Polar Biology最新文献

Data on the spatial and vertical distributions, temperature regime of habitat, size-age and, size-sex structure of Arctic alligatorfish Aspidophoroides olrikii in the Kara Sea based on a recent trawl survey are presented. A total of 104 specimens were caught from 9 (out of 55) trawl stations. Maximum catches of this species were recorded north of the Yamal Peninsula (74°11′–74°25′ N, 69°27′–71°59′E) at depths of 18–21 m in the range of bottom temperatures from -1.49 to -0.96 °C. In trawl catches, individuals aged 2–6 years with a total length of 39–76 mm with a body weight of 0.25–2.91 g were recorded, but fish up to 50 mm length with a body weight of less than 0.5 g dominated. Among individuals over 68 mm in length, the proportion of females increased sharply, reaching 100% with a length of more than 75 mm. It was found that males and females of the Arctic alligatorfish become sexually mature in the third year of life, the former at a length of 47–48 mm, the latter at 52–58 mm long. Maturation of the half males and females occurs in the fourth year with the length of 52–58 mm and 61–63 mm respectively. It is shown that this species is a mesobentophagus, the main prey of all its individuals are amphipods, which make up about 95% of the diet. However, as A. olrikii grows, the number and size of amphipods consumed increase.

Permafrost considerably influences boreal forest ecosystems by constraining the niche space of woody plants. The influence of permafrost on ecosystems could dramatically change with permafrost thawing due to recent rapid climate warming. However, the influence of permafrost on shrub species in the understory of boreal forests is not completely understood. We investigated two closely related common shrubs, Labrador teas (Ericaceae, Rhododendron subsect. Ledum): R. groenlandicum and R. tomentosum, which exist sympatrically in the discontinuous permafrost zone of interior Alaska. We employed field surveys and trait measurements across permafrost gradients under the same climatic conditions to examine the associations among permafrost environments, abundances, and leaf traits of the two species. Contrasting habitat attributes were found between the two species: R. groenlandicum is abundant under shaded, drier, thicker active layer conditions, whereas R. tomentosum is common under more open, wetter, and thinner active layer conditions. This suggests that habitat segregation between these species occurs in the discontinuous permafrost zone. Compared with R. groenlandicum, R. tomentosum, which dominated permafrost conditions, had smaller leaves with smaller specific leaf areas (SLA) and low nitrogen concentrations (i.e., conservative leaves). Moreover, both species presented more conservative leaves under permafrost conditions. These intraspecific variations were mainly directly associated with canopy openness in R. groenlandicum but with active layer thickness in R. tomentosum. In summary, our study suggests that large environmental variations driven by heterogeneous permafrost conditions can lead to the sympatric distributions of closely related shrub species in discontinuous permafrost zones and that conservative leaves can contribute to their adaptation under permafrost conditions.

Little is known about the reproductive biology of the leopard seal (Hydrurga leptonyx), a Southern Ocean predator. Here we observed sexual behavior in wild leopard seals in Laguna San Rafael, Chile during a 2 h courtship interaction between a female and male. The female was hauled out on ice, mostly lying still (69% of the time) or moving (19%). The male was mostly under water (87%) or at the water’s surface (11%). The female made seven in-air calls (i.e., thump pulse, noseblast, blast, growl). The male produced 65 underwater calls (i.e., low- and high-double trills, unidentified trills). The underwater calls appeared to be directed toward the female. After the primary male vocalized for an hour, one or two unidentified leopard seals briefly swam near the female. After leaving the area, we heard underwater calls for another 8 h. The next day, the primary male was hauled out on ice with a swollen genital opening. The male was bleeding from a laceration caudal to the preputial opening, suggesting the male attempted to mate and that the female, or another seal, was responsible for the injury. Together, we find that leopard seal courtship involves a suite of behavioral and acoustic behaviors by both sexes, both in air and under water. This is the first description of leopard seal sexual behavior in the wild. Our study also provides the first evidence that leopard seals mate in South America.

Climate change is a major concern for the future of marine Arctic food webs. Diet shifts of seabirds can be used as indicators of environmental changes such as species compositions of food webs. However, studies on diets are often laborious and costly, while research in vulnerable Arctic environments benefits from short visits for data collection that minimize disturbance to Arctic wildlife and the environment. DNA-metabarcoding techniques are rapidly developing and could be used as an effective method of monitoring diet choice of seabirds. We tested DNA-metabarcoding on seabird faeces collected during short visits of typically around 30 min at breeding colonies of black-legged kittiwake Rissa tridactyla (3 colonies), Brünnich’s guillemot Uria lomvia (2 colonies) and little auk Alle alle (3 colonies). DNA metabarcoding based on COI and 18S of a limited number of faeces samples revealed a wide spectrum of fish species and crustaceans in the diets of these species, comparable with or even exceeding diversity in diet composition found in conventional, more invasive techniques where birds are shot or caught and handled to obtain samples. While previous studies on diet choice of little auk, a crustacean specialist, mainly report small fractions of unidentified fish remains, DNA metabarcoding of faeces revealed a large variety of pelagic and benthic fish species supplementing its diet. We conclude that DNA metabarcoding of seabird faeces can be an effective attribute to diet studies supporting our understanding of changes in numbers and distribution of Arctic seabirds and their marine environment.

In the nutrient-limited Antarctic terrestrial habitat, penguins transfer a significant amount of nutrients from the marine to the terrestrial ecosystem through their depositions (i.e., guano). This guano influences soil physicochemical properties, leading to the formation of ornithogenic soil rich in nutrients and organic matter. We hypothesize that soil prokaryotic communities will be strongly influenced by the contribution of nitrogenous nutrients from penguin rookeries, maintaining the influence over long distances. The objective was to establish how the soil prokaryotic diversity and community structure change with distance from a penguin colony, which provides large amounts of guano and nitrogenous compounds, and to study the effects of these nutrients on the functional role of these communities. Methods include volcanic soil sampling along a 1200 m transect from the penguin active rookery and the characterization of soil nutrient content and soil prokaryotic communities using 16S rRNA high-throughput amplicon sequencing. In contrast to our hypothesis, the results showed that the impact of guano from the penguin colony was restricted to the first 300 m. Probably because the penguin rookery was sheltered, strong wind and wind direction did not affect the transport of nutrients from the penguin rookery. Areas close to the penguin rookery were dominated by Proteobacteria and Bacteroidetes, while areas situated further away were dominated by Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Nitrospirae, and Planctomycetes. Beta diversity analysis among the soil prokaryotic communities revealed a high degree of community heterogeneity, strongly associated with N compound characteristics (NH₄, NO₃, and %N), C, and pH. Inferences from N metabolism genes suggest a high potential of the microbial community for dissimilatory nitrate reduction genes (DNRA) to ammonium, assimilatory nitrate reduction (ANR), and denitrification. Although it is assumed that the nitrogenous compounds of the penguin colonies reach long distances and affect the prokaryotic community, this effect can vary with wind directions or the morphology of the site, reducing the impact of the guano over long distances, as our results indicate. On the other hand, functional predictions give some clues about the main actors in nitrogen cycling, through processes like dissimilatory nitrate reduction, assimilatory nitrate reduction, and denitrification.

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.