The ³H activity and the concentration of 23 metals and metalloids have been analysed in cave ice samples from the perennial cave ice deposit of Vukušić Ice Cave, Velebit Mt., Croatia. The results of tritium measurements exclude a secular age for the upper 2.4 m of ice deposition, and provide clear arguments that the sampled ice sequence consists of frozen post-1950 precipitation. Measured concentrations of most of the analysed elements have largely surmounted reported concentrations of similar elements from local precipitation or Alpine snow/firn/ice records, whereas three metals (Cr, Cu, Pb) show concentrations comparable to them. Principal component analysis was used to select three groups of elements. The Ca-Mg-governed group (PC1) encompasses the bedrock-related components; their fluctuation might thus reflect the past intensity of dissolution in the epikarst. PC2, with the most characteristic elements being Na, Cr and Pb, probably preserved an atmospheric depositional signal. PC3 is governed by Al and Fe. This probably carries the distal, non-karstic crustal signal and hence might be related to atmospheric circulation (i.e., wind direction and speed).

We utilized the random forest (RF) machine learning algorithm, along with nine topographical/morphological factors, namely aspect, slope, geomorphons, plan curvature, profile curvature, terrain roughness index, surface texture, topographic wetness index (TWI), and elevation. Our objective was to identify flood-prone areas along the meandering Kashkan River and investigate the role of topography in riverbank inundation. To validate the flood susceptibility map generated by the random forest algorithm, we employed Sentinel-1 GRDH SAR imagery from the March 2019 flooding event in the Kashkan river. The SNAP software and the OTSU thresholding method were utilized to extract the flooded/inundated areas from the SAR imagery. The results showed that the random forest model accurately pinpointed areas with a “very high” and “high” risk of flooding. Through analysis of the cross-sections and SAR-based flood maps, we discovered that the topographical confinement of the meander played a crucial role in the extent of inundation along the meandering path. Moreover, the findings indicated that the inner banks along the Kashkan river were more prone to flooding compared to the outer banks.

High-altitude saline lakes (located more than 3000 m a.s.l.) provide multiple environmental extremities for polyextremophilic bacteria. In this study, lake sediment samples from Laguna Santa Rosa and microbial mat samples from the warm water pool of Laguna Verde (Puna de Atacama, Chile) were examined by cultivation and pyrosequencing. The 16S rRNA gene-based identification showed that most of the bacterial isolates belonged to different moderately halophilic Marinobacter species (Proteobacteria). Sample-specific occurrence was characteristic of genera Caenispirillum, Halomonas, Idiomarina, Nitratireductor and Salinarimonas (Proteobacteria), Planococcus, Jeotgalibacillus and Paraliobacillus (Firmicutes), Psychroflexus (Bacteroidetes) and Arthrobacter (Actinobacteria). Using cultivation-independent technique, the benthic communities of both lakes were dominated by sequences related to the phyla Proteobacteria and Bacteroidetes. In addition, representatives of phyla Actinobacteria, Chlorobi, Chloroflexi, Cloacimonetes, Cyanobacteria, Deferribacteres, Deinococcus-Thermus, Firmicutes, Gracilibacteria, Latescibacteria, Lentisphaerae, Parcubacteria, Planctomycetes, Spirochaetae, Tenericutes and Verrucomicrobia were present at least 1% relative abundance. Large differences were explored in the bacterial community composition of the sediment and mat samples at the level of the identified families. It is hypothesized that depending on the type of benthic habitat, different bacteria – involved in the phototrophy based primary production as well as the mainly anaerobic biodegradation of organic materials – can participate in the local carbon, nitrogen, and sulfur cycles.

Earth harbors unique environments where only microorganisms adapted to extreme conditions, known as extremophiles, can survive. This study focused on a high-altitude meltwater pond, located in the Puna de Atacama, Dry Andes. The extremophilic bacteria of this habitat must adapt to a range of extremities, including cold and dry climate, high UV radiation, high daily temperature fluctuations, low-nutrient availability, and negative water balance. This study aimed to explore the taxonomic diversity of cultivable extremophilic bacteria from sediment samples of a desiccated, high-altitude, meltwater pond using media with different organic matter contents and different incubation temperatures. Based on the 16S rRNA gene sequence analysis, the isolates were identified as members of the phyla Actinobacteria, Proteobacteria, and Firmicutes. The most abundant genera were Arthrobacter and Pseudoarthrobacter. The isolates had oligocarbophilic and psychrotrophic properties, suggesting that they have adapted to the extreme environmental parameters of their natural habitats. The results indicate a positive correlation between nutrient concentration and temperature tolerance. Graphical abstract