Antarctic Glacier Ice Research Articles

Taxonomic and functional diversity from Antarctic ice-tephra microbial community: ecological insights and potential for bioprospection

Antarctic active volcanoes can disperse pyroclastic minerals at long distances, transporting nutrients and microorganisms to the surrounding glacial environment. The sedimented volcanic materials - called tephras - may interact with glacier ice and produce a unique environment for microbial life. This study aimed to describe the microbial community structure of an Antarctic glacier ice with tephra layers in terms of its taxonomic and functional diversity. Ice samples from Collins Glacier (King George Island) containing tephra layers of Deception Island volcano were analyzed by a whole shotgun metagenomic approach. Taxonomic analysis revealed a highly diverse community dominated by phyla Bacteroidetes, Cyanobacteria and Proteobacteria. The dominant genera were Chitinophaga (13%), Acidobacterium (8%), and Cyanothece (4%), being all of these known to include psychrotolerant and psychrophilic strains. Functional diversity analysis revealed almost complete carbon, nitrogen and sulfur biogeochemical cycles. Carbohydrate metabolism of the ice-tephra community uses both organic and inorganic carbon inputs, where photosynthesis plays an important role through CO2 fixation. Our results also demonstrate a biotechnological potential for this glacial community, with functional annotations for styrene degradation and carotenoid pigment genes. Future metatranscriptomic studies shall further reveal the active strategies and the biotechnology potential of extremophiles from this unique ice-tephra microbial community.

Effects of atmospheric conditions on ice nucleation activity of <i>Pseudomonas</i>

Abstract. Although ice nuclei from bacterial origin are known to be efficient at the highest temperatures known for ice catalysts, quantitative data are still needed to assess their role in cloud processes. Here we studied the effects of three typical cloud conditions (i) acidic pH (ii) NO2 and O3 exposure and (iii) UV-A exposure on the ice nucleation activity (INA) of four Pseudomonas strains. Three of the Pseudomonas syringae strains were isolated from cloud water and the phyllosphere and Pseudomonas fluorescens strain CGina-01 was isolated from Antarctic glacier ice melt. Among the three conditions tested, acidic pH caused the most significant effects on INA likely due to denaturation of the ice nucleation protein complex. Exposure to NO2 and O3 gases had no significant or only weak effects on the INA of two P. syringae strains whereas the INA of P. fluorescens CGina-01 was significantly affected. The INA of the third P. syringae strain showed variable responses to NO2 and O3 exposure. These differences in the INA of different Pseudomonas suggest that the response to atmospheric conditions could be strain-specific. After UV-A exposure, a substantial loss of viability of all four strains was observed whereas their INA decreased only slightly. This corroborates the notion that under certain conditions dead bacterial cells can maintain their INA. Overall, the negative effects of the three environmental factors on INA were more significant at the warmer temperatures. Our results suggest that in clouds where temperatures are near 0 °C, the importance of bacterial ice nucleation in precipitation processes could be reduced by some environmental factors.

Genomic DNA Extracted from Ancient Antarctic Glacier Ice for Molecular Analyses on the Indigenous Microbial Communities

From ancient Antarctic glacier ice, we extracted total genomic DNA that was suitable for prokaryotic 16S rDNA gene cloning and sequencing, and bacterial artificial chromosome (BAC) library and end-sequencing. The ice samples were from the Dry Valley region. Age dating by <TEX>$^{40}Ar/^{39}Ar$</TEX> analysis on the volcanic ashes deposited in situ indicated the ice samples are minimum 100,000-300,000 yr (sample DLE) and 8 million years (sample EME) old. Further assay proved the ice survived freeze-thaw cycles or other re-working processes. EME, which was from a small lobe of the basal Taylor glacier, is the oldest known ice on Earth. Microorganisms, preserved frozen in glacier ice and isolated from the rest of the world over a geological time scale, can provide valuable data or insight for the diversity, distribution, survival strategy, and evolutionary relationships to the extant relatives. From the 16S gene cloning study, we detected no PCR amplicons with Archaea-specific primers, however we found many phylotypes belonging to Bacteria divisions, such as Actinobacteria, Acidobacteria, Proteobacteria <TEX>$({\alpha},\;{\beta},\;and\;{\gamma})$</TEX>, Firmicutes, and Cytophaga-Flavobacterium-Bacteroid$. BAC cloning and sequencing revealed protein codings highly identical to phenylacetic acid degradation protein paaA, chromosome segregation ATPases, or cold shock protein B of present day bacteria. Throughput sequencing of the BAC clones is underway. Viable and culturable cells were recovered from the DLE sample, and characterized by their 16S rDNA sequences. Further investigation on the survivorship and functional genes from the past should help unveil the evolution of life on Earth, or elsewhere, if any.

The global accretion rate of extraterrestrial materials in the last glacial period estimated from the abundance of micrometeorites in Antarctic glacier ice

The accretion rate of micrometeorites in the last glacial period was estimated from the concentrations of micrometeorites in the blue ice around the Yamato Mts. in Antarctica. The samples from this study were collected from the five sampling points (M03, K02, K11, J09 and J10) in the blue ice. The blue ice was melted and filtered, and the micrometeorites were handpicked from the collected “glacial sands”. The weight of the micrometeorites in the blue ice was estimated from the abundance of recovered micrometeorites and the solar noble gas concentrations in the “residue” after handpicking. The age of the blue ice from the K area was estimated to be 27–33 kyr before present based on oxygen isotope data. The estimated accretion rate to the whole Earth ranges from 5300 × 103kg/a to 16000 × 103kg/a. However, the lower end of this range probably represents lower limits due to possible loss of solar noble gases during long residence in the glacier ice. Hence, we estimate that the accretion rate of micrometeorites 27–33 kyr before present to be in the range between (11000 ± 6600) × 103kg/a and (16000 ± 9100) × 103kg/a. These results, as well as the other estimates, suggest that the accretion rate of micrometeorites in the last glacial period was comparable to that in the present. Micrometeorite k]accretion rate k]Antarctica k]last glacial periods k]noble gas k]interplanetary dust particle

Blue Ice Airfields - Airfields on Antarctic glacier ice. M. Mellor and C. Swithinbank 1989. Springfield Va., US Army Cold Regions Research and Engineering Laboratory (CRREL Report 89-21). 105 p, illustrated, soft cover.

Blue Ice Airfields - Airfields on Antarctic glacier ice. M. Mellor and C. Swithinbank 1989. Springfield Va., US Army Cold Regions Research and Engineering Laboratory (CRREL Report 89-21). 105 p, illustrated, soft cover.

Bubbles and Bubble Pressures in Antarctic Glacier Ice

Application of the gas law to fourth-place density measurements of ice samples from two deep drill holes at “Byrd” station and “Little America V”, Antarctica, shows that virtually all density increase beyond the pore close-off density (0.830 g cm−3) can be attributed to compression of the entrapped bubbles of air. Data from “Byrd” station also indicate that the lag between overburden pressure and bubble pressure, initially 4–5 kg cm−2at pore close-off, diminishes to less than 1.0 kg cm−2at about 200 m depth. By substituting the overburden pressure for the bubble pressure in the pressure-density relationship based on the gas law, one can determine ice densities below 200 m more accurately than they can be measuredper seon cores, because of the relaxation that occurs in samples recovered from high confining pressures. This relaxation, resulting in a progressive increase in the bulk volume of the ice with time, is generally attributed to decompression of the entrapped air bubbles following removal of the ice from high confining pressures. However. calculations of the stress in ice due to bubble pressure, together with measurements of bubble sizes in cores from various depths at “Byrd” station, both tend to indicate that there has been negligible decompression of the inclosed bubbles. It is suggested that most of this relaxation may be due to the formation of micro-cracks in the ice. Anomalous bubble pressure–density relations at “Little America V” tend to confirm abundant petrographic evidence of the existence of considerable deformation in the upper part of the Ross Ice Shelf.Studies of crystal–bubble relations at “Byrd” station revealed that the concentration of bubbles in ice remains remarkably constant at approximately 220 bubbles/cm3. Bubbles and crystals were found to be present in approximately equal numbers at pore close-off at 64 m depth, at which level the average bubble diameter was 0·95 mm, decreasing to 0.49 mm at 116 m and to 0·33 mm at 279 m. Despite a ten-fold increase in the size of crystals between 64 and 279 m, the bubbles showed no tendency to migrate to grain boundaries during recrystallization of the ice. The observation that most of the bubbles had assumed substantially spherical shapes by 120 m depth points to essentially hydrostatic conditions in the upper layers of the ice sheet at “Byrd” station.

Bubbles and Bubble Pressures in Antarctic Glacier Ice

Application of the gas law to fourth-place density measurements of ice samples from two deep drill holes at “Byrd” station and “Little America V”, Antarctica, shows that virtually all density increase beyond the pore close-off density (0.830 g cm−3) can be attributed to compression of the entrapped bubbles of air. Data from “Byrd” station also indicate that the lag between overburden pressure and bubble pressure, initially 4–5 kg cm−2 at pore close-off, diminishes to less than 1.0 kg cm−2 at about 200 m depth. By substituting the overburden pressure for the bubble pressure in the pressure-density relationship based on the gas law, one can determine ice densities below 200 m more accurately than they can be measured per se on cores, because of the relaxation that occurs in samples recovered from high confining pressures. This relaxation, resulting in a progressive increase in the bulk volume of the ice with time, is generally attributed to decompression of the entrapped air bubbles following removal of the ice from high confining pressures. However. calculations of the stress in ice due to bubble pressure, together with measurements of bubble sizes in cores from various depths at “Byrd” station, both tend to indicate that there has been negligible decompression of the inclosed bubbles. It is suggested that most of this relaxation may be due to the formation of micro-cracks in the ice. Anomalous bubble pressure–density relations at “Little America V” tend to confirm abundant petrographic evidence of the existence of considerable deformation in the upper part of the Ross Ice Shelf.Studies of crystal–bubble relations at “Byrd” station revealed that the concentration of bubbles in ice remains remarkably constant at approximately 220 bubbles/cm3. Bubbles and crystals were found to be present in approximately equal numbers at pore close-off at 64 m depth, at which level the average bubble diameter was 0·95 mm, decreasing to 0.49 mm at 116 m and to 0·33 mm at 279 m. Despite a ten-fold increase in the size of crystals between 64 and 279 m, the bubbles showed no tendency to migrate to grain boundaries during recrystallization of the ice. The observation that most of the bubbles had assumed substantially spherical shapes by 120 m depth points to essentially hydrostatic conditions in the upper layers of the ice sheet at “Byrd” station.

Creep Tests on Antarctic Glacier Ice

THE strain rate of polycrystalline ice is known to depend on the applied stress, the temperature and the orientation of crystals in the specimen. From laboratory creep tests on randomly oriented ice, Glen1 derived the simple flow law where ε̇ is the strain rate, σ is the stress, and k is constant for a given temperature. Other workers have confirmed the validity of this relationship for the stress range 2–15 bars. From observed minimum strain-rates Glen1 deduced n=3.17; but he considered that a value of 4.2 derived from analysed quasi-viscous creep-rates was a more correct one for randomly oriented ice. Some observations on glacier tunnel deformation tend to confirm Glen's higher value for the exponent2, whilst the closure of a bore-hole in the Greenland ice-cap gave an exponent of 3.773. Other laboratory tests on glacier and commercial ice of high density gave figures ranging from 2.42 to 3.53 with a mean of 2.964. Weertman's dislocation climb theory5 calls for a dependence on stress to the power 4.5. Below a stress of 1 bar the flow mechanism is different and there is an approximation to viscous behaviour, with an exponent of about 1.5 applying.