Polar Biology最新文献

The trophic structures of tundra ecosystems are often viewed as a result of local terrestrial primary productivity. However, other resources can be brought in through long-distant migrants or be directly accessible in coastal areas. Hence, trophic structures may deviate from predictions based on local terrestrial resources. The Arctic fox (Vulpes lagopus) is a small canid that may use marine resources when available. We used stable isotope values in Arctic fox fur and literature data on potential prey to evaluate Arctic fox summer resource use in a mountain tundra without coastal access. The dietary contribution of local prey, presumably mostly rodents, declined with declining rodent abundance, with a subsequent increased contribution of migratory prey relying on marine resources. Stable isotope values did not differ between this terrestrial area and an area with direct coastal access during years of high rodent abundance, but isotope values during low rodent abundances suggested less marine input than in a coastal population feeding primarily on marine prey. Our study shows that marine resources may be used by animals in areas without any coastal access, and we highlight that such partial coupling of ecosystems must be included in the modeling and assessments of tundra environments.

The sub-Antarctic island of South Georgia is surrounded by highly productive waters, supporting dense aggregations of Antarctic krill (Euphausia superba), a vital food source for globally important seabird and marine mammal populations. These waters also support a commercial fishery for Antarctic krill. Regular monitoring of key krill predator species is undertaken at South Georgia to detect any changes in the ecosystem in response to harvesting activities. This monitoring provides essential data but is focused on land-breeding animals during the austral summer, whilst the krill fishery operates exclusively in winter. Here, we report the results of at-sea surveys to investigate abundance and distribution of krill-dependent predators from winter 2010 and 2011, which represented a “poor” krill year and “good” krill year, respectively. Correspondingly in 2011 higher numbers of krill predators were observed; notably Antarctic fur seals (Arctocephalus gazella) across the northern shelf. Spatial overlap between fur seals and the krill fishery occurred mainly within the krill fishery hotspot to the north-east, highlighting the potential for locally high levels of competition. Cetaceans were observed during both survey years, but in low numbers compared to recent studies. Gentoo penguins (Pygoscelis papua) were the most frequently observed penguin species, showing an inshore distribution and almost no overlap with the krill fishery. Diving-petrels (Pelecanoides spp.) were the most abundant flying seabirds, observed across all transects, with particularly high densities to the south in early winter 2010. In conclusion, this survey provides valuable baseline data on the distribution of South Georgia’s predators during the winter months.

Homeostasis of gut microbiota is critical for growth and health of animals. However, the impact of reproduction on penguin gut microbiota remains unclear, despite penguins being sentinel species of the marine environment. Through high-throughput sequencing of 16S rRNA gene, we examined changes in gut microbiota structure and function in captive female Gentoo penguins during the reproductive process, and also assessed the community stability and assembly mechanism. We found that gut microbiota alpha diversity decreased significantly in captive female Gentoo penguins after egg laying. Based on the comparison of gut microbiota compositions and their predicted functions, the Fusobacteria and pathogenicity increased after laying eggs, while Bacteroidetes and carbohydrate metabolism decreased. After laying eggs, the diversity of the gut microbiota decreased continuously until chicks left the nest. The co-occurrence network analysis revealed that the gut microbiota of captive female Gentoo penguins was less complex and more stable after egg laying. On the basis of the null model, deterministic processes drove the gut microbiota assembly in gravid Gentoo penguins, whereas reproductive processes elevated the contribution of stochastic processes. Our study provides insights into the reproductive physiology and gut microbiota assembly in penguins.

Pinnipeds face challenges in maintaining a stable body temperature in two mediums with distinct characteristics: the terrestrial and aquatic environments. Water extracts heat faster than air, so pinnipeds possess adaptations to maintain thermal balance in both environments. When exiting the water, some phocid species develop thermal windows, areas on the body surface displaying higher temperatures than the rest of the body. This mechanism is thought to help in dissipating excess heat from the body. We assessed whether Weddell seals (Leptonychotes weddellii), the southernmost distributed marine mammal, had the capacity to develop thermal windows and investigated the relationship between thermal surface patterns and environmental factors. We obtained infrared images of 45 hauled-out Weddell seals within the western Antarctic Peninsula, during the summer season. Weddell seals presented uniform surface temperatures across body regions (head, torso, front flipper, and hind flipper) suggesting that all body parts have an equal role in keeping thermal balance. The main driver of surface temperature was wind speed, with higher wind speeds resulting in lower surface temperatures. Wind facilitates convective heat transfer to the environment, decreasing the insulating capability of fur. Thus, wind was a more important driver than air temperature and relative humidity. Thermal windows were identified in 49% of the Weddell seals studied and occurred more frequently at higher air temperatures. The development of thermal windows could solve the problem of overheating when seals haul out on land, which is particularly relevant under the warming scenario within the western Antarctic Peninsula.

Rapid changes in sea ice extent and changes in freshwater inputs from land are rapidly changing the nature of Arctic estuarine ecosystems. In the Beaufort Sea, these nearshore habitats are known for their high productivity and mix of marine resident and diadromous fishes that have great subsistence value for Indigenous communities. There is, however, a lack of information on the spatial variation among Arctic nearshore fish communities as related to environmental drivers. In summers of 2017–2019, we sampled fishes in four estuarine ecosystems to assess community composition and relate fish abundance to temperature, salinity, and wind conditions. We found fish communities were heterogeneous over larger spatial extents with rivers forming fresh estuarine plumes that supported diadromous species (e.g., broad whitefish Coregonus nasus), while lagoons with reduced freshwater input and higher salinities were associated with marine species (e.g., saffron cod Eleginus gracilis). West–East directional winds accounted for up to 66% of the community variation, indicating importance of the wind-driven balance between fresh and marine water masses. Salinity and temperature accounted for up to 54% and 37% of the variation among lagoon communities, respectively. Recent sea ice declines provide more opportunity for wind to influence oceanographic conditions and biological communities. Current subsistence practices, future commercial fishing opportunities, and on-going oil and gas activities benefit from a better understanding of current fish community distributions. This work provides important data on fish spatial distributions and community composition, providing a basis for fish community response to changing climatic conditions and anthropogenic use.

Soil mesofauna play pertinent roles in soil processes. For example, microarthropods strongly influence rates of microbial decomposition. The relationship between mesofauna and their environment are understudied in low Arctic ecosystems compared to other regions. A more detailed grasp of these soil assemblages is necessary for understanding the current functioning of these ecosystems. We characterized the soil mesofauna community across different low Arctic habitats to determine which soil properties commonly correlated with soil fauna would best explain their distribution, abundance, and diversity. Samples were taken near five different lakes in northern Finland, in both alpine meadows and sub-alpine birch forests, across a span of available soil habitats (measured by pH, salinity, organic and nitrogen content, soil moisture). Total abundance of the mesofauna community was influenced by a combination of soil factors, but most individual taxa, as well as measures of diversity were best explained by models of one or two influential soil parameters. Poduromorpha springtails and Oribatid mites were best modeled by measures of resource availability, although only Oribatids were significantly, positively related to these resources. All mites and Entomobryomorphid springtails were positively influenced by physicochemical soil moisture and/or salinity. Salinity, in particular, had a strong influence on overall mesofauna community composition. Our results provide further insight into soil fauna assemblages in Northern Finland and further, more extensive research would contribute to a more comprehensive foundation. This will allow for better monitoring of community changes and responses in the face of climate change in the low Arctic.

Several studies have examined the potential impacts of climate change on the abundance and distribution of Antarctic penguin species, particularly in the genus Pygoscelis. However, less attention has been given to traditionally sub-Antarctic penguin species. The Macaroni Penguin (Eudyptes chrysolophus) is one such sub-Antarctic species whose presence in Antarctica has historically been restricted to colonies on the South Shetland Islands and adjacent islands, but their status in the region has not been updated in decades. We compiled census data on all known Macaroni Penguin breeding colonies in the Antarctic Peninsula region in order to estimate the total Antarctic population. We estimate a population of 8053 breeding pairs for the region, which represents an approximately 10.7% increase since the last regional census in 1993. We identify local population changes at different colonies in comparison to historical census data. We also identify vagrant sightings in the region, as they may reflect prospecting of new breeding habitat, especially as ice-free areas continue to expand due to climate change. Our assessment identifies the South Shetland Islands and South Orkney Islands as notable data gaps.

The ice-associated nematode Theristus melnikovi has a long-distance dispersal throughout the Arctic. However, this species’ taxonomic position and phylogenetic relationships remain unresolved. We used an integrative approach of single-specimen barcoding of morphologically identified specimens of T. melnikovi with note on the phylogeny of two new ice-associated species of the family Xyalidae. DNA barcodes (18S and 28S gene markers) were obtained from 13 specimens of T. melnikovi collected from sea ice in the White and Kara Seas. Analysis of the D2D3 region found three genetically distinct lineages of T. melnikovi from the White Sea ice, suggesting that T. melnikovi specimens belong to the cryptic species, with genetic differentiation attributed to limited ice exchange between remote semi-isolated areas and open Arctic seas. The Kara Sea specimens belong to a single species. Our results highlight that using 18S rDNA data alone underestimates species diversity within sympagic nematodes. The barcoded specimens of T. melnikovi could not be distinguished morphologically, as the majority of the sequenced specimens were juveniles (92.3%). Additional comparative analysis of morphological traits was performed on 34 specimens from sea ice in the Barents, White, Kara, and East Siberian Seas, and from sediment in the East Siberian Sea. Our specimens differed from previous descriptions of T. melnikovi by variable body size, amphidial fovea shape, and absence of precloacal supplements and pigment spots. This study contributes to the understanding of the diversity, variability in habitat, and ecology of sympagic nematodes, confirming the need to put together the integration of molecular and morphological methodologies.

We conducted this study to investigate the relationship between environmental stressors and mesozooplankton fluxes in inner Kongsfjorden, Svalbard. The ongoing Arctic amplification, characterized by phenomena such as increased temperatures, glacial and watershed runoff, and diminishing ice cover, poses significant challenges to marine ecosystems. Our multi-year time-series analysis (2010–2018) of mesozooplankton, collected from a moored automatic sediment trap at approximately 87 m depth, aims to elucidate seasonal and interannual variations in fluxes within this Arctic fjord. We integrate meteorological, hydrological, and chemical datasets to assess their influence on zooplankton populations. Principal component analysis reveals the impact of seawater characteristics on mesozooplankton fluxes and composition, while two-way ANOVA highlights the role of seasonality in driving variations in our dataset. We observe a decrease in swimmer fluxes following the maxima mass flux event (from 2013 onwards), coupled with an increase in community diversity, possibly attributed to copepod decline and functional diversity. Notably, sub-Arctic boreal species such as Limacina retroversa have been detected in the sediment trap since 2016. Our continuous multi-year dataset captures the physical, chemical, and biological dynamics in this extreme environment. With Arctic amplification in Kongsfjorden and increasing submarine and watershed runoff, we anticipate significant shifts in mesozooplankton communities in the medium to long-term. This underscores the urgency for further research on their adaptation to changing environmental conditions and the potential introduction of alien species.

According to the ‘selfish herd’ hypothesis, most seabird species breed colonially so that individuals can decrease their risk of predation by forming compact groups. However, costs and benefits associated with colonial breeding may not be evenly distributed among individuals within a colony. At Adélie penguin colonies, individuals nesting on the periphery of subcolonies (distinct groups of nests) may experience higher rates of nest predation by south polar skuas, and thus the optimal aggregation pattern for Adélie penguins may be within groups that minimize the proportion of edge nests. Nevertheless, some penguins choose to nest solitarily, at significant distances from conspecifics. We tracked 50 of these “solitary-nesting” Adélie penguins at Cape Crozier, a large colony on Ross Island, during the 2021 nesting season and compared their breeding success to individuals nesting within subcolony boundaries. We found that both solitary and subcolony nests successfully raised chicks large enough to join crèches and left unattended by adults. However, chicks from solitary nests exhibited a rate of mortality more than six times higher during the transition from nest brooding/guarding to crèche stage. In the 2022 nesting season, we found that solitary nests which had previously hosted actively breeding penguins were more likely to be re-occupied. Solitary nesting therefore appears to be a less-successful alternative to breeding within subcolonies, but enough individuals could be successful with this approach to maintain the apparently disadvantageous behavior and effectively pioneer previously unused locations, possibly including eventual new colony locations.