No abstract

Schirmacher Oasis is one of the few ice-free plateaus in East Antarctica that maintains a unique distribution of over 120 microbial-rich, dynamic freshwater lakes, most of which are unexplored. In this study, we describe the bacterial diversity of the rock-water interface in Lake Tawani(P) using culture-independent Bacterial Tag Encoded FLX Amplicon Pyrosequencing (bTEFAP), clone library construction, and culture-based analysis targeting the eubacterial 16S rRNA gene. Lake Tawani(P)was formed in a fossil valley by the accumulation of snow and glacial melt through surface channels into a low-catchment depression. Overall this lake exhibited thirteen bacterial phyla and one-hundred and twelve genera. The Qiime bioinformatics analysis on the bTEFAP alone exhibited higher coverage of the bacterial composition in Lake Tawani(P) than the clone library construction or culture-based methodology. Particularly due to the higher sensitivity of the bTEFAP approach, we detected and differentiated members of the phyla: Chloroflexi, Gemmatimonadetes, Planctomycetes, Nitrospira, and Candidate Division TM7 that other methods were unable to reveal. Nevertheless we found that the use of multiple approaches identified a more complete bacterial community than by using any single approach. Investigating the bacterial diversity of the Schirmacher Oasis lakes, especially those connected through surface channels and encompassed by valleys, will help unravel the dynamic nature of these unique seasonal, freshwater lakes, which potentially harbors highly adapted bacterial taxa with defined ecological functions.

Schirmacher Oasis and Bharati Promontory in Larsemann Hills of East Antarctica are currently ice-free coastal areas exposed in physiographically different polar periglacial environments. Schirmacher Oasis is bound by the presence of a vast stretch of ice shelf in the north and the polar ice sheet in the south. It exhibits well-developed patterned ground, abundant till deposition, block-fields, episodic development of curvilinear morainic ridges, extensive outwash plains and erratics. In contrast, the occurrence of such depositional features is sparse on Bharati Promontory, where landmass is directly in contact with the ocean. The sedimentary processes vary in their magnitude owing to different physiographic settings in these two geographically separated locations. Scanning electron microscopy of quartz grains shows subsequent reworking under glaciofluvial environment and final deposition of material in glacially scoured basins. The fluvial action is more pronounced in the Schirmacher Oasis than on Bharati Promontory. The transport of sediment by polar ice is mainly through englacial pathways with a minor contribution from the supraglacial component. Discharge of all sizes of sediments ranging from large boulders to glacially abraded rock-flour in varying proportions takes place at the ice–bedrock interface. Granulometric analysis also shows turbulence of transporting media and reworking of sediments before final deposition.

Hymenobacter sp. IS2118, isolated from a freshwater lake in Schirmacher Oasis, Antarctica, produces extracellular polymeric substance (EPS) and manifests tolerance to cold, UV radiation (UVR), and oxidative stress. We report the 5.26-Mb draft genome of strain IS2118, which will help us to understand its adaptation and survival mechanisms in Antarctic extreme ecosystems.

The Himalaya are often referred to as the third pole of the Earth because they host the largest areal extent of glaciation outside the polar regions. Estimating the volume of these glaciers is challenging because the ice thickness of most of the glaciers is not accurately known. Depth profiling of the north-facing Hamtah and Parang glaciers was carried out using ground-penetrating radar surveys. The 6 km long Hamtah glacier and the 2.5 km long Parang glacier, with average widths of 350 and 250 m, respectively, are located in different U-shaped valleys. The depth of the ice–bedrock interface varied from 35 to 95 m in the Hamtah glacier and from 40 to 140 m in the Parang glacier. The valley profiles and ground-penetrating radar data were combined to obtain the volumes of the glaciers. The total volumes of ice in the Parang and Hamtah glaciers were estimated to be 0.179 and 0.375 km3, respectively. Shape analyses of different parts of these glaciers suggest that mathematical equations can be used to describe their sequential development. The retreat rates of the Parang and Hamtah glaciers were estimated to be 11.04 and 16.10 m a−1, respectively.