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ABSTRACTSnow algae are photosynthetic microbes growing on melting snow surfaces, the blooms of which are visible on alpine snowpacks in Japan during the melting season. We characterized the seasonal and altitudinal variations in algal blooms on Mount Gassan, Japan, to assess the influence of vegetation on the algal bloom. From May to July in 2019, we collected colored snow from lower deciduous forest to the upper alpine areas. In the lower forest area, chlorophyll-a concentration in colored snow samples increased concomitantly with deciduous tree budburst, whereas in the alpine area, chlorophyll-a increased from June to July, although at lower levels than in the forest area. The absorption spectra of algal pigments extracted from samples differed among study sites and seasons, with those obtained from forest sites mainly characterized by absorption of chlorophylls and primary carotenoids, whereas those from alpine sites showed an intense secondary carotenoid peak throughout the study period. Chemical solute analyses revealed a general abundance of phosphate in snow, which was significantly higher in forest than in alpine sites and positively correlated with chlorophyll-a concentration. These findings suggest that nutrient supply from the forest canopy largely controls the appearance of colored snow in this area.

Glacier phototroph blooms on the surfaces of ice sheets and glaciers cause albedo reduction, leading to increased melting rates. We observed seasonal changes in the abundance of phototrophs on the Qaanaaq Ice Cap in northwestern Greenland from June to August 2014, and reproduced these changes using numerical and empirical models. The phototroph community on the ice surface mainly consisted of the glacier alga Ancylonema nordenskioldii and the cyanobacterium Phormidesmis priestleyi. The glacier alga appeared on the ice surface in late June, after which its abundance increased exponentially throughout the melting period. A logistic growth model designed for snow algal growth reproduced the measured exponential increases, suggesting that growth could be explained using the model as a function of the ice melting duration. Cyanobacteria appeared and their abundance increased in late July but did not change exponentially thereafter. The abundance of cyanobacteria was explained with an empirical model expressed as a function of the amount of mineral dust on the bare ice surface. Our numerical and empirical models for reproducing glacier algae and cyanobacteria could be useful for quantifying the albedo reduction caused by their growth and the melt rates of the Greenland ice sheet and glaciers in the future.

Abstract Glacier algae, which are photosynthetic microbes growing on ice, considerably reduce the surface albedo of glaciers and accelerate their melting rate. Although the growth of glacier algae can be suppressed by parasitic chytrids, the impact of chytrids on algal populations is still largely unknown. In this study, we described the morphology of the chytrid infecting the glacier alga Ancylonema nordenskioeldii and quantified the prevalence of infection in different habitats on a mountain glacier in Alaska, USA. Microscopic observations revealed three different morphological types of chytrids with distinct rhizoid shapes. Variations in the size of the sporangia were probably because of their different growth stages, indicating that they actively propagated on the glacier. The prevalence of infection did not vary among sites with different elevations but was substantially higher in cryoconite holes (20%) than on ice surfaces (4%) at all sites. This indicates that cryoconite holes are hot spots for chytrid infections of glacier algae, and the dynamics of cryoconite holes might affect the host–parasite interactions between chytrids and the glacier algae, which may in turn alter surface albedo and ice melting.

Global warming effects in temperate and polar regions include higher average temperatures and a decrease in snow cover, which together lead to an increase in the number of freeze–thaw cycles (FTC). These changes could affect the fitness of both terrestrial and aquatic species. In this study, we tested how tardigrades, ubiquitous microscopic invertebrates, face FTC. Tardigrades are amongst the most resistant animals to unfavorable conditions, including long and deep freezing periods, and are an emerging model group for invertebrate ecology and evolution. We used 12 populations of tardigrades, representing different families within order Parachela, inhabiting different ecosystems (glaciers, snow, terrestrial, aquatic), found in various substrates (mosses, sediments in lakes, cryoconite on glaciers, and snow), and originating from different latitudes and altitudes. We estimated the number of cycles required to kill 50% of individuals and tested for its association with ecological characteristics of the natural habitat (e.g., number of months with predicted FTC), while accounting for phylogeny. The most resistant tardigrades to FTC were the ones from mountain areas and glaciers. The estimated number of cycles required to kill 50% of individuals was the highest for mountainous species inhabiting rock pools and cryoconite holes on glaciers (30 and 14 FTC, respectively). Tardigrades from lowlands were the most sensitive to changes, with 50% of individuals dying after three FTC, while lacustrine and subtropical tardigrades required only one FTC to reach 50% mortality. Our study shows that the response to recurrent freezing stress is taxon dependent and related to the local environmental conditions. The predicted increase of FTC cycles will negatively impact tardigrade populations. Considering the abundance and various trophic roles of tardigrades, reduction in population sizes or the disappearance of some fragile species could affect the functioning of both aquatic and terrestrial ecosystems. Tardigrades are candidate indicators of how freeze–thaw cycles impact ubiquitous microscopic metazoans with similar physiological capabilities.

Abstract The oldest oceanic basin (160–180 Ma) in the western Pacific is the birthplace of the Pacific Plate and is thus essential for understanding the formation and evolution of the oceanic plate. However, the upper mantle structure beneath the region has not been thoroughly investigated because of the remoteness and difficulties of long‐term in situ seismic measurements at the ocean bottom. From 2018 to 2019, the Oldest‐1 experiment on the oldest seafloor was conducted as part of the international Pacific Array initiative. We present the first three‐dimensional P‐wave velocity structure down to a depth of 350 km based on the relative travel time residuals of teleseismic earthquakes recorded by 11 broadband ocean‐bottom seismometers operated during the Oldest‐1 experiment. Our result shows a fast P‐wave velocity anomaly (VP perturbation of 2%–4% faster than average) at a depth of 95–185 km beneath the northeast of the study area. This structure is interpreted as evidence of dry, viscous, and rigid materials at depths below the lithosphere. Two slow anomalies (VP perturbation of 2%–4% slower than average) are seen beneath the southwestern and eastern (the oldest seafloor >170 Ma) parts of the array site. The low‐velocity zones are found at depths of 95–305 km. The observed velocity structures can be indicative of plume activities that affected the upper mantle as the Pacific Plate migrated over hotspots from the southeast. Alternatively, the observed velocity features may provide seismic evidence for small‐scale sublithospheric convection.

IntroductionMicrobial communities are important components of glacier and snowpack ecosystems that influence biogeochemical cycles and snow/ice melt. Recent environmental DNA surveys have revealed that chytrids dominate the fungal communities in polar and alpine snowpacks. These could be parasitic chytrids that infect snow algae as observed microscopically. However, the diversity and phylogenetic position of parasitic chytrids has not been identified due to difficulties in establishing their culture and subsequent DNA sequencing. In this study, we aimed to identify the phylogenetic positions of chytrids infecting the snow algae, Chloromonas spp., bloomed on snowpacks in Japan.MethodsBy linking a microscopically picked single fungal sporangium on a snow algal cell to a subsequent sequence of ribosomal marker genes, we identified three novel lineages with distinct morphologies.ResultsAll the three lineages belonged to Mesochytriales, located within “Snow Clade 1”, a novel clade consisting of uncultured chytrids from snow-covered environments worldwide. Additionally, putative resting spores of chytrids attached to snow algal cells were observed.DiscussionThis suggests that chytrids may survive as resting stage in soil after snowmelt. Our study highlights the potential importance of parasitic chytrids that infect snow algal communities.

Abstract Snow ecosystems are an important component of polar and mountainous regions, influencing water regime, biogeochemical cycles and supporting snow specific taxa. Although snow is considered to be one of the most unique, and at the same time a disappearing habitat, knowledge of its taxonomic diversity is still limited. It is true especially for micrometazoans appearing in snow algae blooming areas. In this study, we used morphological and molecular approaches to identify two tardigrade species found in green snow patches of Mt. Gassan in Japan. By morphology, light (PCM) and scanning electron microscopy (SEM), and morphometry we described Hypsibius nivalis sp. nov. which differs from other similar species by granular, polygonal sculpture on the dorsal cuticle and by the presence of cuticular bars next to the internal claws. Additionally, phylogenetic multilocus (COI, 18S rRNA, 28S rRNA) analysis of the second taxon, Hypsibius sp. identified by morphology as convergens-pallidus group, showed its affinity to the Hypsibiidae family and it is placed as a sister clade to all species in the Hypsibiinae subfamily. Our study shows that microinvertebrates associated with snow are poorly known and the assumption that snow might be inhabited by snow-requiring tardigrade taxa cannot be ruled out. Furthermore, our study contributes to the understanding subfamily Hypsibiinae showing that on its own the morphology of specimens belonging to convergens-pallidus group is insufficient in establishing a true systematic position of specimens.

Abstract Background Cryoconite granules are mineral–microbial aggregates found on glacier surfaces worldwide and are hotspots of biogeochemical reactions in glacier ecosystems. However, despite their importance within glacier ecosystems, the geographical diversity of taxonomic assemblages and metabolic potential of cryoconite communities around the globe remain unclear. In particular, the genomic content of cryoconite communities on Asia’s high mountain glaciers, which represent a substantial portion of Earth’s ice masses, has rarely been reported. Therefore, in this study, to elucidate the taxonomic and ecological diversities of cryoconite bacterial consortia on a global scale, we conducted shotgun metagenomic sequencing of cryoconite acquired from a range of geographical areas comprising Polar (Arctic and Antarctic) and Asian alpine regions. Results Our metagenomic data indicate that compositions of both bacterial taxa and functional genes are particularly distinctive for Asian cryoconite. Read abundance of the genes responsible for denitrification was significantly more abundant in Asian cryoconite than the Polar cryoconite, implying that denitrification is more enhanced in Asian glaciers. The taxonomic composition of Cyanobacteria, the key primary producers in cryoconite communities, also differs between the Polar and Asian samples. Analyses on the metagenome-assembled genomes and fluorescence emission spectra reveal that Asian cryoconite is dominated by multiple cyanobacterial lineages possessing phycoerythrin, a green light-harvesting component for photosynthesis. In contrast, Polar cryoconite is dominated by a single cyanobacterial species Phormidesmis priestleyi that does not possess phycoerythrin. These findings suggest that the assemblage of cryoconite bacterial communities respond to regional- or glacier-specific physicochemical conditions, such as the availability of nutrients (e.g., nitrate and dissolved organic carbon) and light (i.e., incident shortwave radiation). Conclusions Our genome-resolved metagenomics provides the first characterization of the taxonomic and metabolic diversities of cryoconite from contrasting geographical areas, highlighted by the distinct light-harvesting approaches of Cyanobacteria and nitrogen utilization between Polar and Asian cryoconite, and implies the existence of environmental controls on the assemblage of cryoconite communities. These findings deepen our understanding of the biodiversity and biogeochemical cycles of glacier ecosystems, which are susceptible to ongoing climate change and glacier decline, on a global scale. Video abstract

Abstract The results show the morphological analyses and spectroscopic studies of snow and glacier algae and their parasitic fungi in Svalbard (High Arctic). Fixed algal cells of two species, Sanguina nivaloides and Ancylonema nordenskioeldii, were imaged using light microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Fluorescence microscopy using Calcofluor white stain supported the observations of parasitic fungi on the algal cells. Images in brightfield microscopy showed chytrid-like fungi penetrating the cells of both algal species. Parasites were found to colonize the cells of A. nordenskioeldii and hypnozygotes of S. nivaloides, while no fungi infected the cyst stages of S. nivaloides. The autofluorescence analysis revealed the ability of S. nivaloides to glow when excited with different wavelengths, while A. nordenskioeldii did not fluoresce. The hypnozygotes of S. nivaloides emitted brighter fluorescence than the cysts, and the most intense luminosity was observed in the UV range. The Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) spectroscopic analysis showed differences in the chemical composition between samples collected from three different sites. Samples dominated by cyst cells were characterized by the presence of an abundant polysaccharide envelope.

Diverse microbial communities live on glacial surfaces, with abundances and diversities dictated by the chemical and physical conditions of the supraglacial environment. Chemical solutes and mineral dust on glacial surfaces are generally derived from the atmosphere as aerosols, but they can also be supplied from glacial ice. In this study, a 56-m ice core from the ablation area of a mountain glacier in the Tien Shan Mountains of Central Asia was analyzed to characterize the chemical solutes and mineral dust in glacial ice. Soluble chemical ion and mineral dust analysis in the ice core showed that their concentrations varied with depth. The most dominant ion was Ca2+ (mean: 79.8 μEq L−1), followed by Cl−, SO42-, NH4+, and NO3−. The mean dust concentration in the glacial ice was 2.5 ×105 number ml−1. Chemical solute and mineral dust concentrations in the samples indicate that melting glacial ice could potentially affect supraglacial conditions. The annual fluxes of the major ions outcropping from glacial ice were estimated based on their concentrations and the observed melt rate of the ice surface. Consequently, they were comparable to or higher than those from the atmosphere. The mean mass flux of mineral dust from glacial ice was greater than that from the atmosphere. Our results showed that glacial ice supplies chemical solutes and mineral dust to the supraglacial environment and that changing melting rates of glacial ice would affect the chemical conditions on the glacier surface and the growth of photoautotrophs on the ablating ice surface.

Abstract Although studies on snow algae and macroinvertebrates have been frequently conducted on snow patches, only few surveys have been focused on microinvertebrates which reach high biomass and play various trophic roles in other cold habitats. The aims of this study were (1) to search for microinvertebrates in seasonal surface snow patches located on the slope of Mt. Gassan, in northern Japan, and (2) to identify factors determining their distribution associated with snow algal blooms of various colorations (orange, green, and golden-brown) collected from the same sampling site over two seasons (2018, 2019). Microscopic observation revealed presence of two major groups of microinvertebrates: Tardigrada and Rotifera. They were concentrated in green snow colored by blooms of Chloromonas sp. in comparison to orange or golden-brown snow and only a few were found in white snow. Mean body length of tardigrades increased throughout the melt season, their intestine content was green and they laid eggs on colored snow. These results suggest that tardigrades preferentially grew and reproduced on green snow patches. Population densities of tardigrades, rotifers and concentration of chlorophyll a were significantly correlated. Our study indicates that green snow patches in temperate mountainous forests constitute important and unique low-temperature ecosystems for microinvertebrates. Snow covered by algae is an unrecognized novel habitats for tardigrades and rotifers.

Diverse microbes have been revealed to live in glaciers worldwide, but only a few biological studies were dedicated to glaciers in tropical Africa. These glaciers are shrinking rapidly and are expected to disappear shortly. In this study, we carried out biological and glaciological field observations on Stanley Glacier, the largest remaining glacier in the Rwenzori Mountains, Uganda, Africa. Microbial aggregates ranging from micrometer to centimeter in size were found on the glacier surface and contained moss and various types of Chlorophyta, among which a new endemic species of green alga. Concentrations of total impurities on the glacier surface, including microbial aggregates, varied spatially and decreased as altitude increased. The large microbial aggregates (larger than 4 cm in diameter) were found only at the glacier surface near the terminus and side margins, where the surface was less frequently covered with snow. It is also shown that the total organic matter on the glacier surface is determined by the timing of snow cover, which affects the quantity of solar radiation reaching the glacier ice surface. Furthermore, the total impurity content was negatively correlated with surface reflectivity, revealing their potential role in albedo reduction at the glacier surface through positive feedback between enhanced meltwater and increased biological growth.

The physical and geochemical characteristics of shallow ice cores drilled in the accumulation area (Western Cwm) of Khumbu Glacier in the Nepal Himalayas in 1980 were analyzed. The two ice cores from different elevations (cores 1 and 2 from 6,100 and 6,400 m a.s.l., respectively) showed distinct stratigraphy: Core 1 consisted of stratified firn layers with a few ice and dust layers, whereas core 2 consisted of unstratified refrozen ice with abundant debris. The mean oxygen-stable isotope was significantly lower in core 2 than in core 1, and the composition of major soluble ions also differed between the ice cores. The mineralogical characteristics of debris in core 2 were in accordance with the geology of the south face of Mt. Everest, indicating that it was supplied from above 7,000 m a.s.l. by avalanches. The distinct stratigraphy and geochemistry suggest that the snow accumulation process differed between the two drilling sites; snow was supplied by precipitation in core 1, whereas in core 2 it was supplied by avalanche with rock debris from the higher site of the south face of Mt. Everest. The two distinct snow accumulation processes are likely to characterize the mass balance and formation of debris covers of the lower ablation area of Khumbu Glacier.

Snow algae are photosynthetic microbes that inhabit the melting snow surface in alpine and polar regions. We analyzed the pigment and species composition of colored snow collected on Mt. Tateyama in Japan during the melting seasons of 2015 and 2016. High-performance liquid chromatographic analyses of the pigments extracted from the colored snow showed that their composition varied within the study area and were classified into four types: Type A (astaxanthin-monoester dominant), Type B (medium astaxanthin-monoester content), Type C (abundant primary carotenoids and free-astaxanthin), and Type D (abundant primary carotenoids and astaxanthin diesters). Types A and B were most commonly observed in the study area, whereas Types C and D appeared only at specific sites. Analysis of the 18S ribosomal RNA (18S rRNA) gene revealed six major amplicon sequence variants (ASVs) of snow algae, belonging to the Sanguina, Chloromonas, and Chlainomonas groups. The relative abundance of the algal ASVs showed that Sanguina was dominant (>48%) in both Types A and B, suggesting that the difference in astaxanthin abundance between the two types was caused by the production of pigments in the algal cells. The algal community structures of Types C and D differed from those of Types A and B, indicating that the primary carotenoids and astaxanthin diesters were derived from certain algal species in these types. Therefore, astaxanthin-rich Sanguina algae mostly induced the red snow that appeared widely in this alpine area; however, they were partially dominated by Chloromonas or Chlainomonas algae, causing different pigment compositions.

Abstract Previous reconstructions of summer temperatures from ice cores have relied on a statistical relationship between a melt layer and temperature observed at nearby stations. This study presents a novel method for reconstructing summer temperatures from melt layers in ice cores using an energy balance model that incorporates heat conduction and meltwater refreezing in the firn. We use the seasonal patterns in the ERA‐Interim reanalysis data set for an ice core site to calculate the amounts of refreezing water within the firn under various summer mean temperature (SMT) and annual precipitation conditions, and prepared calibration tables containing these three variables. We then estimate the SMTs from the refreezing amount and annual accumulation, both of which can be obtained from an ice core. We apply this method to four ice cores that were recovered from sites with different climates: two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai. The reconstructed SMTs show comparable variations with those of observed temperatures at nearby stations. The nonlinear relationship between SMT and melt layer thickness differs between sites, indicating that a single linear approximation cannot be employed to estimate SMT. Sensitivity analyses suggest that the annual temperature range, amount of annual precipitation, and firn albedo (which is a time‐invariant value in the model) significantly affect the relationship between SMT and melt layer thickness. This new method provides an alternative to existing approaches and yields an independent estimate of SMT from ice cores that have been affected by melting.

This study presents an approach to better characterize the P‐wave and S‐wave velocity structure of the seafloor sediment layer using ocean bottom seismometers. The presence of low‐velocity seafloor sediment layers influences the observed seismic record at the seafloor over a broad frequency range, such that detailed knowledge of this sediment structure is essential to predict its effect on teleseismic records. We use the radial component of teleseismic P waves and autocorrelation functions of the radial, vertical, and pressure components of teleseismic P and S waves to obtain sediment layer models using the Markov chain Monte Carlo approach with parallel tempering. Synthetic tests show that the body waves constrain the P‐ and S‐wave impedances and travel times and the P‐ to S‐wave velocity ratio of the sediment layers. The proposed method resolves thin layers at a high resolution, including the uppermost thin (∼50 m to a few hundred meters) low S‐wave velocity layer. Real data applications at sites across the Pacific Ocean that are coincident with previous in situ studies demonstrate the effectiveness of this method in characterizing the seafloor sediment unit. The sediment models characterized by this new approach will allow us to more accurately predict and correct the effects of sediment layers in generating P‐ and S‐wave reverberations. Plain Language Summary: Ocean bottom seismometers are powerful tools for investigating the detailed structure of the oceanic mantle. However, most ocean bottom seismometers are placed above the low‐velocity water‐saturated sediment layer, such that their seismic records are inevitably affected by this seafloor sediment layer. Detailed constraints on the structure of the seafloor sediment layer allow us to accurately predict its effects on the observed seismic records. The seafloor sediment layer may consist of multiple discontinuities and vary regionally. This study proposes a new approach for characterizing the seismic properties of the seafloor sediment layer using teleseismic body waves recorded at ocean bottom seismometers. Synthetic tests show that the method can resolve thin sublayers within the sediment layer, such as a very thin low shear‐wave velocity layer and sharp seismic velocity jumps. Real data applications show that the sediment models obtained using this approach are in good agreement with those obtained from direct measurements and previous body‐wave analyses. Our proposed method will enable more detailed prediction and correction of the influence of the sediment layer on ocean bottom seismometer records, thereby providing more accurate constraints on deeper Earth structures. Key Points: The seismic properties of the seafloor sediment layer are characterized using ocean bottom seismometer teleseismic body‐wave recordsThe P‐ and S‐wave impedances and travel times and the VP/VS values of each sublayer within the sediment layer are resolvedIn situ seafloor sediment structure constraints will enable accurate correction and prediction of shallow structure effects [ABSTRACT FROM AUTHOR]

Pollen grains are commonly found in ice cores, particularly those from mountain glaciers at low to middle latitudes. Because the release of pollen from flowers has a seasonality and varies among the plant species, pollen concentrations in ice cores are useful for distinguishing annual or seasonal layers and inferring past vegetation near glaciers. We analyzed major pollen grains in an 87-m-deep ice core drilled at the top of the Grigoriev Ice Cap (4563 m.a.s.l.) in the Tien Shan Mountains, Kyrgyz Republic. Microscopy showed that mainly five pollen taxa were contained in the ice core. Their abundance fluctuated with the depth of the core, indicating their seasonal deposition on the ice cap, while the seasonality of the stable isotopes was not particularly clear because of melting and refreezing signatures. Based on the pollen profiles, annual layers were determined back in time to 1780 AD at a depth of 63.6 m; at greater depth, they could not be distinguished due to ice layer thinning in the glacier. The pollen assemblages have gradually changed during the last 220 years and were particularly distinctive in the deeper part, suggesting the drastic change of vegetation in this region during the Holocene.

Deep-sea water (DSW) contains multiple minerals and is widely used as drinking water, for cosmetic purposes, and as seasoning. In this study, several types of extract-added water with different levels of hardness (200, 300, 500) were prepared from DSW collected off the coast of Muroto City, Kochi Prefecture. We administrated it to obese mice for two months and tested it for several effects. Although there was no anti-obesity effect for any hardness level in obese mice, the cognitive functions of each DSW-extract-added water-treated group were significantly improved compared to control obese mice in the water maze test. Time-to-fall by the rota-rod test was also dramatically improved in the DSW-extract-added water-treated groups. The levels of triglycerides and blood urea nitrogen were significantly decreased in DSW-extract-added water-treated obese mice. However, these results did not depend on the hardness. Hardness levels of 200 or 300 of DSW-extract-added water had greater effects on cognitive function and serum scores compared to a level of 500. We analyzed DSW using inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry. High concentrations of magnesium and potassium were detected, but sodium was not detected at very high concentrations. Although the detailed mechanisms of its effects are not yet understood, chronic intake of DSW-extract-added water may have a beneficial effect on health.

To understand the geological origins of minerals in cryoconite and the nutrients sources for microbes on glaciers, we analyzed the Sr–Nd isotopic ratios of the four mineral fractions in cryoconites including saline, carbonate, phosphate, silicate and the organic fraction obtained from Gulkana Glacier in Alaska. The isotopes in the silicate mineral fraction exhibited spatial variation within the glacier (87Sr/86Sr: 0.704533–0.709563, εNd (0): −16.0 to 0.5), which can be explained by the different mixing ratios of the two distinct sources: one of the sources is lateral and terminal moraines or soil, and the other is the medial moraine of the glacier. The minerals in the cryoconite at the lower sites in the glacier are likely derived from the former source, whereas those at the upper sites are from latter sources. The mineralogical and elemental compositions also support mixing of the silicate minerals from the two local sources. The Sr isotopic ratios of the organic fraction also showed spatial variation on the glacier in the middle sites – a trend similar to those of the phosphate fraction. The results suggest that the organic matter is mostly the byproducts of microbes using the phosphate minerals as a nutrient source.

Cryoconite holes are water-filled cylindrical holes formed on ablation ice surfaces and commonly observed on glaciers worldwide. Temporal changes of cryoconite holes characteristically

Red-snow algae are red-pigmented unicellular algae that appear seasonally on the surface of thawing snow worldwide. Here, Segawa et al. analyse nuclear ITS2 sequences from snow algae from the Arctic and Antarctica, identifying dominant phylotypes present in both poles as well as endemic organisms.

Surface albedo is an important driver of surface processes that promote glacier melting and is a key variable influencing glacier surface melt. Despite much focus in the literature on variations in albedo and its influence on snow surfaces, little attention has been paid to dust and its impact on bare-ice albedo with respect to glacier melting surfaces. In this paper, spatial changes in glacier albedo were investigated using three Landsat images taken during the ablation season in 2006; temporal variations in albedo were measured by an automatic weather station (AWS) in the ablation zone between 26 June and 1 August 2007 at Urumqi Glacier No. 1 in Tien Shan. Ice and snow samples and reflection spectra at 325–1050 nm were collected in August, 2007 at Urumqi Glacier No. 1. The data suggested that spatial changes in glacier albedo are not prominent after snowfall; however, once ice becomes exposed, glacier albedo varies remarkably and generally increases with elevation, especially around the snow line. Temporal variations are characterized by a large range and high frequency, and most are induced by snowfall, changes in cloud conditions, and surface dust; snowfall and cloud increase glacier albedo. Furthermore, the response of snow albedo is more sensitive to cloud compared with the response of ice albedo. Over a bare ice surface, the albedo generally decreases as the concentration of surface dust increases. Organic matter is a primary factor in reducing the albedo over ice.

The 3D lithological distribution model presented in this data article is related to “Stochastic modeling of 3-D compositional distribution in the crust with Bayesian inference and application to geoneutrino observation in Japan” by Takeuchi et al. (2019) [1]. Our target region is set to the crust and uppermost mantle beneath Japanese main islands and their vicinity. We discretized the target region into 79,968 grid points. We defined 31 rock types; 29 major crustal rock types, plus sediment and mantle. Our lithology model represents a probabilistic distribution map inferred from a seismic tomography model and allows quantitative studies with error estimations, making it fundamentally different from previous models. To enable such quantitative applications, we provide explicit numerical data for the probabilities of the 31 rock types for each grid point. We also provide explicit values of the bulk proportion lithology model at various depths and for the bulk whole crust. Further, a figure of synthetic gravity data is presented to correct a minor error in the related paper [1]. Keywords: Bayesian, Crustal structure, Crustal lithology, Rock composition, Geoneutrinos

We characterize the sources of background noise recorded by an ocean-bottom seismometer array deployed on the oldest oceanic lithosphere of the western Pacific plate. This igneous oceanic crust is blanketed up to 1000 m cover of sediments, making it a unique place to investigate correlations between sediment thickness and background noise levels in the marine environment. Although the data are limited, we found that the thicker sediments attenuated short-period noise levels and amplified long-period noise levels, in agreement with observations made for seismic arrivals in onshore sedimentary basins. Comparison of the noise levels from our Oldest-1 deployment with those (1) in the western Pacific basin, (2) near the Mariana trench, and (3) offshore New Zealand indicates that the Oldest-1 has the highest noise levels in the double-frequency (secondary) microseism band by up to 7 dB. This result was unexpected given the greater water depths (averaging 5800 m) for the Oldest-1 array. However, even at these great depths, we find a strong correlation between significant wave heights and background noise levels in the short-period microseism band (2-5 s). In addition, the Oldest-1 array was subjected to a great number of intense close typhoons than the other arrays and was proximal to a great number of taller seamounts than the other arrays. Finally, tracking noise source azimuths using station pairs led to the identification of a possible new source for the single-frequency microseism band in the coastal areas of Papua New Guinea and Australia. [ABSTRACT FROM AUTHOR]

We modified existing methods of noise reduction to data recorded by Japanese broadband ocean-bottom seismometers (BBOBSs) deployed on the western Pacific seafloor conducted as the Oldest-1 Array observation. We removed the tilt and compliance noise that are dominant in low-frequency seismograms. We estimated the noise transfer function from the horizontal- to vertical-component seismograms to remove tilt noise from the vertical component. Throughout the observation period of about one year, the tilt noise transfer function was time-invariant and in phase at low frequencies (<0.06 Hz), which, in contrast to previous studies, enabled us to apply a constant transfer function and to estimate the tilt of the sensor. We estimated the noise transfer function from the pressure- to the vertical-component records and removed the compliance noise in the frequency range of 0.002-0.02 Hz. As a result of tilt and compliance noise removal, noise levels were reduced by up to 20 dB at frequencies below 0.03 Hz. We show that tilt noise reduction using the constant transfer function is appropriate for Japanese BBOBSs equipped with the CMG-3T sensor. Tilt angles of Oldest-1 Array are estimated as 0.3°-1.1° and maximum tilt directions are along the H1 component of the sensor, which are attributed to the architecture of the CMG-3T sensor. [ABSTRACT FROM AUTHOR]

During the summer ablation season, Arctic glacier surfaces host a wealth of microbial life. Here, the phototroph communities on the ablating bare-ice surface of three valley glaciers on Brøggerhalvøya, Svalbard were investigated. The communities mainly comprised seven taxa of green algae and cyanobacteria, which have been commonly reported on Arctic glaciers. Although the geographical and glaciological settings of the three studied glaciers are similar, there were differences in total phototroph biomass. The community structure was also distinctive among the glaciers: high dominance of a single taxon of green algae (Ancylonema nordenskiöldii) for Midtre Lovénbreen, abundant cyanobacteria for Austre Brøggerbreen, and diverse green algae for Pedersenbreen. The major soluble ions in the surface ice showed that there was no significant difference in meltwater nutrient conditions between the glaciers, but there were lower concentrations of mineral-derived ions on Midtre Lovénbreen. Consequently, the glacier-specific mineral loading and surface hydrology are inferred to explain the contrast in bare ice algal communities between the glaciers. We hypothesize that local, glacier-specific conditions affect algal communities and the associated influences on carbon cycling and ice-surface albedo.

Recent molecular data has strongly suggested that field-collected cysts of snow algae that are morphologically identifiable as the zygotes of Chloromonas nivalis are composed of multiple species. Motile vegetative cells, however, have not been directly obtained from these cysts because of the difficulties involved in inducing their germination. Recently, our comparative molecular analyses, using both field-collected and cultured materials, demonstrated that one Japanese lineage of "C. nivalis zygotes" belongs to C. miwae. Herein, we examined another Japanese lineage of field-collected "C. nivalis zygotes" and a new strain originating from Japan. Our molecular data demonstrated that these two different life cycle stages are conspecific, and that they represent a new species that we herein describe as C. muramotoi sp. nov., based on the vegetative and asexual morphological characteristics of the strain. Multigene phylogenetic analyses showed that this new species was sister to C. miwae. Scanning electron microscopy demonstrated that the cysts of C. muramotoi are different from those of C. miwae, based on the arrangement of the flanges developing on the cell wall.

A multiple parameter dating technique was used to establish a depth/age scale for a 171.3 m (145.87 m w.e.) surface to bedrock ice core (Bl2003) recovered from the cold recrystallization accumulation zone of the Western Belukha Plateau (4115 m a.s.l.) in the Siberian Altai Mountains. The ice-core record presented visible layering of annual accumulation and of δ 18O/δD stable isotopes, and a clear tritium reference horizon. A steady-state glacier flow model for layer thinning was calibrated and applied to establish a depth/age scale. Four radiocarbon (14C) measurements of particulate organic carbon contained in ice-core samples revealed dates for the bottom part of Bl2003 from 9075 ± 1221 cal a BC at 145.2 ± 0.1 m w.e. (0.665 m w.e. from the bedrock) to 790 ± 93 AD at 121.1 m w.e. depth. Sulfate peaks coincident with volcanic eruptions, the Tunguska meteorite event, and the 1842 dust storm were used to verify dating. Analysis of the Bl2003 ice core reveals that the modern Altai glaciers were formed during the Younger Dryas (YD) (~10 950 to ~7500 cal a BC), and that they survived the Holocene Climate Optimum (HCO) (~6500 to ~3600 cal a BC) and the Medieval Warm Period (MWP) (~640 to ~1100 AD). A decrease in air temperature at the beginning and an abrupt increase at the end of the YD were identified. Intensification of winds and dust loading related to Asian desert expansion also characterized the YD. During the YD major ion concentrations increased significantly, up to 50 times for Na+ (background), up to 45 times for Ca2+ and Mg2+, and up to 20 times for SO4 2− relative to the recent warm period from 1993 to 2003. A warm period lasted for about three centuries following the YD signaling onset of the HCO. A significant and prolonged decrease in air temperature from ~2000 to ~600 cal a BC was associated with a severe centennial drought (SCD). A sharp increase in air temperatures after the SCD was coincident with the MWP. After the MWP a cooling was followed gradually with further onset of the Little Ice Age. During the modern warm period (1973–2003) an increase in air temperature is noted, which nearly reaches the average of HCO and MWP air temperature values.

In order to better understand the source of minerals on the dark-colored ice, located in the Greenland ice sheet ablation zone, we analyzed the Sr and Nd isotopic ratios of minerals in cryoconite, which were collected from glaciers in northwest and southwest Greenland. We focused on the following: (i) comparison of the isotopes of minerals in cyroconite with those in sediments from local and distant areas, (ii) regional variations in western Greenland, and (iii) spatial variations across an individual a glacier. The mineral components of the cryoconite showed variable Sr and Nd isotopic ratios (87Sr/86Sr: 0.711335 to 0.742406, εNd (0): -33.1 to -22.9), which corresponded to those of the englacial dust and moraine on and around the glaciers but were significantly different from those of the distant deserts that have been considered to be primary sources of mineral dust on the Greenland Ice Sheet. This suggests that the minerals within the cryoconites were mainly derived from local sediments, rather than from distant areas. The Sr ratios in the northwestern region were significantly higher than those in the southwestern region. This is probably due to geological differences in the source areas, such as the surrounding glaciers in each region. The isotopic ratios further varied spatially within a glacier (Qaanaaq and Kangerlussuaq areas), indicating that the silicate minerals on the glaciers were derived not from a single source but from multiple sources, such as englacial dust and wind-blown minerals from the moraine surrounding the glaciers.

Cryoconite holes (CHs) are water-filled cylindrical holes with cryoconite (dark-coloured sediment) deposited at their bottoms, forming on ablating ice surfaces of glaciers and ice sheets worldwide. Because the collapse of CHs may disperse cryoconite on the ice surface, thereby decreasing the ice surface albedo, accurate simulation of the temporal changes in CH depth is essential for understanding ice surface melt. We established a novel model that simulates the temporal changes in CH depth using heat budgets calculated independently at the ice surface and CH bottom based on hole-shape geometry. We evaluated the model with in situ observations of the CH depths on the Qaanaaq ice cap in Northwest Greenland during the 2012, 2014, and 2017 melt seasons. The model reproduced well the observed depth changes and timing of CH collapse. Although earlier models have shown that CH depth tends to be deeper when downward shortwave radiation is intense, our sensitivity tests suggest that deeper CH tends to form when the diffuse component of downward shortwave radiation is dominant, whereas CHs tend to be shallower when the direct component is dominant. In addition, the total heat flux to the CH bottom is dominated by shortwave radiation transmitted through ice rather than that directly from the CH mouths when the CH is deeper than 10 mm. Furthermore, the tests highlight that the ice surface albedo is a key parameter for accurately reproducing the timing of CH collapse because 0.1 decrease in albedo induces the CH collapse one day earlier. Heat component analysis suggests that CH depth is governed by the balance between the intensity of the diffuse component of downward shortwave radiation and the wind speed. Therefore, these meteorological conditions may be important factors contributing to the recent surface darkening of the Greenland ice sheet and other glaciers via the redistribution of CHs. Coupling the CH model proposed in this study with a climate model should improve our understanding of glacier-surface darkening. [ABSTRACT FROM AUTHOR]

Snow algae are photosynthetic microbes growing on snowpacks and are commonly observed in mountain areas in Japan. In this study, we report the snow algal blooms observed in Mt. Echigo-Komagatake located in Niigata prefecture, Japan. Field investigation was conducted in late June of 2021 on a snow patch located in an alpine zone at an altitude of 2000 m above sea level. Patches of snow with red, green, or brown color were observed on the snowpack. Microscopic observation showed that the colored snow contained various morpho-types of snow algal cells, which appeared to be similar to those previously reported in Japan. The algal communities of the colored snow were mostly dominated by red spherical cells, which is likely to be Sanguina nivaloides, and consistent with those of the red snow reported in other alpine snowpacks in Japan. However, some samples showed a community consisting of various cell types, including multiple species of genus Chloromonas. The difference in community structure may be due to distance from vegetation around the snow patch, nutrient conditions of the snow, and/or growth period of the algae. The snow algal blooms of Mt. Echigo-Komagatake can be characterized by the appearance of various colors and algal communities on a snowpack. [ABSTRACT FROM AUTHOR]

Water samples were analyzed from ponds developed within the debris-covered area of Lirung Glacier (28º 12.9’N, 86º 39.9’E; 4000 m a.s.l.) in the Himalayas of Nepal during the pre-monsoon to post-monsoon period of 1996. Major chemical species were classified into three groups based on their relationships relative to the sum of cations: conservative (SiO2, Ca2+, K+, and Alkalinity), semiconservative (Na+, Mg2+, and SO4 2-) and non-conservative (NH4 +, NO3 - and Cl-). The dominant processes determining the chemical composition of glacier pond water were sulfide oxidation coupled with carbonate dissolution and chemical weathering of aluminosilicate as indicated by the conservative and semi-conservative species. Calcium and alkalinity appeared as the dominant cation and anion, respectively, among all samples within the basin. Compared to the discharge waters at the outlet of the glacier, most of these pond waters have lower major solutes as well as alkalinity. The availability of fresh reactive minerals at the base of the glacier, coupled with higher temperature in discharge waters than in the ponds, may be the prime factors resulting in higher concentrations of most solutes in the discharge waters than in the ponds. In the ponds, higher concentrations of major solutes as well as alkalinity were observed in the monsoon than the pre-monsoon and post-monsoon seasons, suggesting the role of hydrolysis condition in chemical weathering rates. Ponds within the debris area of Lirung glacier in central Nepal Himalaya are likely to increase in importance if global warming accelerates the rate of glacial melting.

Cryoconite is a dark-coloured surface dust deposited on glaciers that consists of wind-blown mineral particles, as well as organic matter derived from microbes living on glaciers. In this paper, we analyse the Sr and Nd isotopic ratios of four mineral fractions (i.e., the saline, carbonate, phosphate, and silicate mineral fractions), as well as the organic fraction, of cryoconite samples obtained from six Asian glaciers (the Altai, Pamir, Tien Shan, Qillian Shan, and Himalayan regions), and discuss their geographical variations in terms of the geological origins of the mineral particles and the biogeochemical processes on the glaciers. The silicate mineral fraction showed lower Sr and higher Nd ratios for the glaciers located to the north (Altai, ^87 Sr/ ^86 Sr: 0.713 490–0.715 284, εNd(0): −6.4 to −5.6), while higher Sr and lower Nd ratios for the glaciers located to the south (Himalayas, ^87 Sr/ ^86 Sr: 0.740 121–0.742 088, εNd(0): −16.4 to −15.7); the ratios were similar to those of desert sand, loess, and river sediments in the respective regions of the glaciers. This result suggests that the silicate minerals within the cryoconites were derived from different sources depending on the geographical locations of the glaciers. The isotopic ratios of the saline, carbonate, and phosphate mineral fractions were distinct from those of the silicate fraction, and were similar to those of evaporites and apatite deposits from the Asian deserts, but also varied geographically, indicating that they are likely to reflect their geological origin. The Sr isotopic ratios of the organic fraction were similar to those of the saline and carbonate fractions from glaciers in the central area (Tien Shan and Qillian Shan), but were higher than those of the saline and carbonate fractions, and lower than the phosphate mineral fraction, in the northern and southern areas. The ratios of organic fraction may be determined from the mixing ratio of calcium sources incorporated by microbes on the glaciers.

Pollen taxon in sediment samples can be identified by analyzing pollen morphology. Identification of related species based on pollen morphology is difficult and is limited primarily to genus or family. Because pollen grains of various ages are preserved at below 0 °C in glaciers and thus are more likely to remain intact or to suffer little DNA fragmentation, genetic information from such pollen grains should enable identification of plant taxa below the genus level. However, no published studies have attempted detailed identification using DNA sequences obtained from pollen found in glaciers. As a preliminary step, this study attempted to analyze the DNA of Pinus pollen grains extracted from surface snow collected from the Belukha glacier in the Altai Mountains of Russia in the summer of 2003. A 150-bp rpoB fragment from the chloroplast genome in each Pinus pollen grain was amplified by polymerase chain reaction, and DNA products were sequenced to identify them at the section level. A total of 105 pollen grains were used for the test, and sequences were obtained from eight grains. From the sequences obtained, the pollen grains were identified as belonging to the section Quinquefoliae . Trees of the extant species Pinus sibirica in the section Quinquefoliae are currently found surrounding the glacier. The consistency of results for this section suggests that the pollen in the glacier originated from the same Pinus trees as those found in the immediate surroundings.

Snow and ice algae are cold tolerant algae growing on the surface of snow and ice, and they play an important role in the carbon cycles for glaciers and snowfields in the world. Seasonal and altitudinal variations in seven major taxa of algae (green algae and cyanobacteria) were investigated on the Gulkana glacier in Alaska at six different elevations from May to September in 2001. The snow algal communities and their biomasses changed over time and elevation. Snow algae were rarely observed on the glacier in May although air temperature had been above 0 ° C since the middle of the month and surface snow had melted. In June, algae appeared in the lower areas of the glacier, where the ablation ice surface was exposed. In August, the distribution of algae was extended to the upper parts of the glacier as the snow line was elevated. In September, the glacier surface was finally covered with new winter snow, which terminated algal growth in the season. Mean algal biomass of the study sites continuously increased and reached 6.3 × 10 μl m ^−2 in cell volume or 13 mg carbon m ^−2 in September. The algal community was dominated by Chlamydomonas nivalis on the snow surface, and by Ancylonema nordenskiöldii and Mesotaenium berggrenii on the ice surface throughout the melting season. Other algae were less abundant and appeared in only a limited area of the glacier. Results in this study suggest that algae on both snow and ice surfaces significantly contribute to the net production of organic carbon on the glacier and substantially affect surface albedo of the snow and ice during the melting season.

Cryoconite granules are naturally occurring microbial structures on glacier surfaces worldwide. They play a key role in carbon and nitrogen cycling in glacier ecosystems and can accelerate the melting of snow and ice. However, detailed mechanism of nitrogen cycling in cryoconite granules remains unclear. Here, we demonstrate that redox stratification affects the spatial distribution of N cycling processes in cryoconite granules. Based on microsensor measurements for O2, NH4+, NO2– and NO3–, we identified the presence of fine-scale redox stratification within cryoconite granules. Cyanobacteria at the surface layer of the granules created oxic conditions, whereas the inner core of the granules was anoxic. Metatranscriptomic analyses indicated the active occurrences of nitrification in the inner core, whereas denitrification actively occurred both in the inner core and the surface layer of the granules. Cyanobacteria in the inner core of the granules were inactive, and likely dead and being degraded, providing carbon and nitrogen to support nitrifiers and denitrifiers. Quantities of nitrification genes/transcripts were greater in large cryoconite granules than small ones, most likely because nitrogen substrates were more abundantly present in the inner core of large granules due to distinct redox stratification. Our results suggest that the development of a granular structure of cryoconite granules can largely affect carbon and nitrogen cycling on glaciers. [ABSTRACT FROM AUTHOR]

Previous studies reconstructing summer temperature from an ice core relied on statistical relationship between melt feature and instrumental temperature observed at a nearby station. This study demonstrates a novel method to reconstruct summer temperature from ice layer thickness in an ice core using an energy balance model, in which heat conduction and refreezing of meltwater in firn are taken into account. Using seasonal patterns of the ERA-Interim reanalysis dataset for an ice core site, we calculated amounts of refreezing water within firn under various settings of summer mean temperature (SMT) and annual precipitation, and prepared lookup tables containing these three variables. We then estimated SMT from the refreezing amount and annual accumulation, both available in an ice core. We applied this method to four ice cores drilled in the sites of different climates; two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai Mountains. Reconstructed SMTs show comparable variations to the temperatures observed at nearby stations. Relationships between SMT and ice layer thickness differ site by site, indicating that a single approximation cannot be applicable to estimate SMT. Sensitivity analyses suggest that annual temperature range, amount of annual precipitation and firn albedo setting significantly affect the relationship between SMT and ice layer thickness. This new method provides alternative and independent estimation of SMT from ice cores affected by melting. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)-light-irradiated europium-doped potassium chloride (KCl:Eu) single crystals exhibit intense photostimulated luminescence (PSL) with a peak at 420 nanometers. The PSL characteristics of UV irradiated KCl:Eu for optical memory application are also investigated.

Temporary broadband seismic observations, consisting of pilot and main observations, were conducted from January 2016 to January 2019 to study the seismic structure of the Earth's deep interior, and the crust and upper mantle structure beneath Thailand. Nearly fifty percent of the forty stations initially deployed were damaged by serious flooding and lightning. Nevertheless, the quality of the data collected permitted an analysis of local earthquakes and teleseismic signals. The data center at the Earthquake Research Institute, The University of Tokyo will provide continuous and event-edited seismograms, with state-of-health information (including clock information) from the spring of 2021. [ABSTRACT FROM AUTHOR]

We recorded P and S waves traveling through the oceanic lithosphere-asthenosphere system (LAS) using broadband ocean-bottom seismometers in the northwest Pacific, and we quantitatively separated the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic LAS.The strong intrinsic attenuation in the asthenosphere obtained at higher frequency (~3 hertz) is comparable to that constrained at lower frequency (~100 seconds) by surface waves and suggests frequency-independent anelasticity, whereas the intrinsic attenuation in the lithosphere is frequency dependent.This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere. [ABSTRACT FROM AUTHOR]

Determination of a response of the sea water column to teleseismic plane wave is important to suppress adverse effects of water reverberations in calculating receiver functions (RFs) using ocean-bottom seismometer (OBS) records. We present a novel non-linear waveform analysis method using the simulated annealing algorithm to determine such a water-layer response recorded by an OBS array. We then demonstrate its usefulness for the RF estimation through its application to synthetic and observed data. Synthetic experiments suggest that the water-layer response constrained in this way has a potential to improve RFs of OBS records drastically even in the high-frequency range (to 4 Hz). By applying it to data observed by the OBS array around the Kii Peninsula, southwestern Japan, we identified a low-velocity zone at the top of the subducting Philippine Sea plate. This zone may represent the incoming fluid-rich sediment layer that has been reported by active-source seismic survey. [ABSTRACT FROM AUTHOR]

Cryoconite granules are aggregations of microorganisms with mineral particles that form on glacier surfaces. To understand the processes by which the granules develop, this study focused on the altitudinal distribution of the granules and photosynthetic microorganisms on the glacier, bacterial community variation with granules size and environmental factors affecting the growth of the granules. Size-sorted cryoconite granules collected from five different sites on Qaanaaq Glacier were analyzed. C and N contents were significantly higher in large (diameter greater than 250 µm) granules than in smaller (diameter 30-249 µm) granules. Bacterial community structures, based on 16S rRNA gene amplicon sequencing, were different between the smaller and larger granules. The filamentous cyanobacterium Phormidesmis priestleyi was the dominant bacterial species in larger granules. Multivariate analysis suggests that the abundance of mineral particles on the glacier surface is the main factor controlling growth of these cyanobacteria. These results show that the supply of mineral particles on the glacier enhances granule development, that P. priestleyi is likely the key species for primary production and the formation of the granules and that the bacterial community in the granules changes over the course of the granule development. [ABSTRACT FROM AUTHOR]

The glacier ice worm, Mesenchytraeus solifugus, is a unique annelid, inhabiting only snow and ice in North American glaciers. Here, we analyzed the taxonomic composition of bacteria associated with M. solifugus based on the 16S rRNA gene. We analyzed four fixed-on-site and 10 starved ice worm individuals, along with glacier surface samples. In total, 1341 clones of 16S rRNA genes were analyzed for the ice worm samples, from which 65 bacterial phylotypes (99.0% cut-off) were identified. Of these, 35 phylotypes were closely related to sequences obtained from their habitat glacier and/or other components of cryosphere; whereas three dominant phylotypes were affiliated with animal-associated lineages of the class Mollicutes. Among the three, phylotype Ms-13 shared less than 89% similarity with database sequences and was closest to a gut symbiont of a terrestrial earthworm. Using fluorescence in situ hybridization, Ms-13 was located on the gut wall surface of the ice worms. We propose a novel genus and species, 'Candidatus Vermiplasma glacialis', for this bacterium. Our results raise the possibility that the ice worm has exploited indigenous glacier bacteria, while several symbiotic bacterial lineages have maintained their association with the ice worm during the course of adaptive evolution to the permanently cold environment. [ABSTRACT FROM AUTHOR]