Glaciers are ecosystems hosting active communities, but the knowledge of the ecological processes that occur in these extreme environments is fragmented. More studies on the biodiversity, trophic networks and energy fluxes on glaciers are needed to better appreciate their ecological contribution on a global scale. This work shows the microbiological results of a research project that aims at describing the biodiversity and the ecological webs of the Forni Glacier (Stelvio National Park, Central Italian Alps). Samples were collected over two consecutive years from different supraglacial habitats, including cryoconite holes (i.e. small ponds full of melting water with a fine-grained sediment on the bottom), supraglacial sediment, bediere (i.e. supraglacial stream water), snow, dirt cones, moraines and ice. Englacial sediment samples and subglacial sediment samples were also collected on the second year. Microbial communities including bacteria, algae and fungi, were characterized by amplicon sequencing for all samples. The most abundant bacterial phyla resulted to be Pseudomonadota, Bacteroidota, Actinomycetota and Cyanobacteria, the most abundant fungal classes resulted to be Microbotryomycetes, Dothideomycetes, Leotiomycetes, Lecanoromycetes and Agaricomycetes, and the most abundant algal phyla resulted to be Chrysocapsales, Prasiolales and Chlamydomonadales. All microbial communities resulted to change according to habitat and sampling time. Finally, the microbiome of "ice fleas" (ice-dwelling glacial springtails) was also characterized from individuals collected on the second year, as they play a crucial role in connecting microbial communities with higher trophic levels. Results showed that all microbiome samples shared only one bacterial Amplicon Sequence Variant (ASV) of the family Comamonadaceae which may be involved in iron oxidation, which has high concentrations on Forni glacier. Overall, these results provide a good description of the microbial biodiversity of the supraglacial environment of Forni glacier and a first insight into the trophic network. Such studies are essential for properly understanding the dynamics of such a threatened ecosystem.
How to cite: Pittino, F., Ambrosini, R., Valle, B., Crosta, A., Varchetta, L., Ficetola, F. G., Di Mauro, B., Gobbi, M., Lencioni, V., Mensa, F. S., Paoli, F., Zawierucha, K., Canedoli, C., Corengia, D., Caccianiga, M., Leoni, B., Dory, F., and Franzetti, A.: Supraglacial microbial communities of Forni glacier, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-145, https://doi.org/10.5194/wbf2026-145, 2026.
Debris-covered glaciers represent unique and ecologically significant cryo-ecosystems that are rapidly evolving under climate change pressures. These environments, characterized by their supraglacial debris layers, create distinct habitats that support specialized microbial communities and influence nutrient cycling processes. Despite their importance in high-altitude regions, the microbial-driven nitrogen cycling mechanisms that facilitate ecosystem development following glacier retreat remain insufficiently understood.We conducted a comprehensive investigation along the debris gradient of the rapidly receding Hailuogou Glacier on the southeastern Tibetan Plateau. Our multidisciplinary approach integrated full-length 16S rRNA and ITS amplicon sequencing with metagenomic analysis to characterize bacterial and fungal communities and their functional potential for nitrogen cycling. Sampling spanned from supraglacial zones through proglacial areas to recently deglaciated forelands, capturing the complete ecological transition from ice-covered to vegetated environments.Our results demonstrate a clear successional pattern in microbial community structure and function. Bacterial diversity showed a significant increase toward the glacier terminus, while fungal diversity exhibited a substantial decline following plant establishment in the foreland. Metagenomic analysis revealed a crucial functional shift in nitrogen cycling pathways: genes associated with nitrification and denitrification (including amoA, nirK, and nosZ) predominated in barren supraglacial debris. Conversely, the key ammonium assimilation gene glnA (glutamine synthetase) showed significant enrichment in proglacial debris, with further increases observed following pioneer plant colonization.The observed enrichment of ammonium assimilation genes suggests a sophisticated microbial adaptation strategy in response to glacier retreat. This functional shift from nitrogen loss pathways to nitrogen assimilation and conservation mechanisms represents a crucial ecological transition that likely facilitates early soil formation and supports primary succession in nutrient-poor environments. The differential response patterns between bacterial and fungal communities highlight their distinct ecological roles in these evolving ecosystems. The identified patterns of microbial succession and functional gene enrichment offer valuable insights for predicting the ecological trajectories of high-altitude cryo-ecosystems under ongoing climate change.
How to cite: Hu, Y., Lu, X., Franzetti, A., and Pittino, F.: Microbial succession and glnA gene enrichment from supraglacial debris to recently deglaciated forefields, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-142, https://doi.org/10.5194/wbf2026-142, 2026.
Arctic lakes are vital freshwater ecosystems that support wildlife, sustain Indigenous communities, and regulate regional biogeochemical cycles. These lakes experience prolonged periods of snow and ice cover, which shape their physical and chemical structure and profoundly influence microbial life. Rapid climate warming is disrupting these seasonal patterns by altering the duration, thickness, and extent of lake ice, with consequences for underwater light availability, stratification, mixing regimes, and nutrient dynamics. Among the most documented impacts is the progressive shortening of the ice-covered period, yet the biological consequences of these changes—particularly for microbial communities—remain insufficiently explored. Given that bacteria drive key ecological processes in Arctic lakes, including organic matter degradation, primary production, and nutrient cycling, understanding their responses to shifting ice conditions is essential for predicting ecosystem trajectories under climate change.
Recent exploratory work in Greenland has revealed that lake ice harbors unexpectedly abundant and metabolically active bacterial communities, often enriched in nitrogen species such as total nitrogen and ammonia compared to underlying waters. These ice-associated assemblages also differ taxonomically and functionally from those in the water column, including exhibiting an enhanced capacity to metabolize complex organic substrates. However, the mechanisms that lead to the development of these distinct microbial communities, their origin (including potential aerosol deposition), and their contributions to nitrogen cycling remain poorly resolved.
In this study, we investigated how ice cover structures microbial communities and nitrogen-transforming processes in lakes from both East and West Greenland. We combined environmental monitoring, ice and water chemistry, 16S rRNA gene sequencing, and metabolic assays to characterize microbial assemblages across ice, water column, and associated aerosol particles. Our findings show that lake ice forms a unique habitat enriched in nutrients and selective physicochemical conditions that promote distinct and active bacterial communities. The elevated nitrogen species and metabolic capacities observed in ice suggest that ice cover may act as both a reservoir and a seasonal pulse of microbial biomass and nutrients to the lake during melt. These insights highlight the ecological significance of ice-associated microbiomes and underscore the potential for ongoing shifts in ice phenology to reshape Arctic lake biogeochemistry in a warming climate.
How to cite: Carratalà Ripollès, A.: Influence of ice cover on bacterial community diversity and structure in remote arctic lakes, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-381, https://doi.org/10.5194/wbf2026-381, 2026.
Cold environments of the Swiss alps and the Arctic, such as glaciers and permafrost soils, are threatened by rising global temperatures and bound to disappear in the future. In spite of the harsh environmental conditions, glaciers and permafrost soils are full of microbial life. However, this microbial life is still poorly researched. Our research focuses on the bioprospecting of Alpine and Polar microorganisms to discover natural products that could be useful for biotechnology or medicine. This is especially relevant now, as these environments are among the most rapidly changing due to climate change. Over the past 20 years we have collected soil and ice samples from a variety of terrestrial cryoenvironments. To bioprospect these ecosystems, we have followed two main approaches. The first involves culturing microbes from these environments and establishing a biobank (cryopreserved microbial strains), which now contains approximately 1230 bacteria and 260 fungi. The second approach involves extracting environmental DNA from the samples to investigate the broader microbial communities present. In both cases, our goal is to reconstruct genomes and apply bioinformatic pipelines to identify genes that may encode bioactive compounds or enzymes of interest—such as those with antimicrobial properties that could help us fight microbial infections and polymer degrading enzymes that might sustain a circular economy for plastic waste. A genomic screen using antiSMASH showed a high diversity of gene clusters encoding secondary metabolites with e.g. antibacterial or antifungal properties in biobank isolates. Plate assays testing select biobank isolates with high genetic potential for antibiotic production such as Pseudomonas and Rhodococcus, showed indeed antifungal properties of these isolates. A further genomic screen using PlasticDB additionally revealed high genetic potential for plastic biodegradation in biobank isolates. Rigorous testing of two isolates using 13C-labelled substrate confirmed their ability to biodegrade untreated polyethylene. These two examples of the use of biobank isolates shows that microorganisms of cold environments are a rich resource.
How to cite: Werz, A., Stierli, B., Brunner, I., Cuartero, J., and Frey, B.: Life in extreme environments – beneficial properties of microbes from cold habitats, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-449, https://doi.org/10.5194/wbf2026-449, 2026.
Soils in cold and high-elevation environments are complex ecosystems composed of multiple, co-occurring biological entities that each harbor distinct microbial communities. Traditional perspectives often examine soil microbial diversity as separate from the microbial communities of the organisms that inhabit it. Here, we seek to challenge such view and propose an alternative and holistic interpretative framework in which the soil meta-community is the sum of different microbial communities belonging to various organisms found within the soil or interacting with it.
Applying this comprehensive view, this study explores soil prokaryote and fungal diversity and the associated microbiota in mammals, invertebrates, and plants in alpine pastures. We sampled soil (Ah horizon), rhizosphere communities (Carex spp., Festuca spp.), soil-dwelling and surface-active invertebrates (nematodes, collembolans, earthworms, beetles), and vertebrates (fecal eDNA of hares, wild ungulates, and livestock) at alpine sites at 2500 m above sea level (a.s.l.). Sampling was conducted at the Long-Term Socio-Ecological Research (LTSER) site Matsch/Mazia (Italy), a model site for studying climate- and land-use-driven change in the European Alps. We compared these high-elevation microbial communities with those from lower alpine pastures to evaluate how climate-related environmental conditions shape microbial interconnectedness.
Our results show that, beyond climatic and edaphic factors, biotic factors, especially the presence of living organisms like animals and plants, significantly shape microbial diversity in alpine soils. Analyses of fungal and bacterial taxa shared among sample types established greater overlaps between microbiota of soil, rhizosphere, and soil-dwelling invertebrates, compared to that of other invertebrates and vertebrates. This finding highlights the central role of soil microbiota and the above- and belowground as well as host- and habitat-specific associations in the alpine meta-community. Importantly, microbial interconnectedness was lower at 2500 m a.s.l. compared to lower elevations, reflecting reduced microbial exchange among soil and animal-associated communities.
Overall, our findings highlight that cold ecosystems host tightly interlinked, but increasingly fragmented, microbiota. Recognizing soils as meta-communities provides new insights into how climate-driven changes in alpine environments may restructure biodiversity and ecosystem functioning.
How to cite: Praeg, N., Rzehak, T., Galla, G., Scholz, M., Seeber, J., Hauffe, H. C., and Illmer, P.: Interconnected Microbial Communities in Alpine Grassland Ecosystems, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-366, https://doi.org/10.5194/wbf2026-366, 2026.
Microbial communities living in extreme environments, such as in low pH alpine stream systems rich in heavy metals, provide a unique opportunity to study biological adaptation strategies. Recently, the appearance of high-alpine streams with white-colored stream sections, characterized by the precipitation of aluminum compounds, in European Alpine rivers has raised questions about the composition and functional capabilities of the associated microbiomes. In this study, we analyzed samples from two locations, Val Lavirun and Val Poschiavo (Engadine, Switzerland), using an integrated approach combining metabarcoding and shotgun metagenomic sequencing to examine both taxonomic diversity and functional microbial potential coping with these extreme environments.
Samples were collected along a defined environmental transect affected by aluminum precipitation, covering three distinct sections: the stream source (clear water), transitional phase (intermediate zone), and precipitation zone (marked by white-colored stream section). This progression alters the water's physicochemical properties and visibly affects its color and turbidity, creating an environmental stress gradient.
Metabarcoding analyses revealed marked differences in microbial community composition between sites and sections (zones). Among prokaryotes, dominant phyla included Actinobacteriota, Bacteroidota, Pseudomonadota, and Planctomycetota, with significant shifts in relative abundance across sampling phases. Fungal communities were largely dominated by Ascomycota and Basidiomycota, while less abundant phyla such as Chytridiomycota and Rozellomycota were detected in specific ecological niches, suggesting functional specialization.
Shotgun metagenomic analysis provided insights into microbial functional potential. CAZy gene profiling highlighted the prevalence of Glycoside Hydrolases and Auxiliary Activities, particularly enzymes involved in lignin and cellulose degradation. NCyc gene analysis revealed distinct expression patterns in nitrogen cycling processes, including denitrification (nirK), nitrification (amoA), and nitrogen fixation (nifH), reflecting microbial adaptation to physicochemical gradients. EggNOG-based functional annotation showed significant variation in genes related to carbohydrate metabolism, energy production, stress response, and defense mechanisms.
This study contributes to a deeper understanding of microbial survival strategies in harsh high-alpine river systems and highlights the importance of integrating taxonomic and functional data to unravel the ecological roles of microorganisms in alpine freshwater habitats.
How to cite: Sannino, C., Varliero, G., Giovagnoli, G., Qi, W., Turchetti, B., Buzzini, P., and Frey, B.: White streams as microbial hotspots: taxonomic and functional insights from alpine river systems, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-131, https://doi.org/10.5194/wbf2026-131, 2026.
The Arctic holds more surface water than any other region on Earth. Yet its freshwater microbial communities remain largely understudied owing to their remoteness and challenging access. Arctic freshwater systems are regarded as sinks for algal-derived carbon. The structure of their microbial communities critically determines whether biogeochemical cycling is dominated by carbon autotrophy or heterotrophy. Hydrological runoff from the terrestrial environment can influence the microbial community structure of these freshwater systems, both through colonization and the input of allochthonous organic matter. In Greenland, climate change has shortened the ice-covered period of inland freshwater systems and increased precipitation. Consequently, Arctic lakes and ponds face greater inputs of dissolved organic matter and nutrients from both the underlying thawing permafrost and from the washed-out surrounding soil. The shorter ice-covered period, coupled with elevated nutrient input, is likely to increase microbial breakdown of organic matter and the release of carbon dioxide and methane. This raises the concern that Arctic freshwater systems will shift to net heterotrophy. Here, we show the differences in prokaryotic community structures between High-Arctic ponds and tundra soils at the species level, while highlighting the relative abundance of heterotrophs and autotrophs. To determine the structure and functional potential of prokaryotic communities, we conducted a genome-resolved metagenomic analysis of permanent and ephemeral ponds, including their upslope tundra soil, in a deglaciated High-Arctic desert. Our study location on the Princess Ingeborg Peninsula (81°36' N, 16°40' W) in Greenland provides a unique opportunity to compare the metagenomes of two habitats exposed to minimal anthropogenic interference. We investigated whether these habitats have the potential to act as carbon sinks or sources and whether tundra soil serves as a potential reservoir for the microbial colonization of newly emerging freshwater systems in the Arctic. Our work provides new insights into Arctic microbial communities, thereby contributing to a better understanding of how climate change could affect biogeochemical cycles in the Arctic region.
How to cite: Burri, B., Shakurova, A., Frey, B., Pernthaler, J., and Andrei, A.-S.: Microbial functional potential of Arctic freshwater ponds and the environmental origin of their diversity, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-263, https://doi.org/10.5194/wbf2026-263, 2026.
Alpine environments are disproportionately affected by anthropogenic climate warming, making them important environments for studying ecosystem responses to rising temperatures. Rising temperatures form feedback loops with soil microbiomes by altering microbial community dynamics, which in-turn impacts greenhouse gas (GHG) emissions and potential further warming. My research aims to identify underlying mechanisms driving microbial community dynamics and GHG fluxes under warming temperatures in the European Alps. More specifically, my research uses controlled laboratory experiments with a synthetic bacterial community to address 1) How does warming impact microbiome composition in alpine ecosystems? 2) How does warming shift the interactions between microbial community members? My work builds upon ongoing field experiments that employ miniature greenhouses, known as “open top chambers”, to locally heat soil at three alpine field sites in the Valais-Wallis region of the Swiss Alps. From these alpine soils, I isolated 12 bacterial strains, each representing a unique genus, to assemble a defined synthetic community. Under controlled laboratory conditions, I grew these strains in monocultures, paired co-cultures, and the full consortia at 10°C and 20°C to simulate a substantial warming scenario. Changes in both relative and absolute abundances will be used to quantify microbe-microbe interactions and assess how their strengths vary with temperature. A knowledge gap exists in studies that link GHG fluxes with genetic profiling of microbial communities in alpine regions, thus my laboratory findings will be also later compared to in-situ field sequencing data of microbial communities and GHG flux measurements. Shifts in microbial community compositions in response to warming will be compared in field and laboratory samples to test for parallel patterns; for example, if similar microbial taxa increase with warmer temperatures in both, this indicates taxa of interest for their GHG metabolisms. Co-occurrences and exclusions between species across temperatures in the natural versus simpler synthetic communities will also be assessed to identify keystone taxa. Understanding how microbial interactions and temperature together impact microbial community composition and associated GHG fluxes will improve predictions of whether alpine ecosystems are likely to act as future sources or sinks of greenhouse gases.
How to cite: Leale, A., Ahlers, L., and Altshuler, I.: Warming in the Alps: impacts on soil microbiomes and microbial interactions, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-452, https://doi.org/10.5194/wbf2026-452, 2026.
Climate change threatens ecosystems worldwide through rising temperatures and altered environmental ecosystems, affecting all organisms, including the microorganisms that regulate biogeochemical cycles and greenhouse gas emissions. These microbial communities play essential roles in nutrient turnover, soil formation, and ecosystem stability, making their responses to climate-driven disturbances critical for predicting future ecosystem functioning. Despite their importance, long-term field experiments investigating how microbial assemblages respond to global change factors—such as warming, altered precipitation patterns, and shifts in vegetation—remain scarce. This scarcity is especially pronounced in high-alpine environments, where harsh climatic conditions, steep environmental gradients, and logistical challenges limit the establishment and maintenance of sustained ecological studies. To address this knowledge gap, we conducted a long-term field experiment for 10 years in the Damma glacier forefield (Switzerland) to assess prokaryotic and fungal community dynamics and ecosystem functions (e.g. greenhouse gas emissions). We simulated two climate change scenarios: experimental warming (~2°C) using open-top chambers (OTCs) and precipitation reduction (~30%). Through image analysis, we found that vegetation cover was significantly higher under warming and precipitation reduction compared to the control. Also, we observed significant treatment effects on CO₂, N₂O, and CH₄ fluxes. Warming and reduced precipitation significantly increased CO₂ emission rates (µmol m⁻² day⁻¹) under both light and dark conditions. In contrast, N₂O emissions showed no significant changes across treatments, while CH₄ fluxes were significantly reduced under light conditions with warming and under dark conditions with reduced precipitation. These changes in greenhouse gas fluxes were accompanied by shifts in microbial community structure: alpha diversity metrics (richness and Shannon index) for both prokaryotes and fungi exhibited significant treatment-by-year interactions, whereas beta diversity was significantly affected by both treatment and year but without treatment-by-year interactions. This suggests that warming and precipitation reduction generate stable compositional differences between microbial communities that persist across years. Collectively, our findings highlight the importance of long-term, multi-year monitoring to accurately assess microbial and ecosystem responses to climate change.
How to cite: Falcó-Ferré, E., Gruntz, B., Stierli, B., Cuartero, J., and Frey, B.: Long-term climate manipulation experiment in a high-alpine soil reveals functional and microbial community shifts, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-253, https://doi.org/10.5194/wbf2026-253, 2026.
Alpine ecosystems are highly vulnerable to climate change, yet the effects of warming on high-altitude soils remain largely unexplored. In particular, it is unclear how soil microbial communities will adapt to rising temperatures and how this will influence greenhouse gas (GHG) fluxes, including methane (CH₄) and carbon dioxide (CO₂). Understanding these microbial responses is crucial for predicting future carbon cycling in these fragile environments.
To address this knowledge gap, we first assessed the biodiversity across ten alpine permafrost affected sites. Results revealed large variations in compositional and functional profiles between sites that were largely driven by differences in vegetation cover (0.01 – 44.8 %), soil pH (3.7 - 7.4), and total organic carbon (0 -11.1 %).
Based on these results we selected four sites that differed distinctly in soil physicochemical parameters and microbial community composition to understand how climate warming affects alpine permafrost-affected soils. Here, we conducted a two-year in-situ study using open-top warming chambers (OTCs) that passively increase soil temperatures, allowing us to study microbial adaptation to warming under realistic field conditions.
Our results showed that GHG flux responses varied considerably between sites: barren soils exhibited minimal biological activity, whereas sparely vegetated soils released CO₂ and removed CH₄, suggesting active microbial methane oxidation. Seasonal and diurnal temperature variations strongly influenced GHG gas fluxes, highlighting the importance of long-term monitoring.
Bacterial community analysis revealed significant differences in composition between sites, and between natural and experimentally warmed soils. Building on this foundation, we are currently conducting metagenomic analyses to resolve the functional potential underpinning these microbial and biogeochemical patterns. This ongoing work aims to link taxonomic shifts to metabolic pathways involved in warming responses and carbon cycling.
Together, these findings deepen our understanding of how European alpine permafrost-affected soils respond to warming and highlight the central role of microbial communities in regulating GHG exchange. Such insights are essential for predicting the future contribution of alpine ecosystems to the global carbon cycle under a changing climate.
How to cite: Ahlers, L., Bourquin, M., Vico Oton, E., Frey, B., Söllinger, A., and Altshuler, I.: Seasonal and experimental warming alter alpine soil microbiomes and in-situ CO2 and CH4 fluxes, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-405, https://doi.org/10.5194/wbf2026-405, 2026.
Global warming has accelerated vegetation expansion across high northern latitudes, reshaping tundra landscapes and altering the balance between carbon uptake and release. As shrubs and other plant functional groups increase in biomass and distribution, the quantity and quality of plant-derived carbon entering soils through root exudates, litter deposition, and rhizosphere processes are expected to change substantially. However, the consequences of these enhanced carbon inputs for soil microbial activity, nutrient cycling, and other key functional processes remain poorly studied, particularly in remote Arctic regions where logistical constraints limit long-term ecological research. This knowledge gap is especially critical given that many of these areas are simultaneously experiencing rapid permafrost thaw, a process that can further modify soil hydrology, organic matter accessibility, and microbial metabolism. Understanding how vegetation expansion interacts with permafrost degradation to shape soil function is therefore essential for predicting future carbon–climate feedback in Arctic ecosystems. To address this knowledge gap, we conducted a four-year field experiment in the High-Arctic (northern Greenland) to test how plant litter inputs affect the microbial metabolic potential and functional processes in the active layer and thawing permafrost soils. For this, we simulated three distinct scenarios: 1) litter amendment effects on active layer soils, 2) permafrost thawing without litter amendment, and 3) permafrost thawing with litter amendment. Our results showed that plant litter inputs had a stronger effect than permafrost thawing (as a proxy for warming) alone, significantly increasing the abundance of genes involved in the breakdown of complex carbon substrates (cellulose, hemicellulose, pectin, and chitin), thereby altering carbon cycling pathways. Litter also increased the abundance of genes involved in nitrogen cycling, ultimately enhancing microbial growth and respiration rates and promoting overall microbial metabolic activity. Our four-year field experiment demonstrates that vegetation expansion—through litter inputs—drives more profound changes in microbial metabolic capacity than warming, with potentially direct implications for carbon dioxide and methane production. Monitoring vegetation-driven transformations of Arctic soil microbiomes is essential for predicting high-latitude greenhouse gas feedback in a warming climate.
How to cite: Cuartero, J., Carla, P.-M., Qi, W., Beat, S., Beat, F., and Varliero, G.: Plant litter inputs increase microbial metabolic capacity more than warming in High-Arctic soils, World Biodiversity Forum 2026, Davos, Switzerland, 14–19 Jun 2026, WBF2026-255, https://doi.org/10.5194/wbf2026-255, 2026.
