Polar Biology最新文献

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.

Dispersal influences many key aspects of plant ecology at both fine- and broad scales. However, dispersal events are challenging to quantify as they are difficult to observe and measure accurately, despite the importance of understanding species’ dispersal capacity. In this study, we quantified dispersal estimates for the dominant vascular flora of sub-Antarctic Marion Island, using a mechanistic model to estimate dispersal potential via anemochory and standardized experiments that simulate dispersal events via zoochory, human activity, and thalassochory, to test if dispersal capacity correlates to contemporary range expansion of the island’s native and alien species. Our results demonstrate the broad range of dispersal potential in the island’s flora and represent the first quantification of the dispersal potential (via multiple vectors) of the dominant vascular flora in the sub-Antarctic. Dispersal potential was not related to range expansion rates of native or alien species, suggesting that other mechanisms are responsible for the variation observed in species range expansion rates. Although this finding contradicts expectations and evidence from some other studies, it is consistent with research conducted in alpine regions (which may be climatically and physiognomically similar to this sub-Antarctic study site) where factors such as demography and competition are more important predictors of species range expansion than their dispersal ability, dispersal syndromes, or dispersal-related traits.

The Pacific sleeper shark Somniosus pacificus is a large-bodied and broad-ranging squaliform shark that occupies diverse habitats throughout the Pacific Ocean. Despite its large size and occurrence as bycatch in various commercial fisheries, little is known about even the most basic aspects of its biology and ecology. Observed declines in certain parts of its range, coupled with life history characteristics associated with low productivity, have led to conservation concerns for this cryptic but charismatic species. Here, we provide a comprehensive review of the current state of knowledge regarding the distribution, diet, life history, and other aspects of the Pacific sleeper shark and present updated fisheries and survey data for the eastern North Pacific Ocean. The most pressing research gaps identified during the course of this review concern habitat use at different life stages and basic life history information. While work is currently in progress to expand our base of knowledge for this species, we recommend a precautionary approach to management until sufficient information becomes available to ensure its conservation.

As the Arctic becomes increasingly accessible to the resource extraction industry, an understanding of the impacts of infrastructure and anthropogenic disturbance on tundra-nesting avian populations is critical. We conducted breeding bird surveys using point counts and Program for Regional and International Shorebird Monitoring (PRISM) rapid surveys at the Hope Bay Project, an underground gold mine in Nunavut, Canada, from 2007 to 2015. We examined the relationship between abundance of total birds, songbirds, and shorebirds with distance from infrastructure, anthropogenic disturbance (i.e., activity at the mine site), and environmental covariates. Contrary to our predictions, anthropogenic disturbance showed no significant effect on bird abundance for either survey type or bird grouping. However, total bird abundance was associated with distance from infrastructure for both survey methods. A relationship with distance to infrastructure, with variability in influence, was also present for songbird point count data and shorebird PRISM data, but was not significant for songbirds recorded during PRISM surveys. Habitat type played a vital role in determining avian abundance, with PRISM surveys showing that wet lowland ecotypes supported higher bird numbers, whereas point count data revealed a more nuanced habitat association, likely reflecting the specific habitat preferences of different songbirds. Our study highlights the need for strategic planning of industrial development, incorporating comprehensive monitoring and ensuring the protection of preferred Arctic-breeding bird habitats. By aligning development projects with environmental objectives, we can ensure the coexistence of industrial interests and the future of avian populations in the Arctic.

Human activities and climate change threaten seabirds globally, and many species are declining from already small breeding populations. Monitoring of breeding colonies can identify population trends and important conservation concerns, but it is a persistent challenge to achieve adequate coverage of remote and sensitive breeding sites. Southern giant petrels (Macronectes giganteus) exemplify this challenge: as polar, pelagic marine predators they are subject to a variety of anthropogenic threats, but they often breed in remote colonies that are highly sensitive to disturbance. Aerial remote sensing can overcome some of these difficulties to census breeding sites and explore how local environmental factors influence important characteristics such as nest-site selection and chick survival. To this end, we used drone photography to map giant petrel nests, repeatedly evaluate chick survival and quantify-associated physical and biological characteristics of the landscape at two neighboring breeding sites on Humble Island and Elephant Rocks, along the western Antarctic Peninsula in January–March 2020. Nest sites occurred in areas with relatively high elevations, gentle slopes, and high wind exposure, and statistical models predicted suitable nest-site locations based on local spatial characteristics, explaining 72.8% of deviance at these sites. These findings demonstrate the efficacy of drones as a tool to identify, map, and monitor seabird nests, and to quantify important habitat associations that may constitute species preferences or sensitivities. These may, in turn, contextualize some of the diverse population trajectories observed for this species throughout the changing Antarctic environment.

Abstract

Organic N (oN, e.g., amino acids) is an important N-resource for plants in soils replete with oN but not inorganic N (iN; i.e., NH₄⁺ and NO₃⁻), such as cold ecosystems with temperature-limited soil decomposition rates. However, sub-Antarctic literature assumes that plants only acquire iN, potentially underestimating plant-available N. We hypothesised that Marion Island (− 46.90°, 37.75°) grasses (Polypogon magellanicus, Poa cookii, Agrostis stolonifera and Poa annua) acquire oN and that oN relative to iN provision affects plant growth. We investigated oN and iN uptake and growth responses in two hydroponics experiments. In situ N (¹⁵N-glycine, ¹⁵NO₃⁻ and ¹⁵NH₄⁺) acquisition was investigated at three field sites with decreasing faunal influence, thus iN input and microbial activity. When plants grown in mire water were supplied with ¹⁵N-glycine or ¹⁵NO₃⁻, root δ¹⁵N enrichment was highest for glycine-supplied plants. In the second hydroponics experiment, plant N-uptake rates (nmol g biomass⁻¹ s⁻¹) were significantly higher for glycine than NO₃⁻, but relative growth rates (g g⁻¹ d⁻¹) lower on glycine. There were species-specific biomass allocation responses to N concentration (4 mM and 0.4 mM) and N-form (glycine and NO₃⁻). Glycine-supplied grasses at the low iN concentration field sites had significantly higher δ¹⁵N enrichment relative to those at sites with high iN, suggesting higher oN uptake when iN is limiting. We demonstrate the importance of accounting for oN acquisition in the sub-Antarctic. As a system with high soil oN relative to iN, plants may predominantly meet N-demands through oN rather than iN acquisition.