Search Results (1,166)

Antarctica’s aerodynamic roughness length (z_0m) is crucial for surface energy exchange and atmospheric modeling, but its remote sensing estimation remains challenging due to complex ice-surface conditions and limited observations. To address these challenges, this study establishes a z_0m retrieval framework derived from the Raupach model using Unmanned Aerial Vehicle (UAV), Reference Elevation Model of Antarctica (REMA), and Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) datasets at three representative Antarctic sites. The results show that UAV benchmarks yield mean z_0m values of 0.009795, 0.011597, and 0.005203 m at Zhongshan Station, Great Wall Station, and Qinling Station, respectively. In experiments with ICESat-2 data, z_0m derived from ATL06 demonstrates accuracy comparable to that from ATL03 (RMSE = 7.45 × 10⁻⁶ m), with the best performance obtained at a 2 km window. Spatially, the agreement with UAV-derived z_0m decreases in the order: REMA > ICESat-2 (IDW-interpolated). The accuracy of REMA and ICESat-2 decreased with terrain complexity, from ice-free zones to the ice-shelf front and finally to the steep ice sheet margin. The elevation and slope variations emerge as dominant controls of z_0m spatial patterns. This study demonstrates the complementary strengths of UAV, REMA, and ICESat-2 datasets in Antarctic aerodynamic roughness estimation, providing practical guidance for data selection and methodology optimization. This study develops an improved z_0m retrieval method for Antarctica, clarifies the applicability and limitations of UAV, REMA, and ICESat-2 data, and provides methodological and data support for simulations of near-surface atmospheric parameters in Antarctica region. Full article

This study examines the occurrence of bacteria resistant to antibiotics and heavy metals in Terra Nova Bay, a coastal area of the Ross Sea in Antarctica that is increasingly recognised as vulnerable to human influence. During the 37th Italian Antarctic Expedition (2021–2022), researchers collected seawater, sediment, and fish samples from the notothenioid species Trematomus bernacchii to evaluate microbial resistance in an environment once considered largely pristine. Fifty heterotrophic bacterial isolates were obtained and tested against twenty-eight antibiotics, revealing a notable presence of multidrug resistance. These multidrug-resistant isolates were then assessed for their tolerance to eight heavy metal salts to understand whether resistance traits extended beyond antimicrobials. Twelve isolates showing resistance to both antibiotics and metals were selected for further genetic screening, targeting key resistance genes linked to tetracycline, vancomycin, sulphonamides, and other antimicrobial classes. The detection of multiple resistance genes in genera such as Pseudomonas, Pseudoalteromonas, and Psychrobacter indicates that both natural selective pressures and local, human-related contamination may be shaping resistance patterns in this region. Overall, the study demonstrates that even remote Antarctic marine ecosystems can host bacteria with complex resistance profiles. While these ecosystems are largely isolated, human activities such as scientific research, tourism, and the introduction of pollutants may contribute to the dissemination of antibiotic resistance genes, raising important ecological and potential public health considerations regarding the spread of resistance in polar environments. Full article

Fast pyrolysis of vegetable oils and residues generates bio-oil (BO), a renewable hydrocarbon source with high acidity that limits its direct use in refineries. In this study, BOs were produced from refined soybean oil (RSO) and waste cooking oil (WCO) at 525 °C in a continuous bench-scale pyrolysis at 525 °C, with a 390 ± 8 g h⁻¹ feed rate, under steady-state conditions. The resulting bio-oils exhibited high acidity (acid index of 145 and 127 mg KOH g⁻¹, respectively) and elevated olefinic and oxygen contents, making them corrosive and unsuitable for co-refining with petroleum. To reduce acidity, ethyl esterification was performed using lipase B from Candida antarctica (CALB), using a Box–Behnken 3³ factorial design. Variables included temperature (40–60 °C), bio-oil:ethanol mass ratio (1:1–1:5), and catalyst concentration (3–10% w/w). The acid index was reduced by up to 76%, with optimal conditions (62 °C, 1:1 mass ratio, 11% CALB) yielding a final value of 28 mg KOH g⁻¹. Similar reductions were obtained for waste cooking oil bio-oil, confirming robustness across feedstocks. CALB retained over 70% activity after three cycles, demonstrating stability. This enzymatic esterification process shows strong potential for lowering bio-oil acidity, enabling integration into petroleum refineries, diversifying feedstocks, and advancing renewable fuel production. Full article

Cold-active lipolytic enzymes enable low-temperature biocatalysis, but remain underexplored in Antarctic actinomycetes. Here, we report the discovery and first-step characterization of a CALB-like cold-active lipolytic enzyme (PanLip) from Pseudonocardia antarctica. Sequence and structure analyses revealed a canonical α/β-hydrolase fold with a conserved Ser–Asp–His triad and short helical elements around the pocket reminiscent of CALB’s α5/α10 lid. Mature PanLip was expressed primarily as inclusion bodies in E. coli; an N-terminally truncation (PanLipΔN) improved solubility and PanLipΔN was purified by Ni–NTA. Far-UV CD confirmed a folded α/β architecture. PanLipΔN favored short-chain substrates (p-NPA, k_cat/K_M = 2.4 × 10⁵ M⁻¹·s⁻¹) but also showed measurable hydrolytic activity toward natural triglycerides, consistently with a lipase-family esterase. The enzyme showed an activity optimum near 25 °C and pH 8.0. The enzyme tolerated low salt (maximal at 0.1 M NaCl), mild glycerol, and selected organic solvents (notably n-hexane), but was inhibited by high salt, Triton X-100, and SDS. AlphaFold predicted high local confidence for the catalytic core; DALI placed PanLip closest to fungal lipases (AFLB/CALB). Temperature-series MD and CABS-flex indicated enhanced surface breathing and flexible segments adjacent to the active site—including a region topologically matching CALB α10—supporting a flexibility-assisted access mechanism at low temperature. Structure-based MSAs did not support a cold adaptation role for the reported VDLPGRS motif. Taken together, these findings position PanLip as a promising cold-active catalyst with CALB-like access control and potential for low-temperature biocatalysis. Full article

Antarctica’s pristine environment and geographical isolation make it an ideal location for conducting research on the global transport and fate of pollutants. Given its unique environmental characteristics, research on this continent is essential for identifying and characterizing the various types of pollution and understanding their transport dynamics. This study employs a comprehensive analytical approach to examine the physico-chemical and chemical characteristics of water samples collected from catchments at the Lions Rump headland, including assessments of pH, specific electrical conductivity, total organic carbon, inorganic analytes (anions, cations, metals and metalloids), and polycyclic aromatic hydrocarbons (PAHs). The results showed that stream waters exhibited neutral to slightly alkaline conditions (pH 7.0–8.1) and relatively high conductivity, indicating a significant contribution of volcanic and marine inputs. TOC concentrations remained low (<2 mg L⁻¹), while elevated levels of Cl⁻ and SO₄²⁻ reflected the strong imprint of halogen deposition. PAHs were detected at low concentrations (41.5–67.4 ng/L), with their distribution pointing to long-range atmospheric transport as the dominant source and additional evidence of re-emission from sediments. The obtained results fill gaps in knowledge about the chemical composition of water, including the levels of potentially toxic substances in areas of Antarctica that are not directly influenced by research stations. Full article

Convection associated with the leading mode of subseasonal variability of the tropical atmosphere, the Madden–Julian Oscillation (MJO), can excite Rossby wave trains that extend well into the extratropics and allow the MJO to modulate many components of the Earth system. To improve our understanding of teleconnections between the MJO and Antarctic sea ice, composite anomalies of daily change in sea ice concentration (ΔSIC) from 1989 to 2019 were binned by phase 0–20 days after an active MJO and compared to anomalies of surface air temperature, the meridional component of surface wind, and sea-level pressure. In May, ΔSIC anomalies were strongest in the Indian Ocean (IO) sector, 16 days after phase 8. There, a wavenumber-three pattern in sea-level pressure anomalies associated with the MJO resulted in anomalously poleward winds and warmer temperatures over the central and eastern IO that were collocated with anomalously negative ΔSIC. Furthermore, anomalously equatorward winds and colder temperatures in the western IO were collocated with anomalously positive ΔSIC. In July, ΔSIC anomalies were strongest in the Weddell Sea (WS) sector nine days after an active MJO in phase 2. There, a wavenumber-three pattern in sea-level pressure anomalies resulted in anomalously poleward winds and warmer temperatures over the western and central WS that were collocated with negative ΔSIC anomalies; anomalously equatorward winds and colder temperatures over the eastern WS were collocated with positive ΔSIC anomalies. In September, the largest ΔSIC anomalies were observed in the IO and WS sectors six days after an active MJO in phase 8. No meaningful modulation of sea ice anomalies was found after an active MJO in November or January. These results extend our understanding of teleconnections between the MJO and Antarctic sea ice on the subseasonal time scale. Full article

Ethyl butyrate is a typical flavor ester with pineapple-banana scents, but the poor yield from natural fruits limits its feasibility in food and fragrance industries. In this study, dendritic fibrous nano-silica (DFNS) was hydrophobically modified with octyl groups (DFNS-C₈) to immobilize Candida antarctica lipase B (CALB) for solvent-free esterification of ethyl butyrate. The immobilized lipase CALB@DFNS-C₈, with the enzyme loading of 354.6 mg/g and the enzyme activity of 0.064 U/mg protein, achieved 96.0% ethyl butyrate conversion under the optimum reaction conditions where the molar ratio of butyric acid to ethanol was 1:3, with a reaction temperature and time of 40 °C and 4 h. Under the solvent-free catalytic reactions, CALB@DFNS-C₈ presented the maximum catalytic efficiency of 35.1 mmol/g/h and retained 89% initial activity after ten reuse cycles. In addition, the immobilized lipase can efficiently catalyze the synthesis of various flavor esters (such as butyl acetate, hexyl acetate, butyl butyrate, etc.) and exhibits excellent thermostability and solvent tolerance. A molecular docking simulation reveals that the hydrophobic cavity around the catalytic triad stabilizes the acyl intermediate and ensures the precise orientation of both acid and alcohol substrates. This work provides new insights into the sustainable production of flavor esters using highly active and recyclable immobilized lipases through rational carrier hydrophobization and structural confinement design. Full article

Antarctica harbors some of the most extreme ecosystems on earth, where only two vascular plants persist. The native grass Deschampsia antarctica provides a model for plant–microbe interactions under intense abiotic stress. We present the first multi-compartmental and multi-kingdom characterization of bacterial and fungal communities associated with D. antarctica across three South Shetland Islands. Metabarcoding revealed strong compartmentalization: the rhizosphere displayed the highest richness and complex bacterial–fungal networks; the root endosphere showed intermediate diversity with keystone taxa such as Rhizobiales and Streptomyces; and the leaf endosphere was simplified, dominated by stress-tolerant taxa including Pseudomonas and Helotiales. Despite marked soil heterogeneity, phosphorus enrichment at Admiralty Bay, base cations at Coppermine Cove, and iron at Byers Peninsula, a conserved core (20 bacterial and 5 fungal genera) persisted, mainly cold-adapted saprotrophs and plant-associated taxa. Fungal assemblages were more responsive to soil chemistry, with site-specific enrichments such as Zymoseptoria and Herpotrichia. Overall, D. antarctica holobionts exhibited a dual strategy: conserved microbial backbones confer stability, while localized assemblages shaped by soil chemistry and geography enhance adaptability. Together, these findings provide one of the most integrative characterizations of the D. antarctica holobiont to date, revealing how conserved and adaptive microbial components support plant resilience under extreme Antarctic conditions and offering valuable insights for predicting biological responses to ongoing climate change. Full article

Several Level-2 solutions for the GRACE(-FO) gravity field exist. We compare five of these solutions using a mascon inversion method to estimate gridded mass change in Antarctica from gravity field grids at orbit height. We compare the mass change for all of Antarctica, as well as for 27 drainage basins. All five solutions show consistent negative mass trends for the period between April 2002 and January 2025 and show a mass accumulation in the East Antarctic basins 12 and 13 during the years 2021, 2022, and the beginning of 2023 but also a rapid mass loss starting in May 2023. While there are regional differences, the error from the Glacial Isostatic Adjustment model exceeds the differences between the solutions looked at in this study. Full article

Antarctic algae have evolved in extreme environmental conditions, developing unique metabolic adaptations with significant biotechnological potential. In this study, we explored the bioactivity of the sea-ice microalga Microglena antarctica by preparing acetone and methanol extracts from biomass cultivated at 4, 8, and 16 °C. These extracts were screened for their in vitro antioxidant properties and inhibitory activities on enzymes related to Alzheimer’s disease (acetylcholinesterase: AChE, butyrylcholinesterase: BChE), type 2 diabetes mellitus (T2DM, α-glucosidase, α-amylase), obesity (lipase), and hyperpigmentation (tyrosinase). Our screening revealed a high capacity of acetone extracts to scavenge the ABTS•⁺ radical (EC₅₀ ranging from 3.57 to 4.18 mg mL⁻¹), along with strong copper chelating activity in both acetone and methanol extracts (EC₅₀ values of 6.31 and 6.41 mg mL⁻¹). Relevant inhibition towards α-amylase (IC₅₀ values of 3.34 and 4.53 mg mL⁻¹) and tyrosinase (with IC₅₀ ranging from 3.82 to 5.47 mg mL⁻¹) was reported for acetone and methanol extracts, respectively. UHPLC-HRMS-based profiling revealed the presence of lipidic molecules, such as glycolipids, phospholipids, and betaine lipids with polyunsaturated carbon chains, together with carotenoids, including canthaxanthin and adonixanthin, which are likely responsible for the observed bioactivities. Full article

The Antarctic ice sheet, Earth’s largest ice mass, is vital to the global climate system. Analyzing its thermal behavior is crucial for sea-level projections and ice shelf assessments; however, internal temperature studies remain challenging due to the harsh environment and limited access to the site. Using ten years of Soil Moisture Active Passive (SMAP) satellite passive microwave brightness temperature (T_B) data (2015–2025), we examined changes in T_B across Antarctica. Results show a stronger warming trend in West Antarctica, with T_B increasing by over 1.5 K over a decade, while East Antarctica remains relatively stable, showing only seasonal summer warming and winter cooling. Furthermore, T_B in the Antarctic region correlates best with internal temperatures at depths of 500–2000 m, as indicated by the effective soil temperature, as demonstrated by the modeling data and the τ-z model’s inference. However, the total enthalpy is inconsistent with the T_B trend and exhibits the opposite effect when combined with the sensing depth. By comparing the weak trend in surface ice temperature changes, we conclude that the T_B warming trend observed on the western side of the Antarctic over the past decade does not originate from the increasing temperatures within the internal ice shelves, which differs from the increase in temperatures at the Antarctic margins. Full article

Nest predation is a major factor limiting avian reproductive success. It depends on factors such as bird community, land use, vegetation structure and landscape. Anthropogenic disturbances in native forests, such as logging and livestock grazing, alter forest structure and understory, potentially affecting nest predation rates. In this study, we analysed the susceptibility of open-cup nests to predation in Nothofagus antarctica forests in Tierra del Fuego (Argentina), comparing 15–50 years ago thinned—T and unthinned forests, the latter classified as open—O, closed—C or very closed—VC. We also identified nest predators through camera traps and the main variables influencing predation using a Generalized Lineal Model. Data were collected from 32 sites representing the four studied categories of canopy cover across two years (256 artificial nests per year). Artificial nest predation rates varied between year (9.4% in 2018 and 40.2% in 2022) and among forest types. In 2018, the O forests had the highest predation rate (50%, 12 in total), whereas in 2022, VC forests showed the greatest predation (38%, 39 in total). Camera traps identified three nest predators: Milvago chimango, Campephilus magellanicus and Xolmis pyrope. In 2018, canopy cover was the only variable that influenced artificial nest predation, while in 2022, tree sapling cover, patch shape, open-cup nester density and tree basal area were the most influential (in that order). We found annual variations driven by different ecological factors in N. antarctica forest of southern Patagonia. Although thinning showed no significant long-term effects on artificial nest predation on this study, more research is needed to understand the influence of low impact forest management in austral bird communities. Full article

The General AntiParticle Spectrometer is a balloon-borne experiment designed to search for low-energy cosmic-ray antinuclei as a potential indirect signature of dark matter. Over the course of at least three long-duration flights over Antarctica, it will explore the sub-$250 \mathrm{M}\mathrm{e}\mathrm{V}/\mathit{n}$ energy range with sensitivity to antideuterons and antihelium, while also extending antiproton measurements below 100 $\mathrm{M}$$\mathrm{e}\mathrm{V}$. The instrument features a tracker built from more than one thousand lithium-drifted silicon detectors, each read out by a dedicated custom integrated circuit. With the first flight scheduled for the austral summer of 2025, a new prototype chip, ANTARES4, has been developed using a commercial 65 $\mathrm{n}$$\mathrm{m}$ complementary metal-oxide semiconductor process for use in the second flight. It integrates eight independent analog channels, each incorporating a low-noise charge-sensitive amplifier with dynamic signal compression, a CR–RC shaping stage with eight selectable peaking times, and on-chip calibration circuitry. The charge-sensitive amplifier uses metal-oxide semiconductor feedback elements with voltage-dependent capacitance to support the wide input energy range from 10 $\mathrm{k}$$\mathrm{e}\mathrm{V}$ to 100 $\mathrm{M}$$\mathrm{e}\mathrm{V}$. Four alternative feedback implementations are included to compare performance and design trade-offs. Leakage current compensation up to 200 $\mathrm{n}$$\mathrm{A}$ per detector strip is provided by a Krummenacher current–feedback network. This paper presents the design and architecture of ANTARES4, highlighting the motivations, design drivers, and performance requirements that guided its development. Full article

Labeling ice cracks in Antarctic near-shore sea ice aerial orthophotos is critical for sea ice cargo route development; rapid, accurate identification and labeling of cracks in UAV imagery aids safe goods transfer between icebreakers and expedition stations, and studying ice crack distribution provides a key basis for assessing sea ice route reliability. Ice cracks have complex morphologies that traditional recognition methods struggle to handle, so this study proposes the ICI-YOLOv8 algorithm to improve sea ice crack detection near Antarctica’s Zhongshan Station, using crack density and fractal dimension to characterize spatial distribution and a Monte Carlo-based numerical model to quantify distribution probability. The algorithm achieves 0.628 accuracy and 0.662 mAP@0.5 (outperforming comparable methods in speed and accuracy) and reaches 0.933 accuracy and 0.657 mAP@0.5 with better generalization than similar models when tested on general remote sensing water datasets; a positive correlation exists between fractal dimension and ice crack density, and Monte Carlo simulation and probability distribution models verify their distribution properties. The proposed algorithm is suitable for rapid summer Antarctic near-shore sea ice crack identification, the numerical model effectively quantifies crack distribution to aid route development, and this study is important for understanding polar ice stability and sea ice route development. Full article

The Lactobacillaceae family encompasses microorganisms of exceptional ecological and biotechnological importance, serving as central agents in food fermentations, health applications, and nutrient cycling across diverse environments. Despite their broad functional and phylogenetic diversity, the global distribution and ecological specialization of Lactobacillaceae are not yet fully understood. In this study, we performed a comprehensive analysis of over 2 million records from the NCBI database to survey and trace the ecological landscape of Lactobacillaceae across thousands of distinct habitats. Our results reveal that food products and animal hosts represent the primary ecological niches for members of this family. The examined taxa exhibit a broad spectrum of ecological strategies, ranging from generalists with wide environmental adaptability to specialists with strict niche preferences. Notably, our findings highlight a profound geographical and ecological sampling bias, with unclassified taxids frequent in animal gastrointestinal tracts, soils, and especially in living plant tissues—habitats identified as promising frontiers for discovering novel biodiversity. The obtained results emphasize the urgent need for expanded sampling efforts in underexplored geographic regions such as Africa, Antarctica, the Arctic, South America, and Central Asia to capture a more complete picture of Lactobacillaceae diversity. The study underscores the necessity of implementing standardized, metadata-rich data deposition practices to enable unbiased, large-scale ecological and evolutionary analyses. Ultimately, these insights not only deepen our fundamental knowledge of Lactobacillaceae diversity but also provide a strategic framework for future bioprospecting, fostering the discovery of novel strains and expanding the biotechnological potential of this influential bacterial family. Full article