Polar Biology最新文献

Several species of loons (or divers; Gaviidae) breed in Arctic Canada, and concern has been raised about their changes in abundance in light of threats such as bycatch and at-sea industrial development. These loons are not well monitored, but we gathered localized count data for three Arctic-nesting loons (Pacific loon Gavia pacifica, red-throated loon G. stellata, and yellow-billed loon G. adamsii) from multiple sources and estimated mean annual population change to estimate species-specific trends over varying time periods. Most breeding ground information between 1996 and 2022 suggested stable numbers for each species, although data were scarce for yellow-billed loon. Trends during the non-breeding season from 1966 to 2021 were estimated for red-throated and Pacific loons from the Christmas Bird Count, a citizen science general bird count, and suggested overall stable or increasing numbers, despite some substantial regional differences. Again, yellow-billed loon numbers were not captured well during the non-breeding season. Aerial winter waterfowl surveys on the east coast of North America (2008–2011, 2014) showed positive trends for red-throated loons for most locations north of 38° latitude and stable trends elsewhere. The paucity of both breeding and non-breeding count data for yellow-billed loons is unfortunate, as this species is found in high numbers in fishing gear in the Arctic. Overall, the limited available data do not suggest that loon populations breeding in the Canadian Arctic have experienced extensive declines, but monitoring of yellow-billed loons should be a priority.

The Antarctic marine ecosystem is largely dominated by Euphausia superba, the most abundant krill species consumed by a wide array of predators, including whales, penguins, flying birds, seals, fish and cephalopods. The current management of the krill fishery follows an ecosystem-based approach which takes into account the distribution, abundance of E. superba and its main predators plus their interactions. Mackerel icefish, Champsocephalus gunnari, was once considered the most abundant meso-pelagic fish species and a very important consumer of E. superba until its population was collapsed by overfishing in the early 90s. Currently, C. gunnari populations are slowly recovering which may increase predation on E. superba. Therefore, in this study, we analyze the distribution and density of E. superba and C. gunnari, gain some insights about the type of foraging strategy of C. gunnari and estimate its consumption of E. superba under three different biomass scenarios of C. gunnari: 7000 (B_t), 70,000 (B_50%) and 140,000 (B₀) t. We focus particularly on the potential area of overlap between C. gunnari and Adélie penguin (Pygoscelis adeliae) off the South Orkney islands. Bayesian geostatistical models were employed to test whether C. gunnari followed an ideal or generalized ideal-free distribution. Spatially explicit consumption estimates were derived under the scenarios of 7000 (B_t), 70,000 (B_50%) and 140,000 (B₀) t of C. gunnari biomass. We found that both species exhibit a higher probability of presence and density north of the South Orkney Islands, where they present a high overlap. The probability of presence of Champsocephalus gunnari was best explained by the ideal-free distribution whereas its acoustic density was best explained by an independent spatial model, showing no relation to the distribution of E. superba. Individual consumption of E. supeba by C. gunnari was estimated to be 153.5 ± 77.9 g ind⁻¹. Thus, current biomass (B_t) would only remove ~ 0.07% of E. superba biomass in the focus area. Under a pre-exploitation biomass level (B₀), C. gunnari would remove ~ 1.4% of E. superba biomass. This study provides novel insights into the relationship between a key species like E. superba and a highly specialized consumer such as C. gunnari around the South Orkney Islands and contributes to fill in an important gap regarding fish consumption of krill in the Antarctic ecosystem.

The protobranch Aequiyoldia eightsii is one of the most common bivalves in Antarctica and for the first time, its population structure was studied in Admiralty Bay, an Antarctic Specially Managed Area (ASMA), to establish a baseline for future monitoring. Density, size structure, length–weight relationship, condition index, and shell morphometry were evaluated at the shallow coastal zone of the bay. High abundance values of A. eightsii were related to sites with greater contributions of mud particles and total organic carbon contents in the sediment, while the condition indexes were higher in Martel Inlet, possibly due to higher food availability. Individuals obtained from gravel-rich sediments were significantly larger than compressed, while rounded forms were observed in sandy and muddy bottoms of the bay. Positive allometric growth was reported in most sites, except Botany Point, where specimens presented an isometric growth. The results demonstrated that the sediment composition and its organic content influence the population structure of A. eightsii as well as biological factors such as predation and recruitment rates. It is also worth noting that the phenotypic shell variability observed for this protobranch species in geographically close sites (hundreds of meters) highlights the importance of local-scale heterogeneity to be considered in future monitoring programmes for Antarctic marine ecosystems.

Alteration and diminution in sea ice cover in the Arctic region will give rise to an intensification and expansion of fishing activities in the Arctic and associated marginal seas. Increased fishing activity, especially in the summer, could pose a direct threat to the millions of seabirds breeding in this region, as well as non-breeding migrants, and potentially result in an increase of bycatch mortality. To inform what conservation and management actions may be needed, an analysis of where seabirds/fisheries interaction are most likely to occur is required. Here, we establish what information would be required to effectively model circumpolar bycatch risk of seabirds in the Arctic, and then we assess the availability of the requisite data. The quality and availability of fishing effort, and bycatch monitoring effort data are not homogeneous among Arctic countries. Undertaking a true circumpolar analysis at this time would be difficult, and with the current data accessibility, many assumptions would have to be made, potentially leading to caveats in the results. Improved communications between the various agencies and institutes working on fisheries and seabirds would strengthen the quantitative basis for future analyses. We offer suggestions on how to improve bycatch estimates and the identification of high-risk areas for seabird bycatch in the Arctic.

Antarctic and Sub-Antarctic pinnipeds are well-known seasonal visitors of the Southwest Atlantic Ocean. According to the literature, at their breeding grounds, they feed mainly on a variety of fish, cephalopods, and crustaceans. During the non-breeding period and far away from its breeding colonies, little is known about their feeding habits. Here, we present records of predation on aquatic birds by Antarctic and Sub-Antarctic pinnipeds off northern Argentinian coast (37°27′ S, 57°06′ W to 41°50' S 65°02' W). We examined the gastrointestinal contents of 22 specimens of three pinnipeds species (Arctocephalus gazella [n = 10], A. tropicalis [n = 11] and Hydrurga leptonyx [n = 1]) collected from 1996 to 2023. Aquatic birds remains were found in the gastrointestinal tracts of three individuals (13.64%): two A. gazella and one H. leptonyx. We identified feathers, and other bird parts by comparing them to specimens from scientific collections and descriptions/illustrations from the literature. Two of the three aquatic birds found in the gastrointestinal tracts were most probably Magellanic Penguins (Spheniscus magellanicus), whereas the other one was a Great grebe (Podiceps major). To our knowledge, this is the first study reporting predation on aquatic birds by Antarctic pinnipeds far from their breeding colonies.

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.