Chemical weathering plays a crucial role in the long-term evolution of Earth’s climate, yet the spatial heterogeneity of the weathering rate and intensity driven by glacial erosion owing to glacial shrinkage worldwide is poorly constrained. Here we develop a global data set of cation denudation rate (CDR) and intensity (CDI) from mountain ranges, glacial regions and glacial catchments worldwide. Contemporary weathering rate and intensity are ~ 2 times higher than two decades ago, 2 ~ 6 times higher than Greenland ice sheet basins and over 2 times higher than whole ice sheet means. Their spatial patterns are characterized by relatively high weathering rate and intensity in low latitudes in contrast to low weathering rate and intensity in high latitudes. This is closely related to glacial erosion involving with temperature, precipitation, discharge, altitude and slope, suggesting that the element mobilization and CO2 budgets caused by glacial chemical weathering are likely to enhance in a warming landscape. We contend that subglacial chemical weathering is far more important than previously thought and should be considered in elemental cycles and carbon cycling.

Pyrite oxidation drives iron and sulfur availability across Earth's subsurface and is partly microbially mediated. Subsurface microbial communities accelerate this process at circumneutral pH directly by weathering pyritic surfaces and indirectly by causing changes to the surrounding microenvironment, thereby further accelerating pyrite weathering. However, our understanding of community structure dynamics and associated biogeochemistry in Fe- and S-rich lithologies, e.g. pyritic coal, is limited. Here, we present the first comprehensive regional and seasonal genus-level survey of bacterial groundwater communities in a pyritic coal-based aquifer in the South Wales Coalfield (SWC), using 16S rRNA gene amplicon sequencing. Seasonal changes in community structure were limited, suggesting limited influence of surface processes on subsurface communities. Instead, hydrogeologically distinct mine water blocks (MWB) and coal rank largely explained bacterial community structure variation across sites. Fe(II)-oxidizing Betaproteobacteriales genera Gallionella and Sideroxydans dominated the bacterial communities across nine sites and seven MWBs, while three sites within a single MWB, were dominated by S-oxidizing Epsilonbacteraeota genera Sulfuricurvum and Sulfurovum. The cooccurrence of pairs of Fe(II)- and S-oxidizing bacterial genera suggests functional redundancy, which coupled with genus-specific morphologies and life strategies, indicates the importance of distinct environmental and ecological niches within the SWC groundwater at seasonal and regional scales.

Sunlight penetrates the ice surfaces of glaciers and ice sheets, forming a water-bearing porous ice matrix known as the weathering crust. This crust is home to a significant microbial community. Despite the potential implications of microbial processes in the weathering crust for glacial melting, biogeochemical cycles, and downstream ecosystems, there have been few explorations of its microbial communities. In our study, we used 16S rRNA gene sequencing and shotgun metagenomics of a Svalbard glacier surface catchment to characterise the microbial communities within the weathering crust, their origins and destinies, and the functional potential of the weathering crust metagenome. Our findings reveal that the bacterial community in the weathering crust is distinct from those in upstream and downstream habitats. However, it comprises two separate micro-habitats, each with different taxa and functional categories. The interstitial porewater is dominated by Polaromonas , influenced by the transfer of snowmelt, and exported via meltwater channels. In contrast, the ice matrix is dominated by Hymenobacter , and its metagenome exhibits a diverse range of functional adaptations. Given that the global weathering crust area and the subsequent release of microbes from it are strongly responsive to climate projections for the rest of the century, our results underscore the pressing need to integrate the microbiome of the weathering crust with other communities and processes in glacial ecosystems.

Microorganisms inhabiting hostile Arctic environments express a variety of functional phenotypes, some of clinical interest, such as haemolytic ability and antimicrobial resistance. We studied haemolytic bacterial isolates from Arctic habitats, assessing their minimum inhibitory concentration (MIC) against antimicrobials. We then performed whole genome sequencing and analysed them for features conferring antimicrobial resistance. MIC data showed that Micromonospora spp. belong to 33% non-wild type (NWT) for erythromycin and penicillin and 22% NWT for tetracycline. Both Pseudomonas spp. belong to 43% NWT for nalidixic acid and streptomycin and 29% NWT for colistin. Finally, the Pedobacter isolate was in 80% NWT for antimicrobials tested. Whole-genome sequencing analyses revealed that fluoroquinolones, tetracyclines, macrolides and penams were the most frequent drug classes against which genotypic resistance was found. Additionally, resistance genes to heavy metals and disinfectants were identified. Our research demonstrates the presence of antimicrobial resistance in bacteria from Arctic habitats and highlights the importance of conservation efforts in these environments, where anthropogenic influence is becoming more evident. Furthermore, our data suggest the possible presence of novel resistance mechanisms, which could pose a threat if the responsible genes are transferable between species or become widespread due to environmental stress and alterations brought about by climate change.

The Krafla geothermal system is located within a volcanic center that periodically erupts basaltic lavas, and has recently attracted an economic interest due to supercritical fluids forming near a shallow magma intrusion (similar to 2 km depth). Here, we discuss new soil CO2 flux and stable isotope data of the CO2 efflux (delta C-13) and hydrothermal calcites (delta C-13, delta O-18) of drill cuttings to estimate both the current magmatic outgassing from soils and the thermal flows in the geothermal system. Soil CO2 emission is controlled by tectonics, following the NNE-SSW fissure swarm direction and a WSW-ENE trend, and accounts for similar to 62.5 t d(-1). While the delta O-18 of the H2O in equilibrium with deep calcites is predominantly meteoric, both the delta C-13 of the soil CO2 efflux and of the fluids from which calcite precipitated have a clear magmatic origin, overlapping the delta C-13 estimated for the Icelandic mantle (-2.5 +/- 1.1 parts per thousand). Estimates based on the soil CO2 emission from the southern part of the system show that these fluxes might be sustained by the ascent and depressurization of supercritical fluids with a thermal energy of similar to 800 MW. Such significant amount of energy might reach 1.5 GW if supercritical conditions extended below the whole investigated area. Finally, we report an increase in the soil CO2 emission of about 3 times with respect to 14 years ago, likely due to recent changes in the fluid extracted for power production or magmatic activity. Pairing the soil CO2 emission with stable isotopes of the efflux and calcite samples has important implications for both volcano monitoring and geothermal exploration, as it can help us to track magmatic fluid upflows and the associated thermal energy.

Adsorption of gases in porous adsorbents such as coal and shale generally exhibits the phenomenon of hysteresis. Most of the previous studies on desorption hysteresis were conducted via experimental tests. However, few theoretical models that represent adsorption-desorption hysteresis of gases in porous sorbents are available. To address this issue, this work develops a new adsorption-desorption model for describing adsorption and desorption isotherms of gases with hysteresis. Particularly, the energetically heterogeneous surfaces of an adsorbent are considered via the patchwise model. Based on the change in site energy distribution, a logarithmically pressure-dependent hysteresis index, which is used to measure the degree of hysteresis, is derived for quantitative assessment of the degree of hysteresis. Besides, the correlation between the desorption isotherm and initialized pressure for desorption is established. The accuracy of the proposed model to adequately describe the adsorption-desorption hysteresis of gas in coal and shale is demonstrated by validating the model against laboratory experiments obtained from the literature. The results indicate that the adsorption isotherm depends significantly on site energy distribution. By comparing the site energy distributions for adsorption and desorption isotherms, it is found that the desorption hysteresis can be attributed to the change in pore size distribution caused by adsorption-induced deformation. The analyses support that the proposed model can be used as an effective tool to quantitatively predict the amount of released gas during desorption, which is significant for designing coalbed methane or shale gas production and assessing long-term CO2 storage behavior.

The rapid warming of the Arctic is threatening the demise of its glaciers and their associated ecosystems. Therefore, there is an urgent need to explore and understand the diversity of genomes resident within glacial ecosystems endangered by human-induced climate change. In this study we use genome-resolved metagenomics to explore the taxonomic and functional diversity of different habitats within glacier-occupied catchments. Comparing different habitats within such catchments offers a natural experiment for understanding the effects of changing habitat extent or even loss upon Arctic microbiota. Through binning and annotation of metagenome-assembled genomes (MAGs) we describe the spatial differences in taxon distribution and their implications for glacier-associated biogeochemical cycling. Multiple taxa associated with carbon cycling included organisms with the potential for carbon monoxide oxidation. Meanwhile, nitrogen fixation was mediated by a single taxon, although diverse taxa contribute to other nitrogen conversions. Genes for sulphur oxidation were prevalent within MAGs implying the potential capacity for sulphur cycling. Finally, we focused on cyanobacterial MAGs, and those within cryoconite, a biodiverse microbe-mineral granular aggregate responsible for darkening glacier surfaces. Although the metagenome-assembled genome of Phormidesmis priestleyi , the cyanobacterium responsible for forming Arctic cryoconite was represented with high coverage, evidence for the biosynthesis of multiple vitamins and co-factors was absent from its MAG. Our results indicate the potential for cross-feeding to sustain P. priestleyi within granular cryoconite. Taken together, genome-resolved metagenomics reveals the vulnerability of glacier-associated microbiota to the deletion of glacial habitats through the rapid warming of the Arctic.

Whillans Subglacial Lake (SLW) lies beneath 801 m of ice in the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and active subglacial drainage network. Here, the geochemical characterization of SLW rare earth elements (REE), trace elements (TE), free amino acids (FAA), and phenolic compounds (PC) measured in lakewater and sediment porewater are reported. The results show, on average, higher values of REEs in the lakewater than in the porewater, and clear changes in all REE concentrations and select redox sensitive trace element concentrations in porewaters at a depth of similar to 15 cm in the 38 cm lake sediment core. This is consistent with prior results on the lake sediment redox conditions based on gas chemistry and microbiological data. Low concentrations of vanillyl phenols were measured in the SLW water column with higher concentrations in porewater samples and their concentration profiles in the sediments may also reflect changing redox conditions in the sediments. Vanillin concentrations increased with depth in the sediments as oxygenation decreases, while the concentrations of vanillic acid, the more oxidized component, were higher in the more oxygenated surface sediments. Collectively these results indicate redox changes occurring with the upper 38 cm of sediment in SLW and provide support for the existence of a seawater source, already hypothesized, in the sediments below the lowest measured depth, and of a complex and dynamic geochemical system beneath the West Antarctic Ice Sheet. Our results are the first to detail geochemical properties from an Antarctic subglacial environment using direct sampling technology. Due to their isolation from the wider environment, subglacial lakes represent one of our planets last pristine environments that provide habitats for microbial life and natural biogeochemical cycles but also impact the basal hydrology and can cause ice flow variations.

While recent efforts to catalogue Earth’s microbial diversity have focused upon surface and marine habitats, 12–20 % of Earth’s biomass is suggested to exist in the terrestrial deep subsurface, compared to ~1.8 % in the deep subseafloor. Metagenomic studies of the terrestrial deep subsurface have yielded a trove of divergent and functionally important microbiomes from a range of localities. However, a wider perspective of microbial diversity and its relationship to environmental conditions within the terrestrial deep subsurface is still required. Our meta-analysis reveals that terrestrial deep subsurface microbiota are dominated by Betaproteobacteria, Gammaproteobacteria and Firmicutes , probably as a function of the diverse metabolic strategies of these taxa. Evidence was also found for a common small consortium of prevalent Betaproteobacteria and Gammaproteobacteria operational taxonomic units across the localities. This implies a core terrestrial deep subsurface community, irrespective of aquifer lithology, depth and other variables, that may play an important role in colonizing and sustaining microbial habitats in the deep terrestrial subsurface. An in silico contamination-aware approach to analysing this dataset underscores the importance of downstream methods for assuring that robust conclusions can be reached from deep subsurface-derived sequencing data. Understanding the global panorama of microbial diversity and ecological dynamics in the deep terrestrial subsurface provides a first step towards understanding the role of microbes in global subsurface element and nutrient cycling.

Melting glacier ice surfaces host active microbial communities that enhance glacial melt, contribute to biogeochemical cycling, and nourish downstream ecosystems; but these communities remain poorly characterised. Over the coming decades, the forecast ‘peak melt’ of Earth’s glaciers necessitates an improvement in understanding the state and fate of supraglacial ecosystems to better predict the effects of climate change upon glacial surfaces and catchment biogeochemistry. Here we show a regionally consistent mean microbial abundance of 10 4 cells mL −1 in surface meltwaters from eight glaciers across Europe and North America, and two sites in western Greenland. Microbial abundance is correlated with suspended sediment concentration, but not with ice surface hydraulic properties. We forecast that release of these microbes from surfaces under a medium carbon emission scenario (RCP 4.5) will deliver 2.9 × 10 22 cells yr −1 , equivalent to 0.65 million tonnes yr −1 of cellular carbon, to downstream ecosystems over the next ~80 years.

The absence of organic compounds from Precambrian iron formations challenges the hypothesis that they were precipitated by microbial oxidation of Fe (II) to Fe (III). The mineral association of iron formations is a mixture of primary and secondary minerals, where the primary mineral hematite was unlikely precipitated directly in the water column by microbes but rather transformed from a precursor biogenic ferrihydrite. Here we address the fate of the associated organic compounds during mineral transformation. We used dynamic force spectroscopy (DFS) to determine the Gibbs free energy of binding (ΔGbu) between hematite and common molecular terminations found in microbial extracellular polymeric substances (EPS) and biofilms: carboxylic, alcohol and phosphate functional groups. We found that the bond between hematite and alcohol group is approximately 2 times stronger than the bond between hematite-carboxyl and hematite-phosphate groups. To address the fate of the strongly bound polymers during transformation, we transformed synthetic ferrihydrite to hematite in presence of glycerol, which has a high density of alcohol groups, glycerol. The amount of mineral associated glycerol was measured before and after the transformation with thermogravimetric analysis (TGA). We show that the transformation of precursor ferrihydrite to hematite releases glycerol highlighting that at least parts of the organic compounds from initial iron formations were desorbed very early during the process of sedimentation. Our results contribute to understanding of sedimentation of iron formations and open new perspectives in investigation of fate of organic compounds in the Precambrian ocean.

The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weathering crust photic zone of the western sector of the ice sheet. Using groundwater techniques, we demonstrate that interstitial water flow is slow (~10 −2 m d −1 ), while flow cytometry enumeration reveals this pathway delivers 5 × 10 8 cells m −2 d −1 to supraglacial streams, equivalent to a carbon flux up to 250 g km −2 d −1 . We infer that cellular carbon accumulation in the weathering crust exceeds fluvial export, promoting biomass sequestration, enhanced carbon cycling, and biological albedo reduction. We estimate that up to 37 kg km −2 of cellular carbon is flushed from the weathering crust environment of the western Greenland Ice Sheet each summer, providing an appreciable flux to support heterotrophs and methanogenesis at the bed.

To establish an approach for a bulk upscaling of a composit material consisting of calcium carbonate and tunable peptoids we here combined three distinct approaches to thoroughly access the underlying kinetic and thermodynamic driving forces for CaCO3 formation on peptoid polymers. We derived the net interfacial free energy for calcite formation on the nanosheets and self-assemblage monolayers of the sheets constituent functional groups (carboxyl, amine and a 1:1 mix) using: nucleation experiments, dynamic force spectroscopy and theoretical modeling (COSMO-RS). We applied nucleation theory to the results and obtain insight into conditions were we can obtain favorable nucleation conditions on the polymers in a highly controlled manner.

Glacier surfaces are active microbial ecosystems which contribute to melt feedback cycles and biogeochemical processes. Despite this recognition, there is a lack of knowledge regarding the transport dynamics and residence time of microbes in this supraglacial habitat. Throughout the ablation season, meltwater is generated across a glacier’s surface and flows through the porous near-surface weathering crust before entering the channelised supraglacial network. Within the weathering crust, solar radiation provides a “photic zone” which, combined with nutrient availability, is conducive for microbial activity. The water flow through this porous near-surface layer provides a transport mechanism for these microbes. However, the nature of controls upon this phenomenon remain unexplored, despite the relevance for cellular export to downstream ecosystems, glacier surface albedo and biogeochemical cycling.To determine potential controls on microbial transport in the weathering crust, we present 913 measurements of microbial cell abundance in supraglacial meltwaters from 11 glaciers across the northern hemisphere. Each measurement is coupled with weathering crust hydraulic conductivity or stream discharge. These data reveal a mean microbial abundance of 2.2 × 104 cells mL-1 (with a range of 103 – 106) in supraglacial meltwaters within the weathering crust and stream channels. Modal microbe size was 1 – 2 μm (56 % of microbes), with 89 % of microbes smaller than 4 μm. No substantiated difference in size distributions between weathering crust and stream meltwaters were observed. No correlation between microbial abundance and near-surface hydraulic conductivity or stream discharge were observed, either across the entire dataset or when considered on a glacier-by-glacier basis. At three glaciers, water temperature and electrical conductivity (a proxy measure for ionic load) were also recorded; but we observe no correlation between these two variables and microbial abundance. Our data suggests weathering crust microbe abundance is consistent across differing glacial environments, and the concentrations entrained in the near-surface equal those seen in supraglacial streams. As such, despite the low transfer rate of meltwater, there appears to be limited evidence for substantial storage or accumulation of biomass in the near-surface weathering crust. Moreover, microbe entrainment does not appear to be driven by primary hydrological controls. Assuming that once liberated within the weathering crust entrained microbes reach channelised supraglacial networks, we estimate a delivery of 1.1 × 109 kg C a-1 to downstream environments globally (excluding Antarctica) to 2100, using existing discharge forecasts. This study represents a crucial first step in examining microbial abundance within, and transport across glacier surfaces and their potential role in biogeochemical process-feedbacks and the inoculation of downstream environments.

The absence of organic compounds from Precambrian iron formations (IF) challenges the hypothesis of the biogenic origin of IF. Here we address the fate of adsorbed organic compounds during transformation from ferrihydrite to hematite. We determined the binding energy between hematite and common molecular terminations found in extracellular polymeric substances and biofilms: carboxylic, hydroxyl and phosphate functional groups. We found that the bond between hematite and hydroxyl groups is approximately 2 times stronger than the bond between hematite-carboxyl and -phosphate groups. We transformed synthetic ferrihydrite to hematite at 90 ºC in presence of glycerol, which has a high density of hydroxyl groups and measured the amount of mineral associated glycerol before and after the transformation. We show that the transformation releases glycerol highlighting that organic compounds adsorbed at precursor ferrihydrite could be desorbed during the process of IF sedimentation and diagenesis. Our results suggest that the absence of organic compounds in IF should not be used as evidence against their biogenic origin.

Although subglacial aquatic environments are widespread beneath the Antarctic ice sheet, subglacial biogeochemistry is not well understood, and the contribution of subglacial water to coastal ocean carbon and nutrient cycling remains poorly constrained. The Whillans Subglacial Lake (SLW) ecosystem is upstream from West Antarctica's Gould‐Siple Coast ~800 m beneath the surface of the Whillans Ice Stream. SLW hosts an active microbial ecosystem and is part of an active hydrological system that drains into the marine cavity beneath the adjacent Ross Ice Shelf. Here we examine sources and sinks for organic matter in the lake and estimate the freshwater carbon and nutrient delivery from discharges into the coastal embayment. Fluorescence‐based characterization of dissolved organic matter revealed microbially driven differences between sediment pore waters and lake water, with an increasing contribution from relict humic‐like dissolved organic matter with sediment depth. Mass balance calculations indicated that the pool of dissolved organic carbon in the SLW water column could be produced in 4.8 to 11.9 yr, which is a time frame similar to that of the lakes’ fill‐drain cycle. Based on these estimates, subglacial lake water discharged at the Siple Coast could supply an average of 5,400% more than the heterotrophic carbon demand within Siple Coast embayments (6.5% for the entire Ross Ice Shelf cavity). Our results suggest that subglacial discharge represents a heretofore unappreciated source of microbially processed dissolved organic carbon and other nutrients to the Southern Ocean.

The Polar Regions have excellent potential for bioprospecting because the microorganisms that live there have adapted to extreme environmental conditions; and these adaptations can be harnessed in a variety of biotechnological applications. In this study, we describe the community structure of a range of different cryospheric habitats to identify environments appropriate for specific bioprospecting activities. Samples were collected from Midtre Lovénbreen glacier and surrounds in Spitzbergen, Svalbard in late June to early July 2017. Many cryospheric environment types were sampled including air, snow, slush, meltwater, cryoconite, proglacial water, soil and seawater. DNA was extracted and prepared for 16S amplicon sequencing. Amplicon sequence variants (ASVs) were assigned using DADA2 and contaminants were removed using the Decontam package in R. We searched the scientific literature for biotechnological applications of abundant community members in each environment. Each environment type displayed a unique community structure, with some physically linked environment types, like glacial snow, slush and meltwater showing continuity through space, and synchronised changes over time. The snow, slush and meltwater habitats were low in biomass and dominated by Gammaproteobacteria, with Cyanobacteria increasing in abundance as melt progressed. Cryoconite was dominated by Cyanobacteria, while sea water was dominated by Bacteriodetes, Gammaproteobacteria and Cyanobacteria. Soil was by far the most biodiverse habitat, with many phyla represented, and a large number of Actinobacteria suitable for antimicrobial discovery. Many of the current EPS, cold-active enzymes, fatty acids, antioxidants and antifreeze proteins are sourced from Proteobacteria and Cyanobacteria, the most abundant phyla in this study.

The kinetics of urea hydrolysis (ureolysis) and induced calcium carbonate (CaCO3) precipitation for engineering use in the subsurface was investigated under aerobic conditions using Sporosarcina pasteurii (ATCC strain 11859) as well as Bacillus sphaericus strains 21776 and 21787. All bacterial strains showed ureolytic activity inducing CaCO3 precipitation aerobically. Rate constants not normalized to biomass demonstrated slightly higher-rate coefficients for both ureolysis (kurea) and CaCO3 precipitation (kprecip) for B. sphaericus 21776 (kurea=0.10±0.03 h−1, kprecip=0.60±0.34 h−1) compared to S. pasteurii (kurea=0.07±0.02 h−1, kprecip=0.25±0.02 h−1), though these differences were not statistically significantly different. B. sphaericus 21787 showed little ureolytic activity but was still capable of inducing some CaCO3 precipitation. Cell growth appeared to be inhibited during the period of CaCO3 precipitation. Transmission electron microscopy (TEM) images suggest this is due to the encasement of cells and was reflected in lower kurea values observed in the presence of dissolved Ca. However, biomass regrowth could be observed after CaCO3 precipitation ceased, which suggests that ureolysis-induced CaCO3 precipitation is not necessarily lethal for the entire population. The kinetics of ureolysis and CaCO3 precipitation with S. pasteurii was further analyzed under anaerobic conditions. Rate coefficients obtained in anaerobic environments were comparable to those under aerobic conditions; however, no cell growth was observed under anaerobic conditions with NO3-, SO42- or Fe3+ as potential terminal electron acceptors. These data suggest that the initial rates of ureolysis and ureolysis-induced CaCO3 precipitation are not significantly affected by the absence of oxygen but that long-term ureolytic activity might require the addition of suitable electron acceptors. Variations in the ureolytic capabilities and associated rates of CaCO3 precipitation between strains must be fully considered in subsurface engineering strategies that utilize microbial amendments.

Given the scatter among the replicate measure of rate constants (Table SI2.1 CMM+) a more defensible statement would be that there is no apparent difference in rate constants between the two microorganisms. This statement is further supported by the observation that for the calcium absent experiments the mean urea hydrolysis rate constant (Table SI2.1 CMM-) for S. pasteurii is greater than for B. sphaericus 21776; the opposite of what was observed for the calcium present experiments.