Search Results (58)

Immunotherapy is a transformative strategy in oncology, yet the development of novel immunomodulatory agents remains essential. This study explores the anti-tumor potential of a structurally unique polysaccharide isolated from an Aspergillus ochraceus (AOP), sourced from the Antarctic Weddell Sea. Using alkaline-assisted extraction and chromatographic purification, we obtained a homogeneous polysaccharide predominantly composed of galactose and mannose, with an average molecular weight of 39.67 kDa. The structure was characterized by an integrated nuclear magnetic resonance spectroscopy and mass spectrometry analysis, revealing that the AOP is composed of β (1→5)-linked galactofuranose units, with a minor substitution by α-D-mannopyranose residues via (1→2) glycosidic bonds at the C2 of the galactofuranose. Functional assays, including CCK8 and wound-healing tests, demonstrated that this polysaccharide, referred to as AOP, inhibited melanoma cell proliferation and migration in a dose-dependent manner. Additionally, the AOP activated RAW264.7 and bone marrow-derived macrophage (BMDM) cells without exhibiting significant cytotoxicity, leading to the release of inflammatory factors such as TNF-α, IL-1β, and IL-6. Mechanistically, the AOP was found to upregulate the expression of CD86 and IFN-γ, while downregulating genes like IL-4 and Arg1. These findings position the AOP as the first documented Antarctic fungal polysaccharide with macrophage-reprogramming capabilities against melanoma, offering novel molecular insights for marine-derived immunotherapeutics. Full article

Seal lice (Anoplura) parasitize amphibious hosts, such as pinnipeds, and are uniquely adapted to an oceanic environment. As obligate, permanent ectoparasites feed on the blood of their hosts and are completely dependent on them. While studies have begun to explore general diving adaptations, research into seal lice’s sensory biology remains limited. In contrast to the vast majority of insects, including human lice, seal lice are devoid of eyes and depend on antennal sensory reception. This study aims to describe the morphology and putative function of antennal sensilla in five seal lice species: Antarctophthirus microchir, A. carlinii, A. lobodontis, A. ogmorhini, and Lepidophthirus macrorhini, which parasitize the South American sea lion, Weddell seal, crabeater seal, leopard seal, and southern elephant seal, respectively. The antennal structures of each species were analyzed using scanning electron microscopy, and eight morphotypes were identified: spine, cuticular lobe, sensilla squamiformia, sensilla chaetica, sensilla basiconica I and II, tuft organs, and pore organs. The morphology of sensilla and their distribution on the antennal flagellum exhibited variability among genera and species. For instance, the southern elephant louse (Lepidophthirus macrorhini) is characterized by the presence of sensilla squamiformia, while Antarctophthirus spp. are distinguished by sensilla chaetica. Full article

Statistical optimization methods serve as fundamental tools for studying sea-ice-related phenomena in the polar regions. To comprehensively analyze the spatial distributions of ice ridge keels, including the draft and spacing distributions, a statistical optimization model was developed with the aim of determining the optimal keel cutoff draft, which differentiates ice ridge keels from sea ice bottom roughness. By treating the keel cutoff draft as the identified variable and minimizing the relative errors between the theoretical and measured keel spatial distributions, the developed model aimed to seek the optimal keel cutoff draft and provide a precise method for this differentiation and to explore the impact of the ridging intensity, defined as the ratio of the mean ridge sail height to spacing, on the spatial distributions of the ice ridge keels. The utilized data were obtained from observations of sea ice bottom undulations in the Northwestern Weddell Sea during the winter of 2006; these observations were conducted using helicopter-borne electromagnetic induction (EM-bird). Through rigorous analysis, the optimal keel cutoff draft was determined to be 3.8 m, and this value was subsequently employed to effectively differentiate ridge keels from other roughness features on the sea ice bottom. Then, building upon our previous research that clustered measured profiles into three distinct regimes (Region 1, Region 2, and Region 3, respectively), a detailed statistical analysis was carried out to evaluate the influence of the ridging intensity on the spatial distributions of the ice ridge keels for all three regimes. Notably, the results closely matched the predictions of the statistical optimization model: Wadhams’80 function (a negative exponential function) exhibited an excellent fit with the measured distributions of the keel draft, and a lognormal function proved to effectively describe the keel spacing distributions in all three regimes. Furthermore, it was discovered that the relationship between the mean ridge keel draft and frequency (number of keels per kilometer) could be accurately modeled by a logarithmic function with a correlation coefficient of 0.698, despite considerable data scatter. This study yields several significant results with far-reaching implications. The determination of the optimal keel cutoff draft and the successful modeling of the relationship between the keel draft and frequency represent key achievements. These findings provide a solid theoretical foundation for analyzing the correlations between the morphologies of the sea ice surface and bottom. Such theoretical insights are crucial for improving remote sensing algorithms for ice thickness inversion from satellite elevation data, enhancing the accuracy of sea ice thickness estimations. Full article

The Southern Ocean, located between Antarctica and the southern tips of South America, Africa and Australia, encompasses an immense area across the southern Atlantic, Pacific and Indian oceans with no clearly defined limits. For the purposes of studying marine heterobranch sea slugs, we consider the Southern Ocean to include all ocean areas located south of latitude 41° S. South of this latitude, we consider different areas and zones: the area of South America (the Patagonia/Magellanic area), the island of Tasmania, the southern island of New Zealand, the Subantarctic area (the Falkland Islands, South Georgia Island, the South Orkney Islands, South Sandwich Island, Bouvet Island, the islands of Crozet and Prince Edward, the Kerguelen Islands, and Macquarie Island) and the area of Antarctica, in which we consider four zones (Weddell Sea, West Antarctica, Ross Sea and East Antarctica). Reviewing all available references and unpublished data from the authors, in total, 394 species of heterobranch sea slugs have been recorded to date in the Southern Ocean > 41° S, with Nudibranchia standing out with 209 species and Cephalaspidea with 90 species. The marine heterobranchs of Tasmania (154 species) and southern New Zealand (120 species) have been well studied. Sea slug fauna of the Antarctic and Subantarctic regions have been the subject of several partial studies; however, there are still many gaps in knowledge across both areas. Eighty-nine different species of sea slug have been recorded so far in strictly Antarctic waters (West Antarctica, 45 species; Weddell Sea, 48 species; Ross Sea, 51 species; East Antarctica, 42 species), while in the various Subantarctic regions, there are 93 species (36 species from South Georgia, 17 species from the South Orkneys, 12 species from south Sandwich, 6 species from Bouvet, 10 species from Prince Edward and Crozet Islands, 15 species from Kerguelen, 3 species from Macquarie Island, 29 species from the Falkland Islands and 71 species from the coast of South America). In the taxonomic section, for each of the species, the location and the authors of the records are indicated, and for many of the species, interesting biological, taxonomic or biogeographic observations are also provided. The importance of sampling in underexplored areas is discussed, as well as greater-depth sampling for a better understanding of the sea slugs of the Southern Ocean. Full article

Polynyas play a crucial role in polar ecosystems, influencing biodiversity, climate regulation, and oceanic processes. This study employs Synthetic Aperture Radar (SAR) data to determine the optimal sea ice concentration threshold for polynya identification, which is established at 75%. We present a dataset of daily polynya distribution in the Arctic and Antarctic from 2013 to 2022, analyzing their spatial patterns, interannual variability, and seasonal dynamics. Our results indicate that coastal polynyas, primarily located near landmasses, dominate both polar regions. The total polynya area in the Antarctic remained relatively stable, averaging approximately 1.86 × 10⁸ km² per year, with an interannual fluctuation of −3.1 × 10⁵ km² per year. In the Arctic, the average polynya area is around 1.59 × 10⁸ km² per year, with an interannual fluctuation of −7.1 × 10⁵ km² per year. Both regions exhibit distinct seasonal cycles: Arctic polynyas peak in May and reach their minimum in September, whereas Antarctic polynyas expand in November and contract to their smallest extent in February. The polynya formation and development result from a complex interplay of multiple factors, with no single variable fully explaining variations in polynyas’ extent. Additionally, the polynya area in the NOW, and Weddell Sea polynyas, exhibit consistent trends with chlorophyll-a concentration, highlighting their role as critical habitats for primary productivity in polar regions. These findings provide key insights into polynya dynamics and their broader implications for climate and ecological processes in polar regions. Full article

The aim of this study was to investigate the presence of Mycoplasma spp. and their identification in seals from Antarctica. During January and February 2010, 59 Antarctic fur seals (Arctocephalus gazella), 17 Weddell seals (Leptonychotes weddellii), and 5 Southern elephant seals (Mirounga leonina) were captured in three Antarctic islands. Oral and genital samples were collected, cultured, and cloned. The Intergenic Spacer Region 16S-23S rDNA (ISR) PCR products were sent for sequencing. Seventy-four (91.4%) out of the eighty-one seals sampled were PCR positive. From those, 57 isolates were cultured. Mycoplasmas were more prevalent in the mouth in comparison to the reproductive tract. The percentage of isolates were 76.3%, 58.8%, and 40.0% for Antarctic fur seals, Weddell seals, and Southern elephant seals, respectively. The ISR sequences divided the isolates into six clusters. Four clusters presented a very high similarity percentage with mycoplasma sequences obtained from seals. However, none of these mycoplasmas have been described to date. Cluster 1 is also close to M. miroungigenitalium. This study represents the first report of Mycoplasma species adapted to Antarctic pinnipeds. The findings contribute to the understanding of the ecology of mycoplasmas in Antarctic pinnipeds. Full article

The Antarctic sea ice concentration (SIC) plays a crucial role in global climate dynamics by influencing atmospheric and oceanic circulation. This study examines SIC variability and its relationship with major climate modes, including the El Niño-Southern Oscillation (ENSO), Pacific-South American (PSA) pattern, Southern Annular Mode (SAM), and Antarctic Dipole (ADP). Using NSIDC satellite-derived sea ice data and ERA5 reanalysis from 1980 to 2022, we analyzed SIC anomalies in the Weddell, Ross, and Bellingshausen and Amundsen (B&A) Seas, assessing their response to climatic forcings across different timescales. Our findings reveal strong linkages between SIC variability and large-scale atmospheric circulation. ENSO-related teleconnections drive a dipolar SIC response, with warming in the Pacific sector and cooling in the Atlantic during El Niño, and the opposite pattern during La Niña. PSA and ADP further modulate this response by altering Rossby wave propagation and heat fluxes, leading to significant SIC fluctuations. The ADP emerges as a dominant driver of interannual SIC anomalies, showing an out-of-phase relationship between the Atlantic and Pacific sectors of the Southern Ocean. Regional SIC trends exhibit contrasting patterns: the Ross Sea shows a significant positive SIC trend, while the B&A and Weddell Seas experience persistent negative anomalies due to enhanced meridional heat transport and stronger westerly winds. SAM strongly influences SIC, particularly in the Atlantic sector, with delayed responses of up to six months, likely due to ice-albedo feedbacks and ocean memory effects. These results enhance our understanding of Antarctic sea ice variability and its sensitivity to large-scale climate oscillations. Given the observed trends and ongoing climate change, further research is needed to assess how these processes will evolve under future warming scenarios. This study highlights the importance of continuous satellite observations and high-resolution climate modeling for improving projections of Antarctic sea ice behavior and its implications for the global climate system. Full article

Powell Basin is an ocean basin formed as a result of the Scotia Sea evolution. The existing tectonic models propose a variety of starting and ending ages for the spreading of the basin based on seafloor magnetic anomalies. Here, we use recent magnetic field data obtained from eight magnetic profiles in Powell Basin to provide insights into the oceanic spreading evolution. The differences found between the number of anomalies on both sides of the axis and the asymmetry in the spreading rates suggest different opening models for different parts of the basin. We propose a spreading model starting in the late Eocene (38.08 Ma) and ending in the early Miocene (21.8 Ma) for the northern part of Powell Basin. For the southern part, the opening started in the late Eocene (38.08 Ma) and ended in the middle Paleogene (25.2 Ma). The magnetic data have been combined with gravity and sediment thickness data to better constrain the age models. The gravity and sediment thickness information allow us to more accurately locate the position of the extinct spreading axis. Geothermal heat flow measurements are used to understand the relationship between the low amplitudes of the magnetic anomalies and the heat beneath them. Our proposed oceanic spreading models suggest that the initial incursions of the Pacific mantle outflow into the Powell Basin occurred in the Oligocene, and the initial incursions of oceanic currents from the Weddell Sea occurred in the Eocene. Full article

The sea ice extent in the Weddell Sea exhibited a positive trend from the start of satellite observations in 1978 until 2016 but has shown a decreasing trend since then. This study analyzes seasonal and interannual variations in sea ice thickness using ICESat-2 laser altimetry data over the Weddell Sea from 2019 to 2022. Sea ice thickness was calculated from ICESat-2’s ATL10 freeboard product using the Improved Buoyancy Equation. Seasonal variability in ice thickness, characterized by an increase from February to September, is more pronounced in the eastern Weddell sector, while interannual variability is more evident in the western Weddell sector. The results were compared with field data obtained between 2019 and 2022, showing a general agreement in ice thickness distributions around predominantly level ice. A decreasing trend in sea ice thickness was observed when compared to measurements from 2003 to 2017. Notably, the spring of 2021 and summer of 2022 saw significant decreases in Sea Ice Extent (SIE). Although the overall mean sea ice thickness remained unchanged, the northwestern Weddell region experienced a noticeable decrease in ice thickness. Full article

Sea ice and its surface snow are crucial components of the energy cycle and mass balance between the atmosphere and ocean, serving as sensitive indicators of climate change. Observing and understanding changes in snow depth on Antarctic sea ice are essential for sea ice research and global climate change studies. This study explores the feasibility of retrieving snow depth on Antarctic sea ice using data from the Chinese marine satellite HY-2B. Using generic retrieval algorithms, snow depth on Antarctic sea ice was retrieved from HY-2B Scanning Microwave Radiometer (SMR) data, and compared with existing snow depth products derived from other microwave radiometer data. A comparison against ship-based snow depth measurements from the Chinese 35th Antarctic Scientific Expedition shows that snow depth derived from HY-2B SMR data using the Comiso03 retrieval algorithm exhibits the lowest RMSD, with a deviation of −1.9 cm compared to the Markus98 and Shen22 models. The snow depth derived using the Comiso03 model from HY-2B SMR shows agreement with the GCOM-W1 AMSR-2 snow depth product released by the National Snow and Ice Data Center (NSIDC). Differences between the two primarily occur during the sea ice ablation and in the Bellingshausen Sea, Amundsen Sea, and the southern Pacific Ocean. In 2019, the monthly average snow depth on Antarctic sea ice reached its maximum in January (36.2 cm) and decreased to its minimum in May (15.3 cm). Thicker snow cover was observed in the Weddell Sea, Ross Sea, and Bellingshausen and Amundsen seas, primarily due to the presence of multi-year ice, while thinner snow cover was found in the southern Indian Ocean and the southern Pacific Ocean. The derived snow depth product from HY-2B SMR data demonstrates high accuracy in retrieving snow depth on Antarctic sea ice, highlighting its potential as a reliable alternative for snow depth measurements. This product significantly contributes to observing and understanding changes in snow depth on Antarctic sea ice and its relationship with climate change. Full article

The diet and feeding behavior of South Polar Skuas (Stercorarius maccormicki) are well studied within the species’ breeding range but are poorly understood on the Haswell Islands. The aim of this study was to determine how South Polar Skuas use available resources during the pre-breeding and breeding periods at the Haswell Archipelago (66°31′ S, 93°01′ E, Davis Sea, Southern Ocean) under conditions of prolonged human activity. I studied pellets, spontaneous regurgitation, and stomach contents of feathered birds to study the diet of skuas and used direct observations of their feeding behavior. South Polar Skuas at the Haswell Islands fed primarily on the Emperor Penguin (Aptenodytes forsteri) colony and on terrestrial resources in the Adélie Penguin (Pygoscelis adeliae) and fulmarine petrel colonies. The dominant prey of skuas were breeding Antarctic penguins. Emperor Penguins and Adélie Penguins make up the bulk of the skuas’ diet in the pre-breeding and breeding periods. Surface feeding at sea was observed in the post-breeding period. In recent decades, kitchen waste supported the skua population. Scavenging (placenta and feces of Weddell seals [Leptonychotes weddellii], frozen eggs, chicks and adults of breeding bird species, kitchen refuse) is the dominant strategy for obtaining food. Adélie Penguin eggs and chicks were the main food items of the South Polar Skuas in the Haswell Archipelago. Skua predation could potentially influence the breeding success of Adélie Penguins and fulmarine petrels, but the extent of the impact is unknown. The impact of the South Polar Skua on Emperor Penguins is negligible because skuas feed mainly on frozen chicks and eggs of the species. Full article

Domestic dogs are currently recognized as being infected by 25 different canine papillomavirus (CPV) types classified into three genera. A short sequence from a novel CPV type was amplified, along with CPV1, from a papilloma (wart) from the mouth of a dog. The entire 7499 bp genome was amplified, and CPV26 contained putative coding regions that were predicted to produce four early proteins and two late ones. The ORF L1 showed less than 62% similarity for all previously sequenced CPV types but over 69% similarity to multiple Omegapapillomavirus types from a variety of Caniform species including the giant panda, Weddel seal, and polar bear. Phylogenetic analysis confirmed CPV26 clusters within the Omegapapillomavirus genus. Specific primers were used to investigate the presence of CPV26 DNA within a series of 37 canine proliferative lesions. CPV26 DNA was amplified from one lesion, a cutaneous papilloma that also contained CPV6. This is the first time a PV type within the Omegapapillomavirus genus has been detected in a non-domestic species and this provides evidence that the omegapapillomaviruses infected a common ancestor of, and then co-evolved with, the Caniform species. Whether CPV26 causes disease is uncertain, but the absence of an E7 protein may suggest low pathogenicity. Full article

We use hindcasts from a state-of-the-art decadal climate prediction system initialized between 1979 and 2017 to explore the predictability of the Antarctic dipole—that is, the seesaw between sea ice cover in the Weddell and Ross Seas, and discuss its implications for Antarctic sea ice predictability. Our results indicate low forecast skills for the Antarctic dipole in the first hindcast year, with a strong relaxation of March values toward the climatology contrasting with an overestimation of anomalies in September, which we interpret as being linked to a predominance of local drift processes over initialized large-scale dynamics. Forecast skills for the Antarctic dipole and total Antarctic sea ice extent are uncorrelated. Limited predictability of the Antarctic dipole is also found under preconditioning around strong warm and strong cold events of the El Niño-Southern Oscillation. Initialization timing and model drift are reported as potential explanations for the poor predictive skills identified. Full article

The characteristics of sea ice leads (SILs) in the Weddell Sea are an important basis for understanding the mechanism of the atmosphere–ocean system in the Southern Ocean. In this study, we derived the sea ice surface temperature (IST) of the Weddell Sea from MODIS thermal images and then generated a daily SIL map for 2015 and 2022 by utilizing the iterative threshold method on the optimised MOD35 cloud-masked IST. The results showed that SIL variations in the Weddell Sea presented remarkable seasonal characteristics. The trend of the SIL area exhibited an initial rise followed by a decline from January to December, characterised by lower values in spring and summer and higher values in fall and winter. SILs in the Weddell Sea were predominantly concentrated between 70~78°S and 60~30°W. The coastal spatial distribution density of the SILs exceeded that of offshore regions, peaking near the Antarctic Peninsula and then near Queen Maud Land. The SIL variation was mainly influenced by dynamical factors, and there were strong positive correlations between the wind field, ocean currents, and sea-ice motion. Full article

Sea ice fraction (SIF) over the Ross/Amundsen/Bellingshausen Sea (RAB) are investigated using the Modern-Era Retrospective Analysis for Research and Application, Version 2 (MERRA-2), focusing on the differences in time-lagged response to ENSO between the late 20th (1980–2000, L20) and the early 21st century (2001–2021, E21). The findings suggest that the typical Antarctic response to ENSO is influenced by changes in ENSO type/intensity, highlighting the need for caution when investigating the Antarctic teleconnection. Time-lagged regressions onto the mature phase of El Niño reveal that the SIF decrease and SST increase over the RAB is relatively weaker in E21 and most pronounced at 0–4 months lag. Conversely, the SIF in L20 continues to decline and reaches its peak at two-season lag (5–7 months). Tropospheric wind, pressure, and wave activity in response to El Niño in L20 show a zonally oriented high/low-pressure areas with two-season lag, enhancing the poleward flow that plays a key role in sea ice melt in the RAB, while this pattern in E21 is insignificant at the same lag. This study suggests that stronger (weaker) and more eastern (central) Pacific ENSOs on average in L20 (E21) are associated with this decadal change in the SIF response to ENSO. Full article