencing of the 16S rRNA marker gene fragment. To clarify the identity of the species, ITS sequencing of the region was performed. The isolates were assigned to six genera and to five families of the order Hyphomicrobiales: Pararhizobium and Neorhizobium (family Rhizobiaceae), Phyllobacterium (Phyllobacteraceae), Microvirga (Methylobacteriaceae), Bosea (Boseaceae) and Tardiphaga (Bradyrhizobiaceae). Isolates from O. putoranica nodules were identified as Neorhizobium galegae, Bosea sp., Bosea vaviloviae, and Tardiphaga robiniae. The isolated nodules of O. mertensiana were identified as Pararhizobium herbae, Tardiphaga robiniae, Microvirga ossetica, and Microvirga sp. Microsymbionts of A. norvegicus were assigned to Bosea psychrotolerans and to Pararhizobium herbae and Tardiphaga robiniae species, while isolates from A. tugarinovii were identified as Phyllobacterium zundukense, Bosea sp., and Tardiphaga robiniae. Symbiotic the nodA gene was detected in strains P. herbae P14/2-4 and P20/1-1, P. zundukense P17/1-7 and P17/3-2, while the nodC gene was not detected in any of the strains. The sterile test tube experiment confirmed the inability of strains P. herbae P14/2-4 and P20/1-1 to form nodules in host plants O. mertensiana and A. norvegicus, as well as in other wild arctic (A. tugarinovii, O. putoranica) and forage legumes (Trifolium repens, Vicia cracca, and Lathyrus pratensis). The results obtained expand the understanding of the taxonomic status and biodiversity of local microsymbionts of wild legumes that grow on the Putorana Plateau. The study of the symbiotic efficiency of Arctic rhizobia will allow us to identify the most promising strains for the development of effective biofertilizers for the cultivation of forage and pasture legumes under the extreme soil and climatic conditions of the Russian Arctic. In turn, the creation of highly adapted legume-rhizobial systems based on valuable genetic resources of Arctic rhizobia strains will expand the range of legume species promising for use in the creation of multi-component agrophytocenoses necessary for the sustainable development of animal husbandry in Arctic regions of Russia.

The deep holes drilled at Vostok Station by the Russian Antarctic Expedition reached the surface of Subglacial Lake Vostok twice — on February 5, 2012 and January 25, 2015. Two unsealings of the largest subglacial water body on Earth, led by Nikolay Vasiliev, have become remarkable events in the history of Antarctic science. To preserve all the twists and turns of this pioneering work for the ice-drilling community, we have compiled and carefully analyzed all the available drilling, geophysical, and glaciological observations made prior to, during, and after the lake piercings. Based on that information, in this paper we have pieced together a detailed narrative of these two unprecedented drilling operations in the hope that the lessons learned may prove useful for future environmental stewardship, scientific investigations, and technological developments related to the exploration of Lake Vostok.

The paper studies the genetic diversity of microorganisms isolated from root nodules of wild populations of the legumes Lathyrus pratensis L., Vicia cracca L., Trifolium repens L., and Astragalus schelichowii Turcz. collected near Norilsk (Arctic Russia). The taxonomic position of the 19 isolates obtained was determined by sequencing the 16S rRNA gene (rrs). The isolates were assigned to four genera of the order Hyphomicrobiales: Rhizobium, Pararhizobium, Bosea and Tardiphaga. Nine fast-growing isolates belonged to the genera Rhizobium and Pararhizobium. ITS region sequencing clarified the species identity of 6 rhizobial isolates. Isolates from V. cracca nodules were identified as Pararhizobium sp., P. herbae. Microsymbionts from T. repens were assigned to Rhizobium sp. and to the species R. beringeri, while isolates from L. pratensis were identified as P. herbae and R. beringeri. Symbiotic nodA and nodC genes were found in the Rhizobium strains P8/5-2, P9/1-1 and P9/3-2 from L. pratensis and T. repens nodules, nodA gene was detected in the Pararhizobium strains P7/3-1, P7/4-1, P7/5-1 from V. cracca nodules. Nine out of ten slow-growing isolates were assigned to the genus Bosea. Three isolates from the nodules of V. cracca were assigned to the species B. psychrotolerans. Six isolates from the nodules of A. schelichowii were identified as B. vaviloviae, B. lathyri and Bosea sp. The strain P22/3-5 isolated from the nodule of A. schelichowii was identified as Tardiphaga robiniae. Simultaneous presence of strains belonging to different genera of the order Hyphomicrobiales was detected in the nodules of V. cracca and A. schelichowii.

Bacterial strains isolated from root nodules of the legume plant Hedysarum arcticum B. Fedtsch growing on Samoylov Island in the Lena River delta (Arctic zone of Yakutia) were assigned to the genera Rhizobium (family Rhizobiaceae) and Mesorhizobium (Phyllobacteriaceae) of the order Hyphomicrobiales (class Alphaproteobacteria) according to the rrs gene sequencing data. According to phylogenetic analysis of concatemers of the atpD, dnaK, gyrB, and rpoB genes, the strains belonged to the species Rhizobium giardinii and Mesorhizobium norvegicum. The strains were shown to be facultative psychrotrophs growing at 5 and 28°C. These microsymbionts are promising for further study of their symbiotic efficiency regarding other forage legume species, with an aim to establish highly productive agrophytocenoses in the Far North.

Abstract Drilling fluid (DF) is one of the main sources of chemical and biological contamination of deep ice cores and lake water samples in the exploration of Subgalcial Antarctic Lake Environments (SALE). In this study, we investigated the contamination of an ice core that represented the first samples of refrozen lake water obtained 1 year after the unsealing of Lake Vostok in 2012. We show that these samples contain inclusions of the DF with a concentration of at least 16.7 mg l−1 (0.0019% or 19 ppmv). This makes it extremely difficult to obtain reliable data on the real chemical composition of the lake water. The focus of our study is the organic components of the DF, which built up in the secondary ice while the water was freezing in the borehole. Of all the possible organic compounds of the DF, only phenol congeners (up to 32.4 mg l−1) and dichlorofluoroethane HCFC-141b (14.4 mg l−1), a DF densifier, were found in the central channel, which is the last part of the core to freeze in the borehole. We conclude that the phenol compounds emerge due to physical processes, namely fractionation, during freezing, rather than any chemical reaction between the DF and the lake water.

Antarctic lake ecosystems provide a rare opportunity to study the evolution and adaptation of microorganisms to extreme conditions, as well as to discover new species useful for biotechnological applications. Four water samples were collected from various layers of the water column of freshwater Lake Radok in East Antarctica. Two regions (v3-v5 and v4-v8) of the 16S rRNA gene were amplified by PCR and sequenced. Twenty dominant phylotypes were detected representing five bacterial phyla (Actinobacteria, α, β and δ Proteobacteria, Bacteroidetes, Planctomycetes, OD1) and two eukaryotic divisions (stramenopiles and green algae). Of these, 16 phylotypes demonstrated ≤98 % identity to the nearest taxa in GenBank and were therefore classified as new unknown species. Seven phylotypes demonstrated ≤90 % identity and thus remained unidentified. Actinobacteria was the most abundant phylum with 157 clones (41 % of the total number) representing 5 phylotypes. A species complex (3 clades from acI-A subgroup) of Candidatus Planktophila limnetica was prevalent in all layers. Representatives of the OD1 phylum and δ-proteobacteria were discovered by sequencing of the v3-v5 region of 16S rRNA, while Planctomycetes, β-proteobacteria and mtDNA of stramenopiles were discovered by sequencing of the v4-v8 region. This highlights the necessity of sequencing at least two 16S rRNA gene regions to gain more data on microbial community characterization. In general, despite the uniformity in the physical and chemical properties in the water column, a prominent stratification of microbial groups was observed, at the levels of both divisions and phylotypes.

Work on the project focused on the following five areas: 1) field works in Antarctica at Vostok and Concordia stations; 2) experimental and theoretical studies in the field of ice core and paleoclimate research; 3) experimental and theoretical works related to the exploration of subglacial Lake Vostok; 4) development of technology and drilling equipment for deep ice coring and exploration of subglacial lakes; 5) upgrading the analytical instrumentation in the Climate and Environmental Research Laboratory (CERL) of the Arctic and Antarctic Research Institute. The main achievements in the field of ice core and paleoclimate research include 1) further elaboration of a new method of ice core dating, which is based on the link between air content of ice and local insolation, 2) investigation of the possible applications of the 17O-excess measurements in ice core to the paleoclimate research, 3) a better understanding of the mechanisms of the formation of relief-related variations in the isotopic content of an ice core drilled in the area of Antarctic megadunes, and 4) obtaining the first reliable data set on the variations of the 17O-excess in the Vostok core corresponding to marine isotope stage 11. As part of our studies of subglacial Lake Vostok, we have obtained a large body of new experimental data from the new ice core recovered from the 5G-3 borehole to the surface of the subglacial lake. Stacked profiles of isotopic composition, gas content and the size and orientation of the ice crystals in the lake ice have been composed from the data of three replicate cores from boreholes 5G-1, 5G-2 and 5G-3. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of Lake Vostok, has been discerned in the three different properties of the accreted ice (the ice texture, the isotopic and gas content of the ice). These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. A considerable part of the funding allocated by the RSF to this project was used for upgrading the analytical instrumentation for ice core studies in the CERL of AARI. Using this grant, we purchased and started working with the Picarro L-2140i, a new-generation laser mass analyzer, and set the upgraded mass spectrometer Delta V Plus into operation. The new equipment was used to carry out research planned as part of the project, including the setting up and carrying out of new measurements of 17О in ice cores.

The main results after the first unlocking into the subglacial Lake Vostok were as follows: the Lake had been opened and not polluted; the water pressure within the lake was not balanced by a column of the drilling liquid that resulted in unplanned rise of water in the borehole up to 340 m. The main problem during the drilling in the lake ice was to prevent a pollution of water by the drilling fluid, which filled the borehole, and thus, to avoid a compression of the fluid which could be the main source of chemical and biological pollution of not only the Lake itself, but also the Lake water samples and ice cores. The article presents results of analysis of causes for the occurrence of phenolic compounds in the central channel in the core of secondary ice, being formed by the lake water that rose into the well after the first penetration (the range of depths was 3426–3450 m). It was found that the process, running within the borehole during the drilling, can be described as the fractionation of phenolic compounds, being contained in the filling liquid, to the water phase with its subsequent freezing. We have developed methods for the determination of concentrations of phenolic compounds in the original aviation kerosene and Freon HCFC-141b: 6. mg·l−1 and 0.032 mg·l−1, respectively. To analyze the composition of phenolic compounds in the extract of real filling liquid, located at the bottom of the borehole, the method of gas chromatography-mass spectrometry (GC-MS) was used. The corresponding peaks were quite well resolved and identified as phenol and its derivatives. The main components of the extract were phenol (20%), 2.5-dimethyl phenol (23,8%), 2,4,6-trimethylphenol, and other congeners of phenol. In our case, the Lake Vostok was not polluted during both, the first and second penetrations, however, the problem of human impact on these pristine and unique subglacial reservoirs remains extremely relevant. This impact includes not only direct water pollution of the lake by the drilling fluid, but also possible changes in organic components of the liquid when contacting with the lake water under natural conditions of a deep well. Our data have demonstrated that using of such complex organic liquids, like aviation kerosene formerly used in many drilling projects, is undesirable when exploring deep Antarctic subglacial lakes. Thus, we come to the conclusion that the drilling fluid, currently used at the Vostok station (in the Vostok borehole), has to be replaced by another more inert fluid that would allow further research and exploration of the Lake Vostok.

The role of aerial dispersal in shaping patterns of biodiversity remains poorly understood, mainly due to a lack of coordinated efforts in gathering data at appropriate temporal and spatial scales. It has been long known that the rate of dispersal to an ecosystem can significantly influence ecosystem dynamics, and that aerial transport has been identified as an important source of biological input to remote locations. With the considerable effort devoted in recent decades to understanding atmospheric circulation in the south-polar region, a unique opportunity has emerged to investigate the atmospheric ecology of Antarctica, from regional to continental scales. This concept note identifies key questions in Antarctic microbial biogeography and the need for standardized sampling and analysis protocols to address such questions. A consortium of polar aerobiologists is established to bring together researchers with a common interest in the airborne dispersion of microbes and other propagules in the Antarctic, with opportunities for comparative studies in the Arctic.

After more than a decade of planning, three attempts were made in 2012–2013 to access, measure in situ properties and directly sample subglacial Antarctic lake environments. First, Russian scientists drilled into the top of Lake Vostok, allowing lake water to infiltrate, and freeze within, the lower part of the ice-core borehole, from which further coring would recover a frozen sample of surface lake water. Second, UK engineers tried unsuccessfully to deploy a clean-access hot-water drill, to sample the water column and sediments of subglacial Lake Ellsworth. Third, a US mission successfully drilled cleanly into subglacial Lake Whillans, a shallow hydraulically active lake at the coastal margin of West Antarctica, obtaining samples that would later be used to prove the existence of microbial life and active biogeochemical cycling beneath the ice sheet. This article summarizes the results of these programmes in terms of the scientific results obtained, the operational knowledge gained and the engineering challenges revealed, to collate what is known about Antarctic subglacial environments and how to explore them in future. While results from Lake Whillans testify to subglacial lakes as being viable biological habitats, the engineering challenges to explore deeper more isolated lakes where unique microorganisms and climate records may be found, as exemplified in the Lake Ellsworth and Vostok missions, are considerable. Through international cooperation, and by using equipment and knowledge of the existing subglacial lake exploration programmes, it is possible that such environments could be explored thoroughly, and at numerous sites, in the near future.

Antarctic subglacial lakes can represent extreme natural habitats for microorganisms from the position of their evolution and adaptation, as well as they can contain the information on Antarctic ice sheet history and climatic changes in their sediments. Now only direct measurements and sampling from these habitats can answer on many fundamental questions. Special precaution should be complied at penetration into these unique relic environments without unfavorable impacts and contamination. A number of recommendations were developed on levels of cleanliness and sterility during direct exploration and research of subglacial environments. Documents considered in the article are the first and necessary steps for appropriate and long-term ecological management of subglacial Antarctic environments. Today there are three projects of subglacial aquatic environment research which are in preparation and realization – the Russian project of Lake Vostok, the similar British project of Lake Ellsworth and the American project on Whillans Ice Stream. The programs of ecological stewardship for direct exploration of these lakes are discussed. All these subglacial aquatic objects of further exploration and research are so various on their structure, age and regime, that only results of all programs as a whole can help to draw us a uniform picture of a subglacial ecological system. Ecological stewardship of these should provide the minimal ecological impact with maximal scientific results. On the basis of existing documents and recommendations the general approaches and the program of ecological stewardship for Lake Vostok research are discussed. Study of drilling fluid, drilling chips, Vostok ice core and the fresh frozen water will allow to make an assessment of biological and chemical contamination as a result of the first penetration and to modify the further stewardship program for the second penetration and direct exploration of lake water.

In November 2010 a new research unit was inaugurated in Arctic and Antarctic Research Institute (St. Petersburg) – Climate and Environmental Research Laboratory (CERL) – that became the first lab in Russia dedicated to the complex studies of ice cores, paleoclimate and subglacial environments in Antarctica. The total investments to construct the laboratory were 28.8 million rubles, provided by Roshydromet and AARI in frames of implementing the program of International Polar Year. The total area of the laboratory is about 300 m² that includes mass-spectrometric and gas analyses labs, cold chambers and utility rooms. The CERL’s equipment comprises laser stable water isotope analyzer Picarro L2120-i, IR mass-spectrometer Delta V Plus, system of gas extraction from ice, facilities for ice petrographic observations, for ice core treatment and storage. Before 2014 CERL was the head unit in the project “Complex studies of Lake Vostok and glaciological investigations of Antarctica” of the sub-program “Antarctica” of the FTP “World Ocean”. Now CERL is the leading organization in International Associated Laboratory “Ice archives of climatic and environmental data” that combines 4 French and 5 Russian scientific research groups. In 2014 the specialists of CERL won a grant of Russian Science Foundation for fundamental scientific works implemented by operating research laboratories. Project 14-27-00030 “Evolution of climate, glaciation and subglacial environments of Antarctica from the deep ice core and Lake Vostok water sample studies” (2014–2016) is intended to refine the reconstruction of Antarctic climate history over the past 400,000 years using the newly developed geochemical methods of ice core studies. Another goal is to develop the approaches to study the hydrological parameters of subglacial Lake Vostok using the samples of lake ice and water. The funding to be received through the grant (58.5 million rubles) will be mainly spent to develop the analytical infrastructure of the laboratory. In particular, we plan to equip the “Delta” with the dual inlet system and “Gas Bench II” device, as well as to purchase the new generation of laser isotope analyzer, Picarro L2140-i. This will allow us to measure precisely the concentrations of deuterium, oxygen 18 and 17 in water, snow and ice samples, to define the О₂/N₂ ratio in the gas probes, as well as to develop new methods of ice core analyses.

Diverse microbial assemblages inhabit subglacial aquatic environments. While few of these environments have been sampled, data reveal that subglacial organisms gain energy for growth from reduced minerals containing nitrogen, iron, and sulfur. Here we investigate the role of microbially mediated sulfur transformations in sediments from Subglacial Lake Whillans (SLW), Antarctica, by examining key genes involved in dissimilatory sulfur oxidation and reduction. The presence of sulfur transformation genes throughout the top 34 cm of SLW sediments changes with depth. SLW surficial sediments were dominated by genes related to known sulfur-oxidizing chemoautotrophs. Sequences encoding the adenosine-5'-phosphosulfate (APS) reductase gene, involved in both dissimilatory sulfate reduction and sulfur oxidation, were present in all samples and clustered into 16 distinct operational taxonomic units. The majority of APS reductase sequences (74%) clustered with known sulfur oxidizers including those within the "Sideroxydans" and Thiobacillus genera. Reverse-acting dissimilatory sulfite reductase (rDSR) and 16S rRNA gene sequences further support dominance of "Sideroxydans" and Thiobacillus phylotypes in the top 2 cm of SLW sediments. The SLW microbial community has the genetic potential for sulfate reduction which is supported by experimentally measured low rates (1.4 pmol cm(-3)d(-1)) of biologically mediated sulfate reduction and the presence of APS reductase and DSR gene sequences related to Desulfobacteraceae and Desulfotomaculum. Our results also infer the presence of sulfur oxidation, which can be a significant energetic pathway for chemosynthetic biosynthesis in SLW sediments. The water in SLW ultimately flows into the Ross Sea where intermediates from subglacial sulfur transformations can influence the flux of solutes to the Southern Ocean.

While it is now recognized that organic matter dominates the present-day atmospheric aerosol load over continents, its sources remain poorly known. The studies of organic species or organic fractions trapped in ice cores may help to overcome this lack of knowledge. Available data on the dissolved (or total) organic carbon (DOC or TOC) content of snow and ice often appear largely inconsistent, and, until now, no critical review has been conducted to understand the causes of these inconsistencies. To draw a more consistent picture of the organic carbon amount present in solid precipitation that accumulates on cold glaciers, we here review available data and, when needed, complete the data set with analyses of selected samples. The different data sets are then discussed by considering the age (modern versus pre-industrial, Holocene versus Last glacial Maximum) and type (surface snow, firn, or ice) of investigated samples, the deployed method, and the applied contamination control. Finally, the OC (DOC or TOC) levels of Antarctic, Greenland, and Alpine ice cores are compared and discussed with respect to natural (biomass burning, vegetation emissions) and anthropogenic sources (fossil fuel combustion) contributing to atmospheric OC aerosol.

Introduction Conclusions References

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Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize high-altitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.

A preliminary study has demonstrated that the structure and species composition of microbial communities associated with events of dust deposition from the Sahara Desert to the Mont Blanc glacier varied considerably between samples originating from different time periods. Even for depositions within a single month, the dominant microbial phylotypes and candidates to colonize the snow pack were different. It is therefore highly probable that the structure and species composition of microbial communities will be different between any events of the kind. Apparently, the phenomenon does not correlate with the time the dust stays in the snow cover and consequently with the probable development of microorganisms in situ (three months, one month, and one week). The reasons for the variation may be the differences in conditions in the epicenter of a specific North African dust storm, as well as the history of the dust transport in the atmosphere. The candidates for joining the snow biome of Mont Blanc turned out to be different for three dust events (DEs) and belong to different, mostly minor, phylotypes related to Crossiella cryophilus ( Actinobacteria ), Devosia limi (α- Proteobacteria ), Deinococcus claudionis Deinococcus-Thermus ), Anabaena sp. ( Cyanobacteria ), and Hymenobacter soli ( Bacteroidetes ). Since all these phylotypes have been previously isolated from soil samples of the Antarctic and Arctic, Arctic snow and ice, and the Alpine belt soils and sedimentary rocks of the glacier bed, they were tentatively ascribed to the group of snow pack colonizers.