The cyanobacterial community of polygon soils at an inland Antarctic nunatak

Inland Antarctic terrestrial ecosystems and biodiversity are poorly understood in comparison with Antarctic coastal regions. Microorganisms, as primary colonists, are integral to Antarctic soil ecosystem development, essential for pedogenesis and structuring the soil, and providing the nutrients necessary for the subsequent establishment of macroorganisms. This study analysed the microbial communities present in polygon soils of Coal Nunatak (Alexander Island, at the southern limit of the maritime Antarctic). Soils were analysed across three polygons (centre and margins) and at three depths (0–1, 1–2, 2–5 cm). Cyanobacterial communities were characterised using two complementary molecular biological approaches, temperature gradient gel electrophoresis and clone library analysis. The three polygons exhibited conspicuous differences in community composition, both between different polygons and spatially (horizontally and vertically) within a single polygon. Comparison of our data with that from previous studies using classical culture and morphological identification techniques clearly shows the need for more intensive research on patterns of microbial diversity in terrestrial habitats throughout the Antarctic. The majority of the 17 cyanobacterial genera identified at Coal Nunatak are thought to have ubiquitous distributions, while none are known only from the Antarctic. Three of the genera present are also known to be capable of being lichen photobionts.     

Immobilization of a 15N-labeled nitrate addition by decomposing forest litter

This paper explores the biological consequences of climate change by integrating the results of a tripartite investigation involving fumarole, field manipulation and laboratory incubation experiments. The geographical region for this research is the maritime Antarctic. Under contemporary climate conditions, the lithosols in this region support only a sparse cryptogamic flora of limited taxonomic diversity and low structural complexity. However, the existence in geothermal areas of temperate species (e.g. Campylopus introflexus, Marchantia polymorpha, Philonotis acicularis) growing outside their normal biogeographical range suggests that elevated temperature and humidity may alter the trajectory of community development towards Magellanic or Patagonian composition. Productivity is also likely to increase, as indicated by significantly greater vegetative biomass recorded beneath climate-ameliorating soil covers than in controls. Barren fellfield soil samples transplanted to the laboratory and incubated at temperatures of 2–25°C show rapid development of moss, algae and lichen propagules in the range 15–25°C. A variety of species develop that have not been recorded in the field. The presence of exotic taxa indicates the existence of a dormant propagule bank in maritime Antarctic soils and suggests that no significant delay is likely to occur between the onset of climate warming and community development: instead, rapid establishment of those species favoured by the new climate conditions will yield a distinct founder effect, with increasing above- and below-ground biomass stimulating biogeochemical cycling. It is argued that the combined results of this synthesis identify generic responses to climate change arising from the importance at high latitudes of low temperature and water availability as limiting factors: subject to other growth resources being non-limiting, a more consistent stimulatory response to climate change may be expected than in temperate or tropical regions. The tripartite approach, encompassing field, microcosm and laboratory methodologies, renders the conclusions more robust than any single study considered in isolation.     

Bacterial Diversity in Three Different Antarctic Cold Desert Mineral Soils

A bacterial phylogenetic survey of three environmentally distinct Antarctic Dry Valley soil biotopes showed a high proportion of so-called “uncultured” phylotypes, with a relatively low diversity of identifiable phylotypes. Cyanobacterial phylotypic signals were restricted to the high-altitude sample, whereas many of the identifiable phylotypes, such as the members of the Actinobacteria, were found at all sample sites. Although the presence of Cyanobacteria and Actinobacteria is consistent with previous culture-dependent studies of microbial diversity in Antarctic Dry Valley mineral soils, many phylotypes identified by 16S rDNA analysis were of groups that have not hitherto been cultured from Antarctic soils. The general belief that such “extreme” environments harbor a relatively low species diversity was supported by the calculation of diversity indices. The detection of a substantial number of uncultured bacterial phylotypes showing low BLAST identities (<95%) suggests that Antarctic Dry Valley mineral soils harbor a pool of novel psychrotrophic taxa.     

Microbial community composition in soils of Northern Victoria Land, Antarctica

Biotic communities and ecosystem dynamics in terrestrial Antarctica are limited by an array of extreme conditions including low temperatures, moisture and organic matter availability, high salinity, and a paucity of biodiversity to facilitate key ecological processes. Recent studies have discovered that the prokaryotic communities in these extreme systems are highly diverse with patchy distributions. Investigating the physical and biological controls over the distribution and activity of microbial biodiversity in Victoria Land is essential to understanding ecological functioning in this region. Currently, little information on the distribution, structure and activity of soil communities anywhere in Victoria Land are available, and their sensitivity to potential climate change remains largely unknown. We investigated soil microbial communities from low- and high-productivity habitats in an isolated Antarctic location to determine how the soil environment impacts microbial community composition and structure. The microbial communities in Luther Vale, Northern Victoria Land were analysed using bacterial 16S rRNA gene clone libraries and were related to soil geochemical parameters and classical morphological analysis of soil metazoan invertebrate communities. A total of 323 16S rRNA gene sequences analysed from four soils spanning a productivity gradient indicated a high diversity (Shannon-Weaver values > 3) of phylotypes within the clone libraries and distinct differences in community structure between the two soil productivity habitats linked to water and nutrient availability. In particular, members of the Deinococcus/Thermus lineage were found exclusively in the drier, low-productivity soils, while Gammaproteobacteria of the genus Xanthomonas were found exclusively in high-productivity soils. However, rarefaction curves indicated that these microbial habitats remain under-sampled. Our results add to the recent literature suggesting that there is a higher biodiversity within Antarctic soils than previously expected.     

Trends in soil characteristics along a recently deglaciated foreland on Anvers Island,Antarctic Peninsula

We assessed patterns in soil development at a recently deglaciated foreland on Anvers Island on the Antarctic Peninsula. Soil samples were collected along transects extending 35 m over bare ground from the edge of a receding glacier; the far end of these transects has been ice free for approximately 20 years. We also compared soils at the far end of these transects under bare ground to those under canopies of isolated individuals of Deschampsia antarctica, a caespitose grass, that had recently colonized the site (established for <6 years). In addition, we compared soils at this young foreland to those in a well-developed tundra island that has been ice free for at least several hundred years. At the foreland site, soil moisture was greatest near the glacier, consistent with proximity to meltwater, and declined with distance from the glacier. This decline in soil moisture may explain the decrease in litter decomposition rates and the greater soil nitrate (NO₃ ⁻) concentrations that we observed with distance from the glacier. The greater soil moisture near the glacier likely promoted leaching and transport of NO₃ ⁻ to drier soils away from the glacier. The presence of D. antarctica at the glacier foreland had little effect on soil properties, which is not surprising considering it had only colonized sampling areas during the previous 5 years. Compared to the foreland, which contained only mineral soil, soil at the older tundra site had a 2.5- to 5-cm-thick organic horizon that had much higher concentrations of total carbon, nitrogen, and NO₃ ⁻.     

Growth,radicle and root hair development ofDeschampsia flexuosa (L.) Trin. seedlings in relation to soil acidity

Deschampsia flexuosa (L.) Trin. is an abundant grass species in the ground flora of acidic beech forests in southern Sweden. Generally, the species is restricted to a limited soil pH range (pH 4–5). The main objective was to study the influence of different soil acidities on germination, initial root development and on the growth of the species. The experiments were carried out under controlled conditions and designed to simulate the physico-chemical conditions present in the field. By using forest soils within the pH range 4.0 to 8.3 and artificial variation in pH (3.2 to 7.6) of soil-water extracts, it was possible to evaluate the influence of soil reaction and the H⁺ per se. In all experiments seeds have been used. Germination was significantly delayed in the very acid soil (pH 4.0) in comparison to the germination in soils within the pH range (4.4 to 6.4). Soil substances, other than the H⁺, might be responsible for this delay in germination, whereas development of the radicle was markedly affected by increasing H⁺ concentrations. Especially the development of root hairs was sensitive to H⁺ and was significantly reduced at a pH<-3.8. By increasing soil acidity the injury symptoms, including curling and discolouring, became more intense and at the highest acidity (pH 3.2) the radicles appeared brown, stunted and the root hairs were lacking. Most favourable growth was obtained at pH 4.4 and 5.0. Soil pH levels above and below this range limited both shoot and root growth. The results showed very good correspondence with observations made in Beech forest soils in southern Sweden, where the species was growing in soils within the pH range 3.9 to 5.1 with a peak growth at pH 4.3. This study shows that in soils at pH≤3.8, the poor development of the radicle may be crucial in the establishment ofDeschampsia flexuosa. Root hair development was more sensitive to soil acidity than radicle elongation. Germination was delayed in very acid Beech forest soils but other factors than the H-ion per se may be responsible for this delay.     

Structure and diversity of soil algal communities from Cierva Point (Antarctic Peninsula)

Cyanobacteria and eukaryotic algae, together with bacteria and fungi, are known to be primary colonizers of mineral soils throughout Antarctica. Their species diversity and soil coverage were studied in 18 soil polygons located at Cierva Point, Antarctic Peninsula. Undisturbed assemblages were dominated by filamentous Cyanobacteria and diatoms, whilst almost 40% of the 49 species recorded were observed only after enrichment culture. Nearly all of the isolates from enrichment cultures were Chlorophyta and Tribophyceae. This revealed a higher degree of complexity than reported for similar communities on Signy Island. Water content and concentrations of nutrients were determined at four representative sites, and did not appear to account for the large inter-polygon variation found in species composition and relative frequencies of occurrence. Variables describing community development were not significantly correlated with either area of the polygons or the minimum distance between them. This suggested that these features are not an important short-range barrier to dispersal for those “weed” species dominating the community. Conversely, the relative frequencies of some of the most common species showed significant correlations with species diversity and soil coverage, and it is suggested that biotic interactions could account to a larger extent for community structure than previously reported from Signy Island fellfields. Accepted: 12 October 1999     

Abundance and diversity of soil invertebrates in the Windmill Islands region,East Antarctica

The harsh climate and patchy distribution of habitable terrestrial ecosystems constrain soil invertebrate communities in continental Antarctica. The Windmill Islands in East Antarctica have a relatively gentle climate by Antarctic standards, and the region supports some of the most well-developed moss beds on the continent. These moss beds and soils are known to sustain invertebrate communities dominated by nematodes, rotifers and tardigrades, but our knowledge of the diversity and composition of these communities remains limited. We extracted soil fauna from 74 soil samples representing a wide range of microhabitats, and 24 moss samples, collected at Clark Peninsula, Bailey Peninsula and Robinson Ridge in the Windmill Islands during the 2012–2013 austral summer. Invertebrates were present in all samples, but densities varied considerably both within and between sites with limited correlation with edaphic variables or cover type. Taxa found included two species of nematodes (Plectus murrayi; Plectus frigophilus), one mite (Nanorchestes antarcticus) as well as tardigrades and rotifers (enumerated only). No springtails were found in this study, but individuals of the genus Cryptopygus were later recovered from moss collected near Casey Station. The Windmill Islands soils and moss beds support dense populations of soil fauna. However, despite the relatively mild climate conditions and favorable soil properties, species diversity is low. The diversity is possibly limited by recent deglaciation and limited dispersal opportunities to the region. Given favorable local conditions, it is likely that colonizing species will perform well, whether these arrive by natural means or are accidentally introduced by humans.     

Aromatic hydrocarbon-degrading bacteria from soil near Scott Base, Antarctica

Hydrocarbons persist in Antarctic soils when fuel oils such as JP8 jet fuel are spilled. For clean-up of hydrocarbon-contaminated soils in Antarctica, bioremediation has been proposed using hydrocarbon-degrading microbes indigenous to Antarctic soils. A number of alkane-degrading bacteria have been isolated previously from Antarctic soils. In this paper we describe the direct isolation of aromatic hydrocarbon-degrading bacteria from oil-contaminated Antarctic soil. Isolates that grew on JP8 jet fuel were characterised for their ability to degrade aromatic and aliphatic hydrocarbons and for growth at a range of temperatures. All isolates were gram-negative, oxidase-positive, rod-shaped bacteria. Representative strains were identified using 16S rDNA sequence analysis as either Sphingomonas spp. or Pseudomonas spp. Aromatic-degrading bacteria from Antarctic soils were psychrotolerant and appear similar to those found worldwide. Accepted: 27 September 1999     

Abiotic nitrate incorporation in soil: is it real?

In acid forest soils nitrate (NO₃⁻) from anthropogenic nitrogen deposition is retained at levels beyond what can be explained by known biological mechanisms. A number of researchers have hypothesized that abiotic NO₃⁻ incorporation into soil organic matter might be responsible for this phenomenon, however studies have been limited to a few temperate forest sites. The goal of this study was to determine if abiotic NO₃⁻ incorporation is important across a wide range of soil types. We collected 44 soils from a number of different ecosystem types in North and South America and measured the extent of abiotic NO₃⁻ incorporation. Significant abiotic nitrate incorporation did not occur in any of the soils examined. We show that the apparent abiotic incorporation observed in previous studies is likely the result of iron interference with NO₃⁻ measurements. Our results suggest that abiotic NO₃⁻ incorporation is not a likely explanation for the high rates of NO₃⁻ retention observed in some ecosystems.     

Soil nematodes and desiccation survival in the extreme arid environment of the antarctic dry valleys

Soil nematodes are capable of employing an anhydrobiotic survivalstrategy in response to adverse environmental conditions. TheMcMurdo Dry Valleys of Antarctica represent a unique environmentfor the study of anhydrobiosis because extremes of cold, salinity,and aridity combine to limit biological water availability.We studied nematode anhydrobiosis in Taylor Valley, Antarctica,using natural variation in soil properties. The coiled morphologyof nematodes extracted from dry valley soils suggests that theyemploy anhydrobiosis, and these coiled nematodes showed enhancedrevival when re-hydrated in water as compared to vermiform nematodes.Nematode coiling was correlated with soil moisture content,salinity, and water potential. In the driest soils studied (gravimetricwater content <2%), 20–80% of nematodes were coiled.Soil water potential measurements also showed a high degreeof variability. These measurements reflect microsite variationin soil properties that occurs at the scale of the nematode.We studied nematode anhydrobiosis during the austral summer,and found that the proportion of nematodes coiled can vary diurnally,with more nematodes vermiform and presumably active at the warmesttime of day. However, dry valley nematodes uncoiled rapidlyin response to soil wetting from snowmelt, and most nematodeactivity in the Dry Valleys may be confined to periods followingrare snowfall and melting events. Anhydrobiosis represents animportant temporal component of a dry valley nematode's lifespan. The ability to utilize anhydrobiosis plays a significantrole in the widespread distribution and success of these organismsin the Antarctic Dry Valleys and beyond.     

Phenanthrene Biodegradation in Soils Using an Antarctic Bacterial Consortium

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in Antarctic soils is limited by low temperatures, lack of adequate levels of nutrients, low number of PAH-tolerant members in the autochthonous microbiota and low bioavailability of contaminants. In the present work, microcosms systems (performed in 1-L glass flasks containing Antarctic soil supplemented with 1744 ppm of phenanthrene) were used to study (i) the effect of biostimulation with a complex organic source of nutrients (fish meal) combined with a surfactant (Brij 700); (ii) the effect of bioaugmentation with a psychrotolerant PAH-degrading bacterial consortium (M10); (iii) the effect of the combination of both strategies. The authors found that combination of biostimulation and bioaugmentation caused a significant removal (46.6%) of phenanthrene after 56 days under Antarctic environmental conditions. When bioaugmentation or biostimulation were applied separately, nonsignificant reduction in phenanthrene concentration was observed. Microtox test showed a low increase in toxicity only in the most efficient system. Results proved that “in situ” bioremediation process of phenanthrene-contaminated soils is possible in Antarctic stations. In addition, inoculation with a psychrotolerant PAH-degrading bacterial consortium in association with a mix of fish meal and a high-molecular-weight surfactant improved phenanthrene removal and should be the selected strategy when the number of hydrocarbons degrading bacteria in the target soil is low.     

Ecological Biogeography of the Terrestrial Nematodes of Victoria Land,Antarctica

The terrestrial ecosystems of Victoria Land, Antarctica are characteristically simple in terms of biological diversity and ecological functioning. Nematodes are the most commonly encountered and abundant metazoans of Victoria Land soils, yet little is known of their diversity and distribution. Herein we present a summary of the geographic distribution, habitats and ecology of the terrestrial nematodes of Victoria Land from published and unpublished sources. All Victoria Land nematodes are endemic to Antarctica, and many are common and widely distributed at landscape scales. However, at smaller spatial scales, populations can have patchy distributions, with the presence or absence of each species strongly influenced by specific habitat requirements. As the frequency of nematode introductions to Antarctica increases, and soil habitats are altered in response to climate change, our current understanding of the environmental parameters associated with the biogeography of Antarctic nematofauna will be crucial to monitoring and possibly mitigating changes to these unique soil ecosystems.     

Antarctic krill breeding facilities at port of nagoya public aquarium

Antarctic fishes and invertebrates, including Antarctic krill, are generally stenothermal, and it is necessary to maintain water temperature about 0°C to keep them in good condition. Because the effects of nitrifying bacteria are limited by the extremely low temperature of about 0°C, biological filtration does not keep up with the deterioration of water quality resulting from the excrement of animals and un-eaten food. It is therefore necessary to exchange seawater frequently in our present cold-water aquarium.

We developed a new system at Port of Nagoya Public Aquarium (PNPA) that keeps Antarctic marine animals in good condition. The improved system increases the temperature of sea water to 10°C prior to biological filtration and thereby increases the effectiveness of the biological filter. The krill-rearing container was constructed inside the main tank so that the water flow inside the rearing container could be stopped. This avoids a rapid reduction of phytoplankton feed due to turnover of the seawater in the system while krill were fed. As a result of these improvements, long-term rearing, mass culture and reproduction of Antarctic krill are possible. We have exhibited Antarctic marine animals since the opening of PNPA in 1992, and we have exhibited Antarctic krill continuously since 1997. In this article, we detail the Antarctic krill breeding facilities at PNPA.     

Stability of ATP in Antarctic mineral soils

The stability of exogenous ATP in Antarctic Ross desert soils has been assessed using bioluminescence monitoring of ATP-supplemented samples. Under typical east Antarctic dry valley summer conditions (−3 to +15°C), exogenous ATP was degraded with a half-life of between 0.5 and 30 h. The rate of degradation was affected, in order of significance, by soil biomass levels, temperature and water content. Such rapid removal of exogenous ATP strongly suggests that extracellular ATP from lysed cells in cold desiccated soils does not make a significant contribution to the standing ATP titre     

Molecular Analysis of Geographic Patterns of Eukaryotic Diversity in Antarctic Soils

We describe the application of molecular biological techniques to estimate eukaryotic diversity (primarily fungi, algae, and protists) in Antarctic soils across a latitudinal and environmental gradient between approximately 60 and 87°S. The data were used to (i) test the hypothesis that diversity would decrease with increasing southerly latitude and environmental severity, as is generally claimed for “higher” faunal and plant groups, and (ii) investigate the level of endemicity displayed in different taxonomic groups. Only limited support was obtained for a systematic decrease in diversity with latitude, and then only at the level of a gross comparison between maritime (Antarctic Peninsula/Scotia Arc) and continental Antarctic sites. While the most southerly continental Antarctic site was three to four times less diverse than all maritime sites, there was no evidence for a trend of decreasing diversity across the entire range of the maritime Antarctic (60 to 72°S). Rather, we found the reverse pattern, with highest diversity at sites on Alexander Island (ca. 72°S), at the southern limit of the maritime Antarctic. The very limited overlap found between the eukaryotic biota of the different study sites, combined with their generally low relatedness to existing sequence databases, indicates a high level of Antarctic site isolation and possibly endemicity, a pattern not consistent with similar studies on other continents.     

Antarctic nematode communities: observed and predicted responses to climate change

The rapidly changing climate in Antarctica is impacting the ecosystems. Since records began, climate changes have varied considerably throughout Antarctica with both positive and negative trends in temperatures and precipitation observed locally. However, over the course of this century a more directional increase in both temperature and precipitation is expected to occur throughout Antarctica. The soil communities of Antarctica are considered simple with most organisms existing at the edge of their physiological capabilities. Therefore, Antarctic soil communities are expected to be particularly sensitive to climate changes. However, a review of the current literature reveals that studies investigating the impact of climate change on soil communities, and in particular nematode communities, in Antarctica are very limited. Of the few studies focusing on Antarctic nematode communities, long-term monitoring has shown that nematode communities respond to changes in local climate trends as well as extreme (or pulse) events. These results are supported by in situ experiments, which show that nematode communities respond to both temperature and soil moisture manipulations. We conclude that the predicted climate changes are likely to exert a strong influence on nematode communities throughout Antarctica and will generally lead to increasing abundance, species richness, and food web complexity, although the opposite may occur locally. The degree to which local communities respond will depend on current conditions, i.e., average temperatures, soil moisture availability, vegetation or more importantly the lack thereof, and the local species pool in combination with the potential for new species to colonize.     

Soil properties and distributions of invertebrates and bacteria from King George Island (Arctowski Station), maritime Antarctic

Soils of the Admiralty Bay region at King George Island, maritime Antarctic are described and analysed for invertebrates and microorganisms. Results showed a great variety of soils: cambisols, umbrisols, regosols, podzols, leptosols, gleysols and relic ornithogenic soils were found. Surface layers, especially of cambisols, umbrisols and podzols, showed a diverse fauna, governed by nematodes, collemboles and mites. The bacterial flora is analysed for total counts and biomass distribution in different layers using epifluorescence microscopy. Influences of soil organic matter can be described by different patterns of mean bacterial cell volumes related to soil cover and depth distributions. Received: 21 February 1997 / Accepted: 28 April 1997     

Diverse viromes in polar regions: A retrospective study of metagenomic data from Antarctic animal feces and Arctic frozen soil in 2012–2014

Antarctica and the Arctic are the coldest places, containing a high diversity of microorganisms, including viruses, which are important components of polar ecosystems. However, owing to the difficulties in obtaining access to animal and environmental samples, the current knowledge of viromes in polar regions is still limited. To better understand polar viromes, this study performed a retrospective analysis using metagenomic sequencing data of animal feces from Antarctica and frozen soil from the Arctic collected during 2012–2014. The results reveal diverse communities of DNA and RNA viruses from at least 23 families from Antarctic animal feces and 16 families from Arctic soils. Although the viral communities from Antarctica and the Arctic show a large diversity, they have genetic similarities with known viruses from different ecosystems and organisms with similar viral proteins. Phylogenetic analysis of Microviridae, Parvoviridae, and Larvidaviridae was further performed, and complete genomic sequences of two novel circular replication-associated protein (rep)-encoding single-stranded (CRESS) DNA viruses closely related to Circoviridae were identified. These results reveal the high diversity, complexity, and novelty of viral communities from polar regions, and suggested the genetic similarity and functional correlations of viromes between the Antarctica and Arctic. Variations in viral families in Arctic soils, Arctic freshwater, and Antarctic soils are discussed. These findings improve our understanding of polar viromes and suggest the importance of performing follow-up in-depth investigations of animal and environmental samples from Antarctica and the Arctic, which would reveal the substantial role of these viruses in the global viral community.