Vestfold Hills Research Articles

Mantle rocks in East Antarctica

Abstract Only three localities of mantle xenoliths are known from all of East Antarctica, occurring at the Jetty Peninsula (Lambert–Amery Rift), Vestfold Hills and Gaussberg volcano. The latter two are spinel-facies peridotites, whereas the Jetty Peninsula rocks also include garnet-spinel lherzolites; all come from Indo-Antarctica. The mantle xenoliths of Jetty Peninsula and Vestfold Hills contain abundant geochemical and mineralogical evidence for multiple enrichment events that are attributed to infiltration of melts and their fluid products. Many of these episodes are spatially related to precursory activity along major trans-lithospheric structures that eventually led to the separation of India from Antarctica. Mantle rocks also occur at Schirmacher Oasis (Dronning Maud Land) and Haskard Highlands (Shackleton Ranges) as blocks tectonically emplaced in high-grade crustal rocks. These show varying degrees of alteration due to reaction with silicic crustal rocks or hydrous fluids: none correspond to unchanged mantle compositions. Geophysical surveys are our only information on the mantle lithosphere beneath the inland ice, and these can be used to infer the locations of thicker lithosphere probably related to cratons by southward extrapolation of coastal geological correlations. Intense local modification of the mantle lithosphere by melt infiltration and fluid movements may influence the large-scale images derived from geophysical data, and may be incorrectly interpreted as homogeneous compositions.

Influence of the polar light cycle on seasonal dynamics of an Antarctic lake microbial community

BackgroundCold environments dominate the Earth’s biosphere and microbial activity drives ecosystem processes thereby contributing greatly to global biogeochemical cycles. Polar environments differ to all other cold environments by experiencing 24-h sunlight in summer and no sunlight in winter. The Vestfold Hills in East Antarctica contains hundreds of lakes that have evolved from a marine origin only 3000–7000 years ago. Ace Lake is a meromictic (stratified) lake from this region that has been intensively studied since the 1970s. Here, a total of 120 metagenomes representing a seasonal cycle and four summers spanning a 10-year period were analyzed to determine the effects of the polar light cycle on microbial-driven nutrient cycles.ResultsThe lake system is characterized by complex sulfur and hydrogen cycling, especially in the anoxic layers, with multiple mechanisms for the breakdown of biopolymers present throughout the water column. The two most abundant taxa are phototrophs (green sulfur bacteria and cyanobacteria) that are highly influenced by the seasonal availability of sunlight. The extent of the Chlorobium biomass thriving at the interface in summer was captured in underwater video footage. The Chlorobium abundance dropped from up to 83% in summer to 6% in winter and 1% in spring, before rebounding to high levels. Predicted Chlorobium viruses and cyanophage were also abundant, but their levels did not negatively correlate with their hosts.ConclusionOver-wintering expeditions in Antarctica are logistically challenging, meaning insight into winter processes has been inferred from limited data. Here, we found that in contrast to chemolithoautotrophic carbon fixation potential of Southern Ocean Thaumarchaeota, this marine-derived lake evolved a reliance on photosynthesis. While viruses associated with phototrophs also have high seasonal abundance, the negative impact of viral infection on host growth appeared to be limited. The microbial community as a whole appears to have developed a capacity to generate biomass and remineralize nutrients, sufficient to sustain itself between two rounds of sunlight-driven summer-activity. In addition, this unique metagenome dataset provides considerable opportunity for future interrogation of eukaryotes and their viruses, abundant uncharacterized taxa (i.e. dark matter), and for testing hypotheses about endemic species in polar aquatic ecosystems.3rEAa4a8EPvdQSJ1TDqSyzVideo

A re-investigation of lake sediment diatoms from the Vestfold Hills, Antarctica, using an updated, fine-grained taxonomy

The non-marine diatom flora of the Antarctic continent is currently being revised as recent work within the Maritime and Sub-Antarctic regions has unveiled a number of new endemic species. The under reporting of endemic species is partially due to the historic ‘force-fitting’ of Antarctic species into European names. Within East Antarctica, the Vestfold Hills are an extensively studied area known for their diversity of lakes spanning a salinity gradient, for which Diatoms of the saline lakes of the Vestfold Hills, Antarctica by Roberts & McMinn (1999) has a primary identification resource for over two decades. To determine if improved taxonomic resolution alters the ecological interpretation of these lakes, 30 prepared lake sediment samples first examined by Roberts & McMinn (1999) were re-analysed using an updated, fine-grained taxonomic approach. Our analyses confirmed the role of salinity and alkalinity in structuring Vestfold Hills diatom communities. Thus, the increased taxonomic resolution did not change the original ecological interpretation. However, the revised flora of the Vestfold Hills features 37 species endemic to the Antarctic Region, including members of Luticola, Sabbea and Halamphora, among others. In total, 183 taxa across 38 genera were observed, in contrast to the 67 taxa reported in the original work. The revised flora, including a larger proportion of endemic species, may improve our understanding of the diatom community in general and has wider implications for both conservation and biodiversity estimates of Antarctica. More widely applied, these data can be incorporated into larger studies of Antarctic microbial biogeography and biodiversity.

Lifting the veil on arid-to-hyperarid Antarctic soil microbiomes: a tale of two oases

BackgroundResident soil microbiota play key roles in sustaining the core ecosystem processes of terrestrial Antarctica, often involving unique taxa with novel functional traits. However, the full scope of biodiversity and the niche-neutral processes underlying these communities remain unclear. In this study, we combine multivariate analyses, co-occurrence networks and fitted species abundance distributions on an extensive set of bacterial, micro-eukaryote and archaeal amplicon sequencing data to unravel soil microbiome patterns of nine sites across two east Antarctic regions, the Vestfold Hills and Windmill Islands. To our knowledge, this is the first microbial biodiversity report on the hyperarid Vestfold Hills soil environment.ResultsOur findings reveal distinct regional differences in phylogenetic composition, abundance and richness amongst microbial taxa. Actinobacteria dominated soils in both regions, yet Bacteroidetes were more abundant in the Vestfold Hills compared to the Windmill Islands, which contained a high abundance of novel phyla. However, intra-region comparisons demonstrate greater homogeneity of soil microbial communities and measured environmental parameters between sites at the Vestfold Hills. Community richness is largely driven by a variable suite of parameters but robust associations between co-existing members highlight potential interactions and sharing of niche space by diverse taxa from all three microbial domains of life examined. Overall, non-neutral processes appear to structure the polar soil microbiomes studied here, with niche partitioning being particularly strong for bacterial communities at the Windmill Islands. Eukaryotic and archaeal communities reveal weaker niche-driven signatures accompanied by multimodality, suggesting the emergence of neutrality.ConclusionWe provide new information on assemblage patterns, environmental drivers and non-random occurrences for Antarctic soil microbiomes, particularly the Vestfold Hills, where basic diversity, ecology and life history strategies of resident microbiota are largely unknown. Greater understanding of these basic ecological concepts is a pivotal step towards effective conservation management.

Enhanced Iron Flux to Antarctic Sea Ice via Dust Deposition From Ice‐Free Coastal Areas

AbstractAntarctic sea ice is an important temporal reservoir of iron which can boost primary production in the marginal ice zone during the seasonal melt. While studies have reported that Antarctic fast ice bears high concentrations of iron due to the proximity to coastal sources, less clear are the biogeochemical changes this iron pool undergoes during late spring. Here we describe a 3‐week time series of physical and biogeochemical data, including iron, from first‐year coastal fast ice sampled near Davis Station (Prydz Bay, East Antarctica) during late austral spring 2015. Our study shows that dissolved and particulate iron concentrations in sea ice were up to two orders of magnitude higher than in under‐ice seawater. Furthermore, our results indicate a significant contribution of lithogenic iron from the Vestfold Hills (as deduced from the comparison with crustal element ratios) to the particulate iron pool in fast ice after a blizzard event halfway through the time series. Windblown dust represented approximately 75% of the particulate iron found in the ice and is a potential candidate for keeping concentrations of soluble iron stable during our observations. These results suggest that iron entrapped during ice formation, likely from sediments, as well as local input of coastal dust, supports primary productivity in Davis fast ice. As ice‐free land areas are likely to expand over the course of the century, this work highlights the need to quantify iron inputs from continental Antarctic dust and its bioavailability for ice algae and phytoplankton.

<p><strong><em>Sabbea</em></strong><strong> gen. nov., a new diatom genus (Bacillariophyta) from continental Antarctica</strong></p>

The non-marine diatom flora of the Antarctic Continent includes several endemic taxa recorded over the past 100 years. One of these taxa, Navicula adminensis D.Roberts & McMinn, was described from the Vestfold Hills, East Antarctica. Detailed light and scanning electron microscopy observations have shown that based on its morphological features, the species does not belong to the genus Navicula sensu stricto. To determine the most closely related genera to N. adminensis, the morphological features of Adlafia, Kobayasiella, Envekadea, Stenoneis, Berkeleya, Climaconeis, and Parlibellus were compared with those of N. adminensis. Although each of these genera shows one or more similar features, none of them accommodates the salient morphological characteristics of N. adminensis. Therefore, a new genus, Sabbea gen. nov., is herein described, and Navicula adminensis is formally transferred to the new genus as Sabbea adminensis comb. nov. The genus Sabbea is characterized by uniseriate striae composed of small, rounded areolae occluded externally by individual hymenes, a rather simple raphe structure with straight, short proximal ends and short terminal raphe fissures, open girdle bands with double perforation and a very shallow mantle.

Late Holocene colonisation of snow petrels (Pagodroma nivea) of the Prince Charles Mountains, Antarctica

The effect of long-term environmental changes on sea bird populations with respect to changes in their breeding and foraging habitats is difficult to assess due to the scarcity of records that go beyond direct observational data. Information on the past distribution of snow petrel Pagodroma nivea (Forster) breeding colonies can be obtained from deposits of their proventricular stomach oil, so-called Antarctic mumiyo. In our study, we present 14C ages of mumiyo deposits from northern and southern Prince Charles Mountains, East Antarctica, to reconstruct the timing of snow petrel occupation at these inland breeding localities. 14C ages indicate a minimum age of snow petrel occupation of 3680 cal year bp. The colonisation post-dates the de-glacial local and regional ice sheet retreat by several thousand years. This either suggests limited accessibility of the inland sites or a lack of suitable nesting locations prior to the Mid-Holocene and/or changes in the marine habitat affecting access to the foraging grounds. 14C ages of mumiyo deposits from Vestfold and Larsemann Hills to the east of Prydz Bay point to a regional pattern of snow petrel dispersal starting in the Mid-Holocene. This suggests environmental changes in the foraging habitat to be the most likely drivers for extending breeding site locations of snow petrels to more inland ice-free areas in the Prydz Bay Region.

Dynamics of penguin population size and food availability at Prydz Bay, East Antarctica, during the last millennium: A solar control

The paleoecology of the Adélie penguin (Pygoscelis adeliae) is controlled by multiple factors. In this study, we analyzed two millennial-scale ornithogenic sediment cores, RNL and RL, from the Vestfold Hills, East Antarctica. Using the Al-normalized phosphorus content of the bulk sediment and carbon/nitrogen fractions in penguin remains, we reconstructed relative changes in the penguin population size of each sub-colony and relative krill abundance in the summer Prydz Bay polynya. Both records are correlated to solar irradiance. At the centennial scale, the penguin population recorded in core RNL decreased from ~1120–860 yr BP, reached a peak from ~860–630 yr BP, remained at a low level from ~630–320 yr BP, and then increased with large fluctuations during the past ~400 years. These changes are all in-phase with the trend of solar irradiance. At the decadal scale, penguin population minima correspond to solar minima from ~490–400 yr BP (Spörer minimum), ~290–220 yr BP (Maunder minimum), and from ~160–120 yr BP (Dalton minimum; whereas population maxima correspond to solar maxima from ~1030–980 yr BP, ~350–290 yr BP, ~210–160 yr BP, ~120–70 yr BP. The population recorded in core RL exhibited the same changes as in RNL during the last 480 years. The reconstructed krill abundance also corresponds to these trends when data are available. This correspondence demonstrates a food-chain mechanism that is related to solar activity and light availability at the ocean surface, which influence the intensity of photosynthesis and phytoplankton productivity, and thus the abundance of krill and apex predators such as penguins. Our findings highlight the fact that despite the various climatic impacts on penguin populations, their effects on the base of the food chain are usually the direct drive.

Mafic dykes in the Rauer Islands and Vestfold Hills (East Antarctica): A chemical and Nd isotopic comparison

The Rauer Islands and neighbouring Vestfold Hills are intruded by numerous mafic dykes. In the latter area the dykes are basically not deformed, albeit metamorphosed in the southwestern part, whereas in the former they are strongly deformed and metamorphosed. In Scherbinina Island they intrude Archaean rocks and their ages are between ca. 2800 Ma and ca. 530 Ma, while in Efremova, Filla, and Hop islands they intrude Mesoproterozoic ca. 1150 Ma or ca. 1000 Ma orthogneiss and pre-date ca. 1000–950 Ma tectonism. A comparison and possible correlation between dykes in the Rauer Islands and the Vestfold Hills is a crucial point in the interpretation of the regional tectonic evolution. We present ICP-MS analyses of trace elements and Nd isotopic data for mafic dykes from Rauer Islands and Vestfold Hills. Two chemically distinct dyke groups are distinguished in the Rauer Islands: low-LILE group which was sampled from Scherbinina, Efremova and west Filla islands, and high-LILE group which was sampled only from Hop and central Filla islands. The low-LILE dykes were emplaced into ca. 1150 Ma orthogneisses and more ancient rocks, but were not found within ca. 1000 Ma orthogneisses, whereas the high-LILE dykes intrude ca. 1000 Ma orthogneiss, but were not found within Archaean rocks. The low-LILE group displays many chemical and Nd isotopic features in common with high-Fe mafic dykes in the Vestfold Hills, but the age uncertainties preclude a correlation. The formation of the high-LILE mafic dykes in the Rauer Islands indicates magmatism in late-orogenic environments at the end of the Rayner Orogeny.Our data argue against direct correlation between mafic dykes in Rauer Islands and Vestfold Hills, in spite of similar tholeiitic whole rock compositions. The Vestfold Hills dykes experienced cooling to the Sm–Nd systematic closure temperature by 790 Ma and subsequent shearing at ca 635 Ma (garnet – whole rock). Considering the data published elsewhere we interpret that the Vestfold and Rauer crustal blocks experienced shared tectonothermal histories since ca 950 Ma but may have been conjugated in the present positions only by the late Neoproterozoic due to horizontal transport along a major transcurrent shear zone.

Precambrian mafic dyke swarms in the Singhbhum craton (eastern India) and their links with dyke swarms of the eastern Dharwar craton (southern India)

Based on trend, cross-cutting relationships and U-Pb dating, Precambrian mafic dykes in the Singhbhum craton, earlier collectively identified as ‘Newer Dolerite Swarm’, have been separated into seven distinct swarms, which are thought to be the plumbing systems for Large Igneous Provinces (LIPs). These Singhbhum swarms range in age from ∼2.80 Ga to ∼1.76 Ga, and include the ∼2.80 Ga NE-SW trending Keshargaria swarm, ∼2.75–2.76 Ga NNE-SSW to NE-SW trending Ghatgaon swarm, the ∼2.26 Ga NE-SW to ENE-WSW trending Kaptipada swarm (based on a new U-Pb ID-TIMS age 2256 ± 6 Ma), the ∼1.77 Ga WNW-ESE trending Pipilia swarm, the early-Paleoproterozoic E-W to ENE-WSW trending Keonjhar swarm, the middle-Paleoproterozoic NW-SE to NNW-SSE trending Bhagamunda swarm, and the late-Paleoproterozoic N-S to NNE-SSW trending Barigaon swarm. Two of the Singhbhum swarms, the ∼2.26 Ga Kaptipada and ∼1.77 Ga Pipilia, are closely matched with the ∼2.26–2.25 Ga Ippaguda-Dhiburahalli and ∼1.79 Ga Pebbair swarms, respectively, of the eastern Dharwar craton. The correlations suggest that the Singhbhum and Dharwar cratons were close enough at these times to share two reconstructed LIPs, a 2.26–2.25 Ga Kaptipada– Ippaguda-Dhiburahalli LIP and a 1.79–1.77 Ga Pipilia-Pebbair LIP, and if so, both swarms must be present in the intervening Bastar craton (candidates are proposed). Also, the 2.76–2.75 Ga Ghatgaon swarm of the Singhbhum craton can be provisionally correlated with ∼2.7 Ga Keshkal swarm of the Bastar craton. The 2.26–2.25 Ga Kaptipada–Ippaguda-Dhiburahalli LIP of the Singhbhum-Bastar-Dharwar reconstruction has age matches in the Vestfold Hills of Antarctica (∼2.24 Ga dykes), the Kaapvaal craton (the ∼2.25–2.23 Ga Hekpoort lavas) and perhaps the Zimbabwe craton (2.26 Ga Chimbadzi troctolite intrusions). The 1.76–1.79 Ga Pipilia-Pebbair LIP of the Singhbhum-Bastar-Dharwar reconstruction has age matches in the North China, Australian Shield, Amazonian, Rio de Plata and Sarmatia cratons. The relevance of these matches for reconstructions will require future testing using paleomagnetic studies. While there are ∼2.7–2.8 Ga LIP-type greenstone belts in many crustal blocks, there are no precise matches with the 2.76–2.75 Ga Ghatgaon swarm of the Singhbhum craton. However, the 2.80 Ga Keshargaria swarm can be potentially linked with units in the Pilbara and Yilgarn cratons.

Genomic variation and biogeography of Antarctic haloarchaea

BackgroundThe genomes of halophilic archaea (haloarchaea) often comprise multiple replicons. Genomic variation in haloarchaea has been linked to viral infection pressure and, in the case of Antarctic communities, can be caused by intergenera gene exchange. To expand understanding of genome variation and biogeography of Antarctic haloarchaea, here we assessed genomic variation between two strains of Halorubrum lacusprofundi that were isolated from Antarctic hypersaline lakes from different regions (Vestfold Hills and Rauer Islands). To assess variation in haloarchaeal populations, including the presence of genomic islands, metagenomes from six hypersaline Antarctic lakes were characterised.ResultsThe sequence of the largest replicon of each Hrr. lacusprofundi strain (primary replicon) was highly conserved, while each of the strains’ two smaller replicons (secondary replicons) were highly variable. Intergenera gene exchange was identified, including the sharing of a type I-B CRISPR system. Evaluation of infectivity of an Antarctic halovirus provided experimental evidence for the differential susceptibility of the strains, bolstering inferences that strain variation is important for modulating interactions with viruses. A relationship was found between genomic structuring and the location of variation within replicons and genomic islands, demonstrating that the way in which haloarchaea accommodate genomic variability relates to replicon structuring. Metagenome read and contig mapping and clustering and scaling analyses demonstrated biogeographical patterning of variation consistent with environment and distance effects. The metagenome data also demonstrated that specific haloarchaeal species dominated the hypersaline systems indicating they are endemic to Antarctica.ConclusionThe study describes how genomic variation manifests in Antarctic-lake haloarchaeal communities and provides the basis for future assessments of Antarctic regional and global biogeography of haloarchaea.

Inverted sediments in the coastal Antarctic lake: Evidence of paleostorm?

The faunal (foraminiferal and diatom abundance) and sedimentological analysis was carried out on two cores collected from a coastal lake in the Vestfold Hills region of Antarctica. Out of a couple of cores collected from the same lake, the one closer to the marine inlet, contained abundant foraminifera and the diatoms were dominant in the second core. The radiocarbon dating of the organic matter revealed that the sediments were inverted, with two sequences of younger sediments overlain by older sediments. The increased abundance of marine microfossils, including both the foraminifera and diatoms in inverted layers, suggests that the sediments were transported from the adjacent shelf. The transport from the shelf is further confirmed by the abundant presence of planktic foraminiferal shells in the sediments. The planktic foraminifera are relatively deeper dwellers and thus confirm the transport of material from relatively deeper water depths. The transport of older marine sediments from the nearby shelf, into the lake against gravity is inferred as a result of storm/cyclone. Two such past storm-cyclone events are inferred as the core includes two sets of inverted sediments. The study suggests that faunal and sedimentological analysis in conjunction with chronology can be applied to infer past instances of extreme events in the high latitude regions.

Penguin colonization following the last glacial-interglacial transition in the Vestfold Hills, East Antarctica

The population history of the Adélie penguin (Pygoscelis adeliae) and its response to climatic and environmental changes have been widely studied in maritime Antarctica and several glacial refugia of Adélie penguins were dated back to the Last Glacial Maximum. However, the process of colony expansion during the subsequent glacial-interglacial transition was less well-documented. In this paper, we investigate an ornithogenic core from Vestfold Hills, East Antarctica, to improve knowledge of postglacial penguin colonization. Local deglaciation occurred around 15.6kyr BP, based on a coarse-grained detrital layer, a date that is earlier than most of those reported in other studies from the same region. Geochemical analysis of the core suggests penguins started colonizing the northern Vestfold Hills around 14.6kyr BP, the oldest geological record in East Antarctica on penguin occupation, and their population exhibited a broadly increasing trend thereafter. The population expanded at approximately 6740yr BP, in the mid-Holocene, which corresponds to a local climatic optimum. Although this inference is based on population changes of local sub-colonies, it corresponds well to reconstructions of regional climate change, and changes in the penguin population based on genetic studies. From a consideration of the results of previous studies of the occupation history of sea birds following deglaciation in the Arctic, as well as other parts of Antarctica, we propose that sea birds colonized the emerging ice-free areas shortly after local glacier retreat. Over geological time-scales, the availability of breeding habitat is a key factor controlling the population size and activity range of Antarctic Adélie penguins.

Lake Sediment Studies in Schirmacher Oasis and Larsemann Hills, East Antarctica – An Indian Perspective

Antarctica plays a vital role in controlling Earth’s climate. Recent data indicates that there are widespread changes in Antarctica, especially the Antarctic Peninsula due to global warming. Therefore collecting past climatic information from ice-cores, marine and lake sediments are extremely important as the data can be utilized in the available models to plausibly model the future climate for the region. Lake sediments are widely found in Schirmacher Oasis, Larsemann Hills and Vestfold Hills in East Antarctica. During the period 2010-2015, considerable amount of work has been done on surficial sediments, water samples from the sediment-water interface and sediment cores from lakes of these regions for different environmental applications, such as provenance, bacterial diversity and paleoclimatic studies. Techniques such as environmental magnetism, geochemistry (organic and inorganic), sedimentology, clay mineralogy, scanning electron microscopy and geochronology have been employed on these sediments to decipher the past climate and environmental changes on different time-scales and to understand the provenance of these sediments. Few paleoclimatic studies are limited to the Holocene whereas a couple of studies document glacial-interglacial climatic variations in Schirmacher Oasis. These studies have a much better chronological framework when compared to the earlier studies. However, there are still issues with the temporal resolution of the data when compared with ice-cores which offers much better sample resolution. It is therefore crucial that future studies on lake sediments from these regions be made on a high-resolution interval which will allow the researchers to have a good correlation with other archives such as ice-cores, etc.

A comparative structural study of nitrogen-rich fulvic acids from various Antarctic lakes

Environmental contextFulvic acids are important naturally occurring organic materials, but unravelling their complex structures remains challenging. This paper suggests chemical analyses to facilitate structural studies of fulvic acids, and to investigate the similarities and differences of fulvic acids from various natural sources. AbstractWe comprehensively examined fulvic acids isolated from three lakes in Vestfold Hills, eastern Antarctica and microbial reference fulvic acid from Pony Lake located in western Antarctica. These fulvic acids were compared in terms of their structural similarities and differences by means of elemental analysis, cross polarisation magic-angle spinning (CP-MAS) 13C NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and tetramethylammonium hydroxide (TMAH) thermochemolysis coupled to gas chromatography–mass spectrometry (GC-MS). The results indicate that these Antarctic fulvic acids show notable differences in chemical composition and structure; in particular XPS demonstrates that the distribution of nitrogen-containing compounds in the nitrogen-rich Antarctic fulvic acids differ significantly from each other. The dissimilarities are also highlighted in terms of quantity and quality of their nitrogenous constituents. For instance, Organic Lake Fulvic Acid (OLFA) contains around 10 times lower amide groups (pyrimidine–peptide N) than Pendant Lake Fulvic Acid (PNFA). It also shows 1.5 times less quaternary amine than Mossel Lake Fulvic Acid (MLFA) and PNFA. According to CP-MAS 13C NMR experiments the carbohydrate content in Vestfold Hills fulvic acid is higher than that of Pony Lake Fulvic Acid (PLFA), suggesting that dissolved organic matter (DOM) from Vestfold Hills Lakes is immature. TMAH–GC-MS demonstrated that Antarctic fulvic acids are enriched in heterocyclic non-aromatic nitrogen-containing components such as pyrimidine structures, with the exception of OLFA. Furthermore, tricyclic terpenoids (dehydroabietic acid) were detected in two out of four fulvic acids tabulated using TMAH–GC-MS. Although diterpenes are commonly associated with plants and fungi, their occurrence in Antarctic fulvic acids could be justified due to their diverse origins from cyanobacteria to aerosols.

Fossil bivalves in marine sediments of Vestfold Hills in Eastern Antarctica

Bivalves collected in Vestfold Hills during the 55th Russian Antarctic Expedition (RAE, 2009−2010) are represented by five species. Four of them (Laternula elliptica, Thracia meridionalis, Adamussium colbecki, and Philobrya sublaevis) were collected in the sediments that filled the coastal lake terraces during the Holocene; these species are still abundant on the Antarctic shelf at present. Bivalves were found in eight samples, with L. elliptica shells and fragments thereof found in seven of those samples. The sample collected near Deep Lake had the most diverse species composition, as it contained all four species named above. Shells of named species widely occurring in present-day Antarctica were found high above sea level in the marine sediments of the oasis. This indicate to the similarity of the oasis habitats in the past and the recent marine conditions. Fragments of shells of the fifth (now extinct) species Ruthipecten tuftsensis were found in glacial–marine sediments of the Marine Plain dating back to the late Pleistocene. The present study of fossil bivalves from the late Cenozoic marine sediments in Vestfold Hills is the first of its kind in Russia.

Mafic Dykes in Rauer Islands and Vestfold Hills (East Antartica): A Geochemical and Nd Isotopic Comparison Arguing Against Their Correlation

Mafic Dykes in Rauer Islands and Vestfold Hills (East Antartica): A Geochemical and Nd Isotopic Comparison Arguing Against Their Correlation

Heterotrophic bacteria in Antarctic lacustrine and glacial environments

Antarctica has the greatest diversity of lakes types on the planet including freshwater, brackish, saline and hypersaline systems, epishelf lakes, ice shelf lakes and lakes and cryoconite holes on glacier surfaces. Beneath the continental ice sheet, there are hundreds of subglacial lakes. These systems are dominated by microbial food webs, with few or no metazoans. They are subject to continuous cold, low annual levels of photosynthetically active radiation and little or no allochthonous nutrient inputs from their catchments. Subglacial lakes function in darkness. Heterotrophic bacteria are a conspicuous and important component of the simple truncated food webs present. Bacterial abundance and production vary between freshwater and saline lakes, the latter being more productive. The bacterioplankton functions throughout the year, even in the darkness of winter when primary production is curtailed. In more extreme glacial habitats, biomass is even lower with low rates of production during the annual melt season. Inter-annual variation appears to be a characteristic of bacterial production in lakes. The factors that control production appear to be phosphorus limitation and grazing by heterotrophic and mixotrophic flagellate protozoa. The evidence suggests high rates of viral infection in bacteria and consequent viral lysis, resulting in significant carbon recycling, which undoubtedly supports bacterial growth in winter. The biodiversity of lacustrine Antarctic heterotrophic bacteria is still relatively poorly researched. However, most of the main phyla are represented and some patterns are beginning to emerge. One of the major problems is that data for heterotrophic bacteria are confined to a few regions served by well-resourced research stations, such as the McMurdo Dry Valleys, the Vestfold Hills and Signy Island. A more holistic multidisciplinary approach is needed to provide a detailed understanding of the functioning, biodiversity and evolution of these communities. This is particularly important as Antarctic lakes are regarded as sentinels of climate change.

Pliocene Mollusca (Bivalvia, Gastropoda) from the Sørsdal Formation, Marine Plain, Vestfold Hills, East Antarctica: taxonomy and implications for Antarctic Pliocene palaeoenvironments

Quilty, P.G., Darragh, T.A., Gallagher, S.J. & Harding, L.A. July 2016. Pliocene Mollusca (Bivalvia, Gastropoda) from the Sørsdal Formation, Marine Plain, Vestfold Hills, East Antarctica: taxonomy and implications for Antarctic Pliocene palaeoenvironments. Alcheringa 40, XXX–XXX. ISSN 0311-5518. Pliocene shallow-water marine sediments at Marine Plain (centred on 68°37.7ʹS; 78°07.8ʹE) and covering approximately 10 km² in the Vestfold Hills, East Antarctica, have yielded six species of gastropods, and 11 species of bivalves from two beds within the Sørsdal Formation. Most of the material is close to in situ but some specimens have been disturbed from their life position; there is no evidence of significant transport. The gastropods include Nacella concinna (Strebel, 1908), Falsimargarita parvispira Quilty, Darragh, Gallagher & Harding sp. nov., indeterminate species of trochids and naticids, Chlanidota (Chlanidota) sp. cf. C. signeyana Powell, 1951, and two species of Trophon/Trophonella. Bivalves include Ennucula sp. aff. E. grayi (d’Orbigny, 1846), Aequiyoldia defossata Quilty, Darragh, Gallagher & Harding, sp. nov., ‘Pectunculina’ sp., Lissarca sp., Austrochlamys anderssoni (Hennig, 1911), Ruthipecten campestris Quilty, Darragh, Gallagher & Harding sp. nov., Adamussium necopinatum Quilty, Darragh, Gallagher & Harding sp. nov., Limatula (Antarctolima) sp. cf. L. hodgsoni (Smith, 1907), Cyclocardia magna Quilty, Darragh, Gallagher & Harding sp. nov., ?Hiatella sp. cf. H. arctica (Linnaeus, 1767) and Laternula elliptica (King, 1832). Preservation varies considerably owing to recrystallization, dissolution or distortion through compaction, so several species are left in open nomenclature. Oxygen isotope data indicate that water temperature was 4–7.5°C at the time of shell growth. Many species or species groups are now extinct or have migrated away from the Antarctic to the sub-Antarctic region. An Antarctic mollusc fauna has been characteristic of the region for much of the Cenozoic. Patrick G. Quilty [ p.quilty@utas.edu.au ], Discipline of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, Tasmania 7001, Australia; Thomas A. Darragh [ tdarragh@museum.vic.gov.au ], Museum Victoria, GPO Box 666 Melbourne, Victoria 3000, Australia; Stephen J. Gallagher [ sjgall@unimelb.edu.au ], School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia; Lucy A. Harding [ harding.lucy.a@edumail.vic.gov.au ], School of Earth Sciences, The University of Melbourne, Victoria 3010, Australia.

Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica

AbstractThe Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time‐frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind‐blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2‐D and 3‐D produce similar resistivity models, where structures in the preferred 3‐D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.