Continental Antarctica Research Articles

First bryophyte records from Diego Ramírez Archipelago: Changing lenses in long-term socio-ecological research at the southernmost island of the Americas

Long-term socio-ecological research requires comprehensive assessments of biodiversity that overcome historical taxonomic biases, such as the strong focus on the vascular flora. This is particularly relevant at high latitudes where the richness of non-vascular plant species exceeds that of vascular species. Additionally, with respect to geographical regions, there is also a marked bias towards ecological and conservation research in the northern hemisphere. In contrast, few studies have investigated patterns of non-vascular species richness in relation to conservation priorities at sub-Antarctic latitudes, particularly in the sub-Antarctic Magellanic ecoregion. In this work, we contribute to overcome such taxonomic, geographical and ecoregional biases by moving outside these limits, and therefore “changing the lenses” that are commonly used to assess and conserve biodiversity. We implemented these new “biocultural lenses” by including, for the first time, bryophytes in the floristic inventory of the southernmost island of the American continent: Gonzalo Island (56°31’16.8’’S; 68°42’53.5’’W) in the Diego Ramirez Archipelago, Chile. The first bryological exploration of the Diego Ramirez archipelago, SW of Cape Horn, revealed a bryophyte flora composed of 14 species, eight liverworts and six mosses. This number of non-vascular plant species almost doubles the eight vascular plants present on the island. Consequently, with our study, we aim to fill a critical gap in the knowledge of the flora of the Diego Ramirez archipelago, and establish an integral floristic characterization for the long-term socioecological research and conservation of the southernmost archipelago of South America. Based on the field material collected, the new nomenclatural combination Chiloscyphus secundifolius (Hook. f. & Taylor) J.J. Engel is proposed. The moss flora comprises Amblystegium serpens, a widespread moss, yet hitherto unknown for sub-Antarctic Chile. The bryoflora of Diego Ramirez has its greatest affinities with that of the sub-Antarctic Magellanic ecoregion and Maritime Antarctica. None of the liverworts present on Gonzalo Island occurs on continental Antarctica; in contrast, four of the six mosses are shared between these two areas.

Molecular Comparison among Three Antarctic Endemic Springtail Species and Description of the Mitochondrial Genome of Friesea gretae (Hexapoda, Collembola)

Springtails and mites are the dominant groups of terrestrial arthropods in Antarctic terrestrial ecosystems. Their Antarctic diversity includes a limited number of species, which are frequently endemic to specific regions within the continent. Advances in molecular techniques, combined with the re-evaluation of morphological characters and the availability of new samples, have recently led to the identification of a number of new springtail species within previously named, but ill-defined, species entities described in the last century. One such species, the neanurid Friesea grisea, originally described from sub-Antarctic South Georgia, was for many years considered to be the only known springtail with a pan-Antarctic distribution. With the recent availability of new morphological and molecular data, it has now been firmly established that the different representatives previously referred to this taxon from the Antarctic Peninsula and Victoria Land (continental Antarctica) should no longer be considered as representing one and the same species, and three clearly distinct taxa have been recognized: F. antarctica, F. gretae and F. propria. In this study, the relationships among these three species are further explored through the sequencing of the complete mtDNA for F. gretae and the use of complete mitogenomic as well as cytochrome c oxidase I data. The data obtained provide further support that distinct species were originally hidden within the same taxon and that, despite the difficulties in obtaining reliable diagnostic morphological characters, F. gretae is genetically differentiated from F. propria (known to be present in different locations in Northern Victoria Land), as well as from F. antarctica (distributed in the Antarctic Peninsula).

Bed topography of Princess Elizabeth Land in East Antarctica

Abstract. We present a topographic digital elevation model (DEM) for Princess Elizabeth Land (PEL), East Antarctica. The DEM covers an area of ∼900 000 km2 and was built from radio-echo sounding data collected during four campaigns since 2015. Previously, to generate the Bedmap2 topographic product, PEL's bed was characterized from low-resolution satellite gravity data across an otherwise large (>200 km wide) data-free zone. We use the mass conservation (MC) method to produce an ice thickness grid across faster flowing (>30 m yr−1) regions of the ice sheet and streamline diffusion in slower flowing areas. The resulting ice thickness model is integrated with an ice surface model to build the bed DEM. Together with BedMachine Antarctica and Bedmap2, this new bed DEM completes the first-order measurement of subglacial continental Antarctica – an international mission that began around 70 years ago. The ice thickness data and bed DEMs of PEL (resolved horizontally at 500 m relative to ice surface elevations obtained from the Reference Elevation Model of Antarctica – REMA) are accessible from https://doi.org/10.5281/zenodo.4023343 (Cui et al., 2020a) and https://doi.org/10.5281/zenodo.4023393 (Cui et al., 2020b).

Amphitropical variation of the algal partners of Pseudephebe (Parmeliaceae, lichenized fungi)

Lichens are present in most terrestrial ecosystems on Earth and colonize extreme habitats, where vascular plants are unable to thrive, due to unique properties of the fungal-algal symbiosis. Here, we explored the phylogeographic structure of green algae engaged in symbiosis with species in the genus Pseudephebe (Parmeliaceae). These often form deep brown to blackish fruticose thalli on acidic rocks, and have partially overlapping distributions: P. minuscula is bipolar and co-occurs with P. pubescens in Europe. Based on a broad sampling, including the Arctic and Antarctica, we focused on photobionts (1) to identify genetic lineages and their phylogenetic assignment, (2) to infer the haplotype distribution in relation with geography and the mycobiont’s identity, and (3) to evaluate spatial genetic structure and polymorphism. Results revealed three Trebouxia clade S lineages (Trebouxia S02, T. suecica and T. angustilobata) associated to Pseudephebe species, with predominant haplotypes distributed throughout the entire geographic distribution, and some, less frequent, shared between widely distant localities. Photobiont switching was evident in the Mediterranean region, and algal co-occurrence was frequent in both mycobionts, which shared the same set of photobionts; this could explain, at least partially, their overlapping distribution. Furthermore, genetic structure was influenced by geography given the substantial percentages of genetic variation (ca. 25–50%) explained by the different delimited eco−/biogeographic regions. In Continental Antarctica, mycobionts showed a high specialization towards the photobionts, which are probably endemic of this climatically extreme region. Taken together, our findings provide further insight about the processes shaping lichen biogeography.

Myco- and photobiont associations in crustose lichens in the McMurdo Dry Valleys (Antarctica) reveal high differentiation along an elevational gradient

Climatically extreme regions such as the polar deserts of the McMurdo Dry Valleys (78° S) in Continental Antarctica are key areas for a better understanding of changes in ecosystems. Therefore, it is particularly important to analyze and communicate current patterns of biodiversity in these sensitive areas, where precipitation mostly occurs in form of snow and liquid water is rare. Humidity provided by dew, clouds, and fog are the main water sources, especially for rock-dwelling crustose lichens as one of the most common vegetation-forming organisms. We investigated the diversity and interaction specificity of myco-/photobiont associations of 232 crustose lichen specimens, collected along an elevational gradient (171–959 m a.s.l.) within the McMurdo Dry Valleys. The mycobiont species and photobiont OTUs were identified by using three markers each (nrITS, mtSSU, RPB1, and nrITS, psbJ-L, COX2). Elevation, positively associated with water availability, turned out to be the key factor explaining most of the distribution patterns of the mycobionts. Pairwise comparisons showed Lecidea cancriformis and Rhizoplaca macleanii to be significantly more common at higher elevations and Carbonea vorticosa and Lecidea polypycnidophora at lower elevations. Lichen photobionts were dominated by the globally distributed Trebouxia OTU, Tr_A02 which occurred at all habitats. Network specialization resulting from myco-/photobiont bipartite network structure varied with elevation and associated abiotic factors. Along an elevational gradient, the spatial distribution, diversity, and genetic variability of the lichen symbionts appear to be mainly influenced by improved water relations at higher altitudes.

Weathering and pedogenesis of sediments and basaltic rocks on Vega Island, Antarctic Peninsula

Vega Island in the Weddell Sea is characterized by a semiarid climate and peculiar soil formation due to its transitional location between warmer and wetter Maritime Antarctica (MA) and drier colder Continental Antarctica (CA). We investigated the main factors and processes involved in soil genesis at Cape Lamb on Vega Island. Thirty pedons were sampled, described and analyzed for morphological, physical, geochemical and mineralogical properties. Twenty-two pedons were classified as Gelisols/Cryosols. Three soil groups were identified: (1) mixed substrates soils (2), acid sulfate soils and (3) basaltic soils. Acid sulfate soils showed the greatest degree of weathering with pronounced acidity due to sulfurization. Basaltic soils were the least developed and presented shallow pedons of skeletic character and high alkalinity. Parent material was the main factor in the differentiation of the studied soils. Climate and landforms were also important. Desert pavement, salinization and ahumic features induced by the semiarid climate, oppose acidification and cryoturbation, characterizing the transitional location of Vega Island. Patterned ground dominates on periglacial highlands, while desert pavements are more common on paraglacial surfaces. Despite the semiarid climate, pedogenesis is active in the studied soils, with clay minerals, sulfate minerals and pedogenic Fe-oxides formation.

Sulfurization, acid-sulfate soils and active layer monitoring at the semiarid Seymour Island, Antarctica

Soils and permafrost occurrence and behavior at the Weddell Sea zone, located in the key zone of climatic transition between Maritime Antarctica and Continental Antarctica, remain little studied. We studied the main chemical, physical and mineralogical properties of representative soil profiles of the northern part of Seymour Island, discussing soil formation processes and the active-layer thermal and water regimes of a representative site. Soil sampling and installation of the monitoring site was carried out in the northern part of Seymour Island. Permafrost was generally detected within the first 100 cm of depth, except at coastal areas, although typical periglacial features (cryoturbation), vegetation growth and organic matter accumulation were negligible or absent. Well-drained soils showed low Electric Conductivity (EC), indicating leaching of salts, whereas near-permafrost layers showed higher values of EC. Salt content and EC increased at lower altitudes. Two major groups of soils were identified: (i) Acid Sulfate Soils (ASS); and (ii) Weakly Developed Alkaline Soils (WDAS). Acid Sulfate Soils develop under the influence of sulfide-containing material under oxidizing conditions, and are the most developed and weathered in the area, presenting significant morphological, mineralogical and chemical traits, such as low pH values, sulfuric B horizons, and the presence of secondary minerals indicating sulfurization process, such as jarosite and low crystallinity iron oxide. Weakly Developed Alkaline Soils develop under low chemical and mineralogical transformation, where physical weathering is a key process. These soils present high pH and high content of primary minerals in the clay fraction, mainly K-feldspars and plagioclase. The active-layer thermal regime is typical of periglacial environments, with seasonal temperature variations of soil around 0 °C, with prevailing negative temperatures. Regional climate was comparable with Continental Antarctica, whereas the pedoclimate (active layer thickness, soil water content) showed closer affinity with Maritime Antarctica. Some soil forming processes are driven by pedoclimate, and favored by the unfrozen and free-drainage conditions during the summer season; however, the main factor influencing soil development is parent material. The main soil formation processes are sulfurization, cryoclasty and halomorphism, since the semiarid dry climate does not favor cryoturbation and organic matter accumulation.

Uncovered Microbial Diversity in Antarctic Cryptoendolithic Communities Sampling three Representative Locations of the Victoria Land.

The endolithic niche represents an ultimate refuge to microorganisms in the Mars-like environment of the Antarctic desert. In an era of rapid global change and desertification, the interest in these border ecosystems is increasing due to speculation on how they maintain balance and functionality at the dry limits of life. To assure a reliable estimation of microbial diversity, proper sampling must be planned in order to avoid the necessity of re-sampling as reaching these remote locations is risky and requires tremendous logistical and economical efforts. In this study, we seek to determine the minimum number of samples for uncovering comprehensive bacterial and fungal diversity, comparing communities in strict vicinity to each other. We selected three different locations of the Victoria Land (Continental Antarctica) at different altitudes and showing sandstone outcrops of a diverse nature and origin—Battleship promontory (834 m above sea level (a.s.l.), Southern VL), Trio Nunatak (1,470 m a.s.l., Northern VL) and Mt New Zealand (3,100 m a.s.l., Northern VL). Overall, we found that a wider sampling would be required to capture the whole amplitude of microbial diversity, particularly in Northern VL. We concluded that the inhomogeneity of the rock matrix and the stronger environmental pressure at higher altitudes may force the communities to a higher local diversification.

Assessing distribution shifts and ecophysiological characteristics of the only Antarctic winged midge under climate change scenarios

Parts of Antarctica were amongst the most rapidly changing regions of the planet during the second half of the Twentieth Century. Even so, today, most of Antarctica remains in the grip of continental ice sheets, with only about 0.2% of its overall area being ice-free. The continent’s terrestrial fauna consists only of invertebrates, with just two native species of insects, the chironomid midges Parochlus steinenii and Belgica antarctica. We integrate ecophysiological information with the development of new high-resolution climatic layers for Antarctica, to better understand how the distribution of P. steinenii may respond to change over the next century under different IPCC climate change scenarios. We conclude that the species has the potential to expand its distribution to include parts of the west and east coasts of the Antarctic Peninsula and even coastal ice-free areas in parts of continental Antarctica. We propose P. steinenii as an effective native sentinel and indicator species of climate change in the Antarctic.

Sun exposure drives Antarctic cryptoendolithic community structure and composition

The harsh environmental conditions of the ice-free regions of Continental Antarctica are considered one of the closest Martian analogues on Earth. There, rocks play a pivotal role as substratum for life and endolithism represents a primary habitat for microorganisms when external environmental conditions become incompatible with active life on rock surfaces, allowing life to spread throughout these regions with extreme temperatures and low water availability. Previous research concluded that altitude and distance from sea do not play as driving factors in shaping microbial abundance and diversity, while sun exposure was hypothesized as significant parameter influencing endolithic settlement and development. With this in mind, eight localities were visited in the Victoria Land along an altitudinal transect from 834 to 3100 m a.s.l. and 48 differently sun-exposed rocks were collected. We explored our hypothesis that changes in sun exposure translate to shifts in community composition and abundances of main biological compartments (fungi, algae and bacteria) using Denaturing Gel Gradient Electrophoresis and quantitative PCR techniques. Major changes in community composition and abundance occurred between north and south sun-exposed samples. As Antarctic endolithic ecosystems are extremely adapted and specialized but scarcely resilient to external perturbation, any shifts in community structure may serve as early-alarm systems of climate change; our findings will be of wide interest for microbial ecologists of extreme environments such as arid and hyper-arid area.

Exchangeable cations and pH drive diversity and functionality of fungal communities in biological soil crusts from coastal sites of Victoria Land, Antarctica

Abstract Ice-free regions in coastal areas of Victoria Land, Antarctica, are patchily distributed, limited in extent and characterized by a simple vegetation of lichens and mosses, growing only for a short period during the austral summer. These organisms are associated with soil particles and microorganisms (e.g., algae, microfungi and bacteria) to make up biological soil crusts (BSCs), found worldwide in cold and/or arid and semi-arid regions, where plant growth is impaired. Despite BSCs being among the most widespread ecosystems throughout coastal ice-free areas of continental Antarctica, fungal components of these communities have received little focus. Through ITS1 DNA metabarcoding of samples from 17 sites of six different localities from 73 to 77°S, in a distance scale from 29 to 411 km among different sites, we provide insights into the diversity, community composition, and functionality of fungal communities of these peculiar ecosystems, deepening our knowledge on how they are related to different edaphic variables (i.e. chemical properties and texture). Although fungal richness was low (59 ± 27 OTUs per sample), we found numerous previously unsequenced, putatively unknown fungal species representing a great part of the sampled communities. Community composition was spatially auto-correlated and appeared to be driven by site-specific differences in environmental conditions, particularly edaphic factors, such as exchangeable cations and pH. These results are of particular interest, as they give a wide characterization of the parameters determining soil colonization in a such limiting environment, especially in the light of global changes that are expected to deeply modify the conditions of this environment.

Discovery of microcystin-producing Anagnostidinema pseudacutissimum from cryopreserved Antarctic cyanobacterial mats

Microcystins (MCs) are secondary metabolites produced by cyanobacteria and have been well-documented in temperate and tropical regions. However, knowledge of the production of MCs in extremely cold environments is still in its infancy. Recently, examination of 100-year-old Antarctic cyanobacterial mats collected from Ross Island and the McMurdo Ice Shelf during Captain R.F. Scott's Discovery Expedition revealed that the presence of MCs in Antarctica is not a new phenomenon. Here, morphological and molecular phylogenetic analyses are used to identify a new microcystin-producing freshwater cyanobacterium, Anagnostidinema pseudacutissimum. The strain was isolated from a deep-frozen (−15 °C) sample collected from a red-brown cyanobacterial mat in a frozen pond at Cape Crozier (Ross Island, continental Antarctica) in 1984–1985. Amplification of the mcyE gene fragment involved in microcystin biosynthesis from A. pseudacutissimum confirmed that it is identical to the sequence from other known microcystin-producing cyanobacteria. Analysis of extracts from this A. pseudacutissimum strain by HPLC-MS/MS confirmed the presence of MC-LR and -YR at concentrations of 0.60 μg/L and MC-RR at concentrations of 0.20 μg/L. This is the first report of microcystin production from a species of Anagnostidinema from Antarctica.

Evidence for Cryptic Diversity in the "Pan-Antarctic" Springtail Friesea antarctica and the Description of Two New Species.

The invertebrate terrestrial fauna of Antarctica is being investigated with increasing interest to discover how life interacts with the extreme polar environment and how millions of years of evolution have shaped their biodiversity. Classical taxonomic approaches, complemented by molecular tools, are improving our understanding of the systematic relationships of some species, changing the nomenclature of taxa and challenging the taxonomic status of others. The springtail Friesea grisea has previously been described as the only species with a “pan-Antarctic” distribution. However, recent genetic comparisons have pointed to another scenario. The latest morphological study has confined F. grisea to the sub-Antarctic island of South Georgia, from which it was originally described, and resurrected F. antarctica as a congeneric species occurring on the continental mainland. Molecular data demonstrate that populations of this taxon, ostensibly occurring across Maritime and Continental Antarctica, as well as on some offshore islands, are evolutionarily isolated and divergent and cannot be included within a single species. The present study, combining morphological with molecular data, attempts to validate this hypothesis and challenges the taxonomic status of F. antarctica, suggesting that two additional new species, described here as Friesea gretae sp. nov. and Friesea propria sp. nov., are present in Continental Antarctica.

A smelly business: Microbiology of Adélie penguin guano (Point Thomas rookery, Antarctica)

Adélie penguins (Pygoscelis adeliae) are the most numerous flightless bird group breeding in coastal areas of Maritime and Continental Antarctica. Their activity leaves a mark on the land in the form of large guano deposits. This guano is an important nutrient source for terrestrial habitats of ice-free Antarctic areas, most notably by being the source of ammonia vapors which feed the surrounding grass, lichen and algae communities. Although investigated by researchers, the fate of the guano-associated microbial community and its role in decomposition processes remain vague. Therefore, by employing several direct community assessment methods combined with a broad culture-based approach we provide data on bacterial numbers, their activity and taxonomic affiliation in recently deposited and decayed Adélie penguin guano sampled at the Point Thomas rookery in Maritime Antarctica (King George Island). Our research indicates that recently deposited guano harbored mostly bacteria of penguin gut origin, presumably inactive in cold rookery settings. This material was rich in mesophilic enzymes active also at low temperatures, likely mediating early stage decomposition. Fresh guano colonization by environmental bacteria was minor, accomplished mostly by ammonia scavenging Jeotgalibaca sp. cells. Decayed guano contained 10-fold higher bacterial numbers with cold-active enzymes dominating the samples. Guano was colonized by uric-acid degrading and lipolytic Psychrobacter spp. and proteolytic Chryseobacterium sp. among others. Several spore-forming bacteria of penguin gut origin persisted in highly decomposed material, most notably uric-acid fermenting members of the Gottschalkiaceae family.

One year of aerosol refractive index measurement from a coastal Antarctic site

Abstract. Though the environmental conditions of the Weddell Sea region and Dronning Maud Land are still relatively stable compared to the fast-changing Antarctic Peninsula, we may suspect pronounced effects of global climate change for the near future (Thompson et al., 2011). Reducing the uncertainties in climate change modeling requires a better understanding of the aerosol optical properties, and for this we need accurate data on the aerosol refractive index (RI). Due to the remoteness of Antarctica only very few RI data are available from this region (Hogan et al., 1979; Virkkula et al., 2006; Shepherd et al., 2018). We calculate the real refractive index of natural atmospheric aerosols from number size distribution measurements at the German coastal Antarctic station Neumayer III. Given the high average scattering albedo of 0.992 (Weller et al., 2013), we assumed that the imaginary part of the RI is zero. Our method uses the overlapping size range (particle diameter D between 120 and 340 nm) of a scanning mobility particle sizer (SMPS), which sizes the particles by their electrical mobility, and a laser aerosol spectrometer (LAS), which sizes the particles by their optical scattering signal at the 633 nm wavelength. Based on almost a complete year of measurement, the average effective refractive index (RIeff, as we call our retrieved RI because of the used assumptions) for the dry aerosol particles turned out to be 1.44 with a standard deviation of 0.08, in a good agreement with the RI value of 1.47, which we derived from the chemical composition of bulk aerosol sampling measurements. At Neumayer the aerosol shows a pronounced seasonal pattern in both number concentration and chemical composition. Despite this, the variability of the monthly averaged RIeff values remained between 1.40 and 1.50. Compared to the annual mean, two austral winter months (July and September) showed slightly but significantly increased values (1.50 and 1.47, respectively). The size dependency of the RIeff could be determined from time-averaged LAS and SMPS number size distributions measured between December 2017 and January 2018. Here we calculated RIeff for four different particle size ranges and observed a slight decrease from 1.47 (D range 116–168 nm) to 1.37 (D range 346–478 nm). We find no significant dependence of the derived RIeff values on the wind direction. Thus we conclude that RIeff is largely independent of the general weather situation, roughly classified as (i) advection of marine boundary layer air masses during easterly winds caused by passing cyclones in contrast to (ii) air mass transport from continental Antarctica under southern katabatic winds. Neumayer, the only relevant contamination source, is located 1.5 km north of the air chemistry observatory, where the measurements were performed. Given that northerly winds are almost absent, the potential impact of local contamination is minimized in general. Indeed our data show no impact of local contamination on RIeff. Just in one case a temporary high-contamination episode with diesel engines operating right next to the measurement site resulted in an unusual high RIeff of 1.59, probably caused by the high black carbon content of the exhaust fumes. To conclude, our study revealed largely constant RIeff values throughout the year without any sign of seasonality. Therefore, it seems reasonable to use a single, constant RIeff value of 1.44 for modeling optical properties of natural, coastal Antarctic sub-micrometer aerosol.

Lecanora muscigena (Lichenized Ascomycota, Lecanorales), a new lichen species in the Lecanora fuscescens group from South Georgia

ABSTRACTCompared to continental Antarctica, the lichen biota of the various subantarctic islands and island groups is poorly documented. Here we describe the new species Lecanora muscigena Øvstedal & Fryday from the subantarctic island of South Georgia from a collection made in 1980 that was previously included as Trapeliopsis sp. A. by Øvstedal & Lewis Smith in their comprehensive account of the Lichens of Antarctica and South Georgia. It is similar to Lecidea globulispora Nyl., which occurs on the nearby Falkland Islands, in having globose ascospores but is clearly distinguished from that species by having a well-developed, creamy-white thallus composed of ±dispersed areoles with effigurate margins containing fumarprotocetraric acid, larger ascospores (c. 7–8 µm diam.) and by its habitat of overgrowing terricolous bryophytes. The new species belongs in the Lecanora fuscescens group, the species of which were usually described in the genus Lecidea due to their poorly developed thalline margin. This group is not congeneric with the type species of Lecanora (L. subfusca (L.) Ach.) but we refrain from erecting a new genus for the group pending a full molecular investigation of its delimitation and systematic position.

Altitude and fungal diversity influence the structure of Antarctic cryptoendolithic Bacteria communities.

Endolithic growth within rocks is a critical adaptation of microbes living in harsh environments where exposure to extreme temperature, radiation, and desiccation limits the predominant life forms, such as in the ice-free regions of Continental Antarctica. The microbial diversity of the endolithic communities in these areas has been sparsely examined. In this work, diversity and composition of bacterial assemblages in the cryptoendolithic lichen-dominated communities of Victoria Land (Continental Antarctica) were explored using a high-throughput metabarcoding approach, targeting the V4 region of 16S rDNA. Rocks were collected in 12 different localities (from 14 different sites), along a gradient ranging from 1000 to 3300 m a.s.l. and at a sea distance ranging from 29 to 96 km. The results indicate Actinobacteria and Proteobacteria are the dominant taxa in all samples and defined a 'core' group of bacterial taxa across all sites. The structure of bacteria communities is correlated with the fungal counterpart and among the environmental parameters considered, altitude was found to influence bacterial biodiversity, while distance from sea had no evident influence.

Increasing knowledge of Antarctic biodiversity: new endemic taxa of tardigrades (Eutardigrada; Ramazzottiidae) and their evolutionary relationships

The underestimation of biodiversity and scarce knowledge of the biogeographic distributions of terrestrial meiofaunal component limit our understanding of the origin of Antarctic fauna. One of its main components is tardigrades; nonetheless studies on tardigrade diversity are still few in the continental Antarctic area. In order to increase our knowledge of the underreported terrestrial meiofaunal communities within continental Antarctica, as well as to provide new information for biogeographic and evolutionary analysis of these communities, the tardigrade diversity of 11 samples collected along the coast of Victoria Land was considered. The application of an integrative approach in which morphological (Light – LM, scanning electron – SEM, and confocal laser scanning microscopy – CSLM) and molecular analysis (18S, 28S, cox1 genes) were combined allowed us to characterize the tardigrade fauna inhabiting mosses, lichens, and cyanobacterial mats of Victoria Land. These analyses allowed the detection of two tardigrade species new to science (Cryoconicus antiarktos sp. nov., Ramazzottius sabatiniae sp. nov.), and the emendation of known species ((Hebesuncus ryani Dastych and Harris, 1994, Ramazzottius nivalis Dastych, 2006, Cryoconicus ljudmilae comb. nov. (Biserov, 1997/98), and Cryoconicus cataphractus (Maucci, 1974)), together with the genus Cryoconicus. The Ramazzottius type of claws was redefined identifying three subtypes. Also, we investigated the phylogenetic position of some problematic/unresolved lineages all belonging to the family Ramazzottiidae. These data increased the knowledge of the biodiversity in Victoria Land, the number of endemic tardigrades in Antarctica, and provided evidence on the origin of Antarctic endemism. Lastly, new methods for integrative taxonomic studies on tardigrades were presented and discussed.

Soil microbial community structure and enzymatic activity along a plant cover gradient in Victoria Land (continental Antarctica)

In continental Antarctica, autotrophs are exclusively represented by cyanobacteria, algae, lichens and mosses. Consequently, Antarctic soil communities are expected to be rather simple and primarily dominated by microorganisms. Recently, a change in abundance of mosses and lichens has been observed in continental Antarctica in response to an increase of the active permafrost layer, but the implication of this change to soil micro-organisms remains little known. Here we aim to clarify to what extent the abundance of mosses and lichens affects soil biogeochemistry in Victoria Land, with a particular focus on soil microbial abundance and associated soil enzymatic activity. To achieve this aim, we assessed the structure of soil microbiome and the activity of hydrolytic C, N, and P enzymes along a gradient in soil physico-chemical conditions and plant cover. Moss cover strongly relates to the amount of soil organic carbon (SOC), soil water and nutrient content. Soils with higher content of organic carbon were characterized by higher microbial biomass and showed a relatively higher abundance of fungi as compared to bacteria. More specifically, PLFAs biomarkers for Actinomycetes and Gram-positive bacteria were mainly associated to soils with lower SOC. In order to sustain a higher microbial biomass, total activity of hydrolytic enzymes increased with increasing SOC content. Eco-enzymatic stoichiometry, based on C to P and C to N ratios, indicates a higher investment in N- and P-hydrolytic enzymes (ratio < 1), particularly at low SOC content. Oppositely, an increase in C-hydrolytic enzyme activity (ratio ≈ 1) was observed with increasing accumulation of organic carbon. Such a result seems to indicate a stronger role of soil pH at low SOC on enzymatic stoichiometry (abiotic control) whereas with increasing accumulation of organic matter the enzymatic stoichiometry is more affected by microbial metabolism (biotic control).

Distribution of the genus Boeckella (Crustacea, Copepoda, Calanoida, Centropagidae) at high latitudes in South America and the main Antarctic biogeographic regions.

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