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Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, psbO). We find evidence of warm phases being associated with high relative diatom abundance, and a marked transition from diatoms comprising <10% of all eukaryotes prior to ~14.5 ka, to ~50% after this time, i.e., following Meltwater Pulse 1A, alongside a composition change from sea-ice to open-ocean species. Our study demonstrates that sedaDNA tools can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and paleo-productivity phases throughout multiple glacial-interglacial cycles. Sedimentary ancient DNA can indicate ecosystem-wide changes. Here, the authors show association between warm phases and high diatom abundance in the Antarctic Scotia Sea, in addition to presenting ancient eukaryote sedimentary DNA spanning the last approximately 1 million years. [ABSTRACT FROM AUTHOR]

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels. A new high-resolution record for the Antarctic Zone shows persistent anti-phasing of high interglacial ocean productivity and high glacial dust deposition, suggesting a close inter-hemispheric coupling of cryosphere, ocean and atmosphere. [ABSTRACT FROM AUTHOR]

The variation of glacier mass balance during the past decades remains poorly known for Duxueshan, Burog Kangri, and Zangser Kangri (DBZ) which are located in the Inner Tibetan Plateau (ITP), a transition zone with shifting influences between the westerlies and the Indian summer monsoon. In the present study, glacier area and mass changes were determined by topographic maps (TOPO), Landsat imagery and multi-temporal digital elevation models (DEMs) generated with TOPO, SRTM, TanDEM-X bistatic interferometric synthetic aperture radar (InSAR) images, and High Mountain Asia 8-m DEMs. On average, the glaciers showed a slight retreat from 343.27 ± 5.23 km2 in 1971 to 334.67 ± 3.21 km2 in 2018 (0.05 ± 0.04% a−1). However, glaciers lost mass at a rate of -0.32 ± 0.03 m w.e. a−1 from 1971 to 2012. For the 1999–2012 and 2012–2017 periods, mass balances of − 0.03 ± 0.16 and 0.09 ± 0.04 m w.e. a−1, respectively, were observed, which represents an approximately equilibrium. Two glaciers also advanced in our investigation period, and we confirmed one of them surged in 2015. [ABSTRACT FROM AUTHOR]

An efficient protocol for the isolation of high-quality DNA from tissues is essential to many aspects of molecular biology. Shed skin is often overlook as a source for high-quality DNA in molecular studies involving frog. In this study, DNA from shed skin of frog was extracted using phenol–chloroform, the DNeasy extraction kit (Qiagen) and an improved salting-out protocol, in comparison with those of skeletal muscle and toe. We found that the improved salting-out procedure obtained the highest DNA yield, and avoided using toxic chemicals such as phenol, chloroform, isoamyl alcohol, and/or guanidine isothiocyanate. The quantity of DNA from shed skin was lower compared to other tissue in Rana dybowskii. Nevertheless, DNA from shed skin was useful for amplifing mtDNA and nuclear DNA using PCR, as were Rana amurensis and Bufo gargarizans. These results indicate that extrating DNA from shed frog skin by improved salting-out protocol is an efficient and safe method for the conservation genetic studies and population genetics without destroy in frogs. [ABSTRACT FROM AUTHOR]

Antarctic sea ice has experienced an increasing trend in recent decades, especially in the Ross Sea and Indian Ocean sectors. Sea ice variability affects greatly the maritime airmass transport from high latitude to Antarctic continent. Here we present a new ice core record of sea salt sodium (ssNa+) concentration at annual-resolution in the Princess Elizabeth Land spanning from 1990 to 2016, showing that this marker could be used as a potential proxy for reconstructing the sea ice extent (SIE) in the Southern Indian Ocean (SIO) given their significant correlation (R = −0.6, P <0.01) over the past 27 years. The correlation and composite analyses results show that the ssNa+ at the 202 km inland from Zhongshan Station and the SIE changes in SIO are closely related to the Indian Ocean Dipole (IOD) and Southern Annular Mode (SAM). The northward wind in central SIO occurs during positive IOD and the strengthened westerlies occurs during positive SAM, both of which favor increased sea ice in SIO and lead to the decreased ssNa+ concentration at the coastal site. [ABSTRACT FROM AUTHOR]

In this study, we determined the entire mitochondrial genome of Rhizomys sumatrensis for the first time. The complete mitogenome sequence was 16,672 bp in length, containing 13 protein coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA) genes; it also featured an origin of replication on the light-strand (OL) and a control region (D-loop). The overall nucleotide composition was as follows: A, 32.5%; T, 31.3%; C, 24.5%; and G, 11.7%, with a total A +T content of 63.8%. The phylogenetic analysis demonstrated a close relationship between R. sumatrensis, R. pruinosus, and R. sinensis. Our observations will help inform further studies on the conservation genetics of the Rhizomys genus. [ABSTRACT FROM AUTHOR]