To understand the use and importance of the Antarctic sea ice to the Ross seal (Ommatophoca rossii), four adult females were tagged with Argos satellite transmitters in the Amundsen Sea, Antarctica. The Ross seal is the least studied of the Antarctic seal species and nothing was previously known about their behaviour in the Amundsen Sea. During almost 1 year, their movements, haul out behaviour and time spent at different temperatures were logged. By comparing their movements with daily ice maps, distances to the ice edge were calculated, and seals dependence on sea ice for resting, breeding and moulting was analysed. The tagged seals spent on average 70.8 % (range 66.8-77.8 %) of their time in the water and hauled out mainly during the moult in December-January, and in late October-mid-November during breeding. During the pelagic period, they were on average 837.5 km (range 587-1,282 km) from the ice edge indicating a fully pelagic life during several months. Their pelagic behaviour suggests that Ross seals, although being an ice obligate species, may adapt comparatively easy to climate change involving ice melting and recession and thereby potentially being less sensitive to the reduction of sea ice than other Antarctic seal species. Although nothing is known about their mating behaviour, they appear to be relatively stationary during moulting and breeding, hence requiring a small ice surface. Although previous studies in other parts of Antarctica have found similar results, still many questions remain about this peculiar species.

During the last few decades, the Arctic has experienced large-scale vegetation changes. Understanding the mechanisms behind this vegetation change is crucial for our ability to predict future changes. This study tested the hypothesis that decreased cryogenic disturbances cause vegetation change in patterned ground study fields (non-sorted circles) in Abisko, Sweden during the last few decades. The hypothesis was tested by surveying the composition of plant communities across a gradient in cryogenic disturbance and by reinvestigating plant communities previously surveyed in the 1980s to scrutinise how these communities changed in response to reduced cryogenic disturbance. Whereas the historical changes in species occurrence associated with decreased cryogenic disturbances were relatively consistent with the changes along the contemporary gradient of cryogenic disturbances, the species abundance revealed important transient changes highly dependent on the initial plant community composition. Our results suggest that altered cryogenic disturbances cause temporal changes in vegetation dynamics, but the net effects on vegetation communities depend on the composition of initial plant species.

Little information exists on biogeochemical transformations in aquatic ecosystems beneath polar ice sheets (i.e., water-saturated sediments, streams, rivers, and lakes) and their role in global elemental cycles. Subglacial environments may represent important sources of atmospheric CO2 and/or CH4 during deglaciation, thus acting as amplifiers in the climate system. However, the role of subglacial environments in global climate processes has been difficult to assess given the absence of biogeochemical data from the basal zones of inland polar ice sheets. Here, we report on the concentrations of CO2, CH4, and H-2 in samples of refrozen basal water recovered at a depth of similar to 3,042 meters below the surface during the North Greenland Ice Core Project (NGRIP). CH4 and H-2 concentrations in the NGRIP samples were approximately 60- and 700-fold higher, respectively, relative to air-equilibrated water, whereas CO2 was similar to fivefold lower. Metabolic pathways such as (1) methanogenesis, (2) organic matter fermentation, carboxydotrophic, and/or methylotrophic activity, and (3) CO2 fixation provide plausible biotic explanations for the observed CH4, H-2,H- and CO2 concentrations, respectively.

Arctic environments have relatively simple ecosystems. Yet, we still lack knowledge of the spatio-temporal dynamics of many Arctic organisms and how they are affected by local and regional processes. The Arctic hare (Lepus arcticus) is a large lagomorph endemic to high Arctic environments in Canada and Greenland. Current knowledge about this herbivore is scarce and the temporal and spatial dynamics of their populations are poorly understood. Here, we present observations on Arctic hares in two sites on north Greenland (Hall and Washington lands) and one adjacent site on Ellesmere Island (Judge Daly Promontory). We recorded a large range of group sizes from 1 to 135 individuals, as well as a substantial variation in hare densities among the three sites (Hall land: 0 animals/100 km2, Washington land 14.5–186.7 animals/100 km2, Judge Daly Promontory 0.18–2.95 animals/100 km2). However, pellet counts suggested that both Hall land and Judge Daly Promontory hosted larger populations at other times. We suggest that our results could have been caused by three spatially differentiated populations with asynchronous population fluctuations. With food limitation being a likely driver behind the observed variation, we argue that food limitation likely interacts with predation and competition in shaping the spatial dynamics of Arctic hares in this region.

For a fish to thrive, the gut must function efficiently. This is achieved through a range of processes, including controlled patterns of gut motility and modifications in gut blood flow. The knowledge of how gut functions in fish are affected by environmental temperature is sparse, and in order to understand how changes in climate may affect fish populations, we need to understand how gut blood flow and gut motility are affected by changes in temperature. By simultaneous recording of gut blood flow, gut motility, cardiac output, heart rate and cardiac stroke volume, in vivo at 4, 9 and 14 A degrees C, the acute thermal sensitivity of a thermal generalist (shorthorn sculpin Myoxocephalu scorpius) was compared to the more strictly Arctic species (Arctic sculpin M. scorpioides). Temperature effects on gut motility were further explored in vitro, using isolated smooth muscles. Elevated water temperatures increased gut blood flow and contractile activity. Contraction frequency increased nearly threefold and gut blood flow almost doubled with the 10 A degrees C increase. Both cardiac output and heart rate increased with temperature, while cardiac stroke volume decreased. The cholinergic agonist carbachol was most potent on smooth muscles at 9 A degrees C. There were no differences between the two species, suggesting that the gastrointestinal and cardiovascular systems of Arctic sculpin, although a more pronounced Arctic species, have similar abilities to cope with acute fluctuations in water temperature as shorthorn sculpin. The impact of increased gut activity at higher temperatures needs further investigation before the effects of climate change can be predicted.

The distribution and ecology of insects in arctic regions are poorly known. The aim of this study was to determine the distribution of galling sawflies in the Canadian arctic and their oviposition preference. The Swedish Tundra Northwest 1999 expedition visited 17 sites in the Canadian arctic. We determined the occurrence of galling sawflies at all the sites and studied the oviposition preference of two leaf-galling sawflies, Eupontania arctica and Pontania nivalis, on Salix reticulata and S. glauca, respectively. Galling sawflies were abundant at only one site, the mainland site at Ivvavik National Park. Only a few galls in total were found at the remaining sites, suggesting that galling sawflies are rare in the higher arctic, and potential explanations for this pattern are discussed. Shoots with leaf galls were longer than shoots without galls on both S. reticulata and S. glauca. These differences could not be explained by a higher number of leaves on longer shoots. This suggests that long shoots are preferred by sawflies because of faster development and better survival of larvae on long shoots.

Rates of decomposition in Arctic soils are regulated by temperature and moisture, but substrate availability is dictated by vegetation inputs, which are also subject to biotic influences. Here, we examine how leaf and litter inputs from individual dwarf shrub species influence soil enzyme activity in a sub-Arctic heath community in Abisko, Sweden. We further consider how foliar damage via insect herbivory (and outbreak) affects the soil community and decomposition. During the peak growing season (July 2011), we assessed how shrub community composition (Empetrum hermaphroditum, Vaccinium myrtillus, V. uliginosum and V. vitis-idaea) determined litter and soil phenol oxidase activity. A periodic severe outbreak of autumn moth larvae (Epirrita autumnata) affected this community in the following year (July 2012), and we used this to investigate its impact on relationships with phenol oxidase activity, soil respiration, soluble NH4 (+) and soluble phenolics; the soluble factors being directly associated with inputs from insect larval waste (frass). Pre-outbreak (2011), the strongest relationship observed was higher phenol oxidase activity with E. hermaphroditum cover. In the outbreak year (2012), phenol oxidase activity had the strongest relationship with damage to the deciduous species V. myrtillus, with greater herbivory lowering activity. For the other deciduous species, V. uliginosum, soil NH4 (+) and phenolics were negatively correlated with foliar larval damage. Phenol oxidase activity was not affected by herbivory of the evergreen species, but there was a strong positive relationship observed between E. hermaphroditum community abundance and soil respiration. We highlight the dominant role of E. hermaphroditum in such sub-Arctic shrub communities and show that even during insect outbreaks, it can dictate soil processes.

Nutrient availability is one of the most important factors controlling Arctic plant productivity. It is also sensitive to climate change, with increased nitrogen (N) mineralization arising from warmer soils and deeper snow. However, warming also tends to reduce snow cover duration, leading to antagonistic effects of climate change on mineralization. Furthermore, since snow melt is also a trigger for seasonal nutrient pulses, changes to snow melt timing may alter seasonal availability to plants. To investigate the impacts of environmental conditions on ecosystem nutrient availability and seasonal dynamics, we undertook regular, high-frequency measurements of soil extractable and plant N and phosphorus (P) concentrations along with winter and summer N and P mineralization rates along a sub-Arctic catchment representing a gradient in temperature, snow melt timing and vegetation composition. Our data show that a delay in snow melt timing of 11 days did not alter the seasonal dynamics of soil or leaf N and P concentrations. Net N mineralization, however, was highest at the warmest site and at the site with the most productive vegetation, while P was strongly immobilized at all sites, both in winter and summer. N:P ratios suggest that plants were generally P limited at all sites, probably due to strong P immobilization. Our data suggest that where warming and resulting vegetation change increase net N mineralization rates, in combination with strong P immobilization this may impose greater P limitation, possibly limiting the extent to which Arctic ecosystems can increase productivity under warming.

Northern peatlands are very sensitive to changes in climate. Impacts of increased temperatures on hydrology, vegetation structure and soil carbon are already well documented from northern peatlands. In contrast, effects of global warming on soil mites, and seasonal effects in particular, have received less attention, even though soil mites are an important component in ecosystems as they contribute to nutrient dynamics and decomposition. We investigated the impacts of long-term (16 years) experimental seasonal climate manipulations (summer warming, winter warming with snow accumulation, and year-round warming) on oribatid (Oribatida) and mesostigmatid (Mesostigmata) mite communities in a peat bog underlain by discontinuous permafrost, in Abisko, Northern Sweden. We found that (1) Year-round warming treatment had neither impact on life-history trait compositions nor on total abundances of oribatid mites, possibly because of opposite effects of summer and winter warming; (2) Small-bodied oribatid mites, in particular those belonging to genera Suctobelba, increased in abundance under the summer warming treatment; (3) The species richness of oribatid mites was negative affected by year-round warming; (4) Mesostigmatid mites, which were not identified to species level, were found to decrease in abundance under year-round warming. Because different mite taxa with different body sizes and diets play distinct roles in carbon and nutrient dynamics, the observed changes in mite communities may impact ecosystem functions in northern peatlands.

We investigated the genetic structure of the presumably small (10-100 pairs) and isolated dunlin (Calidris alpina) population breeding in Svalbard, and compared it with similar data recently published from several dunlin populations in the western Palearctic and East Greenland. Using mitochondrial and nuclear DNA markers, as well as data on bill lengths, we sought to infer the phylogeographic origin of Svalbard dunlins and assess their within-population level of genetic diversity. Only dunlins with haplotypes of the European mtDNA clade (EUR) were found in Svalbard, indicating a close resemblance to dunlin populations in East Greenland and Iceland. Microsatellite data for Svalbard dunlins, as well as their short bills, also supported a western origin. The Svalbard population did not show signs of inbreeding or reduced levels of genetic diversity compared to other investigated populations, which suggests that the population was recently founded or is currently subject to considerable gene flow.

The nocturnal migration of many passerines starts after sunset and reaches peak intensity during the dark hours of the night. Birds destined for high Arctic breeding grounds encounter a special situation, as they will experience continuous daylight when reaching the high latitudes during the final part of spring migration. How does this affect the pattern of nocturnal migration? We consider three alternative hypotheses; that the period of nocturnal flight activity may become compressed, remain unchanged or become disorganized under Arctic light conditions. We tracked migrating birds by radar north of the Arctic Circle (at Abisko, 68A degrees 21’N, 18A degrees 49’E, in Swedish Lapland) and show that the pattern during the night, with a migration peak around midnight, persisted even in continuous daylight when the sun remained above the horizon throughout the 24 h of the day. The flight intensity peak under continuous daylight in spring (midnight sun) was very similar to the corresponding peak in autumn, when the migration took place under twilight conditions. The duration of the flight period under continuous daylight in spring lasted 8-10 h and did not seem to be compressed. We hypothesize that the flight period under midnight sun conditions may in fact be more protracted than during short nights, because of release from twilight cues that tend to synchronize initiation and termination of migratory flights. These cues will thus capture and confine the flight period. The results of this provisional study suggest interesting dynamics in timing of nocturnal migratory flights under seasonally and latitudinally changing day length conditions, which will need detailed documentation by future studies of migration intensity at high-latitude sites.

We analysed circumpolar samples from 68 lakes within the 10 degrees C-July isotherm from Arctic Canada, Nunavut, Greenland, Svalbard, Eastern Siberia, the Beringia region, and Alaska. In total, we found 3 species of Anostraca, 17 of Diplostraca, 1 species of cyclopoid and 14 species of calanoid copepods. Our study identifies a wider distribution for some copepods-e.g. Eurytemora pacifica, Leptodiaptomus sicilis, Arctodiaptomus novosibiricus, Cyclops abyssorum-than previously known. Moreover, one anostracan species, Artemiopsis bungei, was recorded in North America for the first time; and one chydoriid, Chydorus gibbus, is a new species for Greenland. We observed that species richness of crustaceans is lower in lakes that were glaciated during the Quaternary period, compared to those not glaciated (e.g. Chukotski Peninsula, Siberia; Point Barrow, Alaska; and Disko Island, Greenland). This confirms the findings of classic studies: glaciation has strongly affected the biogeography of freshwater crustaceans in circumpolar areas.

We present a phytogeographical comparison between polar (Arctic and Antarctic) and non-polar strains of the cyanobacterial genus Phormidium, which plays a key role in Arctic and Antarctic ecosystems as primary producer. A total of 26 Phormidium strains were studied using a polyphasic approach, 18 from Arctic (Svalbard, Ellesmere Island and Scandinavian Arctic—Abisko) and Antarctic (Antarctic Peninsula—King George and James Ross Island) regions, and 8 from temperate sites (mostly situated in Central Europe). A phylogenetic tree was constructed and compared with similar 16S rRNA sequences retrieved from Genbank. Within the Phormidium autumnale cluster, genetic similarity of 16S rDNA was more related to geographical proximity of strain origin than to morphological similarity. No genetic identity of Phormidium strains from north and south polar regions was found. The cluster Phormidium autumnale apparently belongs to generic entities in which geographical limitation plays a prominent role. However, the cyanobacterial strains found in Europe suggest that the distribution areas of some Phormidium cyanobacteria overlap. The Phormidium autumnale cluster is evidently a very characteristic type and represents an isolated clade within the traditional genus Phormidium. According to morphological features and the structure of trichomes, it is most similar and thus probably belongs to the genus Microcoleus.

Marine invertebrate fauna associated with whale remains has lately attracted a great deal of interest. However, very little is known about this fauna in the Southern Ocean, an area with high abundances of cetaceans. To investigate the Antarctic organisms associated with these substrates, we conducted a study using whale bones in the shallow-waters of Deception Island (South Shetland Islands). In this paper, we describe two new species of Ophryotrocha (O. orensanzi sp. nov. and O. clava sp. nov.) from a minke whale (Balaenoptera acutorostrata) fresh caudal vertebra experimentally deployed for about a year and from an unknown whale vertebra presumably dating back to the early twentieth century whaling operations. Ophryotrocha clava sp. nov., found in relative high abundance in the fresh bone, is hypothesized to be an opportunistic species in the context of Antarctic shallow-water organically enriched environments. Ophryotrocha orensanzi sp. nov. appears to be the same species as the unnamed Palpiphitime sp., near lobifera, formerly reported from a nearby area. Phylogenetic analyses based on the nuclear gene H3 and the mitochondrial genes COI and 16S, using MrBayes and Maximum Likelihood analyses, show that O. clava sp. nov. is close to Iphitime hartmanae and is included in the 'hartmanni' clade, while O. orensanzi sp. nov. falls in the 'lobifera' clade. Remarks about their feeding preferences and ecology are also given. Our findings seem to suggest that members of the genus Ophryotrocha are important components of organically enriched Southern Ocean environments, as has been reported for this clade in other geographic areas.

A 15 week field experiment (austral summer Nov-Mar) was carried out in an intertidal hard bottom platform in Antarctica (King George Island). To test whether grazing and ultraviolet radiation (UVR) influenced the succession of a benthic microalgal assemblage, a two-factorial design was used (1) ambient radiation, > 280 nm; (2) ambient minus UV-B, > 320 nm; (3) ambient minus UVR, > 400 nm versus grazer-no grazer). On four sampling occasions microalgae were identified, counted and carbon contents were calculated. The assemblage was dominated by the diatom genera Navicula and Cocconeis. Biomass was generally low in all treatments but was significantly reduced by grazing throughout the experiment. No significant UV effects were found. Grazer absence particularly favoured diatoms of the genus Cocconeis. We conclude that the Antarctic microalgal assemblage was unaffected by present day UVR whereas grazers acted as important drivers on the intertidal microalgal community structure.