Polar Biology最新文献

As seasonal migratory animals, reindeer inhabit the natural habitats in Arctic regions and have evolved their hindlimb joints to adapt to the complex ground conditions there. Inverse dynamics of the joints is an important tool to study foot functions. Herein, with a motion tracking system and plantar pressure data based on kinematics and inverse dynamics of hindlimbs, we investigated the changes in joint angles, net joint moments, net joint powers, and work of reindeer at different speeds. Reindeer may adopt different movement patterns to efficiently utilize energy and adapt to the demands of different gaits and speeds. The joint ranges of motion (ROM) of the ankle joint (α_b), metatarsophalangeal (MTP) joint (α_c), and interphalangeal joint (α_d) of the hindlimbs were about 20.73°–28.87°, 40.37°–47.69°, and 24.47°–26.18°, respectively. The ankle joint produced positive work to provide propulsion. The positive work done at the ankle joint during walking, slow trotting, and fast trotting was 8.61 × 10^–2, 9.25 × 10^–2, and 15.44 × 10^–2 J·kg⁻¹, respectively. The MTP and interphalangeal joints both absorbed energy during walking, slow trotting, and fast trotting. The energy absorption at the respective speeds was 12.53 × 10^–2, 13.57 × 10^–2, and 19.90 × 10^–2 J·kg⁻¹, respectively, by the MTP joint and was 9.49 × 10^–2, 7.71 × 10^–2, and 10.26 × 10^–2 J·kg⁻¹, respectively, by the interphalangeal joint. The MTP joint and interphalangeal joint of the hindlimbs serve as the primary sites for energy storage and release, functioning as an elastic system. This study contributes to a deeper understanding about the biomechanical properties of hindlimb joints and provides a theoretical basis for designing extremity robots in extreme environments through analyzing the functional characteristics of reindeer foot joints.

Arctic phytoplankton are highly sensitive to seawater physical and chemical conditions, especially in the context of rapid climate change and sea ice loss. We studied the spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores, and clarified their associations with light, temperature and nutrients in the western Barents Sea in late summer 2017, and winter, spring and early summer 2018. Diatoms, composed mainly of Chaetoceros, Fragilariopsis and Thalassiosira, bloomed in spring at the southern border of the marginal ice zone with mean abundance of 1.1 × 10⁶ cells L⁻¹ and biomass of 119.5 µg C L⁻¹, and were observed to follow the retreat of sea ice in the Arctic water to the north at the shelf break near Nansen Basin, contributing to the progression of the summer situation. Dinoflagellates flourished in surface waters south of Svalbard in summer, with maxima of 2.2 × 10⁵ cells L⁻¹ and 78.2 µg C L⁻¹. High abundances and calcite mass of coccolithophores were detected in the southern Barents Sea and southwest of Svalbard in summer, with maxima of 3.3 × 10⁵ cells L⁻¹ and 4.7 µg C L⁻¹. Two distinct phytoplankton assemblages, closely linked with Atlantic water and Arctic water, were geographically separated by the Polar Front in two summers, with a percent similarity below 11.9%, suggesting great influence of the two water masses on large-scale distributions of phytoplankton. Redundancy analysis revealed that temperature was one of the most important factors in shaping the seasonal distributions of diatoms, while irradiance showed positive correlation with dominant dinoflagellates of each season. From the perspectives of phytoplankton composition and carbon biomass, our findings highlight the governing effect of physical seawater conditions on driving seasonal patterns of phytoplankton biogeography, as well as the pivotal role of nutrients in supporting the phytoplankton growing seasons in the western Barents Sea.

Mysis segerstralei is distributed over a wide geographic area and in habitats with a variety of salinity conditions, including marine and brackish waters around Svalbard. The species has seldom been found in freshwater lakes, and the discovery of M. segerstralei in Lake Pulmankijärvi at the border between Northeastern Norway and Finland, may represent the single known freshwater occurrences in western Europe. Svalbard lake systems are characterized by very low water temperatures, long-term ice cover, and low levels of nutrients. Food is thus limited, and chironomids generally dominate the stomach contents in Arctic charr, the only freshwater fish species on Svalbard. Based on several surveys in more than 30 of Svalbard lakes over many decades, M. segerstralei has only been found as food for Arctic charr in Lake Vårfluesjøen. In a later fishery survey, we studied the diet of Arctic charr in this lake. The stomach contents from Arctic charr sampled in the profundal habitats were dominated by M. segerstralei, but the species was also among the most frequent prey items in the littoral and pelagic habitats. This unexpected occurrence of M. segerstralei demonstrates the high importance of mysids even in a low-productive, High Arctic lake.

Nordaustlandet is the northernmost and one of the most inaccessible regions of Svalbard. The lichens of the Nordaustlandet were studied most actively from the mid-nineteenth century to the 40 s of the twentieth century. It was during this period that significant collections of lichens were collected, which still form the basis for some taxonomic studies. Thanks to large-scale research conducted by the Avrorin Polar-Alpine Botanical Garden-Institute of the Kola Science Center of the Russian Academy of Sciences for 3 years (2010–2012), we were able to make a significant contribution to the knowledge of Nordaustlandet lichens. The study of the lichen biota of Murchisonfjorden prompted us to summarise all the information about the lichens and lichenophilous fungi of Nordaustlandet, as well as to evaluate the degree of detection of the lichen flora. The checklist includes 477 lichen species, 2 subspecies and 22 species and one subspecies of lichenicolous fungi, of which Calogaya bryochrysion, Diplotomma lutosum, Flavoplaca flavocitrina, Lecanora intumescens and Zwackhiomyces coepulonus are reported for the first time for the Svalbard archipelago and another 40 species—for Nordaustlandet. The richest in terms of the number of species is Gustav V Land (415 species and two subspecies of lichens and 18 species and one subspecies of lichenicolous fungi). An assessment of lichen biota diversity using an integrated approach based on Hill numbers showed that the data cover a maximum of 80.93% of the total number of lichen species in the study area.

Carrion decomposition has a significant impact on soil chemical profiles. However, soil nutrient research associated with animal carcasses in Antarctica has been relatively scarce, and the effect of penguin carrion decomposition on soil chemical composition is largely unknown. We aimed to determine Antarctica’s soil chemistry profiles associated with penguin carrion. Soil samples were collected from a penguin rookery near King Sejong Station, Barton Peninsula, King George Island, Antarctica. Dry combustion methods were used to identify soil nitrogen and sulfur, while ammonia, nitrate, and phosphate were determined colorimetrically using a spectrophotometer. In addition, total carbon, pH, electrical conductivity, soil moisture, and soil porosity were also determined. Overall, soil chemical properties were not significantly different between the stages of decomposition and the sampling locations. These findings suggest that nutrients from penguin carrion disperse and leach in limited quantities into the soil, probably due to the active scavenging activities by vertebrate scavengers and the slower decomposition rate resulting from cold temperatures in the Antarctic region.

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.