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The Polish Geophysical Expedition to West Antarctica in 1979–1980 was carried out by the Institute of Geophysics, Polish Academy of Sciences. Beside deep seismic soundings, 12 multi-channel seismic profiles, with a total length of ca 1000 km have been recorded north and east of the South Shetland Islands and in the Bransfield Strait, but they have never before been completely interpreted and published. All profiles have been processed with modern processing flow including time migration. Profiles crossing the South Shetland Trench revealed distinct reflector inside continental slope, which has been interpreted as border between buried accretionary prism and overlying slope sediments of glacial-marine origin. Profiles in the Bransfield Strait show traces of the Last Glacial Maximum (LGM) in the form of glacial foreground valleys, with some of them used as weak spots for young age volcanic intrusions. This paper is the first comprehensive geological interpretation of collected dataset and differences between results from other expeditions are discussed.

Antarctic waters are the largest almost untapped diversified resource of our planet. Molecular resources for Antarctic organisms are very limited and mostly represented by sequences used for species genotyping. In this study, we present the first transcriptome for the copepod Rhincalanus gigas, one of the predominant zooplankton species of Antarctic waters. This transcriptome represents also the first molecular resource for an eucalanoid copepod. The transcriptome is of high quality and completeness. The presence of three predicted genes encoding antifreeze proteins and gene duplication within the glutathione metabolism pathway are suggested as possible adaptations to cope with this harsh environment. The R. gigas transcriptome represents a powerful new resource for investigating the molecular basis associated with polar biological processes and ecology.

The South Shetland Trench (SST) northwest of the South Shetland Islands is the only trench along the Pacific margin of the Antarctic Peninsula. Multichannel seismic reflection profile shows very narrow normal faulting zone (about 20 km) on the outer wall of the SST and thick trench-fill sediments (up to 1000 m) on two distinct crustal horst and graben structures in the trench. These structures are rare in the active subduction trenches. On the basis of the implications from these seismic structures and known tectonic history, the following scenarios of subduction activities of the former Phoenix plate are proposed: (1) normal faulting has not occurred since subduction rate in the SST sharply decreased after cessation of seafloor spreading at the West Scotia Ridge at about 6 Ma; and (2) subduction almost stopped after the cessation of spreading in Drake Passage at about 3.3 Ma. Recent contractional structures around the SST are indicative of current crustal shortening (not subduction) accommodating trenchward movement of South Shetland Islands caused by the ongoing extension of Bransfield Basin behind the South Shetland Islands. [ABSTRACT FROM AUTHOR]

Four deep crustal models of the South Shetland Trench (SST) and the Shackleton Fracture Zone (SFZ) off the northern Antarctic Peninsula are presented based on gravity data. The gravity models of the SST suggest that the dip of the subducting crust increases from southwest to northeast ranging from 25° in Line KSL93-5 to 30° in Line KSL93-6 as the age of crust increases along the trench axis. The gravity low observed near the island are is directly associated with the deep forearc basin bounded seaward by a large fault. In the SFZ, the thin crust is concentrated primarily beneath the ridge, where Moho shallows by 2.5 km. A low-density material (about 2.45 g/cm3) assigned to the SFZ ridge is presumably due to serpentinite intrusion. The gravity low associated with the trough is due to the relatively low-density sediments filled in the trough. The crustal thickening to the western slope of the ridge near the triple junction was probably caused by the collision of the SFZ ridge with the Shetland Platform. [ABSTRACT FROM AUTHOR]

Whole genome sequences of four bacterial strains Dietzia maris SST1, Pseudomonas zhaodongensis SST2, Pseudomonas sp. SST3 and Halomonas sulfidaeris SST4, recovered from the South Shetland Trench sediment in Antarctica were analyzed using Ion Torrent sequencing technology. The respective sizes of their genomes (3.88, 4.99, 5.60 and 4.25 Mb) and GC contents (70.0, 60.3, 59.9 and 53.8%) are in agreement with these values of other strains of the species. The bacterial strains displayed promising antimicrobial activity against a number of pathogenic bacterial and fungal species. Whole genomes have been assembled and biosynthetic gene clusters (BGCs) have been identified using the antibiotics and Secondary Metabolite Analysis Shell (antiSMASH) web platform. Comparative analysis of the genome sequences revealed that the strains host abundant BGCs encoding for terpenes, siderophores, arylpolyene, bacteriocins, and lassopeptides. Furthermore, the key stress-related genes were identified and their distribution provided an insight into how these isolates adapt to key marine environmental conditions. This comprehensive study is a contribution to understanding the nature of life on the deep-sea environments. Unlabelled Image • The genomes of four bacterial strains from the South Shetland Trench were sequenced. • The genomes of the SST strains elicited BGCs of different classes of compounds. • Comparative metabolomics analyses revealed the high affinity of SST strains for new chemistry. • The genomes of SST strains contain a large number of genes involved in deep-sea adaptation. [ABSTRACT FROM AUTHOR]

Simple Summary: Compared to more accessible sites, organisms inhabiting Antarctic waters have been poorly investigated. This study provides the first molecular resource (transcriptome from whole individual) for the eucalanoid copepod Rhincalanus gigas, one of the predominant zooplankton species of Antarctic waters. Sequence analyses identified possible adaptation strategies adopted by the organism to cope with cold environments. Among those, we identified in R. gigas transcriptome three predicted genes encoding for antifreeze proteins and gene duplication within the glutathione metabolism pathway. This new molecular resource, provided here, will be useful to study the physiology, ecology, and biology of R. gigas and it increases the information available for polar environments. Antarctic waters are the largest almost untapped diversified resource of our planet. Molecular resources for Antarctic organisms are very limited and mostly represented by sequences used for species genotyping. In this study, we present the first transcriptome for the copepod Rhincalanus gigas, one of the predominant zooplankton species of Antarctic waters. This transcriptome represents also the first molecular resource for an eucalanoid copepod. The transcriptome is of high quality and completeness. The presence of three predicted genes encoding antifreeze proteins and gene duplication within the glutathione metabolism pathway are suggested as possible adaptations to cope with this harsh environment. The R. gigas transcriptome represents a powerful new resource for investigating the molecular basis associated with polar biological processes and ecology. [ABSTRACT FROM AUTHOR]