Polar Research (E-Journal)
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Diving behaviour of adult male white whales (Delphinapterus leucas) in Svalbard, Norway
No full textWhite whales (Delphinapterus leucas) in Svalbard remain near the coast much of the year, spending most of their time in front of tidewater glaciers. In this article, the diving behaviour of adult male white whales in Svalbard (N = 16) is presented based on satellite-relay data loggers that record time and depth of diving as well as positions. The loggers transmitted data for an average of 87 ± 52 days (range 2–163 days). After filtering, 55 359 dives were available for the study. Most of the dives were extremely shallow (13 ± 26 m, maximum 350 m) and of short duration (97 ± 123 s, maximum 31.4 min). At tidewater glacier fronts, the white whales optimized their time at the bottom of dives and spent longer periods resting at the surface after dives, in accordance with what would be expected when foraging. This behaviour was also documented when animals were out in the fjords. When the whales moved between areas around the archipelago, they swam close to the coast, staying right below the surface most of the time, presumably to minimize energy expenditure during transits. When sea ice formed during the winter, the whales were forced offshore into somewhat deeper areas with drifting ice. In these areas, the whales minimized time at the surface and dove somewhat deeper, sometimes reaching the bottom, presumably to feed on neritic prey
Nitrogen isotope fractionation explains the 15N enrichment of Antarctic cryptogams by volatilized ammonia from penguin and seal colonies
No full textVegetation near bird and seal rookeries typically has high δ15N signatures and these high values are linked to the enriched δ15N values of rookery soils. However, Antarctic cryptogams are mostly dependent on atmospheric ammonia (NH3) and volatized NH3 from rookeries is severely depleted in δ15N-NH3. So there is an apparent discrepancy between the isotopically depleted source (NH3) and δ15N-enriched vegetation. In this article, we aim to resolve this discrepancy to better understand the mechanisms and processes involved in isotopic changes during nitrogen transfer between Antarctic marine and terrestrial ecosystems. Under laboratory conditions, we quantified whether volatized NH3 affects the isotopic signature of cryptogams. NH3 volatilizing from penguin guano and elephant seal dung was depleted (44–49‰) in δ15N when captured on acidified filters, compared to the source itself. Cryptogams exposed to the volatized NH3 were enriched (18.8–23.9‰) in δ15N. The moss Andreaea regularis gained more nitrogen (0.9%) than the lichen Usnea antarctica (0.4%) from volatilized NH3, indicating a potential difference in atmospheric NH3 acquisition that is consistent with existing field differences in nitrogen concentrations and δ15N between mosses and lichens in general. This study clarifies the δ15N enrichment of cryptogams resulting from one of the most important nitrogen pathways for Antarctic vegetation
Dynamics and persistence of rabies in the Arctic
No full textRabies is a major issue for human and animal health in the Arctic, yet little is known about its epidemiology. In particular, there is an ongoing debate regarding how Arctic rabies persists in its primary reservoir host, the Arctic fox (Vulpes lagopus), which exists in the ecosystem at very low population densities. To shed light on the mechanisms of rabies persistence in the Arctic, we built a susceptible–exposed–infectious–recovered (SEIR) epidemiological model of rabies virus transmission in an Arctic fox population interacting with red foxes (Vulpes vulpes), a rabies host that is increasingly present in the Arctic. The model suggests that rabies cannot be maintained in resource-poor areas of the Arctic, characterized by low Arctic fox density, even in the presence of continuous reintroduction of the virus by infected Arctic foxes from neighbouring regions. However, in populations of relatively high Arctic fox density, rabies persists under conditions of higher transmission rate, prolonged infectious period and for a broad range of incubation periods. Introducing the strong cyclical dynamics of Arctic prey availability makes simulated rabies outbreaks less regular but more intense, with an onset that does not neatly track peaks in Arctic fox density. Finally, interaction between Arctic and red foxes increases the frequency and/or the intensity of rabies outbreaks in the Arctic fox population. Our work suggests that disruption of prey cycles and increasing interactions between Arctic and red foxes due to climate change and northern development may significantly change the epidemiology of rabies across the Arctic
Are moths the missing pollinators in Subantarctic New Zealand?
No full textOn offshore islands, flowers are typically small, simple in colour and shape and more reliant on wind- or self-pollination than insect-mediated pollination. Islands also tend to have a species-poor pollinating fauna. The New Zealand Subantarctic islands (latitude between about 46° and 60°) have a depauperate pollinator fauna. However, many flowers in this region are large, brightly coloured and apparently completely reliant on insect visitors for pollination. In the absence of bees and butterflies, moths and flies may be particularly important pollinators in the region. Using six Heath moth traps simultaneously over four nights in three different habitat types, 241 moths were caught, representing six species. We found that moths carried pollen identified to four plant species (Bulbinella rossii, Dracophyllum longifolium, Gentianella concinna and Acaena minor), with B. rossii and D. longifolium pollen being most abundant on moth bodies. Weather conditions explained moth abundance and distribution, but neither weather nor the number of moths caught were reliable predictors of their potential as pollinators; moths carried on average more pollen grains from more plant species in the shrubland despite harsh weather conditions and few individuals caught. Local flowering abundances may help explain this trend, with the predominance of D. longifolium flowering in the shrubland and B. rossii in the exposed megaherb field. This study is the first to provide evidence that moths may be capable of acting as pollinators in Subantarctic New Zealand, and that their contribution should not continue to be overlooked
Two species of Lumbricillus (Enchytraeidae, Annelida) new to Antarctica
No full textThe intertidal fauna of the Antarctic Peninsula has a relatively high species diversity, due to its warmer environment compared to other parts of Antarctica. Marine oligochaetes are, in general, one of the most diverse and ecologically important benthic organism groups, at least in the littoral zone. Antarctica has been one of the least studied areas with regard to oligochaete diversity. Here we report two Lumbricillus species (Lumbricillus antarcticus Stephenson, 1932 and Lumbricillus sejongensis sp. nov.) new to Antarctica, found in a tidal pool on the Barton Peninsula, King George Island. The diversity of this genus remains poorly known for Antarctica and the Subantarctic islands, and what we know is based on a few patchy studies
Distribution and environmental correlations of picoeukaryotes in an Arctic fjord (Kongsfjorden, Svalbard) during the summer
No full textPicoeukaryotes are numerous in the summer in the High-Arctic fjord Kongsfjorden, in western Spitsbergen, Svalbard. However, little research has been conducted on the community structure and diversity of picoeukaryotes. We conducted a detailed investigation of the distribution and environmental correlations of picoeukaryotes in Kongsfjorden in July 2012, using 454-pyrosequencing of 18S rDNA and redundant analysis. Eight classes were classified with proportions larger than 1%. These were Mamiellophyceae, Chrysophyceae, Spirotrichea, Telonemea, Cryptophyceae, Bolidophyceae, Picomonadea and Dictyochophyceae. Five genera were classified, with Micromonas (55.6%) and Bathycoccus (7.8%) as the dominant genera. The diversity and composition of the picoeukaryote community were very distinct in different water masses sampled in the water column (i.e., vertically), but were not distinct from station to station (i.e., horizontally). Biodiversity was greater in the Atlantic waters than in glacial waters. Mamiellophyceae, Bolidophyceae, Picomonadea and Dictyochophyceae had significantly different distributions (p < 0.01) in the three water masses (surface water, intermediate water and transformed Atlantic Water). Nitrogen, salinity and temperature were the first three primary environmental factors shaping the community structure of picoeukaryotes
Holocene environmental changes in Dicksonfjorden, west Spitsbergen, Svalbard
No full textMulti-proxy analyses of two sediment cores from Dicksonfjorden were performed to reconstruct Holocene environmental conditions in this northern branch of Isfjorden, the largest fjord system in Svalbard. Factors affecting the depositional processes include shifts in sources of sediments, ice rafting and regional glacio-isostatic rebound. Sediments were derived from Palaeozoic siliciclastics and carbonates occurring at the fjord head and sides, respectively. Their relative contributions were controlled by falling relative sea level and the resulting progradation of the major stream and delta systems closer to the core sites. Deposition of clasts from sea-ice rafting persisted throughout most of the Holocene. Following a period of low, but continuous, clast fluxes (ca. 11 000–7000 calibrated years before the present), ice rafting was most intensive between ca. 7000 and 3000 calibrated years before the present. It can be related to extensive seasonal sea-ice formation caused by regional cooling. The prograding deltas also provided coarse sediments. Reduced ice rafting from ca. 3000 calibrated years before the present suggests enhanced formation of shorefast and/or permanent sea ice, suppressing sea-ice rafting in the fjord, in response to the cool climate and reduced heat flux from Atlantic Water. Episodic inflow of Atlantic Water and low turbidity of surface water can, however, account for a larger amount of marine organic matter produced in the outer fjord. The sedimentary record in Dicksonfjorden, where tidewater glaciers are absent, reflects similar climate and oceanographic variations as reconstructed in fjords on western Spitsbergen that are influenced by tidewater glaciers
A nematode in the mist: Scottnema lindsayae is the only soil metazoan in remote Antarctic deserts, at greater densities with altitude
No full textA decrease in biodiversity and density of terrestrial organisms with increasing altitude and latitude is a well-known ecogeographical pattern. However, studies of these trends are often taxonomically-biased toward well-known organisms and especially those with relatively large bodies, and environmental variability at the local scale may perturb these general effects. Here, we focus on understudied organisms—soil invertebrates—in Antarctic deserts, which are among the driest and coldest places on Earth. We sampled two remote Antarctic sites in the Darwin Glacier area and established an altitudinal gradient running from 210 to 836 m a.s.l. We measured soil geochemistry and organic matter content and linked these parameters with the presence of soil invertebrates. We found three general outcomes, two of which are consistent with general assumptions: (a) the hostile climatic condition of the Darwin Glacier region supports an extremely low diversity of soil metazoans represented by a single nematode species—Scottnema lindsayae; (b) soil geochemistry is the main factor influencing distribution of nematodes at the local scale. Contrary to our expectations, a positive correlation was found between nematode density and altitude. This last observation could be explained by an additional effect of soil moisture as we found this increased with altitude and may be caused by orographic clouds, which are present in this region. To the best of our knowledge such effects have been described in tropical and temperate regions. Potential effect of orographic clouds on soil properties in polar deserts may be a fruitful area of ecological research on soil fauna
A note on digital elevation model smoothing and driving stresses
No full textIce-flow fields, including the driving stress, provide important information on the current state and evolution of Antarctic and Greenland ice-sheet dynamics. However, computation of flow fields from continent-scale DEMs requires the use of smoothing functions and scales, the choice of which can be ad hoc. This study evaluates smoothing functions and scales for robust calculations of driving stress from Antarctic DEMs. Our approach compares a variety of filters and scales for their capacity to minimize the residual between predicted and observed flow direction fields. We find that a spatially varying triangular filter with a width of 8–10 ice thicknesses provides the closest match between the observed and predicted flow direction fields. We use the predicted flow direction fields to highlight artefacts in observed Antarctic velocities, demonstrating that comparison of multiple observational data sets has utility for quality control of continent-scale data sets
How long will an Arctic mountain glacier survive? A case study of Austre Lovénbreen, Svalbard
No full textTo study Arctic valley glacier responses to global climate change, the Elmer/Ice ice-flow model was used to investigate long-term changes in Austre Lovénbreen, a typical polythermal glacier in Svalbard. Evolution and features, including volume, area, ice thickness, runoff and time and mode of glacier disappearance, were projected. Firstly, steady-state simulations were performed to determine the best parameters for the ice-flow model, which were then used to simulate glacial dynamics. Based on the 21st-century Arctic warming trend in the fifth assessment report published by the Intergovernmental Panel on Climate Change, the evolution of the glacier was simulated under three hypothetical climatic scenarios: pessimistic, high-probability and optimistic. The results predicted that the glacier will retreat until disappearance under all three scenarios, and its disappearance time will likely be approximately 111 years (by 2120). Under all scenarios, glacier volume and area reductions will be slow at first, then fast and finally slow again at the end. In particular, glacial runoff will increase markedly until 2070 in the high-probability scenario, and the peak runoff will be double the current value