Paeniglutamicibacter terrestris sp. nov., isolated from phenanthrene-degrading consortium enriched from Antarctic soil

A novel bacterium, designated strain ANT13_2^T, was isolated from a phenanthrene-degrading consortium enriched from a soil sample collected near the Great Wall Station located in the southwestern area of King George Island, Antarctica. Following a polyphasic taxonomic study, a novel species belonging to the genus Paeniglutamicibacter was described. The strain was a Gram-stain-positive bacterium that exhibited a rod-coccus growth cycle. Strain ANT13_2^T grew aerobically at an optimum temperature of 20-25 °C and at pH 7.0-8.0. Ribose, arabinose and glucose were detected as whole-cell sugars. The predominant menaquinone was MK-9. The diagnostic phospholipids were diphosphatidylglycerol, phosphatidylglycerol and an unidentified phospholipid. The predominant cellular fatty acids were anteiso-C_15 : 0 (67.7 %) and anteiso-C_17 : 0 (11.2 %). The DNA G+C content of the genomic DNA was 60.6 mol%. Based on 16S rRNA gene sequence analysis, strain ANT13_2^T showed the highest similarities to Paeniglutamicibacter antarcticus SPC26^T (98.9 %) followed by Paeniglutamicibacter gangotriensis Lz1y^T (98.4 %), Paeniglutamicibacter sulfureus DSM 20167^T (98.3%) and Paeniglutamicibacter kerguelensis KGN15^T (97.9 %). The average nucleotide identity values between strain ANT13_2^T and the type strains of P. antarcticus SPC26^T and P. gangotriensis Lz1y^T were 73.8 and 77.5 %, respectively, which are well below the 95-96 % species circumscription threshold. On the basis of this polyphasic taxonomic study, strain ANT13_2^T is proposed to represent a novel species to be named Paeniglutamicibacter terrestris sp. nov. The type strain is ANT13_2^T (=TBRC 11756^T=NBRC 114615^T).

Diesel in Antarctica and a Bibliometric Study on Its Indigenous Microorganisms as Remediation Agent

Diesel acts as a main energy source to complement human activities in Antarctica. However, the increased expedition in Antarctica has threatened the environment as well as its living organisms. While more efforts on the use of renewable energy are being done, most activities in Antarctica still depend heavily on the use of diesel. Diesel contaminants in their natural state are known to be persistent, complex and toxic. The low temperature in Antarctica worsens these issues, making pollutants more significantly toxic to their environment and indigenous organisms. A bibliometric analysis had demonstrated a gradual increase in the number of studies on the microbial hydrocarbon remediation in Antarctica over the year. It was also found that these studies were dominated by those that used bacteria as remediating agents, whereas very little focus was given on fungi and microalgae. This review presents a summary of the collective and past understanding to the current findings of Antarctic microbial enzymatic degradation of hydrocarbons as well as its genotypic adaptation to the extreme low temperature.

Centennial glacier retreat increases sedimentation and eutrophication in Subantarctic periglacial lakes: A study case of Lake Uruguay

High resolution XRF scanning documented inter-annual paleolimnological changes of a Subantarctic periglacial lake, during a process of centennial glacier retreat in King George Island, Antarctica. Two major paleoenvironmental stages were inferred from the combined analysis of elemental, molecular and isotopic biomarkers, with a boundary or transition set at about 3200 yr BP. The first stage was characterized by a relatively low allochthonous organic content, reduced productivity and nitrogen levels. Such paleoenvironmental conditions are interpreted as a terrestrial system under periglacial influence, where material influx was related to erosion process from the melt water discharge, because of the proximity to the Collins Glacier ice cap. After the major Holocene glacier advance dated at about 3500 yr BP, the ice cap retreat led to the formation of Lake Uruguay, which involved in filling processes leading to moraine deposits, proglacial meltwater channels, and lakes next to the land glacier. During the second stage, with the onset of the Current Warm Period, prior to 1900 CE the stabilization of the Zr/Rb ratio within the laminated sediments documented the origin of the lacustrine sedimentation system, with subsequent increases in the sedimentation rate and biomass content (total nitrogen and organic carbon). Time series analyses revealed that the lake displayed variability cycles related to El Niño Southern Oscillation (ENSO), as reflected by high resolution sedimentological proxies for grain size, weathering, allochthonous inputs from the watershed, increase of biomass and productivity, and changes in redox conditions, all of which displayed similar oscillation cycles from 2 to 6 yr. During this periglacial recession and associated eutrophication process, we detected a striking loss in both bacterial specific richness and diversity as inferred from preliminary selected ancient DNA analyses. Thus, the Antarctic warming scenario leading to glacier depletion appears to exert deterioration consequences on the Subantarctic microbial web.

A calibration of cellulose isotopes in modern prostrate Nothofagus and its application to fossil material from Antarctica

Carbon and oxygen isotopes (δ¹³C and δ¹⁸O) in tree rings are widely used to reconstruct palaeoclimate variables such as temperature during the Holocene (12 thousand years ago - present), and are used increasingly in deeper time. However, their use is largely restricted to arboreal trees, which excludes potentially important data from prostrate trees and shrubs, which grow in high latitude and altitude end-member environments. Here, we calibrate the use of δ¹³C and δ¹⁸O as climatic archives in two modern species of southern beech (Nothofagus) from Tierra del Fuego, Chile, at the southern limit of their current range. We show that prostrate trees are potentially suitable archives for recording climatological means over longer periods (on the order of decades), which opens up these important environments for tree ring isotope analysis. We then apply our new understanding to a remarkable late Neogene (17-2.5 Ma) fossil Nothofagus assemblage from the Transantarctic Mountains, Antarctica, representative of a prostrate tundra shrub growing during a period of significant ice sheet retreat. The δ¹³C of the fossil cellulose was found to be ~4‰ enriched relative to that of the modern tress. This is likely to be due to a combination of a more positive δ¹³C of contemporaneous atmospheric CO₂ and enhanced water use efficiency at the fossil site. Using the cellulose-δ¹⁸O in the fossil wood, we are able to reconstruct precipitation oxygen isotopes over the Antarctic interior for the first time for this time period. The results show that δ¹⁸O_precip over Antarctica was -16.0 ± 4.2‰, around 12‰ enriched relative to today, suggesting changes in the hydrological cycle linked to warmer temperatures and a smaller ice sheet.

Trophic and fitness correlates of mercury and organochlorine compound residues in egg-laying Antarctic petrels

Understanding the drivers and effects of exposure to contaminants such as mercury (Hg) and organochlorine compounds (OCs) in Antarctic wildlife is still limited. Yet, Hg and OCs have known physiological and fitness effects in animals, with consequences on their populations. Here we measured total Hg (a proxy of methyl-Hg) in blood cells and feathers, and 12 OCs (seven polychlorinated biphenyls, PCBs, and five organochlorine pesticides, OCPs) in plasma of 30 breeding female Antarctic petrels Thalassoica antarctica from one of the largest colonies in Antarctica (Svarthamaren, Dronning Maud Land). This colony is declining and there is poor documentation on the potential role played by contaminants on individual physiology and fitness. Carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope values measured in the females' blood cells and feathers served as proxies of their feeding ecology during the pre-laying (austral spring) and moulting (winter) periods, respectively. We document feather Hg concentrations (mean ± SD, 2.41 ± 0.83 μg g^-1 dry weight, dw) for the first time in this species. Blood cell Hg concentrations (1.38 ± 0.43 μg g^-1 dw) were almost twice as high as those reported in a recent study, and increased with pre-laying trophic position (blood cell δ¹⁵N). Moulting trophic ecology did not predict blood Hg concentrations. PCB concentrations were very low (Σ₇PCBs, 0.35 ± 0.31 ng g^-1 wet weight, ww). Among OCPs, HCB (1.02 ± 0.36 ng g^-1 ww) and p, p'-DDE (1.02 ± 1.49 ng g^-1 ww) residues were comparable to those of ecologically-similar polar seabirds, while Mirex residues (0.72 ± 0.35 ng g^-1 ww) were higher. PCB and OCP concentrations showed no clear relationship with pre-laying or moulting feeding ecology, indicating that other factors overcome dietary drivers. OC residues were inversely related to body condition, suggesting stronger release of OCs into the circulation of egg-laying females upon depletion of their lipid reserves. Egg volume, hatching success, chick body condition and survival were not related to maternal Hg or OC concentrations. Legacy contaminant exposure does not seem to represent a threat for the breeding fraction of this population over the short term. Yet, exposure to contaminants, especially Mirex, and other concurring environmental stressors should be monitored over the long-term in this declining population.

A Polar outlook: Potential interactions of micro- and nano-plastic with other anthropogenic stressors

Polar marine ecosystems may have higher sensitivity than other ecosystems to plastic pollution due to recurrent physical and biological features; presence of ice and high UV radiation, slow growth rates and weak genetic differentiation of resident biota, accumulation of persistent organic pollutants and heavy metals, and fast rates of warming and global ocean acidification. Here, we discuss potential sources of and exposure to micro- and nano-plastic in polar marine ecosystems and potential mixture effects of micro- and nano-plastic coupled with chemical and climate related stressors. We address the anthropogenic contaminants likely to be 'high risk' for interactions in Arctic and Antarctic waters for reasons such as accumulation under sea-ice, a known sink for plastic particulates. Consequently, we address the potential for localised plastic-chemical interactions and possible seasonal fluctuations in interactions associated with freeze-thaw events. The risks for keystone polar species are also considered, incorporating the behavioural and physiological traits of biota and addressing potential 'hotspot' areas. Finally, we discuss a possible direction for future research.

DNA photolyase from Antarctic marine bacterium Rhodococcus sp. NJ-530 can repair DNA damage caused by ultraviolet

Marine bacterium Rhodococcus sp. NJ-530 has developed several ultraviolet (UV) adaptive characteristics for survival and growth in extreme Antarctic environment. Rhodococcus sp. NJ-530 DNA photolyase encoded by a 1146 bp photolyase-homologous region (phr) was identified in genome. Quantitative real-time PCR demonstrated that transcriptional levels of phr were highly up-regulated by ultraviolet-B (UV-B) radiation (90 μW·cm^-2) and increased to a maximum of 149.17-fold after exposure for 20 min. According to the results of SDS-PAGE and western blot, PHR was effectively induced by isopropyl-β-d-1-thiogalactopyranoside (IPTG) at the genetically engineered BL21(DE3)-pET-32a( +)-phr construct under the condition of 15 °C for 16 h and 37 °C for 4 h. In terms of in vivo activity, compared with a phr-defective E. coli strain, phr-transformed E. coli exhibited higher survival rate under high UV-B intensity of 90 μW·cm^-2. Meanwhile, the purified PHR, with blue light, presented obvious photorepair activity toward UV-induced DNA damage in vitro assays. To sum up, studying the mechanisms of Rhodococcus sp. NJ-530 photolyase is of great interest to understand the adaptation of polar bacteria to high UV radiation, and such data present important therapeutic value for further UV-induced human skin and genetic damage diseases.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02660-8.

Diversity and Ecology of Chlorophyta (Viridiplantae) Assemblages in Protected and Non-protected Sites in Deception Island (Antarctica, South Shetland Islands) Assessed Using an NGS Approach

Assessment of the diversity of algal assemblages in Antarctica has until now largely relied on traditional microbiological culture approaches. Here we used DNA metabarcoding through high-throughput sequencing (HTS) to assess the uncultured algal diversity at two sites on Deception Island, Antarctica. The first was a relatively undisturbed site within an Antarctic Specially Protected Area (ASPA 140), and the second was a site heavily impacted by human visitation, the Whalers Bay historic site. We detected 65 distinct algal taxa, 50 from within ASPA 140 and 61 from Whalers Bay. Of these taxa, 46 were common to both sites, and 19 only occurred at one site. Algal richness was about six times greater than reported in previous studies using culture methods. A high proportion of DNA reads obtained was assigned to the highly invasive species Caulerpa webbiana at Whalers Bay, and the potentially pathogenic genus Desmodesmus was found at both sites. Our data demonstrate that important differences exist between these two protected and human-impacted sites on Deception Island in terms of algal diversity, richness, and abundance. The South Shetland Islands have experienced considerable effects of climate change in recent decades, while warming through geothermal activity on Deception Island itself makes this island one of the most vulnerable to colonization by non-native species. The detection of DNA of non-native taxa highlights concerns about how human impacts, which take place primarily through tourism and national research operations, may influence future biological colonization processes in Antarctica.

Metabolomics of Dry Versus Reanimated Antarctic Lichen-Dominated Endolithic Communities

Cryptoendolithic communities are almost the sole life form in the ice-free areas of the Antarctic desert, encompassing among the most extreme-tolerant organisms known on Earth that still assure ecosystems functioning, regulating nutrient and biogeochemical cycles under conditions accounted as incompatible with active life. If high-throughput sequencing based studies are unravelling prokaryotic and eukaryotic diversity, they are not yet characterized in terms of stress adaptations and responses, despite their paramount ecological importance. In this study, we compared the responses of Antarctic endolithic communities, with special focus on fungi, both under dry conditions (i.e., when dormant), and after reanimation by wetting, light, and optimal temperature (15 °C). We found that several metabolites were differently expressed in reanimated opposite sun exposed communities, suggesting a critical role in their success. In particular, the saccharopine pathway was up-regulated in the north surface, while the spermine/spermidine pathway was significantly down-regulated in the shaded exposed communities. The carnitine-dependent pathway is up-regulated in south-exposed reanimated samples, indicating the preferential involvement of the B-oxidation for the functioning of TCA cycle. The role of these metabolites in the performance of the communities is discussed herein.

Antarctic Water Tracks: Microbial Community Responses to Variation in Soil Moisture, pH, and Salinity

Ice-free soils in the McMurdo Dry Valleys select for taxa able to cope with challenging environmental conditions, including extreme chemical water activity gradients, freeze-thaw cycling, desiccation, and solar radiation regimes. The low biotic complexity of Dry Valley soils makes them well suited to investigate environmental and spatial influences on bacterial community structure. Water tracks are annually wetted habitats in the cold-arid soils of Antarctica that form briefly each summer with moisture sourced from snow melt, ground ice thaw, and atmospheric deposition via deliquescence and vapor flow into brines. Compared to neighboring arid soils, water tracks are highly saline and relatively moist habitats. They represent a considerable area (∼5–10 km²) of the Dry Valley terrestrial ecosystem, an area that is expected to increase with ongoing climate change. The goal of this study was to determine how variation in the environmental conditions of water tracks influences the composition and diversity of microbial communities. We found significant differences in microbial community composition between on- and off-water track samples, and across two distinct locations. Of the tested environmental variables, soil salinity was the best predictor of community composition, with members of the Bacteroidetes phylum being relatively more abundant at higher salinities and the Actinobacteria phylum showing the opposite pattern. There was also a significant, inverse relationship between salinity and bacterial diversity. Our results suggest water track formation significantly alters dry soil microbial communities, likely influencing subsequent ecosystem functioning. We highlight how Dry Valley water tracks could be a useful model system for understanding the potential habitability of transiently wetted environments found on the surface of Mars.

Cervical air sac oxygen profiles in diving emperor penguins: parabronchial ventilation and the respiratory oxygen store

Some marine birds and mammals can perform dives of extraordinary duration and depth. Such dive performance is dependent on many factors, including total body oxygen (O2) stores. For diving penguins, the respiratory system (air sacs and lungs) constitutes 30-50% of the total body O2 store. To better understand the role and mechanism of parabronchial ventilation and O2 utilization in penguins both on the surface and during the dive, we examined air sac partial pressures of O2 (PO2 ) in emperor penguins (Aptenodytes forsteri) equipped with backpack PO2  recorders. Cervical air sac PO2  values at rest were lower than in other birds, while the cervical air sac to posterior thoracic air sac PO2  difference was larger. Pre-dive cervical air sac PO2  values were often greater than those at rest, but had a wide range and were not significantly different from those at rest. The maximum respiratory O2 store and total body O2 stores calculated with representative anterior and posterior air sac PO2  data did not differ from prior estimates. The mean calculated anterior air sac O2 depletion rate for dives up to 11 min was approximately one-tenth that of the posterior air sacs. Low cervical air sac PO2  values at rest may be secondary to a low ratio of parabronchial ventilation to parabronchial blood O2 extraction. During dives, overlap of simultaneously recorded cervical and posterior thoracic air sac PO2  profiles supported the concept of maintenance of parabronchial ventilation during a dive by air movement through the lungs.

Assessment of fungal diversity present in lakes of Maritime Antarctica using DNA metabarcoding: a temporal microcosm experiment

We evaluated the fungal diversity in two lakes on the South Shetland Islands, using DNA metabarcoding through high-throughput sequencing (HTS). A microcosm experiment was deployed for two consecutive years in lakes on Deception and King George islands to capture potential decomposer freshwater fungi. Analyses of the baits revealed 258,326 DNA reads distributed in 34 fungal taxa of the phyla Ascomycota, Basidiomycota, Mortierellomycota, Chytridiomycota and Rozellomycota. Tetracladium marchalianum, Tetracladium sp., Rozellomycota sp., Fungal sp. 1 and Fungal sp. 2 were the most common taxa detected. However, the majority of the communities comprised intermediate and rare taxa. Both fungal communities displayed moderate indices of diversity, richness and dominance. Only six taxa were detected in both lakes, including the most dominant T. marchalianum and Tetracladium sp. The high numbers of reads of the known aquatic saprotrophic hyphomycetes T. marchalianum and Tetracladium sp. in the baits suggest that these fungi may digest organic material in Antarctic lakes, releasing available carbon and nutrients to the other aquatic organisms present in the complex lake food web. Our data confirm that the use of cotton baits together with HTS approaches can be appropriate to study the diversity of resident freshwater fungi present in Antarctic lakes.

Chasing Waterborne Pathogens in Antarctic Human-Made and Natural Environments, with Special Reference to Legionella spp

Waterborne pathogenic diseases are public health issues, especially for people staying in remote environments, such as Antarctica. After repeated detection of Legionella by PCR from the shower room of Syowa Station, the Japanese Antarctic research station, we wanted to understand the occurrence of waterborne pathogens, especially Legionella, in the station and their potential sources. In this study, we analyzed water and biofilm samples collected from the water facilities of Syowa Station, as well as water samples from surrounding glacier lakes, by 16S rRNA gene-based amplicon sequencing. For Legionella spp., we further attempted to obtain a detailed community structure by using genus-specific primers. The results showed that potentially pathogenic genera were mostly localized in the station, while Legionella spp., Pseudomonas spp., and Mycobacterium spp. were also widely distributed in lakes. Genus-specific analysis of Legionella spp. within the lake environments confirmed the presence of diverse Legionella amplicon sequence variants (ASVs) that were distinctly different from the Legionella ASVs detected in the station. The majority of the Legionella ASVs inhabiting Antarctic lake habitats were phylogenetically distinct from known Legionella species, whereas the ASVs detected in the human-made station tended to contain ASVs highly similar to well-described mesophilic species with human pathogenicity. These data suggest that unexpected Legionella diversity exists in remote Antarctic cold environments and that environmental differences (e.g., temperature) in and around the station affect the community structure.IMPORTANCE We comprehensively examined the localization of potential waterborne pathogens in the Antarctic human-made and natural aquatic environment with special focus on Legionella spp. Some potential pathogenic genera were detected with low relative abundance in the natural environment, but most detections of these genera occurred in the station. Through detailed community analysis of Legionella spp., we revealed that a variety of Legionella spp. was widely distributed in the Antarctic environment and that they were phylogenetically distinct from the described species. This fact indicates that there are still diverse unknown Legionella spp. in Antarctica, and this genus encompasses a greater variety of species in low-temperature environments than is currently known. In contrast, amplicon sequence variants closely related to known Legionella spp. with reported pathogenicity were almost solely localized in the station, suggesting that human-made environments alter the Legionella community.

Ice-Binding Proteins Associated with an Antarctic Cyanobacterium, Nostoc sp. HG1

Ice-binding proteins (IBPs) have been identified in numerous polar algae and bacteria, but so far not in any cyanobacteria, despite the abundance of cyanobacteria in polar regions. We previously reported strong IBP activity associated with an Antarctic Nostoc species. In this study, to identify the proteins responsible, as well as elucidate their origin, we sequenced the DNA of an environmental sample of this species, designated Nostoc sp. HG1, and its bacterial community and attempted to identify IBPs by looking for known IBPs in the metagenome and by looking for novel IBPs by tandem mass spectrometry (MS/MS) proteomics analyses of ice affinity-purified proteins. The metagenome contained over 116 DUF3494-type IBP genes, the most common type of IBP identified so far. One of the IBPs could be confidently assigned to Nostoc, while the others could be attributed to diverse bacteria, which, surprisingly, accounted for the great majority of the metagenome. Recombinant Nostoc IBPs (nIBPs) had strong ice-structuring activities, and their circular dichroism spectra were consistent with the secondary structure of a DUF3494-type IBP. nIBP is unusual in that it is the only IBP identified so far to have a PEP (amino acid motif) C-terminal signal, a signal that has been associated with anchoring to the outer cell membrane. These results suggest that the observed IBP activity of Nostoc sp. HG1 was due to a combination of endogenous and exogenous IBPs. Amino acid and nucleotide sequence analyses of nIBP raise the possibility that it was acquired from a planctomycete.IMPORTANCE The horizontal transfer of genes encoding ice-binding proteins (IBPs), proteins that confer freeze-thaw tolerance, has allowed many microorganisms to expand their ranges into polar regions. One group of microorganisms for which nothing is known about its IBPs is cyanobacteria. In this study, we identified a cyanobacterial IBP and showed that it was likely acquired from another bacterium, probably a planctomycete. We also showed that a consortium of IBP-producing bacteria living with the Nostoc contribute to its IBP activity.

Assessment of heavy metal contamination in the atmospheric deposition during 1950-2016 A.D. from a snow pit at Dome A, East Antarctica

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.

Selenium volatilization from tundra soils in maritime Antarctica

Maritime Antarctica harbors a large number of penguins and seals that provide considerable input of selenium (Se) originating as guano into terrestrial ecosystems. Subsequent Se emissions via biomethylation and volatilization from these sources of Se have not been studied. Here, penguin colony soils (PCS) and adjacent tundra marsh soils (TMS), seal colony soils (SCS) and adjacent tundra soils (STS), and normal upland tundra soils (NTS) were collected in maritime Antarctica. For the first time, Se volatilization and speciation were investigated in these soils through incubation experiments using chemo-trapping method. The Se contents in PCS, SCS, STS and TMS were highly enriched compared with NTS, with organic matter-bound Se accounting for 70%-80%. Laboratory incubations yielded the greatest Se volatilization rates (VR_Se) in PCS (0.20 ± 0.01 μg kg^-1 d^-1), followed by SCS (0.14 ± 0.01 μg kg^-1 d^-1) at low temperature (4 °C). Soil frozen-thawing induced 1-4 fold increase in VR_Se, and the VR_Se continuously increased until the soils fully thawed. The VR_Se showed a significant positive correlation (R² = 0.96, p < 0.01) with soil temperature. Methylated Se species were dominated by dimethylselenide (DMSe) in PCS and dimethyldiselenide (DMDSe) in SCS. Our results imply that the combination of climate warming, frozen-thawing processes, and high-Se inputs from sea animals will significantly increase tundra soil Se volatilization in maritime Antarctica. High VR_Se from penguin colony soils, and significantly elevated Se levels in the mosses close to penguin colony, suggest that volatilization of Se from penguin colony soils play an important role in the mobilization and regional biogeochemical cycling of Se in maritime Antarctica.

Methylmercury biomagnification in coastal aquatic food webs from western Patagonia and western Antarctic Peninsula

Mercury (Hg) is a global pollutant of concern because its organic and more toxic form, methylHg (MeHg), bioaccumulates and biomagnifies through aquatic food webs to levels that affect the health of fish and fish consumers, including humans. Although much is known about trophic transfer of MeHg in aquatic food webs at temperate latitudes in the northern hemisphere, it is unclear whether its fate is similar in biota from coastal zones of the southeastern Pacific. To assess this gap, MeHg, total Hg and food web structure (using δ¹³C and δ¹⁵N) were measured in marine macroinvertebrates, fishes, birds, and mammals from Patagonian fjords and the Antarctic Peninsula. Trophic magnification slopes (TMS; log MeHg versus δ¹⁵N) for coastal food webs of Patagonia were high when compared with studies in the northern hemisphere, and significantly higher near freshwater inputs as compared to offshore sites (0.244 vs 0.192). Similarly, in Antarctica, the site closer to glacial inputs had a significantly higher TMS than the one in the Southern Shetland Islands (0.132 vs 0.073). Composition of the food web also had an influence, as the TMS increased when mammals and seabirds were excluded (0.132-0.221) at a coastal site. This study found that both the composition of the food web and the proximity to freshwater outflows are key factors influencing the TMS for MeHg in Patagonian and Antarctic food webs.

Retrotransposon-based genetic diversity of Deschampsia antarctica Desv. from King George Island (Maritime Antarctic)

Deschampsia antarctica Desv. can be found in diverse Antarctic habitats which may vary considerably in terms of environmental conditions and soil properties. As a result, the species is characterized by wide ecotypic variation in terms of both morphological and anatomical traits. The species is a unique example of an organism that can successfully colonize inhospitable regions due to its phenomenal ability to adapt to both the local mosaic of microhabitats and to general climatic fluctuations. For this reason, D. antarctica has been widely investigated in studies analyzing morphophysiological and biochemical responses to various abiotic stresses (frost, drought, salinity, increased UV radiation). However, there is little evidence to indicate whether the observed polymorphism is accompanied by the corresponding genetic variation. In the present study, retrotransposon-based iPBS markers were used to trace the genetic variation of D. antarctica collected in nine sites of the Arctowski oasis on King George Island (Western Antarctic). The genotyping of 165 individuals from nine populations with seven iPBS primers revealed 125 amplification products, 15 of which (12%) were polymorphic, with an average of 5.6% polymorphic fragments per population. Only one of the polymorphic fragments, observed in population 6, was represented as a private band. The analyzed specimens were characterized by low genetic diversity (uHe = 0.021, I = 0.030) and high population differentiation (F ST = 0.4874). An analysis of Fu's F S statistics and mismatch distribution in most populations (excluding population 2, 6 and 9) revealed demographic/spatial expansion, whereas significant traces of reduction in effective population size were found in three populations (1, 3 and 5). The iPBS markers revealed genetic polymorphism of D. antarctica, which could be attributed to the mobilization of random transposable elements, unique features of reproductive biology, and/or geographic location of the examined populations.

A Previously Undescribed Helotialean Fungus That Is Superabundant in Soil Under Maritime Antarctic Higher Plants

We report a previously undescribed member of the Helotiales that is superabundant in soils at two maritime Antarctic islands under Antarctic Hairgrass (Deschampsia antarctica Desv.). High throughput sequencing showed that up to 92% of DNA reads, and 68% of RNA reads, in soils from the islands were accounted for by the fungus. Sequencing of the large subunit region of ribosomal (r)DNA places the fungus close to the Pezizellaceae, Porodiplodiaceae, and Sclerotiniaceae, with analyses of internal transcribed spacer regions of rDNA indicating that it has affinities to previously unnamed soil and root fungi from alpine, cool temperate and Low Arctic regions. The fungus was found to be most frequent in soils containing C aged to 1,000-1,200 years before present. The relative abundances of its DNA and RNA reads were positively associated with soil carbon and nitrogen concentrations and δ13C values, with the relative abundance of its DNA being negatively associated with soil pH value. An isolate of the fungus produces flask-shaped phialides with a pronounced venter bearing masses of conidia measuring 4.5-6(7) × 1.8-2.5 μm, suggestive of anamorphic Chalara. Enzymatic studies indicate that the isolate strongly synthesizes the extracellular enzyme acid phosphatase, and also exhibits alkaline phosphatase and naphthol-AS-BI-phosphohydrolase activities. Ecophysiological measurements indicate optimal hyphal growth of the isolate at a pH of 4.2-4.5 and a water potential of -0.66 MPa. The isolate is a psychrotroph, exhibiting measureable hyphal growth at -2°C, optimal hyphal extension rate at 15°C and negligible growth at 25°C. It is proposed that the rising temperatures that are predicted to occur in maritime Antarctica later this century will increase the growth rate of the fungus, with the potential loss of ancient C from soils. Analyses using the GlobalFungi Database indicate that the fungus is present in cold, acidic soils on all continents. We advocate further studies to identify whether it is superabundant in soils under D. antarctica elsewhere in maritime Antarctica, and for further isolates to be obtained so that the species can be formally described.

Microbial Diversity of Pinnacle and Conical Microbial Mats in the Perennially Ice-Covered Lake Untersee, East Antarctica

Antarctic perennially ice-covered lakes provide a stable low-disturbance environment where complex microbially mediated structures can grow. Lake Untersee, an ultra-oligotrophic lake in East Antarctica, has the lake floor covered in benthic microbial mat communities, where laminated organo-sedimentary structures form with three distinct, sympatric morphologies: small, elongated cuspate pinnacles, large complex cones and flat mats. We examined the diversity of prokaryotes and eukaryotes in pinnacles, cones and flat microbial mats using high-throughput sequencing of 16S and 18S rRNA genes and assessed how microbial composition may underpin the formation of these distinct macroscopic mat morphologies under the same environmental conditions. Our analysis identified distinct clustering of microbial communities according to mat morphology. The prokaryotic communities were dominated by Cyanobacteria, Proteobacteria, Verrucomicrobia, Planctomycetes, and Actinobacteria. While filamentous Tychonema cyanobacteria were common in all mat types, Leptolyngbya showed an increased relative abundance in the pinnacle structures only. Our study provides the first report of the eukaryotic community structure of Lake Untersee benthic mats, which was dominated by Ciliophora, Chlorophyta, Fungi, Cercozoa, and Discicristata. The eukaryote richness was lower than for prokaryote assemblages and no distinct clustering was observed between mat morphologies. These findings suggest that cyanobacterial assemblages and potentially other bacteria and eukaryotes may influence structure morphogenesis, allowing distinct structures to form across a small spatial scale.

Statistical Optimisation of Phenol Degradation and Pathway Identification through Whole Genome Sequencing of the Cold-Adapted Antarctic Bacterium, Rhodococcus sp. Strain AQ5-07

Study of the potential of Antarctic microorganisms for use in bioremediation is of increasing interest due to their adaptations to harsh environmental conditions and their metabolic potential in removing a wide variety of organic pollutants at low temperature. In this study, the psychrotolerant bacterium Rhodococcus sp. strain AQ5-07, originally isolated from soil from King George Island (South Shetland Islands, maritime Antarctic), was found to be capable of utilizing phenol as sole carbon and energy source. The bacterium achieved 92.91% degradation of 0.5 g/L phenol under conditions predicted by response surface methodology (RSM) within 84 h at 14.8 °C, pH 7.05, and 0.41 g/L ammonium sulphate. The assembled draft genome sequence (6.75 Mbp) of strain AQ5-07 was obtained through whole genome sequencing (WGS) using the Illumina Hiseq platform. The genome analysis identified a complete gene cluster containing catA, catB, catC, catR, pheR, pheA2, and pheA1. The genome harbours the complete enzyme systems required for phenol and catechol degradation while suggesting phenol degradation occurs via the β-ketoadipate pathway. Enzymatic assay using cell-free crude extract revealed catechol 1,2-dioxygenase activity while no catechol 2,3-dioxygenase activity was detected, supporting this suggestion. The genomic sequence data provide information on gene candidates responsible for phenol and catechol degradation by indigenous Antarctic bacteria and contribute to knowledge of microbial aromatic metabolism and genetic biodiversity in Antarctica.

First detection of microplastics in the freshwater of an Antarctic Specially Protected Area

Microplastics have been found in all environmental compartments investigated so far, even reaching remote areas. However, their presence in Antarctic freshwaters has not been yet reported. Here, we investigated the occurrence of microplastics in a stream from an Antarctic Specially Protected Area (Byers Peninsula, Livingston Island - ASPA No. 126), which is subject to stringent environmental protection measures as a result of which it is considered a pristine international reference site for inland waters research. Our results showed the presence of three types of microplastics in a freshwater seasonal stream, namely four polyester fibers, one black and three transparent; two acrylic fibers, one transparent and one red; and two transparent polytetrafluoroethylene films. The length and width of these fibers and films were in the 400-3546 μm (average 1118 μm), and 10-1026 μm (average 199 μm) ranges respectively. The concentration of MP was 0.95 items/1000 m³ with estimated variability in the 0.47-1.43 items/1000 m³ range. This is the first report of the presence of microplastics in Antarctic freshwater with the uniqueness that it is an Antarctic Specially Protected Area, meaning that plastic pollution reached even the most remote and pristine environments in the planet.

Enrichment of perfluoroalkyl substances in the sea-surface microlayer and sea-spray aerosols in the Southern Ocean

Sea-spray (or sea-salt) aerosol (SSA) formation and their subsequent atmospheric transport and deposition have been suggested to play a prominent role in the occurrence of ionizable perfluoroalkyl substances (PFAS) in the maritime Antarctica and other remote regions. However, field studies on SSA's role as vector of transport of PFAS are lacking. Following a multiphase approach, seawater (SW), the sea-surface microlayer (SML) and SSA were sampled simultaneously at South Bay (Livingston Island, Antarctica). Average PFAS concentrations were 313 pg L^-1, 447 pg L^-1, and 0.67 pg m^-3 in SW, the SML and SSA, respectively. The enrichment factors of PFAS in the SML and SSA ranged between 1.2 and 5, and between 522 and 4690, respectively. This amplification of concentrations in the SML is consistent with the surfactant properties of PFAS, while the large enrichment of PFAS in atmospheric SSA may be facilitated by the large surface area of SSA and the sorption of PFAS to aerosol organic matter. This is the first field work assessing the simultaneous occurrence of PFAS in SW, the SML and SSA. The large measured amplification of concentrations in marine aerosols supports the role of SSA as a relevant vector for long-range atmospheric transport of PFAS.

Acute bottlenecks to the survival of juvenile Pygoscelis penguins occur immediately after fledging

Estimating when and where survival bottlenecks occur in free-ranging marine predators is critical for effective demographic monitoring and spatial planning. This is particularly relevant to juvenile stages of long-lived species for which direct observations of death are typically not possible. We used satellite telemetry data from fledgling Adélie, chinstrap and gentoo penguins near the Antarctic Peninsula to estimate the spatio-temporal scale of a bottleneck after fledging. Fledglings were tracked up to 106 days over distances of up to 2140 km. Cumulative losses of tags increased to 73% within 16 days of deployment, followed by an order-of-magnitude reduction in loss rates thereafter. The timing and location of tag losses were consistent with at-sea observations of penguin carcasses and bioenergetics simulations of mass loss to thresholds associated with low recruitment probability. A bootstrapping procedure is used to assess tag loss owing to death versus other factors. Results suggest insensitivity in the timing of the bottleneck and quantify plausible ranges of mortality rates within the bottleneck. The weight of evidence indicates that a survival bottleneck for fledgling penguins is acute, attributable to predation and starvation, and may account for at least 33% of juvenile mortality.

Morphometric and genetic evidence for four species of gentoo penguin

Gentoo penguins (Pygoscelis papua) are found across the Southern Ocean with a circumpolar distribution and notable genetic and morphological variation across their geographic range. Whether this geographic variation represents species-level diversity has yet to be investigated in an integrative taxonomic framework. Here, we show that four distinct populations of gentoo penguins (Iles Kerguelen, Falkland Islands, South Georgia, and South Shetlands/Western Antarctic Peninsula) are genetically and morphologically distinct from one another. We present here a revised taxonomic treatment including formal nomenclatural changes. We suggest the designation of four species of gentoo penguin: P. papua in the Falkland Islands, P. ellsworthi in the South Shetland Islands/Western Antarctic Peninsula, P. taeniata in Iles Kerguelen, and a new gentoo species P. poncetii, described herein, in South Georgia. These findings of cryptic diversity add to many other such findings across the avian tree of life in recent years. Our results further highlight the importance of reassessing species boundaries as methodological advances are made, particularly for taxa of conservation concern. We recommend reassessment by the IUCN of each species, particularly P. taeniata and P. poncetii, which both show evidence of decline.