Polar Desert Research Articles

Grounded icebergs as maternity denning habitat for polar bears (Ursus maritimus) in North and Northeast Greenland

This study provides the first documentation of polar bear (Ursus maritimus) maternity denning in snowdrifts around icebergs frozen into the fast ice or grounded on the seafloor. Based on six den observations in north and northeast Greenland during spring surveys in 2018 and 2019 (109 flight hours), together with observations of 20 adult females with 35 cubs of the year (COYs) in adjacent sea ice, we hypothesize that the use of snowdrifts around icebergs for maternity denning is an established behavior in the region and not a random event. Factors influencing maternity denning in snowdrifts around icebergs may include limited suitable drifts on the nearby terrestrial polar desert due to low precipitation, the presence of suitable wind-blown snow banks regardless of the direction of autumn storm winds, cold and stable habitat throughout the winter denning period, and access to ringed seal (Pusa hispida) pupping habitat in the nearby Northeast Water polynya. This type of maternity denning habitat is only available in glaciated regions of the Arctic where marine-terminating glaciers deposit melange large enough to become grounded offshore and remain in place for months or years. This habitat may become less stable or disappear with long-term climate warming.

Microbial Biomass, Carbon Stocks, and CO2 Emission in Soils of Franz Josef Land: High-Arctic Tundra or Polar Deserts?

The biomass of prokaryotes and fungi, organic carbon stocks, and CO2 emission were studied in the Cryosols and Leptosols of Franz Josef Land. The highest carbon stocks were found in the Eutric Leptosols (Loamic, Humic) formed in the wind-sheltered areas (23.2 kg C/m2 in the upper 50 cm), as well as in Turbic Cryosols (Humiс) that contained organic matter buried by cryoturbation (13.7–20.7 kg C/m2). The number of prokaryotes varied between 0.14 and 2.10 billion cells/g of soil, and the maximum values of their biomass were found in the litter. The fungal biomass varied from tens to hundreds of mg/g of soil depending on the type of soil and biotope. The share of spores was more than a half of the total fungal biomass in 80% of cases. Spores and mycelium were mainly represented by small forms with a diameter of up to 2–3 microns. The length of the fungal mycelium ranged from 4 to 272 m/g of soil. The maximum development of fungi was observed in the lichen biocrusts and moss litters. The fungal biomass decreased exponentially with the depth of horizons, and at the same time the share of prokaryotes in microbial biomass increased by several times. The share of microbial carbon in the total organic carbon was higher in soils of barrens (the most extreme habitats among the studied ones) as compared with the soils of local tundra areas (12.7 versus 2.5%, respectively). The levels of СО2 emission from the surface of undisturbed soils varied in the range of 1.6–91.7 mg C–CО2/m2 per hour and differed by tens of times between barrens and tundra areas. The studied soils are close to the soils of the Arctic tundra when compared by their carbon stocks and CO2 emission values; however, their microbial biomass values and their distribution are close to the soils of Antarctica and hot deserts.

Radiocarbon chronology and environmental context of Last Glacial Maximum human occupation in Switzerland

Central Europe during the Last Glacial Maximum (LGM) was dominated by polar desert and steppe-tundra biomes. Despite this, a human presence during this time period is evident at several locations across the region, including in Switzerland, less than 50 km from the Alpine ice sheet margin. It has been hypothesised that such human activity may have been restricted to brief periods of climatic warming within the LGM, but chronological information from many of these sites are currently too poorly resolved to corroborate this. Here we present a revised chronology of LGM human occupation in Switzerland. AMS radiocarbon dating of cut-marked reindeer (Rangifer tarandus) bones from the sites of Kastelhöhle-Nord and Y-Höhle indicates human occupation of Switzerland was most likely restricted to between 23,400 and 22,800 cal. BP. This timeframe corresponds to Greenland Interstadial 2, a brief warming phase, supporting the hypothesis that human presence was facilitated by favourable climatic episodes. Carbon, nitrogen and sulphur stable isotope analysis of the fauna provides palaeoenvironmental information for this time period. These findings contribute to our understanding of human activity in ice-marginal environments and have implications for understanding cultural connections across central Europe during the LGM.

Could Cryoturbic Diapirs Be Key for Understanding Ecological Feedbacks to Climate Change in High Arctic Polar Deserts?

AbstractHigh Arctic polar deserts cover 26% of the Arctic. Increasing temperatures are predicted to significantly alter polar desert freeze‐thaw and biogeochemical cycles, with important implications for greenhouse gas emissions. However, the mechanisms underlying these changing cycles are still highly uncertain. Cryoturbic, carbon‐rich Bhy horizons (diapirs) in frost boils are key nutrient sources for Salix arctica. We hypothesized that diapirism leads to organic carbon characteristics that alter microbial pathways, which then control root foraging and greenhouse gas production. During July and August 2013, we characterized soil properties and examined gross nitrogen transformation rates in frost boils both with and without diapirs in two High Arctic polar deserts (dolomite and granite) near Alexandra Fjord (78°51′N 75°54′W), Ellesmere Island, Nunavut, Canada. Diapiric frost boils had 18% higher soil organic carbon in the dolomitic and 9% higher in the granitic deserts, and 29% higher total dissolved nitrogen in the dolomitic desert. However, diapirs decreased gross nitrogen mineralization rates by 30% in the dolomitic and by 48% in the granitic deserts. Attenuated total reflectance Fourier transformed mid‐infrared spectroscopy revealed greater concentrations of polysaccharides and recalcitrant carbon in diapiric versus nondiapiric frost boils. These increased polysaccharide concentrations likely facilitate diapirism as soil viscosity increases with polysaccharides. Lower microbial activity or ectomycorrhizae that are known to colonize S. arctica may accumulate total dissolved nitrogen in diapirs. Our results suggest geomorphologic‐plant‐microbe interactions may underlie important patterns of geochemical cycling in arctic systems. Thus, polar desert frost boils should represent a key focus of future investigations of climate change in arctic systems.

Impacts of Degrading Ice‐Wedges on Ground Temperatures in a High Arctic Polar Desert System

AbstractIce‐wedge ice is the most widespread type of massive ice found in the continuous permafrost zone. Polygonal networks of ice‐wedges drive environmental changes and feedback that will likely be exacerbated with future climate change. Recent decadal‐scale observations have shown that ice‐wedges are degrading rapidly within the entire Circum‐Arctic Region but observations of feedback associated with ground temperature regimes are still lacking in many areas. We present over a year's worth of field observations from an area with cold (−16.5°C), thick (>500 m) continuous permafrost and a mean annual air temperature of −19.7°C in the Canadian high Arctic. Topographic surveys, thaw depths, vegetation cover, soil moisture, and annual shallow (12 cm) ground temperature measurements were collected for seven ice‐wedge troughs and two polygon centers in a high‐centered polygon system. We show that geomorphic changes caused by ice‐wedge degradation generate new responses in soil moisture, vegetation cover, and snow distribution that create a mosaic of ground temperatures that range by 5.1°C for mean annual, 2.5°C in summer, and 15.2°C in winter between polygon‐centers and ice‐wedge troughs. Our results show that snow redistribution due to wind induces the cooling of polygon centers, thus promoting new thermal contraction cracking and ice‐wedge formation. We provide an example based on high‐resolution remote sensing data on how these ice‐wedge trough densities vary spatially in our study area. Capturing these fine scale geomorphic differences and resulting ground temperatures will be critical to accurately assess future changes of these common Arctic landscapes.

The distribution and relative ecological roles of autotrophic and heterotrophic diazotrophs in the McMurdo Dry Valleys, Antarctica.

ABSTRACTThe McMurdo Dry Valleys (MDV) in Antarctica harbor a diverse assemblage of mat-forming diazotrophic cyanobacteria that play a key role in nitrogen cycling. Prior research showed that heterotrophic diazotrophs also make a substantial contribution to nitrogen fixation in MDV. The goals of this study were to survey autotrophic and heterotrophic diazotrophs across the MDV to investigate factors that regulate the distribution and relative ecological roles of each group. Results indicated that diazotrophs were present only in samples with mats, suggesting a metabolic coupling between autotrophic and heterotrophic diazotrophs. Analysis of 16S rRNA and nifH gene sequences also showed that diazotrophs were significantly correlated to the broader bacterial community, while co-occurrence network analysis revealed potential interspecific interactions. Consistent with previous studies, heterotrophic diazotrophs in MDV were diverse, but largely limited to lakes and their outlet streams, or other environments protected from desiccation. Despite the limited distribution, heterotrophic diazotrophs may make a substantial contribution to the nitrogen budget of MDV due to larger surface area and longer residence times of lakes. This work contributes to our understanding of key drivers of bacterial community structure in polar deserts and informs future efforts to investigate the contribution of nitrogen fixation to MDV ecosystems.

Trophic Selective Pressures Organize the Composition of Endolithic Microbial Communities From Global Deserts.

Studies of microbial biogeography are often convoluted by extremely high diversity and differences in microenvironmental factors such as pH and nutrient availability. Desert endolithic (inside rock) communities are relatively simple ecosystems that can serve as a tractable model for investigating long-range biogeographic effects on microbial communities. We conducted a comprehensive survey of endolithic sandstones using high-throughput marker gene sequencing to characterize global patterns of diversity in endolithic microbial communities. We also tested a range of abiotic variables in order to investigate the factors that drive community assembly at various trophic levels. Macroclimate was found to be the primary driver of endolithic community composition, with the most striking difference witnessed between hot and polar deserts. This difference was largely attributable to the specialization of prokaryotic and eukaryotic primary producers to different climate conditions. On a regional scale, microclimate and properties of the rock substrate were found to influence community assembly, although to a lesser degree than global hot versus polar conditions. We found new evidence that the factors driving endolithic community assembly differ between trophic levels. While phototrophic taxa, mostly oxygenic photosynthesizers, were rigorously selected for among different sites, heterotrophic taxa were more cosmopolitan, suggesting that stochasticity plays a larger role in heterotroph assembly. This study is the first to uncover the global drivers of desert endolithic diversity using high-throughput sequencing. We demonstrate that phototrophs and heterotrophs in the endolithic community assemble under different stochastic and deterministic influences, emphasizing the need for studies of microorganisms in context of their functional niche in the community.

СПЕКТРАЛЬНЫЕ ХАРАКТЕРИСТИКИ ТУНДРОВЫХ И ЛЕСОТУНДРОВЫХ ЛАНДШАФТОВ В ГОДЫ ЛЕТНИХ ТЕМПЕРАТУРНЫХ АНОМАЛИЙ

The warming at high latitudes, remaining in recent years, has a direct impact on arctic and subarctic landscapes. Possible changes of this landscapes under the climate warming are closely related with regulatory mechanisms for the underlying surface temperature. The circumstances of forming radiation and evapotranspirational regulatory mechanisms for the surface temperature were explored for tundra (from arctic to southern) and forest tundra landscapes of Novaya Zemlya and Western Siberia. The MODIS data of surface spectral characteristics were used, and more specifically albedo (Al) and surface temperature (Ts) for July 2000-2019. The work shows that the radiation regulatory mechanism of the surface temperature is dominated in glacial and polar desert landscapes of Arctic and Subarctic with a predominance of stony and rubble types of surfaces with lichens. At the same time, radiative surface temperature control mechanism in mountain and arctic tundra of Novaya Zemlya almost does not depend on weather anomalies and so far has a little implication for the temperature trend. In the mainland and forest tundra, the evapotranspirational regulatory mechanism for the surface temperature starts to prevail. This is supported by the increasing of monthly average air temperatures to 15-16°С, which is beneficial to the vegetation diversity. In subzones of the southern and forest tundra, the connection of albedo and surface temperature depends on altitudes, slope exposure and especially on extreme temperature anomalies. In basins, or hydromorphic complexes, in cold years against the backdrop of wetlands the regulatory mechanism for the surface temperature prevails, and in warm years the humidity decreasing leads to the highest vegetation development and the connection type can turn into the evapotranspirational one. On the high grounds the return process is observed, which is also connected with the changes in humidification conditions. In forest tundra, where the air temperature rises and the canopy height increases, the evapotranspirational mechanism of spectral parameters Al–Ts connections is weakening. As a result, in southern and forest tundra two balanced steady states of the connection types of surface spectral characteristics can exist in relation to lighting conditions and temperature anomalies.

First pre-modern record of the gyrfalcon (Falco rusticolus) in north-east Greenland

Gyrfalcon (Falco rusticolus) is the largest falcon in the world. It inhabits a wide range of climate zones in the Northern Hemisphere, from boreal forests in the south of its range to the arid polar deserts of the High Arctic. In Greenland, because of the harsh, remote environments in which gyrfalcons live, research related to the contemporary and pre-modern periods has been limited to the north-west, central west and central east coasts, with no specific investigations being conducted for the north-east. Here, we report the first pre-modern record of a gyrfalcon in north-east Greenland, located at 80.4°N in Kronprins Christian Land. Skin tissue from a decaying gyrfalcon’s body was radiocarbon dated to 769–944 CE (common era) using a terrestrial-only calibration curve, and 1182–1456 CE using a marine-only calibration curve. Since the gyrfalcon has a mixed terrestrial/marine diet, the actual age can be said to belong between these two groups. This limited data, therefore places the presence of the gyrfalcon in north-east Greenland during a period of prolonged elevated temperatures and climate stress associated with the Medieval Climate Anomaly. Whether the gyrfalcon was part of a larger population or a straggler, and whether the species survived the whole of the Medieval Climate Anomaly in north-east Greenland, is unknown.

The Hydroecology of an Ephemeral Wetland in the McMurdo Dry Valleys, Antarctica

AbstractThe McMurdo Dry Valleys is a polar desert on the coast of East Antarctica where ephemeral wetlands become hydrologically active during warm and sunny summers when subsurface flows are generated from melting snowfields. To understand the structure and function of polar wetland ecosystems, we investigated the hydroecology of one such wetland, the Wormherder Creek wetland, during the warm and sunny summer of 2008 – 2009, when the wetland was hydrologically reactivated. Conservative tracer (LiCl) was injected for a 2‐hr period into a stream above the wetland to determine flow path orientations and hydrologic residence times. Tracer results indicated that surface water is rapidly exchanged with wetland groundwater and wetland residence times may exceed two austral summers. Major ion concentrations were uniform in samples from surface water and shallow groundwater throughout the wetland. Microbial mats in the wetland had high autotrophic index values (the ratios of chlorophyll a [Chl‐a]/ash‐free dry mass), ranging from 9 to 38 μg Chl‐a/mg ash‐free dry mass, indicative of actively photosynthesizing mat communities. The diatom communities in the mats were relatively uniform compared to those in mats from regularly flowing McMurdo Dry Valleys streams, with four endemic and one widespread diatom taxa of the genus Luticola accounting for an average of 86% of the community. These results indicate that the hydrologic characteristics of the wetland contribute to uniform geochemical conditions. In turn, uniform geochemical conditions may explain the high autotrophic index values of the microbial mats and relatively low spatial variation of the diatom community.

Water tracks intensify surface energy and mass exchange in the Antarctic McMurdo Dry Valleys

Abstract. The hydrologic cycle in the Antarctic McMurdo Dry Valleys (MDV) is mainly controlled by surface energy balance. Water tracks are channel-shaped high-moisture zones in the active layer of permafrost soils and are important solute and water pathways in the MDV. We evaluated the hypothesis that water tracks alter the surface energy balance in this dry, cold, and ice-sheet-free environment during summer warming and may therefore be an increasingly important hydrologic feature in the MDV in the face of landscape response to climate change. The surface energy balance was measured for one water track and two off-track reference locations in Taylor Valley over 26 d of the Antarctic summer of 2012–2013. Turbulent atmospheric fluxes of sensible heat and evaporation were observed using the eddy-covariance method in combination with flux footprint modeling, which was the first application of this technique in the MDV. Soil heat fluxes were analyzed by measuring the heat storage change in the thawed layer and approximating soil heat flux at ice table depth by surface energy balance residuals. For both water track and reference locations over 50 % of net radiation was transferred to sensible heat exchange, about 30 % to melting of the seasonally thawed layer, and the remainder to evaporation. The net energy flux in the thawed layer was zero. For the water track location, evaporation was increased by a factor of 3.0 relative to the reference locations, ground heat fluxes by 1.4, and net radiation by 1.1, while sensible heat fluxes were reduced down to 0.7. Expecting a positive snow and ground ice melt response to climate change in the MDV, we entertained a realistic climate change response scenario in which a doubling of the land cover fraction of water tracks increases the evaporation from soil surfaces in lower Taylor Valley in summer by 6 % to 0.36 mm d−1. Possible climate change pathways leading to this change in landscape are discussed. Considering our results, an expansion of water track area would make new soil habitats accessible, alter soil habitat suitability, and possibly increase biological activity in the MDV. In summary, we show that the surface energy balance of water tracks distinctly differs from that of the dominant dry soils in polar deserts. With an expected increase in area covered by water tracks, our findings have implications for hydrology and soil ecosystems across terrestrial Antarctica.

Severity of the present-day climate in the Polar regions of Siberia

Over the period 1981–2015 severe climatic conditions on the North of Siberia (area within 66–162° E above the Polar Circle) were characterized by significant space-time variations of air temperature at the cold period of the year. This conclusion is made on the basis of analysis of observations made about 13 hour of local time. Positive changes in the mean seasonal air temperature were observed here in October–April. The largest rates of air temperature rise with a pronounced gradient to the West were noted in high latitudes, i.e. in Arctic glacial and polar desert landscapes. The change in weather severity which is one of characteristics of the climate discomfort was analyzed by means of the Arnoldi index (TA). This index reflects the combined effect of negative temperatures and stiff wind on the thermal state of the open surface of the human body. Together with the space-time dynamics of the actual TA values, important values of TA are its threshold values (more than 30 and more than 45 units) which determine a degree of discomfort. Duration of these periods, limiting a possibility of a person's stay in the open air, is also extremely important as well. In recent decades (1981–2015), the spatial differentiation of the number of days (from 80 to 160) limiting the human’s stay in the open air reflects in the main fluctuations of the air temperature and wind regime in polar landscapes. Slight warming (a rise of the air temperature) and small wind speed variability during the period from October to April in 1981–2015 resulted in a certain decrease in the index of weather severity in relation to the period 1966–1980, since the last one did not did not go beyond limit of the interannual variability. Despite the stable increase in the air temperature in 1981–2015, no tendency to reduction of the number of days limiting human’s stay in the open air was noted. The duration of this period for 1981–2015 is similar to that observed in 1936–1964, and we believe that this is suggestive of manifestation of the cyclicity of atmospheric processes and is agreed with a gradual decrease in the rate of the temperature rise. In the last period duration of the period limiting human stay in the open air in the considered area remains high and ranges from 3.5 (to the west of 80° E) to 5 months on islands and capes of the region. So, as is demonstrated by the above example of space-time dynamics of the weather severity index at the time about 13 hours of local time, no decrease in the level of discomfort in polar Siberia is found.

The geochemistry of glacial deposits in Taylor Valley, Antarctica: Comparison to upper continental crustal abundances

Wet-based glacial deposits have been used traditionally as an analog for upper continental crust (UCC) abundances. To provide more information on the validity of using glacial deposits from wet-based glaciers, samples deposited by the dry-based polar glaciers located in Taylor Valley, Antarctica, were collected. Stream channel sediments, comprised of igneous, metamorphic, and sedimentary rocks initially deposited as glacial tills by polar glaciers, were analyzed by XRF, ICP-MS, and SEM. Based on the Chemical Index of Alteration values and A–CN–K ternary diagram, there are low levels of chemical weathering in these tills. Additionally, major and trace element geochemical data are compared to the average UCC values. The observed discrepancies between the mean UCC and Antarctic samples develop from the existence of mafic components, most likely the McMurdo Volcanic Group and Ferrar Dolerite, being present in the Taylor Valley tills. Even though the mafic material typically comprises 3–7% of the till, the volcanic rocks have a significant influence on the tills’ bulk geochemistry. The existence of this mafic fraction in the dry-based glacial tills results from the reduced rate of weathering, as compared to wet-based glaciers. Geochemical analyses of the dry-based glacial tills in polar deserts, such as those found in Taylor Valley, may provide a better representative composition of the original material than wet-based glaciers and need to be incorporated into upper continental crust calculations.

A nematode in the mist: Scottnema lindsayae is the only soil metazoan in remote Antarctic deserts, at greater densities with altitude

A decrease in biodiversity and density of terrestrial organisms with increasing altitude and latitude is a well-known ecogeographical pattern. However, studies of these trends are often taxonomically-biased toward well-known organisms and especially those with relatively large bodies, and environmental variability at the local scale may perturb these general effects. Here, we focus on understudied organisms—soil invertebrates—in Antarctic deserts, which are among the driest and coldest places on Earth. We sampled two remote Antarctic sites in the Darwin Glacier area and established an altitudinal gradient running from 210 to 836 m a.s.l. We measured soil geochemistry and organic matter content and linked these parameters with the presence of soil invertebrates. We found three general outcomes, two of which are consistent with general assumptions: (a) the hostile climatic condition of the Darwin Glacier region supports an extremely low diversity of soil metazoans represented by a single nematode species—Scottnema lindsayae; (b) soil geochemistry is the main factor influencing distribution of nematodes at the local scale. Contrary to our expectations, a positive correlation was found between nematode density and altitude. This last observation could be explained by an additional effect of soil moisture as we found this increased with altitude and may be caused by orographic clouds, which are present in this region. To the best of our knowledge such effects have been described in tropical and temperate regions. Potential effect of orographic clouds on soil properties in polar deserts may be a fruitful area of ecological research on soil fauna.

Rapid initialization of retrogressive thaw slumps in the Canadian high Arctic and their response to climate and terrain factors

An increase in retrogressive thaw slump (RTS) activity has been observed in the Arctic in recent decades. However, a gap exists between observations in high Arctic polar desert regions where mean annual ground temperatures are as cold as −16.5 °C and vegetation coverage is sparse. In this study, we present a ∼30 year record of annual RTS observations (frequency and distribution) from 1989 to 2018 within the Eureka Sound Lowlands, Ellesmere and Axel Heiberg Islands. Record summer warmth in 2011 and 2012 promoted rapid RTS initialization, increasing active slumps from 100 in a given year or less to over 200 regionally and promoting RTS initiation in previously unaffected terrain. Differential GPS and remote sensing observations of 12 RTSs initiated during this period (2011–2018) provided a mean headwall retreat rate for all RTSs of 6.2 m yr−1 and for specific RTSs up to 26.7 m yr−1. To better understand the dynamics of climate and terrain factors controlling RTS headwall retreat rates we explored RTS interactions by correlating headwall retreat with climate factors (thawing degree days, annual rainfall and annual snowfall) and terrain factors (aspect and slope). Our findings indicate a sensitivity of cold permafrost in the high Arctic to climate-driven thermokarst initiation, but the decoupling of RTS dynamics from climate appears to occur over time for individual RTS as terrain factors take on a greater role controlling headwall retreat. Detailed observations of thermokarst development in a high Arctic polar desert permafrost setting are important as it demonstrates the sensitivity of this system to changes in summer temperatures and highlight differences to changes occurring in other Arctic permafrost regions.

Microbial diversity of an Antarctic subglacial community and high-resolution replicate sampling inform hydrological connectivity in a polar desert.

Antarctic subglacial environments host microbial ecosystems and are proving to be geochemically and biologically diverse. The Taylor Glacier, Antarctica, periodically expels iron-rich brine through a conduit sourced from a deep subglacial aquifer, creating a dramatic red surface feature known as Blood Falls. We used Illumina MiSeq sequencing to describe the core microbiome of this subglacial brine and identified previously undetected but abundant groups including the candidate bacterial phylum Atribacteria and archaeal phylum Pacearchaeota. Our work represents the first microbial characterization of samples collected from within a glacier using a melt probe, and the only Antarctic subglacial aquatic environment that, to date, has been sampled twice. A comparative analysis showed the brine community to be stable at the operational taxonomic unit level of 99% identity over a decade. Higher resolution sequencing enabled deconvolution of the microbiome of subglacial brine from mixtures of materials collected at the glacier surface. Diversity patterns between this brine and samples from the surrounding landscape provide insight into the hydrological connectivity of subglacial fluids to the surface polar desert environment. Understanding subice brines collected on the surfaces of thick ice covers has implications for analyses of expelled materials that may be sampled on icy extraterrestrial worlds.

Bryophytes of Zhelania Cape, Severny Island, Novaya Zemlya Archipelago in the Russian Arctic

We present the results of a revsion of an extensive set of collections of bryophytes from the Novaya Zemlya Archipelago northern extremity, the northern‐most sector of polar deserts, which until now has been poorly explored in terms of the bryophyte flora. The checklist produced includes 24 liverwort and 135 moss species. Thirteen species, viz. Lophoziopsis propagulifera, Scapania degenii, Brachytheciastrum collinum, Bryoerythrophyllum cf. rubrum, Bucklandiella microcarpa, Campylium laxifolium, C. longicuspis, Dicranum schljakovii, Drepanium recurvatum, Flexitrichum gracile, Grimmia longirostris, Hamatocaulis vernicosus and Pseudocalliergon angustifolium are reported for the first time from the polar desert region. Though in number of species known the area loses only to the more intensively studied NE Land of Svalbard, a comparative analysis suggests that our study area is still incompletely known and suffers from ‘phytosociological sampling’ which underestimates the number of small pioneer mosses. A comparative analysis based on published data on other areas of the polar desert region is presented but the results does not confirm previously proposed floristic subdivisions of the polar desert region and may be strongly influenced by incomplete and biased sampling. Some species have a higher share in the vegetation cover of the polar desert region than elsewhere, thus contributing to its segregation and among these are mostly calciphilous/basiphilous species.

Harnessing long-read amplicon sequencing to uncover NRPS and Type I PKS gene sequence diversity in polar desert soils.

The severity of environmental conditions at Earth's frigid zones present attractive opportunities for microbial biomining due to their heightened potential as reservoirs for novel secondary metabolites. Arid soil microbiomes within the Antarctic and Arctic circles are remarkably rich in Actinobacteria and Proteobacteria, bacterial phyla known to be prolific producers of natural products. Yet the diversity of secondary metabolite genes within these cold, extreme environments remain largely unknown. Here, we employed amplicon sequencing using PacBio RS II, a third generation long-read platform, to survey over 200 soils spanning twelve east Antarctic and high Arctic sites for natural product-encoding genes, specifically targeting non-ribosomal peptides (NRPS) and Type I polyketides (PKS). NRPS-encoding genes were more widespread across the Antarctic, whereas PKS genes were only recoverable from a handful of sites. Many recovered sequences were deemed novel due to their low amino acid sequence similarity to known protein sequences, particularly throughout the east Antarctic sites. Phylogenetic analysis revealed that a high proportion were most similar to antifungal and biosurfactant-type clusters. Multivariate analysis showed that soil fertility factors of carbon, nitrogen and moisture displayed significant negative relationships with natural product gene richness. Our combined results suggest that secondary metabolite production is likely to play an important physiological component of survival for microorganisms inhabiting arid, nutrient-starved soils.

The microbial diversity of a sulfur-rich and saline cold pool in the Canadian high Arctic

Currently, the surface of Mars cannot sustain liquid water, but there is evidence suggesting that water was present in the Noachian. Although water might exist in the subsurface of Mars, it could not sustain in the present day unless it was highly saline. Thus, saline springs in polar desert environments are analogues with which to investigate martian conditions. An example of this is Axel Heiberg Island, located in a region of continuous permafrost in the Canadian High Arctic, which hosts sulfidic and highly saline springs. In this study, cultivation-dependant and independent techniques were used to investigate the microbial diversity of a sediment sample collected from a saline cold (3–8 °C) pool at Colour Peak Springs on Axel Heiberg. Both DNA and RNA were extracted from the samples, and the microbial community was characterised using the 16S rRNA gene from the extracted nucleic acids. The metabolic profile was characterised by screening DNA and cDNA for functional genes relating to the cycling of carbon (coxL, xoxF, cbbL), nitrogen (nifH, nosZ, nod) and sulfur (dsrB, soxB). The community profiles were used to inform enrichment strategies, allowing for the isolation and characterisation of several halophilic isolates including strains of Marinobacter, Halomonas, Halanaerobium and Loktanella. Through this work we have been able to develop an in-depth characterisation of the metabolic and phylogenetic diversity that is present and viable within this analogue site. This allows us to start building an understanding of the underlying mechanisms and strategies that enable organisms to persist in these environments.

Nematodes in a polar desert reveal the relative role of biotic interactions in the coexistence of soil animals

Abiotic factors are major determinants of soil animal distributions and their dominant role is pronounced in extreme ecosystems, with biotic interactions seemingly playing a minor role. We modelled co-occurrence and distribution of the three nematode species that dominate the soil food web of the McMurdo Dry Valleys (Antarctica). Abiotic factors, other biotic groups, and autocorrelation all contributed to structuring nematode species distributions. However, after removing their effects, we found that the presence of the most abundant nematode species greatly, and negatively, affected the probability of detecting one of the other two species. We observed similar patterns in relative abundances for two out of three pairs of species. Harsh abiotic conditions alone are insufficient to explain contemporary nematode distributions whereas the role of negative biotic interactions has been largely underestimated in soil. The future challenge is to understand how the effects of global change on biotic interactions will alter species coexistence.