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The increased availability of quality genomic data has greatly improved the scope and resolution of our understanding of the recent evolutionary history of wild species adapted to extreme environments and their susceptibility to anthropogenic impacts. The guanaco (Lama guanicoe), the largest wild ungulate in South America, is a good example. The guanaco is well adapted to a wide range of habitats, including the Sechura Desert, the high Andes Mountains to the north, and the extreme temperatures and conditions of Navarino Island to the south. Guanacos also have a long history of overexploitation by humans. To assess the evolutionary impact of these challenging habitats on the genomic diversity, we analyzed 38 genomes (∼10 to 16×) throughout their extensive latitudinal distribution from the Sechura and Atacama Desert to southward into Tierra del Fuego Island. These included analyses of patterns of unique differentiation in the north and geographic region further south with admixture among L. g. cacsilensis and L. g. guanicoe. Our findings provide new insights on the divergence of the subspecies ∼800,000 yr BP and document two divergent demographic trajectories and to the initial expansion of guanaco into the more southern portions of the Atacama Desert. Patagonian guanacos have experienced contemporary reductions in effective population sizes, likely the consequence of anthropogenic impacts. The lowest levels of genetic diversity corresponded to their northern and western limits of distribution and some varying degrees of genetic differentiation. Adaptive genomic diversity was strongly linked with environmental variables and was linked with colonization toward the south followed by adaptation., Competing Interests: Conflict of Interest The authors declare that they have no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)

This is one of the first papers to study the ionospheric effects of two solar eclipses that occurred in South America and Antarctica under geomagnetic activity in different seasons (summer and autumn) and their impact on the equatorial ionization anomaly (EIA). The changes in total electron content (TEC) during the 15 February 2018 and 30 April 2022 partial solar eclipses will be analyzed. The study is based on more than 390 GPS stations, Swarm-A, and DMSP F18 satellite measurements, such as TEC, electron density, and electron temperature. The ionospheric behaviors over the two-fifth days on both sides of each eclipse were used as a reference for estimating TEC changes. Regional TEC maps were created for the analysis. Background TEC levels were significantly higher during the 2022 eclipse than during the 2018 eclipse because ionospheric levels depend on solar index parameters. On the days of the 2018 and 2022 eclipses, the ionospheric enhancement was noticeable due to levels of geomagnetic activity. Although geomagnetic forcing impacted the ionosphere, both eclipses had evident depletions under the penumbra, wherein differential vertical TEC (DVTEC) reached values <−40%. The duration of the ionospheric effects persisted after 24 UT. Also, while a noticeable TEC depletion (DVTEC ∼−50%) of the southern EIA crest was observed during the 2018 eclipse (hemisphere summer), an evident TEC enhancement (DVTEC > 30%) at the same crest was seen during the eclipse of 2022 (hemisphere autumn). Swarm-A and DMSP F18 satellite measurements and analysis of other solar eclipses in the sector under quiet conditions supported the ionospheric behavior. [ABSTRACT FROM AUTHOR]

The classification of Cystoclonium obtusangulum has been questioned since the species was first described by Hooker and Harvey as Gracilaria? obtusangula. The objective of this study was to provide the first comprehensive taxonomic analysis of Cystoclonium obtusangulum, based on DNA sequences coupled with morphological observations made on syntype specimens and new collections. Sequence divergences of rbcL, UPA, and COI‐5P, and maximum‐likelihood phylogenies for rbcL and 18S demonstrated that specimens identified as Cystoclonium obtusangulum represent a clade of two distinct species that are distantly related to the generitype Cystoclonium purpureum. A new genus, Meridionella gen. nov., is proposed for this clade. The two species placed in this new genus were morphologically indistinguishable cryptic species, but have disjunct distributions, with Meridionella obtusangula comb. nov. found from temperate to cold coasts of South America and the Falkland Islands and Meridionella antarctica sp. nov., occurring in Antarctic waters. Vegetative and reproductive characters of Meridionella gen. nov. are described, and implications of our results for the biogeography of the family Cystocloniaceae are discussed. [ABSTRACT FROM AUTHOR]

We analyzed the single‐grain mineralogical composition of aeolian dust transported to central East Antarctica for provenance purposes. Comparison with data from the last glacial period shows for the first time disappearance of carbonates during the Holocene related to sea level rise and suppressed deflation from the Argentinean continental shelf, exposed during Marine Isotope Stage 2. Zeolites, related to alteration of volcanic glass in the subglacial/periglacial environment of Patagonia, show a similar behavior. The remaining minerals, remarkably similar between the two climatic periods, are compatible with a Pampean and Patagonian provenance, but Holocene data show a more pronounced volcanic and metamorphic imprint and presence of minerals related to warm climate weathering environments compatible with an additional contribution from subtropical latitudes of South America. These results do not imply a major large‐scale reorganization of atmospheric circulation after the last climatic transition. Plain Language Summary: Aeolian mineral dust particles transported through the atmosphere from the austral continents to the Antarctic ice sheet represent a tracer of atmospheric circulation and transport, as well as being a source of information about environmental conditions within dust source regions. Many lines of evidence suggest that central East Antarctic dust is sourced from South America during the last glacial period, whereas there is not a general consensus about dust provenance during the Holocene. A major limitation to this problem is represented by the extremely low dust concentration in Antarctic ice during interglacials. In this study, we analyzed the single‐grain mineralogy of more than 2,300 mineral dust particles transported by winds to Dome C during four different time windows within the Holocene, the current interglacial. Comparing results with those obtained from dust deposited during the last glacial period, we observe that some minerals that are typically associated to glacial climate conditions in Patagonia almost disappear during Holocene, while the remaining minerals are compatible with a South American provenance in both climate periods. Data thus suggest that the dominant atmospheric circulation patterns did not experience a significant change with climate. However, data suggest an additional contribution from subtropical South American latitudes during Holocene. Key Points: The mineralogy of more than 2,300 aeolian dust particles windblown to central East Antarctica (Dome C) during the Holocene was identifiedDisappearance of carbonate dust during the Holocene relates to sea level rise and suppressed deflation from the Argentinean shelfAeolian dust suggests Pampean and Patagonian provenance in the Holocene and a lower latitude contribution, without major circulation changes [ABSTRACT FROM AUTHOR]

Global biodiversity is both declining and being redistributed in response to multiple drivers characterizing the Anthropocene, including synergies between biological invasions and climate change. The Antarctic marine benthos may constitute the last biogeographic realm where barriers (oceanographic currents, climatic gradients) have not yet been broken. Here we report the successful settlement of a cohort of Mytilus cf. platensis in a shallow subtidal habitat of the South Shetland Islands in 2019, which demonstrates the ability of this species to complete its early life stages in this extreme environment. Genetic analyses and shipping records show that this observation is consistent with the dominant vectors and pathways linking southern Patagonia with the Antarctic Peninsula and demonstrates the potential for impending invasions of Antarctic ecosystems.

Contaminant levels are lower in Antarctica than elsewhere in the world because of its low anthropogenic activities. However, the northern region of the Antarctic Peninsula, is close to South America and experiences the greatest anthropogenic pressure in Antarctica. Here, we investigated, in two Antarctic Peninsula islands, intra and interspecific factors that influence the concentrations of 17 trace elements (TEs) in blood and feathers of three penguin species breeding sympatrically in relation to their trophic ecology assessed via a stable isotopic approach (C, N and S). Geographical location, foraging zone (δ 13 C and δ 34 S) and diet influences the interspecific difference, and sex and maturity stage diet influence the intraspecific difference of Pygoscelis penguins. Penguins from Livingston showed higher values (mean, ng. g -1 , dry weight - dw) of Zn (103), Mn (0.3), and Fe (95) than those from King George Island (Zn: 80, Mn: 1.9, and Fe: 11). Gender-related differences were observed, as males showed significantly higher values (mean, ng. g -1 , dw) of Rb (3.4) and δ 15 N in blood of gentoo, and Ca (1344) in Adélie feathers. Chicks of gentoo and Adélie presented higher Zn, Mg, Ca, and Sr and lower 13 C values in blood than adults. The highest concentrations (mean, ng. g -1 , dw) of Cd (0.2) and Cu (26), and the lowest δ 15 N values were found in chinstrap. Geographical, intraspecific (i.e., ontogenetic and gender-related) and interspecific differences in feeding seemed to have influenced TE and stable isotope values in these animals. The TE bioaccumulation by penguins may have also been influenced by natural enrichment in environmental levels of these elements, which seems to be the case for Fe, Zn, and Mn. However, the high level of some of the TEs (Mn, Cd, and Cr) may reflect the increase of local and global human activities., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The Drake Passage is an oceanic gateway of about 850 km width located between South America and the Antarctic Peninsula that connects the southeastern Pacific Ocean with the southwestern Atlantic Ocean. It is an important gateway for mantle flow, oceanographic water masses, and migrations of biota. This sector developed within the framework of the geodynamic evolution of the Scotia Arc, including continental fragmentation processes and oceanic crust creation, since the oblique divergence of the South American plate to the north and the Antarctic plate to the south started in the Eocene. As a consequence of its complex tectonic evolution and subsequent submarine processes, as sedimentary infill and erosion mainly controlled by bottom currents and active tectonics, this region shows a varied physiography. We present a detailed map of the bathymetry and geological setting of the Drake Passage that is mainly founded on a new compilation of precise multibeam bathymetric data obtained on 120 cruises between 1992 and 2015, resulting in a new Digital Bathymetric Model with 200 × 200 m cell spacing. The map covers an area of 1,465,000 km2 between parallels 52°S and 63°S and meridians 70°W and 50°W at scale 1:1,600,000 allowing the identification of the main seafloor features. In addition, the map includes useful geological information related to magnetism, seismicity and tectonics. This work constitutes an international cooperative effort and is part of the International Bathymetric Chart of the Southern Ocean project, under the Scientific Committee on Antarctic Research umbrella. [ABSTRACT FROM AUTHOR]

Antarctic trace element records could provide important insights into the impact of human activities on the environment over the past few centuries. In this study, we investigated the atmospheric concentrations of 14 representative heavy metals (Al, As, Cd, Co, Cu, Fe, K, Mg, Mn, Pb, Sb, Sr, Tl and V) from 174 samples collected in a 4-m snow pit at Dome Argus (Dome A) on the East Antarctic Plateau, covering the period from 1950 to 2016 A.D. We found great variability in the annual concentration of all metals. The crustal enrichment factors suggest that the concentrations of some heavy metals (Cd, Sb, Cu, As and Pb) were likely influenced by anthropogenic activities in recent decades. An analysis of source regions suggests that heavy metal pollution at Dome A was largely caused by human activities in Australia and South America (e.g. mining production, leaded gasoline). Based on the relationship between the trace elements fluxes and sea ice concentration (SIC), sea surface temperature (SST) and annual mean air temperature at 2 m above the ground (T 2m ), our analysis shows that deposition and transport of atmospheric aerosol at Dome A were influenced by circum-Antarctic atmospheric circulations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Polydolopidae is a family of Palaeogene marsupials recorded from outcrops in southern South America and the Antarctic Peninsula. They are mostly represented by skull fragments or maxillary, dentary and molar remains. A taxonomic and systematic revision is carried out with the inclusion of a phylogenetic analysis encompassing almost every polydolopid species and five marsupial species found to be related to them in previous analyses (Bonapartherium hinakusijum , Epidolops ameghinoi , Microbiotherium tehuelchum , Prepidolops didelphoides and Roberthoffstetteria nationalgeographica). The Polydolopidae was recovered as a monophyletic group, even though no resolution about its sister-group can be found. The following genera are recovered: Antarctodolops , Amphidolops , Archaeodolops , Eudolops , Hypodolops gen. nov. , Kramadolops , Pliodolops , Pseudolops and two unidentified genera (Gen. et sp. indet 1 and 2). One genus and three new species are recognized. The family appeared at the beginning of the Palaeocene and disappeared during the Early Oligocene. The extinction of the group could be related to climatic deterioration in the Early Oligocene, when temperature and the humidity dropped, provoking desertification in the region where Polydolopids evolved. [ABSTRACT FROM AUTHOR]

We here investigate the spatial and temporal variability of eolian dust particle sorting recorded in the Dome B (77° 05′ S, 94° 55’ E) ice core, central East Antarctica, during Marine Isotope Stage (MIS) 2. We address the question whether such changes reflect variable transport pathways from a unique source area or rather a variable apportionment from diverse Southern Hemisphere sources transported at different elevation in the troposphere. The Sr-Nd radiogenic isotope composition of glacial dust samples as well as single-particle Raman mineralogy support the hypothesis of a single dust provenance both for coarse and fine mode dust events at Dome B. The southern South American provenance of glacial dust in Antarctica deduced from these results indicate a dust composition coherent with a mixture of volcanic material and minerals derived from metamorphic and plutonic rocks. Additionally, Dome B glacial samples contain aragonite particles along with diatom valves of marine benthic/epiphytic species and freshwater species living today in the northern Antarctic Peninsula and southern South America. These data suggest contribution from the exposed Patagonian continental shelf and glacial outwash plains of southern Patagonia at the time when sea level reached its minimum. Our results confirm that dust sorting is controlled by the relative intensity of the two main patterns of tropospheric dust transport onto the inner Plateau, i.e. fast low-level advection and long-range high-altitude transport including air subsidence over Antarctica. [ABSTRACT FROM AUTHOR]

Recent studies show that the ozone layer will recover by the middle part of this century. This is a significant result arising from the Montreal Protocol, and highlights the success of this environmental protection agreement. Climate change projections show that Total Ozone Content (TOC) levels will increase significantly by the end of this century, mainly at higher latitudes. This increase may result in a reduction of the adverse effects of UV radiation overexposure. By contrast, reduced UV radiation levels at the surface of the Earth can result in reduced levels of vitamin D synthesis among the inhabitants of these regions. In this study we provide estimates for the UVI, erythemal, and vitamin-D weighted daily doses for ten different locations in South America and Antarctica. Our calculations were based on ozone projections provided by climate models set forth in the last IPCC report. Results show that the increase of TOC levels in middle and high latitude regions may result in decreased UVI and UV doses throughout the century. In high latitudes, erythemal doses and vitamin D synthesis doses may be reduced by up to 22 and 39%, respectively, if anthropogenic emissions continue to rise throughout the century. Furthermore, there may be reductions of up to 9 and 12%, respectively, in mid-latitudes (20°S to 35°S). Significant variations at Equatorial sites were not observed. In most of South America, the attenuation in UVR caused by increases in TOC during the 21st century is neither enough to promote protective effects from this radiation, nor for the lack of UVR for vitamin D synthesis. The incidence of UVR in tropical and sub-tropical areas of the continent will continue to be a public health risk for the entire 21st century during all seasons, regardless of the climatic scenarios. Our results can be used as an important tool for health studies focusing on the excess and/or lack of sun exposure. [ABSTRACT FROM AUTHOR]

This paper describes the first results of polycyclic aromatic hydrocarbons (PAHs) and spheroidal carbonaceous particles (SCPs) in sediment cores of Admiralty Bay, Antarctica. These markers were used to assess the local input of anthropogenic materials (particulate and organic compounds) as a result of the influence of human occupation in a sub-Antarctic region and a possible long-range atmospheric transport of combustion products from sources in South America. The highest SCPs and PAHs concentrations were observed during the last 30 years, when three research stations were built in the area and industrial activities in South America increased. The concentrations of SCPs and PAHs were much lower than those of other regions in the northern hemisphere and other reported data for the southern hemisphere. The PAH isomer ratios showed that the major sources of PAHs are fossil fuels/petroleum, biomass combustion and sewage contribution generally close to the Brazilian scientific station. [Copyright &y& Elsevier]

Abstract: Anatomically preserved gymnosperm axes are relatively abundant in Permian localities of Antarctica, but their anatomy has rarely been studied in detail, which limits comparison with other Gondwanan morphotaxa. Here we describe a silicified trunk collected from the Upper Permian Buckley Formation at Coalsack Bluff, in the central Transantarctic Mountains. The trunk has a small heterogeneous pith approximately 4mm in diameter containing conspicuous sclerotic nests, endarch primary xylem maturation, paired leaf traces, and secondary xylem of the Araucarioxylon type. Comparison with contemporaneous gymnosperm axes from Antarctica indicates that the Coalsack Bluff trunk represents a new Permian morphotaxon for the region. The anatomical characters of the pith and secondary xylem suggest an affinity with the genus Kaokoxylon Kräusel, previously reported from Permian and Triassic localities of Southern Africa, South America, India, and Australia. [Copyright &y& Elsevier]

Forty-one species in five genera of bitentaculate cirratulids are reported from new collections from South America, the Southern Ocean, and seas around Antarctica. Twenty-seven species are new to science; one new genus is described to deal with some species formerly identified as Chaetozone. New records, synonymies, and new combinations are reported. Previous records are reviewed with type specimens of most species reexamined and redescribed. The sub-Antarctic species Aphelochaeta cincinnata (Ehlers, 1908) does not occur in Antarctica: the numerous published records of this species instead belong to several new species. The types of Tharyx epitocus Monro, 1930, and Tharyx fusiformis Monro, 1939, have spines in posterior setigers and are referred to other genera. Among the 41 species treated in this study, 11 belong to Aphelochaeta, eight are new; eight species belong to Caulleriella, six are new; six species belong to Chaetocirratulus n. gen., three are new; 12 species belong to Chaetozone, seven are new; and four species belong to Tharyx, three are new. Numerous samples come from slope and abyssal depths, expanding our knowledge of the distribution of Southern hemisphere deep-sea cirratulids.

From an inversion of ≈7000 crossings of 37 magnetic reversals between chrons C1n (0.78 Ma) and C13 (33.7 Ma) and numerous crossings of 43 transform faults and fracture zones in the central and southern Atlantic basin, we estimate finite rotations and stage angular velocities that describe South America plate motion relative to Africa (Nubia), and via plate circuit closures relative to the Antarctic and North America plates. Our newly estimated Nubia–South America rotations, which are spaced at ≈1-Myr intervals, reveal for the first time a transition from steady motion before 24–22 Ma to continuously slowing motion since 20 Ma, including a previously unknown, sudden spreading rate slowdown at 7–6 Ma, when similar declines in seafloor spreading rates also occurred in the northern Atlantic and Arctic basins and along the Southwest Indian Ridge. Geodetic measurements from Nubia and South America, which record the instantaneous plate motion, corroborate the slowdown and indicate it has continued to the present. Our newly determined North America–South America rotations and angular velocities indicate that the pole for this plate pair was stationary from 20 to 12 Ma, but has migrated steadily southward since ≈12 Ma, causing the plate motion direction to change by up to 90° anticlockwise along parts of the diffuse oceanic plate boundary. Since ≈14 Ma, the plate motion rates have averaged 3±0.5 mm yr−1 of N–S to NW–SE-directed divergence near the Mid-Atlantic Ridge and 1–2 mm yr−1 of obliquely convergent motion near the Lesser Antilles Trench, consistent with geodetic estimates. Our new Antarctic–South America rotations and angular velocities predict that American–Antarctic Ridge seafloor spreading rates and plate slip directions have slowed gradually by 60 per cent and rotated 5–7° clockwise since 20 Ma in response to the post-20 Ma slowdown in Nubia–South America seafloor spreading rates. Fracture zone flow lines that are predicted with the new Antarctic–South America rotations agree well with the trends of fracture zone valleys and ridges that flank the American–Antarctic Ridge, offering independent evidence for the accuracy of our new rotations. The Antarctic–South America rotations for chrons C5n.2 (11.1 Ma) and C6no (19.7 Ma) predict that 15–40 km less seafloor has accreted since these times than is indicated by identifications of these two reversals along the American–Antarctic Ridge. Slow westwards movement of the previously postulated Sur microplate with respect to the South America plate may explain the discrepancy—a strong test of this hypothesis awaits better magnetic anomaly data from this remote seafloor spreading centre. [ABSTRACT FROM AUTHOR]

To better understand the biodiversity-biogeographic polar connections between southern South America and Antarctica (SSA & A), we used benthic communities of hydroids as a model to investigate marine assemblages by evaluating classic spatial divisions at different geographical resolutions. Using a georeferenced dataset of 249 species and multivariate analyses, we investigated species' distribution, composition and biogeographic connectivity, and defined assemblages of ecoregions and provinces for the area. Hotspots of rich biodiversity at risk of depletion were defined. Analyses of ecoregions have a more stratified biogeographic structure, and reveal critical regions susceptible to loss of diversity. Analyses of provinces show a clear division between Atlantic-Pacific and Antarctic-Subantartic assemblages, with high biogeographic isolation of the Subantarctic islands. Depending on spatial resolution, the biogeographic position of the Magellan area is spatially contradictory, clustering on the one hand with SSA ecoregions and on the other with Antarctic provinces. Our patterns appear to be driven by different combinations of processes and barriers, reflected in the stratified distribution of hydroids. The high level of endemism and concentration of species at the edge of distribution in the Magellan area and Scotia Arc suggest their transitional nature and particular importance for understanding the historical and ecological connections between SSA & A. [ABSTRACT FROM AUTHOR]

Mineral dust aerosols represent an active component of the Earth's climate system, by interacting with radiation directly, and by modifying clouds and biogeochemistry. Mineral dust from polar ice cores over the last million years can be used as paleoclimate proxy, and provide unique information about climate variability, as changes in dust deposition at the core sites can be due to changes in sources, transport and/or deposition locally. Here we present results from a study based on climate model simulations using the Community Climate System Model. The focus of this work is to analyze simulated differences in the dust concentration, size distribution and sources in current climate conditions and during the Last Glacial Maximum at specific ice core locations in Antarctica, and compare with available paleodata. Model results suggest that South America is the most important source for dust deposited in Antarctica in current climate, but Australia is also a major contributor and there is spatial variability in the relative importance of the major dust sources. During the Last Glacial Maximum the dominant source in the model was South America, because of the increased activity of glaciogenic dust sources in Southern Patagonia-Tierra del Fuego and the Southernmost Pampas regions, as well as an increase in transport efficiency southward. Dust emitted from the Southern Hemisphere dust source areas usually follow zonal patterns, but southward flow towards Antarctica is located in specific areas characterized by southward displacement of air masses. Observations and model results consistently suggest a spatially variable shift in dust particle sizes. This is due to a combination of relatively reduced en route wet removal favouring a generalized shift towards smaller particles, and on the other hand to an enhanced relative contribution of dry coarse particle deposition in the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

We have measured black carbon (BC) concentrations at Syowa Station, Antarctica, since February 2005. The measured BC concentrations in 2005–2016 were corrected to equivalent BC (EBC) concentrations using Weingartner's method. Seasonal features of EBC concentrations, long-range transport from mid-latitudes to the Antarctic coast, and their origins were characterized. Results show that daily median EBC concentrations were below the detection limit (0.2 ng m -3) to 63.8 ng m -3 at Syowa Station (median, 1.8 ng m -3 ; mean, 2.7 ng m -3 during the measurement period of February 2005–December 2016). Although seasonal features and year-to-year variations in EBC concentrations were observed, no long-term trend of EBC concentrations was clear during our measurement period. Seasonal features of EBC concentrations showed a spring maximum during September–October at Syowa Station. To elucidate EBC transport processes, origins, and the potential source area (PSA), we compared EBC data to backward trajectory analysis and chemical transport model simulation. From comparison with backward trajectory, high EBC concentrations were found in air masses from the marine boundary layer. This finding implies that transport via the marine boundary layer was the most important transport pathway to EBC concentrations at Antarctic coasts. Some EBC was supplied to the Antarctic region by transport via the upper free troposphere. Chemical transport model simulation demonstrated that the most important origins and PSA of EBC at Syowa Station were biomass burning in South America and southern Africa. Fossil fuel combustion in South America and southern Africa also have important contributions. The absorption Ångström exponent (AAE) showed clear seasonal features with 0.5–1.0 during April–October and maximum (1.0–1.5) in December–February. The AAE features might be associated with organic aerosols and mixing states of EBC. [ABSTRACT FROM AUTHOR]

Abstract: The South America–Antarctica plate system shows many oceanic accretionary systems and subduction zones that initiated and then stopped. To better apprehend the evolution of the system, geodynamic reconstructions (global) have been created from Jurassic (165Ma) to present, following the techniques used at the University of Lausanne. However, additional synthetic magnetic anomalies were used to refine the geodynamics between 33Ma and present. The reconstructions show the break up of Gondwana with oceanisation between South America (SAM) and Antarctica (ANT), together with the break off of ‘Andean’ geodynamical units (GDUs). We propose that oceanisation occurs also east and south of the Scotian GDUs. Andean GDUs collide with other GDUs crossing the Pacific. The west coast of SAM and ANT undergo a subsequent collision with all those GDUs between 103Ma and 84Ma, and the Antarctic Peninsula also collides with Tierra del Fuego. The SAM–ANT plate boundary experienced a series of extension and shortening with large strike-slip component, culminating with intra-oceanic subduction leading to the presence of the ‘V-’ and ‘T-’ anomalies in the Weddell Sea. From 84Ma, a transpressive collision takes place in the Scotia region, with active margin to the east. As subduction propagates northwards into an old and dense oceanic crust, slab roll-back initiates, giving rise to the western Scotia Sea and the Powell Basin opening. The Drake Passage opens. As the Scotian GDUs migrate eastwards, there is enough space for them to spread and allow a north–south divergence with a spreading axis acting simultaneously with the western Scotia ridge. Discovery Bank stops the migration of South Orkney and ‘collides with’ the SAM–ANT spreading axis, while the northern Scotian GDUs are blocked against the Falkland Plateau and the North-East Georgia Rise. The western and central Scotia and the Powell Basin spreading axes must cease, and the ridge jumps to create the South Sandwich Islands Sea. The Tierra del Fuego–Patagonia region has always experienced mid-oceanic ridge subduction since 84Ma. Slab window location is also presented (57–0Ma), because of its important implication for heat flux and magmatism. [Copyright &y& Elsevier]

Current climate models project that Antarctic sea ice will decrease by the end of the twenty-first century. Previous studies have suggested that Antarctic sea ice changes have impacts on atmospheric circulation and the mean state of the Southern Hemisphere. However, little is known about whether Antarctic sea ice loss may have a tangible impact on climate extremes over the southern continents and whether ocean–atmosphere coupling plays an important role in changes of climate extremes over the southern continents. In this study, we conduct a set of fully coupled and atmosphere-only model experiments forced by present and future Antarctic sea ice cover. It is found that the projected Antarctic sea ice loss by the end of the twenty-first century leads to an increase in the frequency and duration of warm extremes (especially warm nights) over the southern continents and a decrease in cold extremes over most regions. The frequency and duration of wet extremes are projected to increase over South America and Antarctica, whereas changes in dry days and the longest dry spell vary with regions. Further Antarctic sea ice loss under a quadrupling of CO2 leads to similar but larger changes. Comparison between the coupled and atmosphere-only model experiments suggests that ocean dynamics and their interactions with the atmosphere induced by Antarctic sea ice loss play a key role in driving the identified changes in temperature and precipitation extremes over southern continents. By comparing with global warming experiments, we find that Antarctic sea ice loss may affect temperature and precipitation extremes for some regions under greenhouse warming, especially Antarctica. [ABSTRACT FROM AUTHOR]

Contrasting the extensive research on summer atmospheric rivers (ARs) in the Antarctic Peninsula (AP), winter AR impacts are less understood. This study examines a unique warming event from 1 to 3 July 2023, using in situ winter observations and ERA5 reanalysis. On 2 July, Frei station experienced an extreme warm event with a temperature of 2.7°C and a significant rise in the freezing level, coinciding with winter rainfall. A pressure dipole pattern over the AP, with contrasting circulations over Bellingshausen and Weddell Seas, facilitated an AR, carrying warm, humid air initially from South America/Atlantic and then the southeast Pacific. This shift resulted in anomalous water stable isotope composition in precipitation. Trends suggest a strengthening winter pressure dipole, associated with increased AR frequency and higher temperatures in northern AP. These findings highlight the importance of winter observations in exploring AR impacts, bridging knowledge gaps about winter AR behaviors. Plain Language Summary: The Antarctic Peninsula is increasingly witnessing climate extremes during summer, while the understanding of such extremes in winter remains limited. Our study explores a significant warming event in the northern Peninsula in early July 2023, utilizing recent winter in situ observations and atmospheric analysis. On 2 July, an exceptional temperature of 2.7°C was recorded, significantly altering the atmospheric freezing level and causing rainfall instead of snow. Our analysis revealed a unique atmospheric pattern around the Peninsula, characterized by varying air movements over the Bellingshausen and Weddell Seas. This pattern facilitated an "atmospheric river," a flow of warm and moist air from lower latitudes, including continental South America/Atlantic and the southeast Pacific, as reflected in the precipitation's water stable isotope composition. This event is indicative of a potential trend toward more frequent and severe occurrences, emphasizing the urgent need for comprehensive winter research in the Antarctic Peninsula to understand the broader implications of extreme weather events and climate change. Key Points: Early July 2023 had extreme winter warmth with rainfall in the northern Antarctic Peninsula, favored by an atmospheric riverIn recent decades, strengthened winter pressure dipole has directed northerly warm and moist air, resulting in warm events in the regionWe highlight the need for expanded winter research in the Antarctic Peninsula to better understand climate change and extreme weather events [ABSTRACT FROM AUTHOR]

Purpose: Pinaceae (pine family) trees are native to the Northern Hemisphere and their invasion into the Southern Hemisphere is a growing problem threatening biological diversity. Pinaceae are ectomycorrhizal (ECM) and their invasions are facilitated by non-native and co-invasive ECM fungi. Nothofagaceae species (southern beeches) are dominant overstory trees across large swaths of the Southern Hemisphere and are the only widespread ECM trees native to southern South America (SSA). This observational study investigates the in situ impact of Pinaceae invasions upon native soil fungi associated with Nothofagaceae hosts in SSA. Methods: We performed soil nutrient testing and metabarcode sequencing of fungi in the rhizosphere of Nothofagus antarctica and Nothofagus dombeyi invaded by Pinaceae trees to determine whether co-invasive fungi might impact native soil fungi. Sampling transects extended from invasions into adjacent Nothofagus stands without invasive Pinaceae. Results: The fungal community composition of the Nothofagaceae rhizosphere was dominated by plant-associated Mortierellaceae OTUs in metabarcode data. Mortierellaceae OTU relative abundance was significantly reduced near invasions of Pinus contorta (Pinaceae). Invasions of Pseudotsuga menziesii (Pinaceae) and Pinus contorta were associated with reduced relative abundance of Nothofagus-associated ECM OTUS in the Nothofagus rhizosphere. Pinus contorta invasions were also associated with reduced soil organic matter, total carbon, total phosphorus, and total nitrogen. Conclusion: Further empirical study is warranted to investigate the hypothesis that Mortierellaceae and Pinaceae-specific /suillus-rhizopogon ECM fungi compete for nutrients bound in soil organic matter. Such competition may have potential long-term legacy effects upon post-invasion restoration efforts and implications for Pinaceae invasions globally. [ABSTRACT FROM AUTHOR]

Three east Antarctic ice cores (Dome B, EPICA-Dome C and Komsomolskaia) give evidence for a uniform dust input to the polar plateau during the last glacial maximum (LGM)/Holocene transition (20 to 10 kyr BP) and the87Sr/86Sr versus143Nd/144Nd isotopic signature of the mineral particles highlights a common provenance from southern South America at that time. However, the size distribution of dust from the three ice cores highlights important differences within the east Antarctic during the LGM and shows clearly opposite regional trends during the climatic transition. Between Dome B and Dome C the timing of these changes is also different. A geographical diversity also arises from the different phasing of the short-term (multi-secular scale) dust size oscillations that are superposed at all sites on the main trends of glacial to interglacial changes. We hypothesize the dust grading is controlled by size fractionation inresponse to its atmospheric pathway, either in terms of horizontal trajectory or in altitude of transport. Such mechanism is supported also by the dust size changes observed during a volcanic event recorded in Vostok ice. Ice core dust size data suggest preferential upper air subsidence over the EDC-KMS region and easier penetration of relatively lower air masses to the DB area during the LGM. At the end of the last glacial period and during the climatic transition the region of relatively higher subsidence progressively moved southward. The scenario proposed, supported also by the LGM/Holocene regional changes of snow accumulation, likely operates even at sub-millennial time scale. [ABSTRACT FROM AUTHOR]

Despite their perceived inaccessibility, the marine intertidal and benthic environments of Antarctica, southern Africa and South America have continued to provide marine natural products for chemists with unique opportunities to study the secondary metabolite constituents and chemical ecology of a diverse array of marine gastropod molluscs. This review covers the literature up to 31 January 2005 and describes the structures and, where applicable, biological activities of 100 secondary metabolites isolated from 21 species of marine gastropod molluscs. Not unexpectedly, the chemistry of chemically defended shell-less opisthobranchs dominates the natural product studies of molluscs collected from these regions of the southern hemisphere.

The Scotia Sea is a complex geological area located in the Southern Ocean which evolution is closely linked to the opening of the Drake Passage. Structural highs of continental nature derived from the former continental bridge between South America and the Antarctic Peninsula surround the abyssal plains of the Scotia Sea, restricting small isolated sedimentary basins along its southern margin. Morpho-structural and seismo-stratigraphic analyses of multichannel seismic reflection profiles, and additional geophysical data available in the region, have been conducted, decoding regional and global implications of the basins' evolution. The main aim of this work is to describe the stratigraphic evolution of the southern Scotia Sea basins, from their opening in the back-arc tectonic context of the Scotia Sea, to the last oceanographic changes which have carried on global climatic implications. The evolution of the south Scotia Sea occurred through two major tectonic stages registered in the sedimentary record of the region: 1) the end of the subduction in the northwest part of the Weddell Sea during the early Miocene, which shortened the back-arc subduction trench generating a major change in the regional tectonic field that determined the evolution of the southern basins towards two different types of passive margins: magma-poor and magma-rich; and 2) the full development of the southern Scotia Sea basins during the middle Miocene, that led to the opening of deep oceanic gateways along the South Scotia Ridge. Interplay among tectonics, oceanography and climate is proposed to control the regional sedimentary stacking pattern, with coeval changes globally identified. [ABSTRACT FROM AUTHOR]

The native solitary ascidian Corella eumyota Traustedt, 1882) is commonly found in the Southern Hemisphere in the cold-temperate waters of the Subantarctic and Antarctic regions. Its recent spread into the Northern Hemisphere throughout the NE Atlantic gave the species the status of invasive. Together with its widespread distribution, reports on its wide variability (several distinct morphological characters, genetic discontinuities and also possible misidentifications) cast doubt on the taxonomic status of different populations of this species. This work, based on the observation, quantification and analysis of specific morphological characters in specimens collected at five different localities of South America and Antarctica, strongly indicates that there are two different species: C. eumyota from South America and Corella antarctica Sluiter, 1905) from Antarctica, which has been till now considered a junior synonym of the former. The species clearly differ in the arrangement of the gonadal ducts, the size of the larvae and the shape of the anus, among other characters. Morphological variation displays a defined, discrete grouping supporting a clear differentiation into two species. This result shows the need for careful inspection of specimens to avoid wrong interpretations in a context of changes of marine biota due to biological invasions. [ABSTRACT FROM AUTHOR]

The morphology of corellids (Ascidiacea) has led to numerous misidentifications and wrong taxonomic decisions over the last century. Paradoxically, the morphology has also enabled new species to be identified and ancient entities to be re-established in the Southern Hemisphere. There are many examples of the integration of morphological and molecular data leading to the same taxonomic conclusions, and therefore we aimed to analyse DNA sequences of the gene cytochrome oxidase subunit I of currently accepted species within Corellidae occurring in the Southern Hemisphere. Haplotype networks along with phylogenetic trees and genetic distances not only corroborate the distinction between Corella eumyota and Corella antarctica, but also separate the latter into two potential groups, one located in Terre Adélie and the other in the Antarctic Peninsula (AP). Furthermore, the C. antarctica group from the AP was closely related to the allied abyssal species, Corynascidia suhmi from Terre Adélie. Although the number of new sequences is reduced, our results are congruent with a long record of suspicion on the matter and stress the need for deeper and more extensive investigation of this ascidian family. [ABSTRACT FROM AUTHOR]

Lepidoziaceae are the third‐largest family of liverworts, with about 860 species distributed on all continents. The evolutionary history of this family has not been satisfactorily resolved, with taxa such as Micropterygioideae yet to be included in phylogenetic analyses. We inferred a dated phylogeny of Lepidoziaceae using a data set consisting of 13 genetic markers, sampled from 147 species. Based on our phylogenetic estimate, we used statistical dispersal‐vicariance analysis to reconstruct the biogeographic history of the family. We inferred a crown age of 197 Ma (95% credible interval 157–240 Ma) for the family in the Australian region, with most major lineages also originating in the same region. Micropterygioideae are placed as the sister group to Lembidioideae, with these two lineages diverging from each other about 132 Ma in the South American–Australian region. With South America and Australia being connected through Antarctica at the time, our results suggest a circum‐Antarctic link between Micropterygioideae and the rest of the family. Crown Micropterygioideae were inferred to have arisen 45 Ma in South America before the continent separated from Antarctica. Extinction from southern temperate regions might explain the present‐day restriction of Micropterygioideae to the Neotropics. Our study reveals the influence of past geological events, such as continental drift, on the evolution and distribution of a widespread and diverse family of liverworts. [ABSTRACT FROM AUTHOR]

Aim: The homogenisation of historically isolated gene pools has been recognised as one of the most serious conservation problems in the Antarctic. Lichens are the dominant components of terrestrial biotas in the Antarctic and in high mountain ranges of southern South America. We study the effects of dispersal strategy and migration history on their genetic structure to better understand the importance of these processes and their interplay in shaping population structure as well as their relevance for conservation. Location: Maritime Antarctic and southern South America. Methods: Populations of three fruticose lichen species, Usnea aurantiacoatra, U. antarctica and Cetraria aculeata, were collected in different localities in the Maritime Antarctic and southern South America. Usnea aurantiacoatra reproduces sexually by ascospores, whereas the other two species mostly disperse asexually by symbiotic diaspores. Samples were genotyped at 8–22 microsatellite loci. Different diversity and variance metrics, Bayesian cluster analyses and Discriminant Analysis of Principal Components (DAPC) were used to study population genetic structure. Historical migration patterns between southern South America and the Antarctic were investigated for U. aurantiacoatra and C. aculeata by approximate Bayesian computation (ABC). Results: The two vegetative species display lower levels of genetic diversity than U. aurantiacoatra. Antarctic populations of C. aculeata and South American populations of U. aurantiacoatra display much stronger genetic differentiation than their respective counterparts on the opposite side of the Drake Passage. Usnea antarctica was not found in South America but shows comparably low levels of genetic differentiation in Antarctica as those revealed for U. aurantiacoatra. Phylogeographic histories of lichens in the region differ strongly with recent colonisation in some instances and potential in situ persistence during Last Glacial Maximum (LGM) in others. Patterns of genetic diversity indicate the presence of glacial refugia near Navarino Island (South America) and in the South Shetland Islands. ABC analyses suggest that C. aculeata colonised the Antarctic from Patagonia after the LGM. Results for U. aurantiacoatra are ambiguous, indicating a more complex population history than expressed in the simplified scenarios. Main Conclusions: Mode of propagation affects levels of genetic diversity, but the location of glacial refugia and postglacial colonisation better explains the diversity patterns displayed by each species. We found evidence for glacial in situ survival of U. aurantiacoatra on both sides of the Drake Passage and postglacial colonisation of Antarctica from South America by C. aculeata. Maintaining the strong genetic differentiation of Antarctic populations of C. aculeata requires strict conservation measures, whereas populations of U. aurantiacoatra are exposed to a much lower risk due to their higher diversity and connectivity. [ABSTRACT FROM AUTHOR]

The present contribution is motivated by the frequent occurrence of traces generated by lichens on the fossil record, the usual and erroneous attribution of them to plant roots, and the scarce information published about bioerosive damage caused by lichens. As a result, two different patterns were identified on the surface and inside the fossil bones and teeth. The first one is characterised by the presence of lines clearer than the rest of the surface, produced by the hyphae and interrupted by small pits corresponding to the apothecia. These traces are often confused with Corrossichnia and Sphenoichnia, a situation that leads to taphonomic and palaeoecological misinterpretation. The second pattern, more unnoticed among other visible traces, consists of isolated pits without any other surficial trace distributed in the fossil surface. These pits can be confused with perforations made by many organisms. However, the presence of apothecia and, in some cases, also hyphae on the fossil remains, allows the accurate identification of the causal agent and the mechanism of action by which it occurs. [ABSTRACT FROM AUTHOR]

Aim: Antarctica's remote and extreme terrestrial environments are inhabited by only two species of native vascular plants. We assessed genetic connectivity amongst Antarctic and South American populations of one of these species, Colobanthus quitensis, to determine its origin and age in Antarctica. Location: Maritime Antarctic, sub‐Antarctic islands, South America. Taxon: Antarctic pearlwort Colobanthus quitensis (Caryophyllaceae). Methods: Four chloroplast markers and one nuclear marker were sequenced from 270 samples from a latitudinal transect spanning 21–68° S. Phylogeographic, population genetic and molecular dating analyses were used to assess the demographic history of C. quitensis and the age of the species in Antarctica. Results: Maritime Antarctic populations consisted of two different haplotype clusters, occupying the northern and southern Maritime Antarctic. Molecular dating analyses suggested C. quitensis to be a young (<1 Ma) species, with contemporary population structure derived since the late‐Pleistocene. Main conclusions.: The Maritime Antarctic populations likely derived from two independent, late‐Pleistocene dispersal events. Both clusters shared haplotypes with sub‐Antarctic South Georgia, suggesting higher connectivity across the Southern Ocean than previously thought. The overall findings of multiple colonization events by a vascular plant species to Antarctica, and the recent timing of these events, are of significance with respect to future colonizations of the Antarctic Peninsula by vascular plants, particularly with predicted increases in ice‐free land in this area. This study fills a significant gap in our knowledge of the age of the contemporary Antarctic terrestrial biota. Adding to previous inferences on the other Antarctic vascular plant species (the grass Deschampsia antarctica), we suggest that both angiosperm species are likely to have arrived on a recent (late‐Pleistocene) time‐scale. While most major groups of Antarctic terrestrial biota include examples of much longer‐term Antarctic persistence, the vascular flora stands out as the first identified terrestrial group that appears to be of recent origin. [ABSTRACT FROM AUTHOR]

Black carbon (BC) is an important climate-forcing agent that affects snow albedo. In this work, we present a record of refractory black carbon (rBC) variability, measured from a 20 m deep snow and firn core drilled in West Antarctica (79 ∘ 55 ′ 34.6 ′′ S, 94 ∘ 21 ′ 13.3 ′′ W, 2122 m above sea level) during the 2014–2015 austral summer. This is the highest elevation rBC record from West Antarctica. The core was analyzed using the Single Particle Soot Photometer (SP2) coupled to a CETAC Marin-5 nebulizer. Results show a well-defined seasonality with geometric mean concentrations of 0.015 µ g L -1 for the wet season (austral summer–fall) and 0.057 µ g L -1 for the dry season (austral winter–spring). The core was dated to 47 years (1968–2015) using rBC seasonality as the main parameter, along with sodium (Na), sulfur (S) and strontium (Sr) variations. The annual rBC concentration geometric mean was 0.03 µ g L -1 , the lowest of all rBC cores in Antarctica referenced in this work, while the annual rBC flux was 6.25 µ g m -2 a -1 , the lowest flux in West Antarctica rBC records. No long-term trend was observed. Snow albedo reductions at the site due to BC were simulated using SNICAR online and found to be insignificant (- 0.48 %) compared to clean snow. Fire spot inventory and BC emission estimates from the Southern Hemisphere suggest Australia and Southern Hemisphere South America as the most probable emission sources of BC to the drilling site, whereas HYSPLIT model particle transport simulations from 1968 to 2015 support Australia and New Zealand as rBC sources, with limited contributions from South America. Spectral analysis (REDFIT method) of the BC record showed cycles related to the Antarctic Oscillation (AAO) and to El Niño–Southern Oscillation (ENSO), but cycles in common with the Amundsen Sea Low (ASL) were not detected. Correlation of rBC records in Antarctica with snow accumulation, elevation and distance to the sea suggests rBC transport to East Antarctica is different from transport to West Antarctica. [ABSTRACT FROM AUTHOR]

Worldwide, the implementation of forest management guidelines has tried to mimic natural forest dynamics. The Oliver forest stand dynamics model has been successful in bridging natural forest dynamics associated with the disturbances of various spatial scales and silviculture also related to various spatial scales of management. However, the application of this model (and others) is restricted to tall forests.We claim here that the general research and commercial interest bias towards tall tree species has permeated silviculture and forest management, and that both the stand dynamics of short‐stature tree species and their treatment have remained largely unexplored and unknown.Using one short‐stature tree species, Nothofagus antarctica, as a model system, we show that this species indeed follows a stand dynamic different from other tall Nothofagus‐dominated forests in southern South America. This species forms short, mature, even‐aged stands without large canopy gaps that promote tree regeneration. With this in mind, we propose a conceptual ecology‐based silvicultural guideline focusing on the creation of strip cuts or gaps along with topsoil scarification to ensure regeneration and forest reorganization after disturbances.Policy implications. The acknowledgement that short‐stature tree species follow a stand dynamic different from tall tree species necessarily implies that they must be managed differently. This recognition, along with the implementation of ecology‐based silvicultural recommendations, represents strong arguments to make modifications to forest legislation that, together, must be aimed at conservation and sustainable forest management. [ABSTRACT FROM AUTHOR]

Viral nervous necrosis (viral encephalopathy and retinopathy) is caused by piscine nodavirus (Nodaviridae, Betanodavirus). Since 1986, this highly infectious virus has caused mass mortalities of up to 100% in farmed saltwater and freshwater fish around the world (with the exception of South America and Antarctica), affecting >60 species across 10 orders. The Atlantic blue marlin (Makaira nigricans Lacépède, 1802) is a top-level predator found throughout the tropical waters of the Atlantic and Indo-Pacific oceans. Despite their popularity as a sportfish, relatively little is known about the Atlantic blue marlin and other billfish. We describe here chronic betanodavirus infection in a juvenile Atlantic blue marlin, which is, to our knowledge, the first report of disease in M. nigricans. [ABSTRACT FROM AUTHOR]

We present a Rare Earth Elements (REE) record determined on the EPICA ice core drilled at Dronning Maud Land (EDML) in the Atlantic sector of the East Antarctic Plateau. The record covers the transition from the last glacial stage (LGS) to the early Holocene (26 600-7500 yr BP) at decadal to centennial resolution. Additionally, samples from potential source areas (PSAs) for Antarctic dust were analyzed for their REE characteristics. The dust provenance is discussed by comparing the REE fingerprints in the ice core and the PSA samples. We find a shift in variability in REE composition at ∼15 000 yr BP in the ice core samples. Before 15 000 yr BP, the dust composition is very uniform and its provenance was most certainly dominated by a South American source. After 15 000 yr BP, multiple sources such as Australia and New Zealand become relatively more important, although South America remains the major dust source. A similar change in the dust characteristics was observed in the EPICA Dome C ice core at around ∼15 000 yr BP, accompanied by a shift in the REE composition, thus suggesting a change of atmospheric circulation in the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

Copepods are present in numerous aquatic environments, playing key roles in food webs, and are thought to be useful indicators of environmental change. Boeckella is a calanoid copepod genus distributed mainly in the Southern Hemisphere, with 14 species reported at higher southern latitudes in South America and Antarctica. We present an updated database of these 14 species of Boeckella generated from a combination of three sources: 1) new field sampling data, 2) published records, and 3) Global Biodiversity Information Facility (GBIF), to provide a comprehensive description of the geographic distribution of the genus south of latitude 40°S in southern South America and the three main terrestrial biogeographic regions of Antarctica. The database includes 380 records, 62 from field sampling, 278 from the literature and 40 from GBIF. Southern South America, including the Falkland/Malvinas Islands, had the highest species richness and number of records (14 and 297, respectively), followed by the sub-Antarctic islands (5 and 34), South Orkney Islands (2 and 14), South Shetland Islands (1 and 23), Antarctic Peninsula (1 and 10) and finally continental Antarctica (1 and 2). Boeckella poppei Mrázek, 1901 is the only representative of the genus, and more widely the only terrestrial/freshwater invertebrate, currently reported from all three main biogeographic regions in Antarctica (sub-Antarctic islands, maritime and continental Antarctic). Future development of molecular systematic studies in this group should contribute to assessing the correspondence between morphological taxonomy and molecular evolutionary radiation. [ABSTRACT FROM AUTHOR]

The continuous ice core record extends 800,000 years into the past, covering the period of 100,000-year glacial cycles, but not the transition from 40,000-year glacial cycles (the Mid-Pleistocene Transition, 1.2–0.7 million years ago). A primary goal of the International Partnership in Ice Core Sciences is therefore to retrieve a 1.5-million-year-old continuous ice core, increasing our understanding of this major change in the climate system and thus of fundamental climate forcings and feedbacks. However, complex glacial processes, limited bedrock data, and surprisingly young basal ice in previous cores necessitate careful reconnaissance studies before extracting a full core. Ice borehole optical logging reflects the ice dust content and may be used to date ice quickly and inexpensively if a reference record is known. Here we explore the relationship between ice dust records and well-dated marine dust records from sediment cores in the southern Atlantic and Pacific Oceans, which lie along paths of dust sources to Antarctica. We evaluate how representative these records are of Antarctic dust both through the existing ice core record and during the older target age range, suggesting that a newly published 1.5 million year record from site U1537 near South America is likely the most robust predictor of the Oldest Ice dust signal. We then assess procedures for rapid dating of potential Oldest Ice sites, noting that the ability to detect dating errors is an essential feature. We emphasize that ongoing efforts to identify, recover, date, and interpret an Oldest Ice core should use care to avoid unfounded assumptions about the 40 kyr world based on the 100 kyr world. [ABSTRACT FROM AUTHOR]

Despite strong historical biogeographical links between benthic faunal assemblages of the Magellan region of South America and the Antarctic Peninsula, very few studies have documented contemporary movement and gene flow in or out of the Southern Ocean, especially across the Antarctic Polar Front (APF). In fact, oceanographic barriers such as the APF and Antarctica's long geologic isolation have substantially separated the continents and facilitated the evolution of endemic marine taxa found within the Antarctic region. The Southern Ocean benthic sea slug complex, Doris "kerguelenensis," are a group of direct‐developing, simultaneous hermaphrodites that lack a dispersive larval stage. To date, there are 59 highly divergent species known within this complex. Here, we provide evidence to show intraspecific genetic connectivity occurs across the APF for multiple species within the D. "kerguelenensis" nudibranch species complex. We addressed questions of genetic connectivity by examining the phylogeographic structure of the three best‐sampled D. "kerguelenensis" species and another three trans‐APF species using the protein coding mtDNA gene, cytochrome oxidase I. We also highlight alternative refugia uses among species with the same life history traits (i.e., benthic and direct developers) and for some species, extremely large distributions are established (e.g., circumpolarity). By improving our sampling of these nudibranchs, we gain better insight into the population structure and connectivity of the Antarctic region. This work also demonstrates how difficult it is to make generalizations across Antarctic marine species, even among ecologically‐similar, closely related species. [ABSTRACT FROM AUTHOR]

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Deschampsia P. Beauv. is a cosmopolitan grass genus, which grows in cold and temperate regions, including about 15 species growing in South America and Antarctica. The species delimitation is difficult due to the high phenotypic plasticity and the likely occurrence of hybridization which generates species complexes with high morphological affinity. This work aims to describe the cytogenetic traits of the South American species of Deschampsia, highlighting similarities and differences in a phylogenetic context. We report the chromosome number of seven species of Deschampsia and Deyeuxia eminens for the first time, verifying that basic chromosome number x = 13 is shared by all the species. We found that the phylogenetic relationships are in agreement with the morphological affinities described in the species revisions, and the species of Deschampsia and Deyeuxia Sect. Stylagrostis form a well-supported clade. Despite the variation from x = 13 reported for populations of Deschampsia in the northern hemisphere, all the South American and Antarctic taxa studied here have a conserved basic chromosome number. Polyploids were found in several species, which suggests that genomic duplication is a recurrent process in the evolutionary history of Deschampsia. In contrast with the conserved chromosome morphology, the rDNA pattern showed high intra- and inter-specific variability and it is related to the phylogeny. Particularly, the complex of D. cespitosa is polymorphic for the distribution pattern of rDNA, as was also seen for molecular and morphological traits. Our results suggest that the common ancestor between Deschampsia and Deyeuxia sec. Stylagrostis could have had chromosomal characteristics currently shared by both. The incorporation of new chromosomal, molecular, and morphological data in Deyeuxia species will allow clarification of the close phylogenetic relationship with Deschampsia, in which reticulation and hybridization events cannot be excluded. [ABSTRACT FROM AUTHOR]

Hiatella is among the most poorly understood bivalve genera. Most of the species remain known only from shell morphology, which has proved to be extremely variable in the group. Few studies have addressed their anatomy and biology, and no studies have combined morphological, anatomical and biological characters with molecular characters. This has led to the hiatellids all around the world being regarded as a single, widely distributed species. This contribution represents a step towards a better understanding of hiatellids worldwide by providing the first integrative study of the species occurring in southern South America. Three entities are recognized: Hiatella meridionalis , Hiatella barnea and Hiatella umbonata sp. nov. To understand their intraspecific variability, all the species are carefully described and figured, based on large series of specimens. Saxicava chilensis , Saxicava mollis , Saxicava lebruni and Saxicava subantarctica are considered synonyms of H. meridionalis ; a lectotype for S. subantarctica is designated; and S. antarctica and S. frigida are regarded as nomina dubia. This study suggests that worldwide living hiatellids might have originated from South American species and that reduction/loss of hinge teeth during ontogeny and life on hard substrates or on/inside other invertebrates would represent derived traits within the genus Hiatella. [ABSTRACT FROM AUTHOR]

Size-segregated particulate air samples were collected during the austral summer of 2016–2017 at Palmer Station on Anvers Island, western Antarctic Peninsula, to characterize trace elements in aerosols. Trace elements in aerosol samples – including Al, P, Ca, Ti, V, Mn, Ni, Cu, Zn, Ce, and Pb – were determined by total digestion and a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS). The crustal enrichment factors (EF crust) and k -means clustering results of particle-size distributions show that these elements are derived primarily from three sources: (1) regional crustal emissions, including possible resuspension of soils containing biogenic P, (2) long-range transport, and (3) sea salt. Elements derived from crustal sources (Al, P, Ti, V, Mn, Ce) with EF crust<10 were dominated by the coarse-mode particles (>1.8 µm) and peaked around 4.4 µm in diameter, reflecting the regional contributions. Non-crustal elements (Ca, Ni, Cu, Zn, Pb) showed EF crust>10. Aerosol Pb was primarily dominated by fine-mode particles, peaking at 0.14–0.25 µm , and likely was impacted by air masses from southern South America based on air mass back trajectories. However, Ni, Cu, and Zn were not detectable in most size fractions and did not present clear size patterns. Sea-salt elements (Ca, Na + , K +) showed a single-mode distribution and peaked at 2.5–4.4 µm. The estimated dry deposition fluxes of mineral dust for the austral summer, based on the particle-size distributions of Al measured at Palmer Station, ranged from 0.65 to 28 mg m -2 yr -1 with a mean of 5.5±5.0 mg m -2 yr -1. The estimated dry deposition fluxes of the target trace elements in this study were lower than most fluxes reported previously for coastal Antarctica and suggest that atmospheric input of trace elements through dry deposition processes may play a minor role in determining trace element concentrations in surface seawater over the continental shelf of the western Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

We examined the seasonal cycle of radon concentration observed at King Sejong Station (KSG, 62°S), Antarctic Peninsula, during the period 2013–2016. The distribution of monthly radon concentration was found to be highly positively skewed from March through October (austral autumn to spring) due to large numbers of short-lived periods of high radon concentration. The global atmospheric chemistry model (CAM-Chem), which includes all global terrestrial sources of radon except for those in Antarctica, well reproduces the observed seasonal cycle of monthly-mean radon concentration at KSG. Further offline experiments suggest that uncertainties in radon emissions over South America and the Southern Ocean should be improved for the simulations of radon in Antarctica. The results demonstrate that seasonally varying transport of radon in the boundary layer from South America substantially affects the seasonality of monthly mean radon concentration at KSG. The composite analyses further reveal that high radon events at KSG are the result of a distinct east-west dipole-like structure associated with surface cyclonic circulation over the Bellingshausen Sea and anticyclonic circulation in the Weddell Sea. This atmospheric pattern provides favorable conditions for radon transport into KSG from the northwest. The relationship between radon concentration at KSG and climate variability is also discussed in this study. • Seasonality of Radon-222 observed at King Sejong Station (KSG, 62°S) was compared for the first time with the result of the global atmospheric chemistry model (CAM-Chem). • CAM-Chem relatively well reproduces the observed seasonal cycle of monthly-mean radon concentration which is sensitively affected by high radon evens. • High radon events are the result of a distinct east-west dipole-like surface atmospheric circulation pattern associated with surface cyclonic circulation over the Bellingshausen Sea and anticyclonic circulation in the Weddell Sea. [ABSTRACT FROM AUTHOR]

The exposure of a research team to chigger mites in southern Chile allowed the first identification of a trombiculid species as vector and reservoir of scrub typhus outside the tsutsugamushi triangle, providing unique insights into the ecology and transmission of this recently discovered rickettsial infection in South America. [ABSTRACT FROM AUTHOR]

Electric field measurements at Vostok station in Antarctica reveal that the El Niño—Southern Oscillation (ENSO) has a statistically significant effect on the global electric circuit, as earlier predicted by simulations. Analysis of 10 October‐February periods during 2006–2016 indicates that the shape of the diurnal variation of the surface electric field is significantly different for El Niño and La Niña years, with an especially pronounced deviation during the super El Niño of 2015/16. During strong El Niños the potential gradient relative to the diurnal mean is generally higher than usual around 8:00–14:00 UTC and lower than usual around 16:00–0:00 UTC; La Niñas are characterized by the opposite behavior. Simulations with the Weather Research and Forecasting model imply that the observed patterns are the result of changes in the global distribution of electrified clouds over the Pacific Ocean, Maritime Continent, and South America during ENSO events. Plain Language Summary: The El Niño—Southern Oscillation (ENSO) is one of the most remarkable modes of climate variability on Earth. Being made up of irregularly alternating warm (El Niño) and cold (La Niña) phases, the ENSO affects atmospheric circulation, global temperature and rainfall patterns, agriculture, and economic output. Recent simulations have suggested that changes in global convection patterns due to ENSO should also affect surface atmospheric electric fields and currents in remote regions of the planet. Here, we present electric field measurements performed during 2006–2016 at Vostok station in the Antarctic that reveal clear patterns related to ENSO as earlier predicted by simulations. Measurements show that the shape of the diurnal variation of the surface electric field is significantly different for El Niño and La Niña years (with an especially pronounced effect during the super El Niño of 2015/16), which, according to simulations, is the result of changes in the global distribution of electrified clouds over the Pacific Ocean, Maritime Continent, and South America during ENSO events. This provides further evidence of the influence of climate fluctuations on the Earth's global electromagnetic environment. Key Points: Electric field measurements in Antarctica show that strong El Niños and La Niñas consistently impact the atmospheric global circuitFor the super El Niño event of 2015/16, the anomalies in the global electric circuit are especially pronouncedSimulations show that the observed effect is due to changes in deep convection over the Pacific Ocean, Maritime Continent, and South America [ABSTRACT FROM AUTHOR]