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The Laptev Sea is a major Marginal Sea in the Western Arctic Ocean. The Arctic amplification brought by global warming influences the hydrological properties of rivers passing through the permafrost zone, which would alter the biological community structure at continental margin. In this study, the structure, assembly, and gene expression of planktonic microbial communities in two estuaries (Protoka Ularovskaya River Estuary, PURE; Lena River Estuary, LRE) of Laptev Sea were examined to investigate the environmental effects of polar rivers. PURE and LRE exhibited distinct environmental characteristics: low temperature and high salinity for PURE, and high temperature and low salinity for LRE, influenced by runoff size. Salinity more closely influenced microbial communities in LRE, with freshwater species playing a significant role in community composition. The findings revealed differences between two estuaries in community composition and diversity. Prokaryotes and microeukaryotes had shown different assembly patterns in response to habitat changes caused by terrestrial freshwater input. Furthermore, compared with the PURE, the co-occurrence and inter-domain network of the LRE, which was more affected by terrestrial input, was more complex and stable. Functional gene prediction revealed a higher gene expression of methane metabolism in LRE than in PURE, particularly those related to methane oxidation, and this conclusion could help better explore the impact of global warming on the methane cycle in the Arctic Marginal Seas. This study explored the increased freshwater runoffs under the background of global warming dramatically affect Arctic microplankton communities from community structure, assembly and gene expression aspects., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Mercury has become a ubiquitous hazardous element even ending up in pristine areas such as the Arctic, where it biomagnifies and leaves especially top predators vulnerable to potential health effects. Here we investigate total mercury (THg) concentrations and dietary proxies for trophic position and habitat foraging (δ 15 N and δ 13 C, respectively) in fur of 30 Arctic wolves collected during 1869-1998 in the Canadian High Arctic and Greenland. Fur THg concentrations (mean ± SD) of 1.46 ± 1.39 μg g -1 dry weight are within the range of earlier reported values for other Arctic terrestrial species. Based on putative thresholds for Hg-mediated toxic health effects, the studied Arctic wolves have most likely not been at compromised health. Dietary proxies show high dietary plasticity among Arctic wolves deriving nutrition from both marine and terrestrial food sources at various trophic positions. Variability in THg concentrations seem to be related to the wolves' trophic position rather than to different carbon sources or regional differences (East Greenland, the Foxe Basin and Baffin Bay area, respectively). Although the present study remains limited due to the scarce, yet unique historic study material and small sample size, it provides novel information on temporal and spatial variation in Hg pollution of remote Arctic species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Nordic Seas are the subarctic seas connecting the Arctic Ocean and North Atlantic Ocean with complex water masses, experiencing an abrupt climate change. Though knowledge of the marine virosphere has expanded rapidly, the diversity of viruses and their relationships with host cells and water masses in the Nordic Seas remain to be fully revealed. Here, we establish the Nordic Sea DNA virome (NSV) data set of 55,315 viral contigs including 1,478 unique viral populations from seven stations influenced by both the warm Atlantic and cold Arctic water masses. Caudovirales dominated in the seven NSVs, especially in the warm Atlantic waters. The major giant nucleocytoplasmic large DNA viruses (NCLDVs) contributed a significant proportion of the classified viral contigs in the NSVs (32.2%), especially in the cold Arctic waters (44.9%). The distribution patterns of Caudovirales and NCLDVs were a reflection of the community structure of their hosts in the corresponding water masses and currents. Latitude, pH, and flow speed were found to be key factors influencing the microbial communities and coinfluencing the variation of viral communities. Network analysis illustrated the tight coupling between the variation of viral communities and microbial communities in the Nordic Seas. This study suggests a probable linkage between viromes, host cells, and surface water masses from both the cool Arctic and warm Atlantic Oceans. IMPORTANCE This is a systematic study of Nordic Sea viromes using metagenomic analysis. The viral diversity, community structure, and their relationships with host cells and the complex water masses from both the cool Arctic and the warm Atlantic oceans were illustrated. The NCLDVs and Caudovirales are proposed as the viral characteristics of the cold Arctic and warm Atlantic waters, respectively. This study provides an important background for the viromes in the subarctic seas connecting the Arctic Ocean and North Atlantic Ocean and sheds light on their responses to abrupt climate change in the future.

Arctic warming associated with global climate change poses a significant threat to populations of wildlife in the Arctic. Since lipids play a vital role in adaptation of organisms to variations in temperature, high-resolution mass-spectrometry-based lipidomics can provide insights into adaptive responses of organisms to a warmer environment in the Arctic and help to illustrate potential novel roles of lipids in the process of thermal adaption. In this study, we studied an ecologically and economically important species-Arctic char (Salvelinus alpinus)-with a detailed multi-tissue analysis of the lipidome in response to chronic shifts in temperature using a validated lipidomics workflow. In addition, dynamic alterations in the hepatic lipidome during the time course of shifts in temperature were also characterized. Our results showed that early life stages of Arctic char were more susceptible to variations in temperature. One-year-old Arctic char responded to chronic increases in temperature with coordinated regulation of lipids, including headgroup-specific remodeling of acyl chains in glycerophospholipids (GP) and extensive alterations in composition of lipids in membranes, such as less lyso-GPs, and more ether-GPs and sphingomyelin. Glycerolipids (e.g., triacylglycerol, TG) also participated in adaptive responses of the lipidome of Arctic char. Eight-week-old Arctic char exhibited rapid adaptive alterations of the hepatic lipidome to stepwise decreases in temperature while showing blunted responses to gradual increases in temperature, implying an inability to adapt rapidly to warmer environments. Three common phosphatidylethanolamines (PEs) (PE 36:6|PE 16:1_20:5, PE 38:7|PE 16:1_22:6, and PE 40:7|PE 18:1_22:6) were finally identified as candidate lipid biomarkers for temperature shifts via machine learning approach. Overall, this work provides additional information to a better understanding of underlying regulatory mechanisms of the lipidome of Arctic organisms in the face of near-future warming., (© 2021 John Wiley & Sons Ltd.)

Although microbial exopolysaccharides (EPSs) are applied in different fields, no EPS has been used to protect human skin cells against UV-induced oxidative stress. The EPS produced by the Arctic bacterium Polaribacter sp. SM1127 has high moisture-retention ability and antioxidant activity, suggesting its good industrial potentials. In this study, we improved the EPS production of SM1127 and evaluated its protective effect on human dermal fibroblasts (HDFs) against UV-induced oxidative stress. With glucose as carbon source, the EPS yield was increased from 2.11 to 6.12 g/L by optimizing the fermentation conditions using response surface methodology. To lower the fermentation cost and decrease corrosive speed in stainless steel tanks, whole sugar, whose price is only 8% of that of glucose, was used to replace glucose and NaCl concentration was reduced to 4 g/L in the medium. With the optimized conditions, fed-batch fermentation in a 5-L bioreactor was conducted, and the EPS production reached 19.25 g/L, which represents the highest one reported for a polar microorganism. Moreover, SM1127 EPS could maintain the cell viability and integrity of HDFs under UV-B radiation, probably via decreasing intracellular reactive oxygen species level and increasing intracellular glutathione content and superoxide dismutase activity. Therefore, SM1127 EPS has significant protective effect on HDFs against UV-induced oxidative stress, suggesting its potential to be used in preventing photoaging and photocarcinogenesis. Altogether, this study lays a good foundation for the industrialization of SM1127 EPS, which has promising potential to be used in cosmetics and medical fields.

A Gram-stain-negative, facultatively anaerobic, flagellated and rod-shaped bacterium, designated strain SM1901 T , was isolated from a brown algal sample collected from Kings Bay, Svalbard, Arctic. Strain SM1901 T grew at -4‒30 °C and with 0-7.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed DNA and Tween 80. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SM1901 T was affiliated with the genus Shewanella , showing the highest sequence similarity to the type strain of Shewanella litoralis (97.5%), followed by those of Shewanella vesiculosa , Shewanella livingstonensis and Shewanella saliphila (97.3 % for all three). The major cellular fatty acids were summed feature 3 (C 16 : 1 ω 7 с and/or C 16 : 1 ω 6 с ), C 16 : 0 , C 18 : 0 , iso-C 15 : 0 and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinones were ubiquinones Q-7, Q-8, menaquinones MK-7(H) and MK-8. The genome of strain SM1901 17 : 1 was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901 ω 8 с was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar T was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901 T was 40.5 mol%. Based on the polyphasic evidence presented in this paper, strain SM1901 T was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar Shewanella species, within the genus Shewanella , for which the name Shewanella polaris sp. nov. is proposed. The type strain is SM1901 T (=KCTC 72047 T =MCCC 1K03585 T ).