Vestfold Hills Research Articles

The Vestfold Hills are alive: characterising microbial and environmental dynamics in Old Wallow, eastern Antarctica.

Old Wallow is an underexplored, hyper-arid coastal desert in Antarctica's Vestfold Hills. Situated near an elephant seal wallow, we examined how stochastic nutrient inputs from the seal wallow affect soil communities amid environmental changes along a spatially explicit sampling transect. We hypothesized that nutrient levels would be elevated due to proximity to the seal wallow, influencing community distributions. While the soil bacterial and eukaryotic communities at the phylum level were similar to other terrestrial environments, analysis at class and family levels revealed a dominance of unclassified taxa that are often linked to marine environments. Elevated nutrient concentrations (NO3 -, SO4 2-, SO3) were found at Old Wallow, with conductivity and Cl- levels up to 10-fold higher at the lowest elevation soils, correlating with significantly (p < 0.05) higher abundances of halophilic (Halomonadaceace) and uncultivated lineages (Ca Actinomarinales, unclassified Bacillariophyta and unclassified Opisthonkonta). An improved Gradient Forest model was used to quantify microbial responses to 26 soil gradients at OW, revealing variable responses to environmental predictors and identifying critical environmental thresholds or drivers of community turnover. Major tipping points were projected for eukaryotes with SO4 2-, pH, and SO3, and for bacteria with moisture, Na2O, and Cl-. Thus, the Old Wallow ecosystem is primarily shaped by salt, sulphate, and moisture and is dominated by uncultivated taxa, which may be sensitive to environmental changes once critical tipping points are reached. This study provides critical baseline data for future regional monitoring under threats of environmental change.

Effects of increasing soil moisture on Antarctic desert microbial ecosystems.

Overgeneralization and a lack of baseline data for microorganisms in high-latitude environments have restricted the understanding of the microbial response to climate change, which is needed to establish Antarctic conservation frameworks. To bridge this gap, we examined over 17,000 sequence variants of bacteria and microeukarya across the hyperarid Vestfold Hills and Windmill Islands regions of eastern Antarctica. Using an extended gradient forest model, we quantified multispecies response to variations along 79 edaphic gradients to explore the effects of change and wind-driven dispersal on community dynamics under projected warming trends. We also analyzed a second set of soil community data from the Windmill Islands to test our predictions of major environmental tipping points. Soil moisture was the most robust predictor for shaping the regional soil microbiome; the highest rates of compositional turnover occurred at 10-12% soil moisture threshold for photoautotrophs, such as Cyanobacteria, Chlorophyta, and Ochrophyta. Dust profiles revealed a high dispersal propensity for Chlamydomonas, a microalga, and higher biomass was detected at trafficked research stations. This could signal the potential for algal blooms and increased nonendemic species dispersal as human activities increase in the region. Predicted increases in moisture availability on the Windmill Islands were accompanied by high photoautotroph abundances. Abundances of rare oligotrophic taxa, such as Eremiobacterota and Candidatus Dormibacterota, which play a crucial role in atmospheric chemosynthesis, declined over time. That photosynthetic taxa increased as soil moisture increased under a warming scenario suggests the potential for competition between primary production strategies and thus a more biotically driven ecosystem should the climate become milder. Better understanding of environmental triggers will aid conservation efforts, and it is crucial that long-term monitoring of our study sites be established for the protection of Antarctic desert ecosystems. Furthermore, the successful implementation of an improved gradient forest model presents an exciting opportunity to broaden its use on microbial systems globally.

Extremophile hypolithic communities in the Vestfold Hills, East Antarctica – ERRATUM

Extremophile hypolithic communities in the Vestfold Hills, East Antarctica – ERRATUM

Extremophile hypolithic communities in the Vestfold Hills, East Antarctica

Abstract The Vestfold Hills are a 400 km2, isolated ice-free oasis in eastern Antarctica featuring large areas with translucent quartz rocks that provide habitat for hypolithic microbial communities underneath. We used high-throughput DNA sequencing of 16S and 18S ribosomal RNA amplicons to characterize bacterial and eukaryotic hypolithic communities across the Vestfold Hills. We found high-level, local heterogeneity in community structure consistent with limited dispersal between hypoliths. Hypolithic communities were dominated by heterotrophic Bacteroidetes (mean bacterial relative read abundance: 56%) as well as Cyanobacteria (35%), with the eukaryote component often dominated by Chlorophyta (43%). Small but significant proportions of the variation in microbial community composition and function were explained by soil salinity (5–7%) and water availability (8–11%), with distinct taxa associated with different salinities and water availabilities. Furthermore, many inferred bacterial metabolic pathways were enriched in hypolithic communities from either dry or high-salinity sites. Vestfold Hills hypolithic habitats are likely to be local refuges for bacterial and eukaryotic diversity. Gradients in soil salinity and water availability across the Vestfold Hills, in addition to the number and diversity of lake types and fjords as potential source populations, may contribute to the observed variation in the extremophile, hypolithic microbial community composition.

Diminishing numbers of male southern elephant seals (Mirounga leonina Pinnipedia: Phocidae, Linnaeus, 1758) at the Vestfold Hills, East Antarctica (1957–2022)

Abstract A proportion of the southern elephant seal (Mirounga leonina) population that breeds in the Kerguelen Plateau region seasonally migrates between their natal sub-Antarctic islands and moult haul-out locations on the Antarctic coastline. Analyses of survey data collated for one moult location at the Vestfold Hills, East Antarctica, showed that there had been no appreciable change in the timing (phenology) of maximum seal arrivals between 1974 and 2022; however, the maximum number of seals moulting at that site had declined by ~90% over the same time interval. Spatial analyses showed rates of population change were survey area dependent, as seal numbers decreased most rapidly at haul-out areas closest to the permanently occupied Davis Station, suggesting that a relationship exists between seal numbers and human activities. The range of potential factors that contribute to population change for southern elephant seals moulting at the Vestfold Hills includes changes in status at primary source populations, one of which has not been surveyed since the 1990s, and species relocation. Should numbers of southern elephant seals in the Vestfold Hills continue to decrease at the current average rate of change (-7.78 seals/year) the species could vanish from the area by c. 2040.

Incidental pinnipeds at high latitudes of the Vestfold Hills, Prydz Bay, East Antarctica

AbstractSpecies distributions are predicted to change with future climate-associated ecosystem changes such that so-called ‘vagrant’ individuals may become established or re-establish in areas currently thought to be beyond their principle ranges. Survey data were collated for occurrences of pinniped (seal) species at very high latitudes of the Vestfold Hills, East Antarctica. Aside from Weddell seals (Leptonychotes weddellii) and southern elephant seals (Mirounga leonina), which aggregate annually at the Vestfold Hills to breed and/or moult, three other pinniped species were observed with the recession of the fast-ice edge. Leopard seal (Hydrurga leptonyx) occurrences increased with an increase in a seasonally abundant prey resource, and crabeater seals (Lobodon carcinophaga) were seen at a time that coincides with their moult period. Occurrences of sub-adult male Antarctic fur seals (Arctocephalus gazella) increase the known southward range for this species and may reflect population increases at source populations in the Kerguelen Plateau area. Although there were no direct sightings of Ross seals (Ommatophoca rossii), their presence close to the Vestfold Hills was detected by underwater passive acoustic monitoring. Sightings of obligate drift-ice species and sub-Antarctic fur seals may change at the Vestfold Hills with climate-mediated changes in sea-ice conditions.

Thermotectonic evolution of the Rauer Group and Vestfold Hills in Prydz Bay: implications for Neoproterozoic assembly of the East Antarctic Shield

The Rauer Group and Vestfold Hills are critical components of the East Antarctic Shield and are believed to have been parts of the supercontinents Rodinia and Gondwana. The Rauer Group is characterized by Archean to Pan-African thermal history, while the Pan-African signature in the Vestfold Hills is restricted to its southwestern margin. The correlation between the Rauer Group and Vestfold Hills remains controversial, while the significance of amalgamation between these two terranes remains unclear. Most importantly, the precise nature and timing of the Rauer-Vestfold contact is disputed. In this review, we compare the available structural, metamorphic, geochronological and geophysical data in these two East Antarctic terranes and suggest that (i) the Rauer Group and Vestfold Hills of East Antarctica were amalgamated during the late Mesoproterozoic to early Neoproterozoic (∼1000 Ma), and (ii) the Rauer-Vestfold contact is located beneath the Sørsdal Glacier in the East Antarctic Shield. Finally, we argue that juxtaposition of the Rauer-Vestfold contiguous crustal unit with the Eastern Ghats Province (EGP)-Rayner amalgam took place in the Pan-African time (∼500 Ma).

Evidence of Paleoproterozoic metamorphism in Vestfold Hills, East Antarctica: Insights from phase equilibria modelling and monazite CHIME dating

The Vestfold Hills sector on the coastal fringe of the Princess Elizabeth Land forms part of an Archean to Paleoproterozoic aged cratonic nucleus of the East Antarctic Shield. A charnockite-granite association from the Mossel Gneiss Group in the northern region of the Vestfold Hills is investigated in this work to characterise the metamorphic-magmatic evolution of the area. Conventional thermometry and phase equilibria modelling indicate that the charnockite formed as a result of ultra-high temperature metamorphism at low-intermediate pressure (∼4 kbar). Phase equilibria modelling, reveals that the melt-integrated charnockite composition is a restitic product of a protolith of quartz diorite composition which underwent isobaric heating (peak temperature up to 960 °C) at 4 kbar pressure followed by anatexis. The anatexis of the quartz diorite protolith also resulted in the formation of the associated granitic melt. U–Th-PbTotal ages obtained from monazites of the granite integrated with CHIME ages extracted using the isochron method indicate an emplacement age of ∼2200 Ma and two younger events are recorded at ∼2000 Ma and ∼1700 Ma. The younger ages are ascribed to the resetting during the emplacement of younger basalt dykes that cross cut the charnockite-granite sequence. Vestfold Hills’ geological correlations with Indian and Australian cratons are discussed considering this new data.

Typization of Lakes of the East Antarctica Oases

The urgency of creating a new complex typization of lakes of the East Antarctica oases is dictated not only by the desire to summarize accumulated Antarctic lakes’ data but also by the need to obtain the most informative characteristics of lake hydrological regime in the region for solving a wide applied problems’ range. Features of lake water level changes were used as a criterion in developing the complex typization of lakes of the East Antarctica oases for the first time, in contrast to existing classifications. The study was based on the analysis of literary and archive materials (the Larsemann Hills, the Schirmacher oasis, the Banger Hills, the Molodezhnyi oasis, the Vestfold Hills, and the McMurdo Dry Valleys), as well as our own expeditionary data (field seasons of 2017–2022, the Larsemann Hills). A group of indirect criteria (presence and type of natural dam, position in the cascade, flowage type, etc.) is proposed in addition to a group of direct criteria (duration of the lake filling phase, water level rise, etc. requiring organization of field observations) to obtain a holistic view of the water level regime of lakes. It is important that characteristics of the most indirect criteria can be obtained by visual reconnaissance surveys or by maps and remote sensing data. The identified 4 types (outbursting, tendentious, transit, and tidal) and 8 subtypes of lakes were illustrated by generalized graphs of water level changes, which objectively characterize the features of the lake hydrological regime. The openness of the typization suggests the opportunities for actualization with the accumulation of new scientific knowledge and data.

Imaging of crustal structure beneath the Larsemann Hills, Antarctica using scattered wave technique – First Results

The crustal structure in terms of crustal thickness, shear wave velocities and Poisson's ratio plays a crucial role in understanding and/or deciphering the tectonic setting and its evolution. The receiver function analysis, H–K stacking and inversion techniques are the widely used tools to determine these parameters. In the present study, the data obtained from the first-ever established broadband seismological observatory at Larsemann Hills, East Antarctica has been utilized for the P receiver function (PRF) analysis and H–K stacking to decipher the crustal thickness, Poisson's ratio and the intra-crustal layer. Further, the obtained PRFs were inverted using Bayesian inversion to get the crustal structure. The results obtained from H–K analysis reveal a crustal thickness of ∼37.9 km and the corresponding Poisson's ratio is 0.19. The inversion technique also yielded consistent results, indicating a Moho depth of ∼37 km with a velocity jump from 4.1 km/s to 4.6 km/s and an intra-crustal layer at around 16 km with a velocity jump from 3.95 km/s to 4.06 km/s. It indicates a Poisson's ratio of 0.20. These findings suggest that the crust beneath the Larsemann Hills is felsic in nature and has high crustal shear wave velocity. Further, the variation in the crustal thickness along the coast of the Princess Elizabeth Land (PEL) region, ranging from 37.9 km to 36 km with the intra-crustal layer variation from 16 km to 13 km distinguishes the Neoproterozoic Larsemann Hills from the Archean-Mesoproterozoic Vestfold Hills.

Isotopic behavior and age interpretations of U-Pb, Sm-Nd, and 40Ar/39Ar systems in polymetamorphic granulite terranes: A case study from the Prydz Belt and adjacent Vestfold Block, East Antarctica

A combined zircon U-Pb, garnet-based mineral−whole-rock Sm-Nd, and hornblende/biotite 40Ar/39Ar geochronological study was conducted on polymetamorphic granulite-facies rocks from the Prydz Belt and adjacent Vestfold Block in East Antarctica. Zircon U-Pb data and zircon-garnet rare earth element distributions indicate that granulite-facies mineral assemblages of the Meknattane Nunataks−Hamm Peak area and the Reinbolt Hills in the Prydz Belt were formed at ca. 1000−900 Ma. Some Grenville-aged (i.e., late Mesoproterozoic to early Neoproterozoic) zircons underwent partial U-Pb resetting, without new growth, during Pan-African-aged (i.e., late Neoproterozoic to Cambrian) metamorphism. Mineral−whole-rock Sm-Nd dating yielded isochron ages of 865−672 Ma for the Meknattane Nunataks−Hamm Peak area, 504−483 Ma for the Reinbolt Hills, and 670−589 Ma for the Vestfold Hills. These results suggest that Pan-African-aged reworking was inhomogeneous, leading to either partial or complete resetting of the garnet Sm-Nd isotopic system in different areas. Apparently, Sm-Nd ages might have geological meaning only when the isotopic system of garnet (including other contemporaneous minerals) has been completely reset. In this regard, garnet-based Sm-Nd geochronology is less robust when applied to polymetamorphic granulite terranes. Hornblende 40Ar/39Ar dating produced an older age of 526 Ma for the Vestfold Hills, whereas biotite 40Ar/39Ar ages showed slight differences among the studied areas, with ages of 514−497 Ma for the Meknattane Nunataks−Hamm Peak area, 482−467 Ma for the Reinbolt Hills, and 520−509 Ma for the Vestfold Hills. These age patterns imply that 40Ar/39Ar dating of minerals can constrain the cooling time of the latest metamorphic event only, and cooling times to the Ar closure temperature of biotite differ among different parts of the Prydz Belt. Integration of the new results with available Sm-Nd and 40Ar/39Ar data indicates that the Prydz Belt underwent rapid tectonic uplift and cooling from lower to mid- and upper-crustal depths during postorogenic evolution. The Vestfold Block might have been located at the margin of the high-temperature Prydz Belt and underwent relatively low-temperature reworking and earlier cooling during the Pan-African-aged orogeny.

Evaluation of Coliform and Faecal Coliform Bacteria in the Lakes of Broknes and Grovnes Peninsula, East Antarctica

More than 150 lakes on different peninsulas and islands are situated in the Larsemann Hills. The Larsemann Hills is an ice-free area and are located halfway between the Vestfold Hills and the Amery Ice Shelf on the southeastern coast of Prydz Bay, Princess Elizabeth Land, and East Antarctica. During 34th Indian Scientific Expedition to Antarctica (ISEA) from 2014 to 2015, twenty lake water samples in triplicates were collected from the Broknes &amp; Grovnes peninsula. Coliform and fecal coliform bacteria were analyzed in these samples. Out of twenty, eleven lake water samples were found to be contaminated with coliform bacteria. However, fecal coliform bacteria were absent in all the lake water samples. Coliforms are found in the lakes of Broknes peninsula (P2 Lake &amp; P3 Lake) and Grovnes peninsula (L1C NG, L1D NG, L1E NG, L7 NG, L7A NG, L7B NG, L2 SG, L4 SG &amp; L5 SG). Antarctic lakes water is being polluted due to anthropogenic activities caused by various research activities and tourism. The present study confirms the presence of coliform bacteria in the lakes of East Antarctica which indicates an alarming situation and needs to be investigated further.

Population structure of an Antarctic aquatic cyanobacterium

BackgroundAce Lake is a marine-derived, stratified lake in the Vestfold Hills of East Antarctica with an upper oxic and lower anoxic zone. Cyanobacteria are known to reside throughout the water column. A Synechococcus-like species becomes the most abundant member in the upper sunlit waters during summer while persisting annually even in the absence of sunlight and at depth in the anoxic zone. Here, we analysed ~ 300 Gb of Ace Lake metagenome data including 59 Synechococcus-like metagenome-assembled genomes (MAGs) to determine depth-related variation in cyanobacterial population structure. Metagenome data were also analysed to investigate viruses associated with this cyanobacterium and the host’s capacity to defend against or evade viruses.ResultsA single Synechococcus-like species was found to exist in Ace Lake, Candidatus Regnicoccus frigidus sp. nov., consisting of one phylotype more abundant in the oxic zone and a second phylotype prevalent in the oxic-anoxic interface and surrounding depths. An important aspect of genomic variation pertained to nitrogen utilisation, with the capacity to perform cyanide assimilation and asparagine synthesis reflecting the depth distribution of available sources of nitrogen. Both specialist (host specific) and generalist (broad host range) viruses were identified with a predicted ability to infect Ca. Regnicoccus frigidus. Host-virus interactions were characterised by a depth-dependent distribution of virus type (e.g. highest abundance of specialist viruses in the oxic zone) and host phylotype capacity to defend against (e.g. restriction-modification, retron and BREX systems) and evade viruses (cell surface proteins and cell wall biosynthesis and modification enzymes).ConclusionIn Ace Lake, specific environmental factors such as the seasonal availability of sunlight affects microbial abundances and the associated processes that the microbial community performs. Here, we find that the population structure for Ca. Regnicoccus frigidus has evolved differently to the other dominant phototroph in the lake, Candidatus Chlorobium antarcticum. The geography (i.e. Antarctica), limnology (e.g. stratification) and abiotic (e.g. sunlight) and biotic (e.g. microbial interactions) factors determine the types of niches that develop in the lake. While the lake community has become increasingly well studied, metagenome-based studies are revealing that niche adaptation can take many paths; these paths need to be determined in order to make reasonable predictions about the consequences of future ecosystem perturbations.2GZ5fuYNnhGp9HukxerBaXVideo

Complete genome of Nocardioides aquaticus KCTC 9944T isolated from meromictic and hypersaline Ekho Lake, Antarctica.

Nocardioides aquaticus KCTC 9944T is an aerobic, non-motile, Gram-positive, psychrotolerant, non-spore-forming bacterium isolated from the surface water of Ekho Lake in the Vestfold Hills, East Antarctica. This meromictic lake separated from Antarctic seawater thousands of years ago exhibits steep gradients of salinity and temperature in the upper layer of the water column. The cells of N. aquaticus thriving in Ekho Lake are able to grow in wide ranges of temperature (3 to 43.5°C) and salinity (0 to 15% NaCl). Here, we sequenced the complete genome of N. aquaticus KCTC 9944T, aiming to better understand the adaptation of this bacterium to the strong environmental gradients at the molecular level. The genome consists of 4,580,814bp (G+C content of 73.2%) with a single chromosome, 4432 protein-coding genes, 51 tRNAs and 2 rRNA operons. The genome possesses genes for the Entner-Doudoroff pathway, photoheterotrophy, the conversion of acetate to acetyl-CoA, gluconeogenesis, and energy storage that are all advantageous to oligotrophic bacteria. The presence of genes involved in osmotic balance, fatty acid desaturation, cold and heat shock responses, and the oxygen affinities of respiratory oxidases are likely associated with high tolerance to strong gradients of salinity, temperature and oxygen concentration.

Rapid ice sheet response to deglacial and Holocene paleoenvironmental changes in eastern Prydz Bay, East Antarctica

Prydz Bay lies at the terminus of one of East Antarctica's largest glacial systems and is a key region for understanding the response of the ice sheet to past and future environmental changes. In this study, we explore the dynamics and paleo-geometry of the ice sheet in eastern Prydz Bay, using a combination of bathymetric features on the seafloor to delineate past flow patterns, and cosmogenic nuclide dating of glacial deposits on land to constrain ice sheet terminus chronologies. Large streamlined bedforms on the sea floor record the existence of a primary ice stream in Svenner Channel, collecting ice from multiple tributary ice streams and discharging into the main trunk stream of the Lambert Glacier-Amery Ice Shelf system in Prydz Channel. The location and orientation of the north-eastern tributary to this ice stream also provide evidence for a substantial independent ice dome on the outer shelf at Four Ladies Bank. Exposure of ice-free areas at outer Rauer Group and Vestfold Hills indicates that grounding line retreat across eastern Prydz Bay was largely complete by ∼14 ka BP, and the ice margin had retreated to within ∼1 km of its present position by ∼10 ka BP. Onshore moraines record periods of ice margin retreat during the middle (∼6 ka BP) and very late (∼0.5 ka BP) Holocene coinciding with local warm periods. Subsidence recorded in modern Global Navigation Satellite System (GNSS) observations suggests the regional ice sheet was smaller than at present in the period between the middle and very late Holocene advances. The unusually dynamic ice sheet behaviour in this area is attributed to the smooth, reverse-slope bed characteristics of eastern Prydz Bay, which enabled rapid retreat of the ice sheet margin several hundred kilometres during deglacial events.

Orographic Flow Influence on Precipitation During an Atmospheric River Event at Davis, Antarctica

AbstractIntense snowfall sublimation was observed during a precipitation event over Davis in the Vestfold Hills, East Antarctica, from 08 to 10 January 2019. Radar observations and simulations from the Weather Research and Forecasting model revealed that orographic gravity waves (OGWs), generated by a north‐easterly flow impinging on the ice ridge upstream of Davis, were responsible for snowfall sublimation through a foehn effect. Despite the strong meridional moisture advection associated with an atmospheric river (AR) during this event, almost no precipitation reached the ground at Davis. We found that the direction of the synoptic flow with respect to the orography determined the intensity of OGWs over Davis, which in turn directly influenced the snowfall microphysics. We hypothesize that turbulence induced by the OGWs likely enhanced the aggregation process, as identified thanks to dual‐polarization and dual‐frequency radar observations. This study suggests that despite the intense AR, the precipitation distribution was determined by local processes tied to the orography. The mechanisms found in this case study could contribute to the extremely dry climate of the Vestfold Hills, one of the main Antarctic oases.

Remarkably coherent population structure for a dominant Antarctic Chlorobium species

BackgroundIn Antarctica, summer sunlight enables phototrophic microorganisms to drive primary production, thereby “feeding” ecosystems to enable their persistence through the long, dark winter months. In Ace Lake, a stratified marine-derived system in the Vestfold Hills of East Antarctica, a Chlorobium species of green sulphur bacteria (GSB) is the dominant phototroph, although its seasonal abundance changes more than 100-fold. Here, we analysed 413 Gb of Antarctic metagenome data including 59 Chlorobium metagenome-assembled genomes (MAGs) from Ace Lake and nearby stratified marine basins to determine how genome variation and population structure across a 7-year period impacted ecosystem function.ResultsA single species, Candidatus Chlorobium antarcticum (most similar to Chlorobium phaeovibrioides DSM265) prevails in all three aquatic systems and harbours very little genomic variation (≥ 99% average nucleotide identity). A notable feature of variation that did exist related to the genomic capacity to biosynthesize cobalamin. The abundance of phylotypes with this capacity changed seasonally ~ 2-fold, consistent with the population balancing the value of a bolstered photosynthetic capacity in summer against an energetic cost in winter. The very high GSB concentration (> 108 cells ml−1 in Ace Lake) and seasonal cycle of cell lysis likely make Ca. Chlorobium antarcticum a major provider of cobalamin to the food web. Analysis of Ca. Chlorobium antarcticum viruses revealed the species to be infected by generalist (rather than specialist) viruses with a broad host range (e.g., infecting Gammaproteobacteria) that were present in diverse Antarctic lakes. The marked seasonal decrease in Ca. Chlorobium antarcticum abundance may restrict specialist viruses from establishing effective lifecycles, whereas generalist viruses may augment their proliferation using other hosts.ConclusionThe factors shaping Antarctic microbial communities are gradually being defined. In addition to the cold, the annual variation in sunlight hours dictates which phototrophic species can grow and the extent to which they contribute to ecosystem processes. The Chlorobium population studied was inferred to provide cobalamin, in addition to carbon, nitrogen, hydrogen, and sulphur cycling, as critical ecosystem services. The specific Antarctic environmental factors and major ecosystem benefits afforded by this GSB likely explain why such a coherent population structure has developed in this Chlorobium species.FJebgLEuwcBu4fPtsFrHHTVideo abstract

Environmental DNA metabarcoding for monitoring metazoan biodiversity in Antarctic nearshore ecosystems.

Antarctic benthic ecosystems support high biodiversity but their characterization is limited to a few well-studied areas, due to the extreme environment and remoteness making access and sampling difficult. Our aim was to compare water and sediment as sources of environmental DNA (eDNA) to better characterise Antarctic benthic communities and further develop practical approaches for DNA-based biodiversity assessment in remote environments. We used a cytochrome c oxidase subunit I (COI) metabarcoding approach to characterise metazoan communities in 26 nearshore sites across 12 locations in the Vestfold Hills (East Antarctica) based on DNA extracted from either sediment cores or filtered seawater. We detected a total of 99 metazoan species from 12 phyla across 26 sites, with similar numbers of species detected in sediment and water eDNA samples. However, significantly different communities were detected in the two sample types at sites where both were collected (i.e., where paired samples were available). For example, nematodes and echinoderms were more likely to be detected exclusively in sediment and water eDNA samples, respectively. eDNA from water and sediment core samples are complementary sample types, with epifauna more likely to be detected in water column samples and infauna in sediment. More reference DNA sequences are needed for infauna/meiofauna to increase the proportion of sequences and number of taxa that can be identified. Developing a better understanding of the temporal and spatial dynamics of eDNA at low temperatures would also aid interpretation of eDNA signals from polar environments. Our results provide a preliminary scan of benthic metazoan communities in the Vestfold Hills, with additional markers required to provide a comprehensive biodiversity survey. However, our study demonstrates the choice of sample type for eDNA studies of benthic ecosystems (sediment, water or both) needs to be carefully considered in light of the research or monitoring question of interest.

Geochemical and palaeomagnetic characteristics of the Vestfold Hills mafic dykes in the Prydz Bay region: implications of a Paleoproterozoic connection between East Antarctica and Proto-India

Abstract The Archean age granite gneiss basement along the Prydz Bay coastline in East Antarctica hosts north–south-, east–west-, NE–SW- and NW–SE-trending mafic dyke swarms in the Vestfold Hills region that intruded between 2420 and 1250 Ma. The orientations of dykes do not show a direct correlation with the dyke geochemistry. Instead the dykes can be broadly discriminated into high-Mg and Fe-rich tholeiites. The former type is more siliceous, large ion lithophile elements (LILEs), high field strength elements (HFSEs) and light REEs enriched crystallized from a fractionated melt with a notable crustal component or fluid enrichment through the previous subduction process. The Fe-rich tholeiites are less siliceous, have lower abundances of LILEs and REEs, that indicates derivation from an undifferentiated, primitive melt. The geochemical characteristics of both types underline a shallow level and a high degree of melting in the majority of cases, and a broadly island arc basalt (IAB) affinity. Palaeomagnetic analysis of hand samples shows directional groups consistent with geochemical groupings. The Vestfold Hills dykes show a possible linkage with the coeval mafic dykes in the Eastern Dharwar and Bastar cratons of the South Indian Block, based on the similarity in the Paleoproterozoic palaeolatitudes.

Shedding Light on Microbial "Dark Matter": Insights Into Novel Cloacimonadota and Omnitrophota From an Antarctic Lake.

The potential metabolism and ecological roles of many microbial taxa remain unknown because insufficient genomic data are available to assess their functional potential. Two such microbial “dark matter” taxa are the Candidatus bacterial phyla Cloacimonadota and Omnitrophota, both of which have been identified in global anoxic environments, including (but not limited to) organic-carbon-rich lakes. Using 24 metagenome-assembled genomes (MAGs) obtained from an Antarctic lake (Ace Lake, Vestfold Hills), novel lineages and novel metabolic traits were identified for both phyla. The Cloacimonadota MAGs exhibited a capacity for carbon fixation using the reverse tricarboxylic acid cycle driven by oxidation of hydrogen and sulfur. Certain Cloacimonadota MAGs encoded proteins that possess dockerin and cohesin domains, which is consistent with the assembly of extracellular cellulosome-like structures that are used for degradation of polypeptides and polysaccharides. The Omnitrophota MAGs represented phylogenetically diverse taxa that were predicted to possess a strong biosynthetic capacity for amino acids, nucleosides, fatty acids, and essential cofactors. All of the Omnitrophota were inferred to be obligate fermentative heterotrophs that utilize a relatively narrow range of organic compounds, have an incomplete tricarboxylic acid cycle, and possess a single hydrogenase gene important for achieving redox balance in the cell. We reason that both Cloacimonadota and Omnitrophota form metabolic interactions with hydrogen-consuming partners (methanogens and Desulfobacterota, respectively) and, therefore, occupy specific niches in Ace Lake.