Polar Biology最新文献

Abstract

Birds often have to choose their nest site location along a food safety axis, balancing nest predation danger with the food requirements of themselves and their offspring. This is probably most important for precocial species, such as most shorebirds, in which both chicks and parents need access to food resources in the surroundings of the nest, at least during the first days of life of the chicks. In many Arctic ecosystems, shorebird nests are typically prone to predation by both avian and terrestrial predators, especially in lemming-poor years. Among other factors, the strength of the trophic interactions between shorebirds, their prey, and their predators depend on how all of these are distributed across space. During two breeding seasons in northern Taimyr, North-Central Russia, we investigated how the spatial distribution of red knot Calidris canutus and little stint Calidris minuta nests and broods overlaps with the local food landscape and also with the distribution of avian predators and their main prey, lemmings. We found that the two shorebird species use different habitats that vary in arthropod community structure in accordance with the birds’ diet: while little stints selected lower elevations where chironomid midges Chironomidae are more abundant, red knots selected higher elevations where crane flies Tipulidae are more abundant. Furthermore, little stints share low-elevation habitats with lemmings and predators, while red knots inhabit higher elevations averted by both lemmings and avian predators. We found higher nest predation for little stint nests than for red knots nests, especially in a low-lemming year. Our results thus support the idea that food web interactions are driven by landscape and community aspects.

Over the past 40 years, the significance of microzooplankton grazing in oceanic carbon cycling has been highlighted with the help of dilution experiments. The ecologically relevant Western Antarctic Peninsula (WAP) ecosystem in the Southern Ocean (SO), however, has not been well studied. Here we present data from dilution experiments, performed at three stations around the northern tip of the WAP to determine grazing rates of small zooplankton (hetero- and mixotrophic members of the 0.2–200 µm size fraction, SZP) on auto- and heterotrophic members of the < 200 µm plankton community as well as their gross growth. While variable impacts of SZP grazing on carbon cycling were measured, particulate organic carbon, not the traditionally used parameter chlorophyll a, provided the best interpretable results. Our results suggested that heterotrophic picoplankton played a significant role in the carbon turnover at all stations. Finally, a comparison of two stations with diverging characteristics highlights that SZP grazing eliminated 56–119% of gross particulate organic carbon production from the particulate fraction. Thus, SZP grazing eliminated 20–50 times more carbon from the particulate fraction compared to what was exported to depth, therefore significantly affecting the efficiency of the biological carbon pump at these SO sites.

Southern Rockhopper Penguins Eudyptes chrysocome chrysocome exhibit marked intra-clutch egg size dimorphism and engage in obligate brood reduction of the first and smaller laid egg, with the rearing of the two nestlings occurring only on rare occasions. Studying the sex ratio of hatchlings within a brood in this species, under this breeding strategy context, is essential to understanding population dynamics. The objectives of this study were to analyze egg size dimorphism within the broods, determine the offspring sex ratio, and investigate if the hatchling sex ratio was determined by hatching order and egg volume to discuss potential biases in the context of brood reduction. We molecularly assessed hatchlings’ sex ratio according to the hatching order at Isla Pingüino, Argentina (3 years, n = 68 broods). Sex ratio was not different from the expected 50:50 proportion in all the studied years. In this sense, we found a balanced sex ratio in the first hatchlings, typically the survivors of the brood reduction process. Although not significant, we found a bias toward females in the second hatchlings. Assuming less energy is required to raise a female compared to a male, because of its smaller size; this strategy might enhance the chances of raising two nestlings if conditions are optimal. Southern Rockhopper Penguins at Isla Pingüino appear to exhibit a strategic sex allocation evident in the second but not in the first hatchlings, which might be consistent with its out-of-the-norm exponential growth population.

Blue mussels Mytilus have returned to the high Arctic region of Svalbard in the beginning of twenty-first century after being absent for almost a 1000 years. Not only M. edulis had arrived in Svalbard, but also a complex of sympatric species including M. edulis, M. galloprovincialis, M. trossulus, and some of their hybrids, which may have a wide range of origins from both sides of the North Atlantic. Mussels were first found in the sublittoral at the entrance to Isfjorden, west coast of Spitsbergen island, and are spreading in other areas, and recently were also found in the intertidal zone. Here, we report viable larvae that were recovered from within the mantle cavity of mussels from the lower intertidal shore collected in late July 2019 and 2021 in Trygghamna, Isfjorden. The identity of larval and adult mussels was confirmed by sequencing of barcode region. Larvae ranged in size from 178 to 376 µm, from mussels 21 to 57 mm in shell length, and estimated to range over 3 to 12 years. It remains unclear whether the larval retention within the mantle cavity results from an intake of near shore concentrations and whether this may lead to larviphagy.

Antarctica is considered one of the most inhospitable places to life due to its low temperatures and lack of liquid water. However, meiofauna taxa such as tardigrades not only thrive, but also show remarkable biodiversity in this habitat. Tardigrades are a phylum of small animals (less than 1 mm in length) mainly known for their ability to withstand freezing and desiccation, which are common stressors in Antarctica. The tardigrade genus Mesobiotus is widely distributed and abundant in Antarctica, particularly in the Antarctic Peninsula, where it is been hypothesized it was present even before the continent froze. Different Mesobiotus species have been recorded from the Antarctic Peninsula, but most are based on DNA data and lack assignment to described species. We used integrative taxonomy methods (DNA and morphology combined) on a novel population of Mesobiotus aradasi from Antarctic Peninsula. The latter allowed us to link previous molecular and morphological records of this species and to build a comprehensive map of its distribution. We show that this species is present across almost all the Antarctic Peninsula, whereas there are no records of it for any other Antarctica region. This study highlights the importance of integrating molecular and morphological methodologies and their complementarity when working with biodiversity and distribution data. The M. aradasi distribution highlights its endemicity in the Antarctic Peninsula and calls for attention to possible future threats to this species.

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.