Polar Biology最新文献

Recent studies have documented poleward shifts in heavily targeted fish stocks on the Bering Sea Shelf. This study investigated whether commercial fishing vessels in the region have also shifted their distribution poleward in recent years. We used Vessel Management System data generated between January 1, 2013, and December 31, 2022, to identify regions over the shelf where vessel activity increased (emerging hot spots) and where it decreased (emerging cold spots) during this time period. We hypothesized that emerging hot spots would occur at the northern edge of the vessel operating range, while emerging cold spots would occur at the southern edge. Overall, northward shifts in vessel distribution were most evident during October–February and July–August, when the range of emerging hots spots was centered 204–515 km to the N, NE, or NW of the center of the range of emerging cold spots. The trend was strongest in August, when emerging hot spots were widespread in the Northern Bering Sea. We did not attempt to identify factors driving these distributional shifts, but the timing of shifts did coincide with the busiest fishing seasons over the Bering Sea Shelf and, in part, the open seasons for walleye pollock (Gadus chalcogrammus). If groundfish populations continue to move poleward with climate change, this study may serve as a window into the early stages of a long-term redistribution of commercial fishing effort in the Bering Sea, a region supporting one of the largest fishing industries in the world.

In the Southern Atlantic Ocean, asteroids are abundant among the benthic taxonomic groups. The development patterns include a pelagic larva (planktotrophic/lecithotrophic), or a retained larva (internal/oral retention). The main objective was to revise the Asteroidea species composition from the Southern Atlantic (including marine protected areas) and to study their development patterns in relation to environmental conditions. Information was compiled from oceanographic surveys, scuba diving, and the GBIF database. Four species have extended their distribution. The Isla de los Estados island (SIE) and Namuncurá/Burdwood Bank II Marine Protected Area (N MPA II) are separated as independent clusters. SIE would be functioning as a geographical barrier, and N MPA II presents deep sea species. Namuncurá/Burdwood Bank Marine Protected Area (N MPA) presented a majority of protected development species, while in the Beagle Channel, most registered species presented free-planktotrophic larvae. Species with free-planktotrophic larvae and oral brooding strategies are more likely in shallower waters, while internal brooding species occur in deeper waters. Species with free-lecithotrophic larvae are more probable in middle depths, below the euphotic layer. These results are expected to make a valuable contribution to better understanding the general distribution and development patterns of Asteroidea from subantarctic waters, a group of organisms that are top predators of benthic communities.

An invasive predator eradication campaign is planned for 2024 on Amsterdam Island, one of world’s top priority island for seabird conservation. In order to monitor the effects on seabird colonies post-eradication, a survey of burrow-nesting species and population monitoring of albatrosses, penguins, skuas and terns was organised pre-eradication. Several counting techniques and acoustic methods were used to infer presence/absence of burrow-nesting species and to estimate abundance of other species, as well as genetic methods for species identification. In total 14 breeding (or probably breeding) seabird species were detected on Amsterdam Island, among which eight burrowing petrels including two species never described on the island: the Juan Fernandez petrel Pterodroma externa and the sooty sherwater Ardenna grisea. Based on these new data, the introduced mammal eradication campaign on Amsterdam, if successful, will likely be extremely beneficial for seabird conservation, and may also favor the colonization of Amsterdam by new seabird species.

The Weddell seal (Leptonychotes weddellii) is a fast-ice obligate species that plays an important role as both predator and prey within the high-latitude, coastal Southern Ocean. Weddell seals are affected by pressures of marine resource extraction and variation in sea-ice extent and characteristics that are affected by climate. Thus, monitoring their population dynamics provides an indicator of the effectiveness of fisheries management, and impacts of changing climate in the high latitude Southern Ocean ecosystem. Satellite imagery is increasingly being used to monitor the populations of this species, but assessment techniques require a better understanding of the environmental factors influencing the likelihood that individuals will be on the sea-ice and therefore visible in a satellite image. Addressing that goal, we captured 5054 trail camera photos during spring 2017 in the 24-h light at Cape Royds, Antarctica, and then counted seals on the fast ice every 30 min over 59 days. Using a generalised additive model (63% deviance explained) we described the haulout behaviour of non-breeding Weddell seals according to time of day, date, air temperature, pressure, solar radiation, and wind speed. We found that the seals’ haulout cycle is driven to a significant degree by weather variables, primarily temperature and wind speed. Quantifying these haulout patterns can be used to determine the time of day, and under what conditions, that most seals are hauled out. Integrating environmental parameters to correct time-of-day patterns would allow better cross-site abundance comparisons, leading to better Weddell seal population estimates for the Ross Sea region and the wider coastal Antarctica.

The host/parasite relationship is a key tool for understanding the role of parasitism in the feeding ecology of Antarctic seabirds. Especially, birds with extensive migratory routes through isolated regions are particularly sensitive to new infections. Although research on parasitic diSseases in Antarctic birds is sparse and information is fragmentary, an increasing number of studies are currently underway in this area. The present study aims to provide new information on parasitic helminths in the Southern Giant Petrel Macronectes giganteus in some nesting areas from South Shetland Island and Antárctic Península, integrating different parasitological techniques. A total of 126 faecal samples, 16 regurgitates and six dead individuals (five adults and one chick) were analysed for helminth parasites. Members of four helminth groups (Cestoda, Digenea, Nematoda, Acanthocephala) represented the parasitic diversity of the Southern Giant Petrel in the studied localities. All dead birds analysed (P = 100%) harboured helminth parasites, additionally P = 49.2% of the faecal samples and P = 6.25% of the regurgitated individuals presented at least one of the different helminth groups found in the viscera. The combination of three diagnostic techniques allowed us to determine the presence of nine helminth species (Cosmocephalus obvelatus, Stegophorus macronectes, Stegophorus diomedeae, Contracaecum sp., Parorchites zederi, Tetrabothrius heteroclitus, Diphylobotrium sp., Corynosoma shackletoni, and Renicolidae). In addition, juvenile specimens of Tetrameres sp. and Anisakis sp. were found in the eviscerated host. We discuss the trophic relationships of the hosts and their influence in the helminth infestations. This study provides new knowledge about the parasitic diversity of the Southern Giant Petrel in its nestling areas with new records of helminth species in Antarctica.

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.