Thermal photogrammetry on a permafrost rock wall for the active layer monitoring.

Permafrost and active layer models often cannot explain the high spatial variability, especially in heterogeneous environments like the mountainous regions due to their scarce resolution, paucity of climatic data and topographic details. In this study, we want to introduce a new application of the unmanned aerial vehicle (UAV) in thermal photogrammetry to model the active layer thickness (ALT) of an alpine rock wall through the computation of the thermal inertia and compare the results with a widespread ALT model. On the Gran Zebrù South rock wall, 8 thermal UAV surveys has been conducted in 4 different summer days during 2021-2022 in order to have two 3D thermal models per day at different solar radiation inputs. By analyzing topographic data, visible imagery and the thermal models, the apparent thermal inertias (ATIs) have been converted into heat transfer coefficients (HTCs) and then into ALT of 2021 and 2022. These maps have been validated through the placement of thermistors at different elevations and with variable depths (2, 15 and 40 cm from the rock surface). The resulting ALT has been compared with the Stefan's solution and the alpine permafrost index map (APIM), which showed large underestimations and a noncorrespondence with permafrost occurrence. The average ALT increase of 29.3 cm from 2021 to 2022 has been discussed regarding permafrost formation/degradation future trend under the climatic change and potential risks of alpine areas.

The Unusual Dominance of the Yeast Genus Glaciozyma in the Deeper Layer in an Antarctic Permafrost Core (Adélie Cove, Northern Victoria Land) Is Driven by Elemental Composition.

Rock glaciers are relatively common in Antarctic permafrost areas and could be considered postglacial cryogenic landforms. Although the extensive presence of rock glaciers, their chemical-physical and biotic composition remain scarce. Chemical-physical parameters and fungal community (by sequencing the ITS2 rDNA, Illumina MiSeq) parameters of a permafrost core were studied. The permafrost core, reaching a depth of 6.10 m, was divided into five units based on ice content. The five units (U1-U5) of the permafrost core exhibited several significant (p < 0.05) differences in terms of chemical and physical characteristics, and significant (p < 0.05) higher values of Ca, K, Li, Mg, Mn, S, and Sr were found in U5. Yeasts dominated on filamentous fungi in all the units of the permafrost core; additionally, Ascomycota was the prevalent phylum among filamentous forms, while Basidiomycota was the dominant phylum among yeasts. Surprisingly, in U5 the amplicon sequence variants (ASVs) assigned to the yeast genus Glaciozyma represented about two-thirds of the total reads. This result may be considered extremely rare in Antarctic yeast diversity, especially in permafrost habitats. Based on of the chemical-physical composition of the units, the dominance of Glaciozyma in the deepest unit was correlated with the elemental composition of the core.

Antarctic Salt-Cones: An Oasis of Microbial Life? The Example of Boulder Clay Glacier (Northern Victoria Land).

The evaporation of a localized, highly saline water body of the Boulder Clay debris-covered glacier, in the Northern Victoria Land, probably generated the accumulation of mirabilite (Na2SO4 × 10H2O) and thenardite (Na2SO4) in a glacier salt-cone. Such an extremely cold and salty environment resembles the conditions on Mars, so it can be considered a terrestrial analog. The study was aimed at gaining a first glimpse at the prokaryotic community associated with Antarctic mirabilite and thenardite minerals and also to find clues about the origin of the salts. For this purpose, samples were analyzed by a next generation approach to investigate the prokaryotic (Bacteria and Archaea) diversity. Phylogenetic analysis allowed the identification of Bacteroidota, Actinobacteriota, Firmicutes, and Gammaproteobacteria as the main bacterial lineages, in addition to Archaea in the phylum Halobacterota. The genera Arthrobacter, Rhodoglobus, Gillisia, Marinobacter and Psychrobacter were particularly abundant. Interestingly, several bacterial and archaeal sequences were related to halotolerant and halophilic genera, previously reported in a variety of marine environments and saline habitats, also in Antarctica. The analyzed salt community also included members that are believed to play a major role in the sulfur cycle.

Fungal communities in European alpine soils are not affected by short-term in situ simulated warming than bacterial communities.

The impact of global warming on biological communities colonizing European alpine ecosystems was recently studied. Hexagonal open top chambers (OTCs) were used for simulating a short-term in situ warming (estimated around 1°C) in some alpine soils to predict the impact of ongoing climate change on resident microbial communities. Total microbial DNA was extracted from soils collected either inside or outside the OTCs over 3 years of study. Bacterial and fungal rRNA copies were quantified by qPCR. Metabarcoding sequencing of taxonomy target genes was performed (Illumina MiSeq) and processed by bioinformatic tools. Alpha- and beta-diversity were used to evaluate the structure of bacterial and fungal communities. qPCR suggests that, although fluctuations have been observed between soils collected either inside and outside the OTCs, the simulated warming induced a significant (p < 0.05) shift only for bacterial abundance. Likewise, significant (p < 0.05) changes in bacterial community structure were detected in soils collected inside the OTCs, with a clear increase of oligotrophic taxa. On the contrary, fungal diversity of soils collected either inside and outside the OTCs did not exhibit significant (p < 0.05) differences, suggesting that the temperature increase in OTCs compared to ambient conditions was not sufficient to change fungal communities.

Acceleration of climate warming and plant dynamics in Antarctica.

The strong air temperature warming between the 1950s and 2016 in the Antarctic Peninsula region1 exceeded the global average warming2,3 with evident impacts on terrestrial ecosystems and the two native Antarctic vascular plants Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl.4-10 Subsequently, a short but intense cooling occurred from the Antarctic Peninsula to the South Orkney Islands (1999-2016),1,11-13 impacting terrestrial ecosystems, with reduced lichen growth14 and no further expansion of D. antarctica in the Argentine Islands.5 The strong warming trend is predicted to resume15 with expansion of ice-free areas and continued impacts on the abiotic and biotic components of terrestrial ecosystems including the ingression of non-native species3,8,16,17 as recently recorded at Signy Island (South Orkney Islands).18-20 In this study we document acceleration in the expansion of D. antarctica and C. quitensis in the last decade (2009-2018) at Signy Island, where the air temperature warming trend resumed in summer after 2012. We hypothesize that the striking expansion of these plants is mainly triggered by summer air warming and release from the limitation of fur seal disturbance. We also hypothesize that the "pulse" climatic event of the strong air cooling detected in 2012 did not appear to influence the vegetation community dynamics on this island. This is the first evidence in Antarctica for accelerated ecosystem responses to climate warming, confirming similar observations in the Northern Hemisphere. Our findings support the hypothesis that future warming will trigger significant changes in these fragile Antarctic ecosystems.

Prokaryotic Diversity and Metabolically Active Communities in Brines from Two Perennially Ice-Covered Antarctic Lakes.

The genomic diversity of bacteria and archaea in brines (BC1, BC2, and BC3) from two adjacent and perennially frozen Antarctic lakes (L16 and L-2) in the Boulder Clay (BC) area was investigated together with the metabolically active fraction of both communities, by analyzing the bulk rRNA as a general marker of metabolic activity. Although similar bacterial and archaeal assemblages were observed at phylum level, differences were encountered when considering the distribution in species. Overall, the total bacterial communities were dominated by Bacteroidetes. A massive occurrence of flavobacterial sequences was observed within the metabolically active bacterial communities of the BC1 brine, whereas the active fractions in BC2 and BC3 strongly differed from the bulk communities being dominated by Betaproteobacteria (mainly Hydrogenophaga members). The BC lakes also hosted sequences of the most thermally tolerant archaea, also related to well-known hyperthermophiles. Interestingly, RNA sequences of the hyperthermophilic genus Ferroglobus were retrieved in all brine samples. Finally, a high abundance of the strictly anaerobic methanogens (such as Methanosarcina members) within the active community suggests that anoxic conditions might occur in the lake brines. Our findings indicate perennially ice-covered Antarctic lakes as plausible terrestrial candidates for the study of the potential for extant life on different bodies of our solar system.

Effects of Heavy Ion Particle Irradiation on Spore Germination of Bacillus spp. from Extremely Hot and Cold Environments.

Extremophiles are optimal models in experimentally addressing questions about the effects of cosmic radiation on biological systems. The resistance to high charge energy (HZE) particles, and helium (He) ions and iron (Fe) ions (LET at 2.2 and 200 keV/µm, respectively, until 1000 Gy), of spores from two thermophiles, Bacillushorneckiae SBP3 and Bacilluslicheniformis T14, and two psychrotolerants, Bacillus sp. A34 and A43, was investigated. Spores survived He irradiation better, whereas they were more sensitive to Fe irradiation (until 500 Gy), with spores from thermophiles being more resistant to irradiations than psychrotolerants. The survived spores showed different germination kinetics, depending on the type/dose of irradiation and the germinant used. After exposure to He 1000 Gy, D-glucose increased the lag time of thermophilic spores and induced germination of psychrotolerants, whereas L-alanine and L-valine increased the germination efficiency, except alanine for A43. FTIR spectra showed important modifications to the structural components of spores after Fe irradiation at 250 Gy, which could explain the block in spore germination, whereas minor changes were observed after He radiation that could be related to the increased permeability of the inner membranes and alterations of receptor complex structures. Our results give new insights on HZE resistance of extremophiles that are useful in different contexts, including astrobiology.

Intra- and inter-cores fungal diversity suggests interconnection of different habitats in an Antarctic frozen lake (Boulder Clay, Northern Victoria Land).

A perennially frozen lake at Boulder Clay site (Victoria Land, Antarctica), characterized by the presence of frost mounds, have been selected as an in situ model for ecological studies. Different samples of permafrost, glacier ice and brines have been studied as a unique habitat system. An additional sample of brines (collected in another frozen lake close to the previous one) was also considered. Alpha- and beta-diversity of fungal communities showed both intra- and inter-cores significant (p < 0.05) differences, which suggest the presence of interconnection among the habitats. Therefore, the layers of frost mound and the deep glacier could be interconnected while the brines could probably be considered as an open habitat system not interconnected with each other. Moreover, the absence of similarity between the lake ice and the underlying permafrost suggested that the lake is perennially frozen based. The predominance of positive significant (p < 0.05) co-occurrences among some fungal taxa allowed to postulate the existence of an ecological equilibrium in the habitats systems. The positive significant (p < 0.05) correlation between salt concentration, total organic carbon and pH, and some fungal taxa suggests that a few abiotic parameters could drive fungal diversity inside these ecological niches.

Cultivable Bacterial Communities in Brines from Perennially Ice-Covered and Pristine Antarctic Lakes: Ecological and Biotechnological Implications.

The diversity and biotechnological potentialities of bacterial isolates from brines of three Antarctic lakes of the Northern Victoria Land (namely Boulder Clay and Tarn Flat areas) were first explored. Cultivable bacterial communities were analysed mainly in terms of bacterial response to contaminants (i.e., antibiotics and heavy metals) and oxidation of contaminants (i.e., aliphatic and aromatic hydrocarbons and polychlorobiphenyls). Moreover, the biosynthesis of biomolecules (antibiotics, extracellular polymeric substances and enzymes) with applications for human health and environmental protection was assayed. A total of 74 and 141 isolates were retrieved from Boulder Clay and Tarn Flat brines, respectively. Based on 16S rRNA gene sequence similarities, bacterial isolates represented three phyla, namely Proteobacteria (i.e., Gamma- and Alphaproteobacteria), Bacteroidetes and Actinobacteria, with differences encountered among brines. At genus level, Rhodobacter, Pseudomonas, Psychrobacter and Leifsonia members were dominant. Results obtained from this study on the physiological and enzymatic features of cold-adapted isolates from Antarctic lake brines provide interesting prospects for possible applications in the biotechnological field through future targeted surveys. Finally, findings on contaminant occurrence and bacterial response suggest that bacteria might be used as bioindicators for tracking human footprints in these remote polar areas.

Microbial Assemblages in Pressurized Antarctic Brine Pockets (Tarn Flat, Northern Victoria Land): A Hotspot of Biodiversity and Activity.

Two distinct pressurized hypersaline brine pockets (named TF4 and TF5), separated by a thin ice layer, were detected below an ice-sealed Antarctic lake. Prokaryotic (bacterial and archaeal) diversity, abundances (including virus-like particles) and metabolic profiles were investigated by an integrated approach, including traditional and new-generation methods. Although similar diversity indices were computed for both Bacteria and Archaea, distinct bacterial and archaeal assemblages were observed. Bacteroidetes and Gammaproteobacteria were more abundant in the shallowest brine pocket, TF4, and Deltaproteobacteria, mainly represented by versatile sulphate-reducing bacteria, dominated in the deepest, TF5. The detection of sulphate-reducing bacteria and methanogenic Archaea likely reflects the presence of a distinct synthrophic consortium in TF5. Surprisingly, members assigned to hyperthermophilic Crenarchaeota and Euryarchaeota were common to both brines, indicating that these cold habitats host the most thermally tolerant Archaea. The patterns of microbial communities were different, coherently with the observed microbiological diversity between TF4 and TF5 brines. Both the influence exerted by upward movement of saline brines from a sub-surface anoxic system and the possible occurrence of an ancient ice remnant from the Ross Ice Shelf were the likely main factors shaping the microbial communities.

Permafrost is warming at a global scale.

Permafrost warming has the potential to amplify global climate change, because when frozen sediments thaw it unlocks soil organic carbon. Yet to date, no globally consistent assessment of permafrost temperature change has been compiled. Here we use a global data set of permafrost temperature time series from the Global Terrestrial Network for Permafrost to evaluate temperature change across permafrost regions for the period since the International Polar Year (2007-2009). During the reference decade between 2007 and 2016, ground temperature near the depth of zero annual amplitude in the continuous permafrost zone increased by 0.39 ± 0.15 °C. Over the same period, discontinuous permafrost warmed by 0.20 ± 0.10 °C. Permafrost in mountains warmed by 0.19 ± 0.05 °C and in Antarctica by 0.37 ± 0.10 °C. Globally, permafrost temperature increased by 0.29 ± 0.12 °C. The observed trend follows the Arctic amplification of air temperature increase in the Northern Hemisphere. In the discontinuous zone, however, ground warming occurred due to increased snow thickness while air temperature remained statistically unchanged.

A thin ice layer segregates two distinct fungal communities in Antarctic brines from Tarn Flat (Northern Victoria Land).

Brines are hypersaline solutions which have been found within the Antarctic permafrost from the Tarn Flat area (Northern Victoria Land). Here, an investigation on the possible presence and diversity of fungal life within those peculiar ecosystems has been carried out for the first time. Brines samples were collected at 4- and 5-meter depths (TF1 and TF2, respectively), from two brines separated by a thin ice layer. The samples were analyzed via Illumina MiSeq targeting the ITS region specific for both yeasts and filamentous fungi. An unexpected high alpha diversity was found. Beta diversity analysis revealed that the two brines were inhabited by two phylogenetically diverse fungal communities (Unifrac value: 0.56, p value < 0.01; Martin's P-test p-value < 0.001) characterized by several specialist taxa. The most abundant fungal genera were Candida sp., Leucosporidium sp., Naganishia sp. and Sporobolomyces sp. in TF1, and Leucosporidium sp., Malassezia sp., Naganishia sp. and Sporobolomyces sp. in TF2. A few hypotheses on such differentiation have been done: i) the different chemical and physical composition of the brines; ii) the presence in situ of a thin layer of ice, acting as a physical barrier; and iii) the diverse geological origin of the brines.

Prokaryotic Abundance and Activity in Permafrost of the Northern Victoria Land and Upper Victoria Valley (Antarctica).

Victoria Land permafrost harbours a potentially large pool of cold-affected microorganisms whose metabolic potential still remains underestimated. Three cores (BC-1, BC-2 and BC-3) drilled at different depths in Boulder Clay (Northern Victoria Land) and one sample (DY) collected from a core in the Dry Valleys (Upper Victoria Valley) were analysed to assess the prokaryotic abundance, viability, physiological profiles and potential metabolic rates. The cores drilled at Boulder Clay were a template of different ecological conditions (different temperature regime, ice content, exchanges with atmosphere and with liquid water) in the same small basin while the Dry Valleys site was very similar to BC-2 conditions but with a complete different geological history and ground ice type. Image analysis was adopted to determine cell abundance, size and shape as well as to quantify the potential viable and respiring cells by live/dead and 5-cyano-2,3-ditolyl-tetrazolium chloride staining, respectively. Subpopulation recognition by apparent nucleic acid contents was obtained by flow cytometry. Moreover, the physiological profiles at community level by Biolog-Ecoplate™ as well as the ectoenzymatic potential rates on proteinaceous (leucine-aminopeptidase) and glucidic (ß-glucosidase) organic matter and on organic phosphates (alkaline-phosphatase) by fluorogenic substrates were tested. The adopted methodological approach gave useful information regarding viability and metabolic performances of microbial community in permafrost. The occurrence of a multifaceted prokaryotic community in the Victoria Land permafrost and a large number of potentially viable and respiring cells (in the order of 104-105) were recognised. Subpopulations with a different apparent DNA content within the different samples were observed. The physiological profiles stressed various potential metabolic pathways among the samples and intense utilisation rates of polymeric carbon compounds and carbohydrates, mainly in deep samples. The measured enzymatic activity rates suggested the potential capability of the microbial community to decompose proteins and polysaccharides. The microbial community seems to be appropriate to contribute to biogeochemical cycling in this extreme environment.

Pressurized brines in continental Antarctica as a possible analogue of Mars.

Interest in brines in extreme and cold environments has recently increased after they have been found on Mars. Those brines can be potential new subsurface habitats for peculiar ecosystems. In the McMurdo Dry Valleys of the Antarctic, the best analogue for Mars conditions, only a few cases of brines have been identified in some perennially frozen lakes and in one case in an underground aquifer. Here, we present the occurrence of pressurized brines in a shallow perennially ice-covered lake south of 70°S in an ice-free area of Victoria Land, Antarctica. For the first time, we also imaged, by means of ground penetrating radar data, the existence of a pingo-like-feature (PLF) formed by the extrusion of brines, which has also been confirmed by borehole evidence. Those brines are fed by an underground talik external to the lake basin, enhancing the possibility of unexploited ecosystems that could find an analogue in Martian environments.

Accelerating climate change impacts on alpine glacier forefield ecosystems in the European Alps.

In the European Alps the increase in air temperature was more than twice the increase in global mean temperature over the last 50 years. The abiotic (glacial) and the biotic components (plants and vegetation) of the mountain environment are showing ample evidence of climate change impacts. In the Alps most small glaciers (80% of total glacial coverage and an important contribution to water resources) could disappear in the next decades. Recently climate change was demonstrated to affect higher levels of ecological systems, with vegetation exhibiting surface area changes, indicating that alpine and nival vegetation may be able to respond in a fast and flexible way in response to 1-2 degrees C warming. We analyzed the glacier evolution (terminus fluctuations, mass balances, surface area variations), local climate, and vegetation succession on the forefield of Sforzellina Glacier (Upper Valtellina, central Italian Alps) over the past three decades. We aimed to quantify the impacts of climate change on coupled biotic and abiotic components of high alpine ecosystems, to verify if an acceleration was occurring on them during the last decade (i.e., 1996-2006) and to assess whether new specific strategies were adopted for plant colonization and development. All the glaciological data indicate that a glacial retreat and shrinkage occurred and was much stronger after 2002 than during the last 35 years. Vegetation started to colonize surfaces deglaciated for only one year, with a rate at least four times greater than that reported in the literature for the establishment of scattered individuals and about two times greater for the well-established discontinuous early-successional community. The colonization strategy changed: the first colonizers are early-successional, scree slopes, and perennial clonal species with high phenotypic plasticity rather than pioneer and snowbed species. This impressive acceleration coincided with only slight local summer warming (approximately -0.5 degree C) and a poorly documented local decrease in the snow cover depth and duration. Are we facing accelerated ecological responses to climatic changes and/or did we go beyond a threshold over which major ecosystem changes may occur in response to even minor climatic variations?