Abstract. Red snow blooms are visually similar but can be composed of different algal species and cell morphologies across sites, and the factors determining this spatial heterogeneity remain poorly understood. In this study, we investigated spatial variation in community structure, algal cell size, and morphology along gradients of elevation across a glacier and its forefield in Alaska. Microscopic observations revealed that the ice-based snowpack was dominated by spherical cells, whereas the soil-based snowpack was characterized by a higher abundance of non-spherical cells and larger spherical cells. Molecular analyses revealed that Sanguina predominated in the ice-based snowpack, while the relative abundance of other genera, including Chloromonas and Rosetta, were more abundant in the soil-based snowpack. Redundancy analysis showed that community structure was explained primarily by snow depth and elevation, whereas it was not significantly influenced by nutrient concentrations. Generalized linear models further indicated that size of spherical cell decreased with elevation, and the proportion of non-spherical cells decreased with snow depth. These results suggest that while snowmelt-driven environmental gradients govern the overall morphological and phylogenetic variability of red snow algae, the underlying substrate (ice vs. soil) also contributes to community turnover, likely by providing access to distinct local cell reservoirs during melt progression. Collectively, these factors shape the taxonomic composition, morphotype assemblage, and spatial development of red snow blooms.

The Arctic region is undergoing rapid environmental changes due to global climate warming. Among the Arctic regions, the surface temperature in the northern Barents Sea, where the Svalbard archipelagos are located, has increased more significantly than in other areas over the last 40 years. This warming results in the loss of sea ice in the ocean and glacier ice in terrestrial areas. These changes in surface conditions may impact the emission of bioaerosols from the Earth's surface, which play a crucial role in ecosystem dynamics and cloud formation. However, there is still limited temporal monitoring in Svalbard and also in entire Arctic. Therefore, in this study, we focus on assessing the temporal changes in bioaerosols during the summer to autumn season in Ny-Ålesund, Svalbard using DNA metabarcoding approaches. Bioaerosol samples were collected using a vacuum pump with a flow rate of 40 LPM onto HEPA-style filters at the outdoor observatory of the Veksthuset building in Ny-Ålesund. Filters were replaced every 24-72 hours from July to November 2022. Those were then preserved in DNA storage medium (DNA/RNA shield) and transported to the laboratory under frozen conditions. Following particle concentration and DNA extraction, we amplified and sequenced three DNA metabarcoding regions (16S, 18S, and ITS) using the MiSeq platform (Illumina). Seasonal variations in the observed number of Amplicon Sequence Variants (ASVs) from each barcoding region reveal distinct patterns. These patterns are characterized by elevated ASV counts during the summer (ITS and 18S) and autumn (16S). Microbial communities within the 16S region at the phylum level remain relatively stable throughout the entire season. Conversely, communities within the 18S and ITS regions undergo significant changes in mid-September and after October, coinciding with the terrestrial area being covered by seasonal snowpack. In the presentation, we will provide a more detailed explanation of community changes at the ASV level and discuss the distinctive seasonal patterns observed.

Methane release is considered to be from human activities, Arctic Ocean, and the terrestrial regions such as wetland, lakes, geological seeps in the Arctic although glaciers have not been considered a source of methane emissions. A large amount of methane has been observed at the terminus of large glaciers and ice sheet, associated with methane-saturated meltwater runoff. We observed several glaciers in Alaska and found methane emissions from the runoff water of the small mountain glaciers. The observation periods, which was the beginning of the ablation season for the glacier, were June 12-14, 2022, and June 3-9, 2023. We measured methane and CO2 concentrations in ambient air over the water with a portable gas analyzer G4301 (Picarro, Inc.). Dissolved methane concentrations in runoff water were measured using the method of Morishita et al. (2015). The maximum methane concentration in the ambient air near the runoff water was higher than the background level, and the concentration decreased as the gas analyzer moved away from the tunnel. The dissolved methane concentration in runoff water was saturated. These results suggest that the high concentration methane observed in the ambient air near the glacier terminus was released from the runoff water saturated by methane underneath of the glaciers. This study was supported by ArCSII project (JPMXD1420318865).

Recent studies have observed high methane concentrations in runoff water and the ambient air at various glacier sites, including the Greenland Ice Sheet, the glacier forefield in Svalbard, and the ice cap in Iceland. This study extends these findings to smaller mountain glaciers in Alaska. Methane and carbon dioxide concentrations in the ambient air near the meltwater outlet, fluxes of these gases at the surface of runoff water and riverbank sediments, and dissolved methane content in the runoff water were measured at four glaciers. Three of the four glaciers showed conspicuous signals of methane emissions from runoff water, with the Castner Glacier terminus exhibiting a methane concentration three times higher than background levels, along with elevated dissolved methane levels in the runoff water. This study marks the detection of significant methane emissions from small mountain glacier runoff, contributing to the understanding that mountain glaciers also release methane into the atmosphere.

The diversity of bacteria associated with alpine lichens was profiled. Lichen samples belonging to the Umbilicariaceae family, commonly known as rock tripe lichens, were gathered from two distinct alpine fellfields: one situated on Mt. Brennkogel located in the Eastern European Alps (Austria), and the other on Mt. Stanley located in the Rwenzori mountains of equatorial Africa (Uganda). The primary aim of this research was to undertake a comparative investigation into the bacterial compositions, and diversities, identifying potential indicators and exploring their potential metabolisms, of these lichen samples. Bulk genomic DNA was extracted from the lichen samples, which was used to amplify the 18S rRNA gene by Sanger sequencing and the V3-V4 region of the 16S rRNA gene by Illumina Miseq sequencing. Examination of the fungal partner was carried out through the analysis of 18S rRNA gene sequences, belonging to the genus Umbilicaria ( Ascomycota ), and the algal partner affiliated with the lineage Trebouxia ( Chlorophyta ), constituted the symbiotic components. Analyzing the MiSeq datasets by using bioinformatics methods, operational taxonomic units (OTUs) were established based on a predetermined similarity threshold for the V3-V4 sequences, which were assigned to a total of 26 bacterial phyla that were found in both areas. Eight of the 26 phyla, i.e. Acidobacteriota , Actinomycota , Armatimonadota , Bacteroidota , Chloroflexota , Deinococcota , Planctomycetota , and Pseudomonadota , were consistently present in all samples, each accounting for more than 1% of the total read count. Distinct differences in bacterial composition emerged between lichen samples from Austria and Uganda, with the OTU frequency-based regional indicator phyla, Pseudomonadota and Armatimonadota , respectively. Despite the considerable geographic separation of approximately 5430 km between the two regions, the prediction of potential metabolic pathways based on OTU analysis revealed similar relative abundances. This similarity is possibly influenced by comparable alpine climatic conditions prevailing in both areas.

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.

Glacier retreat due to the warming climate is remarkable all over the world. In addition to climate warming, the “biological albedo reduction”, which the pigmented algae reduce the albedo of the glacier, enhances ice melting. Therefore, the spatial distribution of those algae is important for the glacier's mass balance. Although the altitude result in the air temperature and the duration of snow cover is recognized as the factor to affect the spatial distribution, the distribution pattern is more heterogeneous in the same altitude area. To understand the heterogeneity of snow algae and associating microbes and their effects on the glacier albedo, both eukaryotic and prokaryotic communities were analyzed using an amplicon sequencing approach in the dense coverage of the ablation area of a single glacier (total 54 sites over Gulkana Glacier, AK, USA). Furthermore, microbial diversities were analyzed with environmental factors such as carbon contents and nutrients. As a result, we found the green algae amplicon sequence variants (ASVs) closely related to the pigmented algae, Sanguina nivaloides, and Chlainomonas sp. from the surface ice and cryoconite and will show the spatial variation of microbial community structures and diversities and the relationship between the environmental factors.

Snow-ice microbes, which adapted to harsh conditions such as low temperature and high dose of UV, inhabit the cryospheric environments. They cause unique phenomena represented by colored snow and ice occurring with blooms of snow and glacier ice algae, and cryoconite holes formed by filamentous cyanobacteria with inorganic matter. These phenomena also darken glacial surface and have a significant effect on the albedo of snow and ice. It is important to understand factors controlling the abundance of all microbes including consumers of algae and cyanobacteria (tardigrades and rotifers) for evaluating the collective influence of biological communities on albedo (biological albedo reduction: BAR). However, most studies have focused only on each taxon (algae, cyanobacteria, fungi or heterotrophic bacteria), and there is a lack of information on whole microbial communities. In this study, we aimed to describe spatiotemporal changes of microbial communities, and discuss the process of their growth and the factors determining their distribution. The fieldworks were carried out from June to September of 2022 on Gulkana Glacier in the Alaska Range, Alaska. Three different types of samples (snow, bare-ice, cryoconite) were collected spatially at maximum 51 points across the glacier. Microscopic observation and analysis of Chlorophyll a concentration, which is a proxy for the total abundance of snow and glacier ice algae, revealed that the algae were most abundant around the snow line and that their maximum occurred in the end of July (1.0 × 103 μg/m2) and in the middle of August (7.8 × 103 μg/m2) on the snow and ice surfaces, respectively. Their distribution in the ice area showed a similar spatial pattern throughout the season, higher abundance in the upper right side and lower in the left side. Consumers of algae (tardigrades and rotifers) were found only in the upper parts of the glacier. These results suggest that each microbial species on the glacier have different distribution and that their growth is associated with local characteristics such as microtopography of the glacier surfaces. In this presentation, we will show more data of spatial distribution of chemical composition, total impurities, and concentration of each microbe in all three surface types and discuss the factors of their growth and distribution.

Cold-adapted prokaryotes are diverse, and they are potential sources of cold-active enzymes and freeze-resistant proteins that can be used as cryoprotectants in food and pharmaceutical industries, hence leveraging bioeconomy in Africa. However, the diversity of cold-adapted prokaryotes on Lewis Glacier and African equatorial glaciers is understudied for diversity and bioprospecting potential. Our recent study on Lewis Glacier on Mount Kenya using 16S rRNA amplicon sequences revealed abundant and diverse prokaryotic community structures across the glacier and its foreland. The major bacterial phyla identified from the glacier included Cyanobacteria, Proteobacteria, Bacteroidetes, and Actinobacteria, which are likely to be extinct in the next decades due to climate change and rapid glacier disappearance. The fine- and broad-scale amplicon sequence analyses of these cold-adapted species would significantly contribute to the United Nations Sustainable Development Goals Number for improved bioeconomy and shared prosperity across Africa.

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.

Cryoconite is a mixture of mineral and organic material covering glacial ice, playing important roles in biogeochemical cycles and lowering the albedo of a glacier surface. Understanding the differences in structure of cryoconite across the globe can be important in recognizing past and future changes in supraglacial environments and ice-organisms-minerals interactions. Despite the worldwide distribution and over a century of studies, the basic characteristics of cryoconite, including its forms and geochemistry, remain poorly studied. The major purpose of our study is the presentation and description of morphological diversity, chemical and photoautotrophs composition, and organic matter content of cryoconite sampled from 33 polar and mountain glaciers around the globe. Observations revealed that cryoconite is represented by various morphologies including loose and granular forms. Granular cryoconite includes smooth, rounded, or irregularly shaped forms; with some having their surfaces covered by cyanobacteria filaments. The occurrence of granules increased with the organic matter content in cryoconite. Moreover, a major driver of cryoconite colouring was the concentration of organic matter and its interplay with minerals. The structure of cyanobacteria and algae communities in cryoconite differs between glaciers, but representatives of cyanobacteria families Pseudanabaenaceae and Phormidiaceae, and algae families Mesotaeniaceae and Ulotrichaceae were the most common. The most of detected cyanobacterial taxa are known to produce polymeric substances (EPS) that may cement granules. Organic matter content in cryoconite varied between glaciers, ranging from 1% to 38%. The geochemistry of all the investigated samples reflected local sediment sources, except of highly concentrated Pb and Hg in cryoconite collected from European glaciers near industrialized regions, corroborating cryoconite as element-specific collector and potential environmental indicator of anthropogenic activity. Our work supports a notion that cryoconite may be more than just simple sediment and instead exhibits complex structure with relevance for biodiversity and the functioning of glacial ecosystems.

Glaciers are among the coldest ecosystems that support psychrophilic taxa, and also act as water sources that shape downstream ecosystems. Tropical glaciers have gained special attention due to their unusual geography and rapid melting, which has major biological, economical and cultural consequences. These glaciers are located between the Tropics of Cancer and Capricorn, and within the influence of the Intertropical Convergence Zone. Such "cold islands" in a tropical climate, which are rapidly losing ice volume and surface area, seem to be a forgotten habitat for unique taxa and ecological communities. According to rules of the IUCN ecosystems red list, tropical glaciers should be classified as critically endangered. The consequences of losing these fragile ecosystems are dire, in the context of natural and urban systems.

This is a data set for using the glacier algae and filamentous cyanobacteria models (Onuma et al., under review). The content is as below. - data: observed data (bio-volume, mineral weight, EC, pH and meteorological conditions) on the bare ice surface in Qaanaaq Ice Cap (CSV files). And, model input and output data (CSV files). - python: programs for the visualization (python scripts) - figure: png files created by the python scripts

The worldwide distribution of microinvertebrates on glaciers, the coldest biome, is poorly known. Owing to their tolerance to hostile conditions, small size and dispersal abilities, nematodes, tardigrades and rotifers are considered cosmopolitan and together inhabit various ecosystems. In this study, we investigated their global distribution in cryoconite holes - a type of freshwater reservoir forming directly in the glacial ice that creates biodiversity hotspots on glaciers. We analysed cryoconite samples (using classical microscopic observations and environmental DNA metabarcoding) from 42 glaciers located around the world (the Arctic, Subarctic, Scandinavia, the Alps, the Caucasus, Siberia, Central Asia, Africa, South America and Antarctica), as well as using literature data. Samples from Antarctic, Karakoram and the Alps were analysed using next-generation sequencing (NGS) and classical observations under microscopes, while all other samples were analysed by microscope alone. Three general outcomes were found: (1) tardigrades and rotifers represented the most common invertebrates in cryoconite holes; (2) tardigrades and rotifers often coexisted together, with one or the other dominating, but the dominant taxon varied by region or by glacier; (3) nematodes - the most abundant, hyperdiverse and widespread metazoans on Earth, including in environments surrounding and seeding glacial surfaces - were consistently absent from cryoconite holes. Despite the general similarity of environmental conditions in cryoconite holes, the distribution of tardigrades and rotifers differed among glaciers, but not in any predictable way, suggesting that their distribution mostly depended on the random dispersal, extreme changes of supraglacial zone or competition. Although nematodes have been found in supraglacial habitats, cryoconite hole environments seem not to provide the necessary conditions for their growth and reproduction. Lack of physiological adaptations to permanently low temperatures (similar to 0 degrees C) and competition for different food resources in the cryoconite hole environment may explain the absence of nematodes in cryoconite holes.

Airborne pollens cause pollinosis and have the potential to affect microphysics in clouds; however, the number of monitored species has been very limited due to technical difficulties for the morphotype identification. In this study, we applied an eDNA approach to the airborne pollen communities in the suburbs of the Tokyo metropolitan area in Japan, within a mixed urban, rural, and mountain landscape, revealing pollen seasonality of various taxa (a total of 78 families across the period) in the spring season (February to May). Those taxa distinctly shifted in the season, especially in the beginning of February and the middle of April. Air temperature shift was an obvious key factor to affect the airborne pollen community, while the influence of other meteorological factors, such as wind speed, humidity, and precipitation, was not clear. Taxonomic classification of major Amplicon Sequence Variants (ASVs) indicates multiple pollen sources, including natural forest, planted forest, roadside, park lands, and horticultural activities. Most major ASV belongs to Japanese cedar (Cryptomeria japonica), which is the most notable allergen that causes pollinosis in Japan, peaking in mid-February to March. Backward trajectory analysis of air masses suggests that the Japanese cedar and other Cupressaceae plantation forests in the western mountains were a significant source of airborne pollen communities detected at our sampling site. Other major plant pollen sources, including Japanese zelkova (Zelkova serrata) and ginkgo (Ginkgo biloba), emanated from the nearby parks or roadside regions. This study's approach enables us to visualize the phenology of multiple pollen, including timing and duration. Long-term monitoring of this type would provide additional insight into understanding the role of climate change on pollen transmission and links to flowering events.

: Currently occurring rapid warming in the Arctic could affect global environmental changes through sea level rise and remote atmospheric effect. The surface melting of the Greenland Ice Sheet (GrIS) involves various uncertainties, which are issues to be elucidated for accurate climate projections. To clarify how the atmosphere, snow/ice, and glacial microbes in the GrIS affect the ice sheet change under global warming, the SIGMA and SIGMA-II projects were conducted from FY2011 to FY2019. In parallel, big Arctic research projects such as GRENE and ArCS were also done, which accelerated the Japanese Greenland researches. This paper describes the research results of the SIGMA and SIGMA-II projects as well as the related research projects in the categories of (1) in-situ observations of the atmosphere, snow/ice, and glacial microbes, (2) ice core drilling, (3) satellite observation, and (4) numerical modeling. Furthermore , we discuss current issues in these studies, a linkage to the Cryosphere subject of recently launched ArCS II Project, and the importance of capacity building.

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.

Here, we present a multi‐season study of ice‐nucleating particles (INPs) active via the immersion freezing mechanism, which took place in north‐central Argentina, a worldwide hotspot for mesoscale convective storms. INPs were measured untreated, after heating to 95°C, and after hydrogen peroxide digestion. No seasonal cycle of INP concentrations was observed. Heat labile INPs, which we define as “biological” herein, dominated the population active at −5 to −20°C, while non‐heat‐labile organic INPs (decomposed by peroxide) dominated at lower temperatures, from −20 to −28°C. Inorganic INPs (remaining after peroxide digestion), were minor contributors to the overall INP activity. Biological INP concentration active around −12°C peaked during rain events and under high relative humidity, reflecting emission mechanisms independent of the background aerosol concentration. The ratio of non‐heat‐labile organic and inorganic INPs was generally constant, suggesting they originated from the same source, presumably from regional arable topsoil based on air mass histories. Single particle mass spectrometry showed that soil particles aerosolized from a regionally common agricultural topsoil contained known mineral INP sources (K‐feldspar and illite) as well as a significant organic component. The INP activity observed in this study correlates well with agricultural soil INP activities from this and other regions of the world, suggesting that the observed INP spectra might be typical of many arable landscapes. These results demonstrate the strong influence of regional continental landscapes, emitting INPs of types that are not yet well represented in global models.

Microorganisms are ubiquitous and highly diverse in the atmosphere. Despite the potential impacts of airborne bacteria found in the lower atmosphere over the Southern Ocean (SO) on the ecology of Antarctica and on marine cloud phase, no previous region-wide assessment of bioaerosols over the SO has been reported. We conducted bacterial profiling of boundary layer shipboard aerosol samples obtained during an Austral summer research voyage, spanning 42.8 to 66.5°S. Contrary to findings over global subtropical regions and the Northern Hemisphere, where transport of microorganisms from continents often controls airborne communities, the great majority of the bacteria detected in our samples were marine, based on taxonomy, back trajectories, and source tracking analysis. Further, the beta diversity of airborne bacterial communities varied with latitude and temperature, but not with other meteorological variables. Limited meridional airborne transport restricts southward community dispersal, isolating Antarctica and inhibiting microorganism and nutrient deposition from lower latitudes to these same regions. A consequence and implication for this region’s marine boundary layer and the clouds that overtop it is that it is truly pristine, free from continental and anthropogenic influences, with the ocean as the dominant source controlling low-level concentrations of cloud condensation nuclei and ice nucleating particles.

As the Arctic warms at twice the global rate, radiative feedbacks from clouds will lead to compounding impacts on the surface energy budget that affect both regional and global weather, and climate. In a future warmer world, the Arctic is projected to become cloudier. However, the formation and evolution of Arctic clouds remain highly uncertain in part due to a limited understanding of current and future sources of ice nucleating particles (INPs). In particular, the sources and abundance of biologically-derived INPs are poorly characterized, yet they may be pivotal for cloud ice formation, especially at temperatures in which Arctic mixed-phase clouds (AMPCs) persist (i.e. >−15 °C). Here, we show for the first time that permafrost is a remarkably rich source of biologically-derived INPs, both heat labile (probably proteinaceous) and other organic INPs of biomolecular origin (41%–100% and 99%–100% of the total INPs, respectively). INP concentrations in 1000 to 30 000 year old permafrost were comparable to the most active of other Arctic and midlatitude soil sources (up to 1010 INPs per gram of soil). Thawing of permafrost—which promotes metabolic activity in microbes—and subsequent mobilization of those soils directly into the atmosphere or into lakes, rivers, and the ocean, suggests the intriguing possibility that increasing emissions of INPs from this hitherto overlooked reservoir could be widespread, and, in time, greatly impact Arctic cloud cloud glaciation and radiative properties. This discovery is timely given the rapidly-thawing permafrost in Alaska and across Earth’s high latitudes. Since permafrost covers 15% of Northern Hemisphere land, this novel and prevalent INP source may become central to predictions of aerosol-cloud-precipitation interactions in AMPCs.