Polar Biology最新文献

Microbial communities of the Arctic Ocean are poorly described in comparison to aquatic environments of other regions regarding their patterns of distribution and change. The present work aims to investigate free-living bacterial communities (size fraction 0.22–1.5 μm) of different Arctic seas regions, from the river discharge area to the continental slope. Illumina MiSeq metabarcoding analysis using V3–V4 region of 16S rRNA gene was employed to study the microbial diversity of 11 Arctic seawater samples, collected from the surface and near-bottom layers in the Kara and Laptev Seas in August–September 2018. Additionally, we determined environmental parameters, bacterial abundance, biomass, and respiratory activity. Redundancy analysis, Spearman’s rank correlation, and multiple linear regression analysis were used to reveal environmental factors that modulate the bacterial community structure. The differences in the free-living bacterial community composition were associated with environmental characteristics of water layers (salinity and temperature) rather than with geographical area. Although the communities from all examined sites were dominated by Gammaproteobacteria and Alphaproteobacteria followed by Flavobacteriia and Actinobacteria, they showed distinct variations in the distribution at all taxonomical levels. No archaeal taxa were observed. The distribution patterns of the quantitative parameters of total bacterial community were not associated with defined environmental characteristics.

The coastal wetlands of northern Chilean Patagonia are relevant sites for the conservation of migratory waterbirds. The aim of this paper is to compare different marine coastal wetlands to identify which factors influence the structure of bird assemblages. Sediment samples were collected, and the birds were surveyed in four wetlands: Chullec, Curaco de Vélez and Quinchao on Quinchao Island, and Putemún on Chiloé Island in 4 seasonal sampling campaigns. The composition of the sediment did not change during the year, with a predominance of sandy sediments except in Putemún where gravel dominates. The size of the sediment particle decreased from the upper (0 to 30 m) to the lower (100 m) intertidal. The abundances of benthic organisms varied between intertidal levels in all wetlands and seasonally in Chullec and Curaco de Vélez, being lower during warm seasons. Thirty-four species of birds were recorded with Anatidae, Laridae and Scolopacidae showing the highest species richness. A principal component analysis clustered the wetlands of Quinchao Island and the variables that account for 35.8% of the variance are sandy sediments, the presence of Scolopacidae, Laridae, Furnariidae and Haematopodidae among birds and Polychaeta, Malacostraca and Enopla in the benthos. In the wetlands of Quinchao Island there was a relationship between the composition of the sediment, distribution, and type of benthic communities with the presence of some bird taxa. The bird assemblages change seasonally and were similar to each other during warm seasons, probably due to the availability of food for migratory birds and sediment characteristics.

Sightings of vagrant walruses in Europe have been known since historic times, yet whether this phenomenon remains constant or changes over time is unclear. In this study, we conducted a comprehensive cross-reference of information on vagrant walruses observed in temperate Europe (below 61° N) between 1923 and 2022 utilising data from the Global Biodiversity Information Facility depository. In addition, we conducted an online search of records from the last ten years, resulting in a detailed reconstruction of the movements of the most recently observed individuals. We estimated that between 31 and 36 different individuals have been observed over the last century, with most of these likely originating from the Svalbard region and only a few from Greenland. A comparison in the yearly number of records showed a significant increase over time, suggesting that vagrant walruses reach Europe as a result of a combination of climatic and meteorological events as well as of demographic changes in the populations of the North Atlantic.

Hybridization between species and the establishment of hybridization barriers can influence the diversification of species. Antarctic notothenioid fishes represent a prime example of marine adaptive radiation that diversified in the icy waters of Antarctica from an ancestral population that innovated antifreeze glycoproteins. The processes by which Antarctic notothenioid species evolved, however, remain elusive, and interspecific hybridization or the establishment of hybridization barriers between lineages may have influenced species diversification. To evaluate the current hybridization potential of notothenioids, we performed an experimental in vitro fertilization cross between two sympatric and congeneric notothen species using oocytes from the bullhead notothen Notothenia coriiceps and sperm from the marbled notothen N. rossii. Resulting embryos developed to late gastrula/early neurula stages and then suddenly died. Genetic analyses of embryos and parents demonstrated that the embryos lacked detectable paternal DNA and were thus gynogenetic. While premating barriers are likely to exist between the two species, this experiment suggests a strong postmating, prezygotic reproductive barrier preventing hybridization between the sister species due to gametic incompatibility in this directional cross. Our study provides novel information on mechanisms that may have contributed to the divergence and maintenance of these two ecologically important congeneric species.

We report on an occurrence of ocular albinism in sub-Antarctic fur seal (Arctocephalus tropicalis) pups born on Marion Island, Prince Edward Archipelago. While previous observations have documented pups with atypical lanugo pelage colorations, this is the first case involving hypopigmentation of both fur and other tissues, including the eyes and nails. During the austral summer of 2021/22, we encountered four sub-Antarctic fur seal pups displaying this anomalous pigmentation. These anomalous individuals were found along two beaches on the island’s western side and one beach on the eastern side during an island-wide fur seal census. Although the characteristics observed strongly suggest ocular albinism, confirmation would be necessary through genetic analyses. The absence of melanin in mammalian eyes is known to compromise visual acuity, which may likely result in reduced survival beyond the weaning period, explaining the paucity of such adults in this well-observed population.

We examined associations between adolescent self-reported hunger, health risk behaviors, and adverse experiences during the 2018-2019 school year. Youth Risk Behavior Survey data were pooled from 10 states. Prevalence ratios were calculated, and we assessed effect measure modification by sex. The prevalence of self-reported hunger was 13%. Self-reported hunger was associated with a higher prevalence of every health risk behavior/adverse experience analyzed, even after adjusting for sex, grade, and race/ethnicity. Sex did not modify associations. Findings underscore needs for longitudinal research with more robust measures of adolescent food insecurity to clarify the temporality of relationships.

The diversity of bacteria associated with lichens has received increasing attention. However, studies based on next-generation sequencing of microbiomes have not yet been conducted in the Arctic and Subarctic regions. In this study, rock-dwelling lichens belonging to the Umbilicariaceae family were sampled from the Arctic and Subarctic biological zones. The primary research purpose was to undertake a comparative investigation of the bacterial composition and diversity, identify potential indicators, and explore their potential metabolic pathways. 18S rRNA gene sequences of the fungal partner belonging to the genus Umbilicaria (Ascomycota) and the algal partner affiliated with the lineage Trebouxia (Chlorophyta). Comparing Umbilicaria spp. with a previous study in the Antarctic zone, the fungal partners were more inclined to cluster by sampling region. Operational taxonomic units (OTUs) were established based on a predetermined similarity threshold for V3-V4 sequences, which were ascribed to 19 bacterial phyla, and ten of them were consistently present in all samples. The most distinct zonal indicator genera based on OTU frequencies from Arctic and Subarctic lichens were Capsulimonas (Armatimonadota) and Jatrophihabitans (Actinomycota), respectively. Although the Subarctic zone had higher biodiversity and species richness based on alpha-diversity, the beta-diversity showed that the main species of bacterial communities were not significantly different, and the predictions of metabolic pathways based on the bacterial microbiome in lichen samples from the two zones were similar. These findings provide evidence that the geographical and/or bioclimatic environment and the different lichen-forming fungal species mainly and partially influence bacterial microbiomes and metabolic pathways.

Supplementary information: The online version contains supplementary material available at 10.1007/s00300-024-03303-3.

Abstract

Cryobacterium spp. are Gram-positive bacteria that inhabit diverse geographical locations, particularly extremely cold environments like the Polar Regions. However, strategies that enable them to survive in harsh Antarctic environments are not fully understood. In this study, we conducted a comparative genomic analysis of the Antarctic Cryobacterium sp. SO2 as well as other members of the Cryobacterium genus. Phylogenetic analysis revealed that strain SO2 formed a distinct cluster with the validly described species: C. adonitolivorans, C. actose, C. soli, C. arcticum, and C. zongtaii. Comparative analysis based on ANI and AAI indicated that strain SO2 is a novel species. Relative Synonymous Codon Usage (RSCU) of Cryobacterium species exhibits a bias towards codon ending with G/C. The genomes of all strains harbored numerous genes associated with environmental-associated stress responses, including oxidative stress response, general stress response, heat-stress response, cold-stress response, cell envelope alteration, and osmotic stress response. Strain SO2 and related strains possess genes involved in breaking down and utilization of both plant and animal carbohydrate-containing materials. KEGG annotation indicated that strain SO2 and related species shared almost the same genes for the metabolism of trehalose (TreS, partial TPS/TPP, and TreY-TreZ pathway) and glycogen (classical and non-classical pathway). The results from this work helped us to better understand the genomic characteristics of Cryobacterium spp. in terms of genomic diversity and adaptation strategies, which may have significant implications for biotechnology and climate change research.