High Arctic Site Research Articles

Endorhizal Fungi in Ranunculus from Western and Arctic Canada: Predominance of Fine Endophytes at High Latitudes

Ranunculus roots were sampled across a latitudinal transect encompassing 52 oN and 82 oN, for years spanning 1963-2007. Samples from 2004 and later were preserved in formalin; earlier samples were taken from herbarium accessions. Roots were examined for colonization by arbuscular mycorrhizae, fine endophyte, and septate endophyte fungi using lactofuchsin-stained material imaged with epifluorescence microscopy. Endorhizal quantitation was assessed for each endorhizal morphotype. Roots from High Arctic (79 oN-82 oN) and mid-latitude (52 oN-54 oN) sites both contained all three endorhizal morphotypes; however, overall fungal colonization was almost three-fold higher in mid- latitude samples. Most Ranunculus root colonization (29 % of the root length) in High Arctic samples was from fine endophyte fungi, whereas fine endophyte colonization was ~ 20 % of root length in mid-latitude roots. In contrast, arbuscular mycorrhizal colonization was 2 % of root length in High Arctic samples and 57 % in mid-latitude samples. Septate endophyte colonization was 11 % and 36 % of root length for High Arctic and mid-latitude samples, respectively. These values are consistent with our previous results for other taxa, and suggest that fine endophytes are important contributors to soil microbial diversity as related to plant survival and competitiveness in the high latitudes.

Shorebird and Passerine Abundance and Habitat Use at a High Arctic Breeding Site: Creswell Bay, Nunavut

Shorebirds and passerines were surveyed at Creswell Bay, Somerset Island, in the High Arctic Ecozone (Canadian Arctic Islands) during the breeding season (June and July, 1995–97) and in August 1995 (post-breeding). The study area, situated on the north and south sides of Creswell Bay, consisted of sedge marsh and sedge wetland in the lowest areas, with shrub tundra dominated by Dryas spp. or Cassiope spp. and sparse herbaceous tundra over more upland areas. Surveys were carried out on 400 x 400 m plots distributed among the vegetation types according to their relative amounts within the study areas (34 plots in 1995; 33 plus 56 new plots in 1997). Eleven shorebird and three passerine species were observed during the surveys. Densities of breeding shorebirds were similar in 1995 and 1997 (37.3 and 33.1 birds/km2), while in 1996 a late spring with heavy snow cover resulted in reduced numbers of birds and no breeding. Shorebirds and passerines were much more numerous in sedge marsh and sedge wetland. White-rumped sandpiper ( Calidris fuscicollis ) and red phalarope ( Phalaropus fulicarius ) were the most abundant shorebirds breeding at Creswell Bay, and Lapland longspur ( Calcarius lapponicus ) was the most abundant breeding passerine. White-rumped sandpiper and sanderling ( Calidris alba ) were the most numerous species present after the breeding period. American golden-plover ( Pluvialis dominica ), red phalarope, and white-rumped sandpiper showed significant habitat preferences. An estimated 10 341 (± 6596; 95% CI) shorebirds were on the north area in 1995 and 14 840 (± 10 744) on both areas in 1997. The estimated maximum numbers over both years of white-rumped sandpiper (6769 ± 3725) and buff-breasted sandpiper ( Tryngites subruficollis ) (908 ± 1169) at Creswell Bay were more than 1% of the species’ estimated national populations (1.5% and 5.1%, respectively). This abundance, along with the relatively high species diversity at this high-latitude site, warrants its continued status as a Canadian Wildlife Service “key habitat site,” and every possible effort should be made to ensure its long-term protection.

A comparison of annual and seasonal carbon dioxide effluxes between sub-Arctic Sweden and High-Arctic Svalbard

Recent climate change predictions suggest altered patterns of winter precipitation across the Arctic. It has been suggested that the presence, timing and quantity of snow all affect microbial activity, thus influencing CO2 production in soil. In this study annual and seasonal emissions of CO2 were estimated in High-Arctic Adventdalen, Svalbard, and sub-Arctic Latnjajaure, Sweden, using a new trace gas-based method to track real-time diffusion rates through the snow. Summer measurements from snow-free soils were made using a chamber-based method. Measurements were obtained from different snow regimes in order to evaluate the effect of snow depth on winter CO2 effluxes. Total annual emissions of CO2 from the sub-Arctic site (0.662–1.487 kg CO2 m–2 yr–1) were found to be more than double the emissions from the High-Arctic site (0.369–0.591 kg CO2 m–2 yr–1). There were no significant differences in winter effluxes between snow regimes or vegetation types, indicating that spatial variability in winter soil CO2 effluxes are not directly linked to snow cover thickness or soil temperatures. Total winter emissions (0.004– 0.248 kg CO2 m–2) were found to be in the lower range of those previously described in the literature. Winter emissions varied in their contribution to total annual production between 1 and 18%. Artificial snow drifts shortened the snow-free period by 2 weeks and decreased the annual CO2 emission by up to 20%. This study suggests that future shifts in vegetation zones may increase soil respiration from Arctic tundra regions.

Total filterable mercury and 210Pb in the Canadian Arctic air

Total filterable mercury (TFM) and lead-210 ((210)Pb) were measured for a one-year air particulate sample series collected weekly at Resolute (74.7 degrees N, 95.0 degrees W), a Canadian high Arctic site, during July 1999 and June 2000. The measurements showed a clear time lag of two months between the peak concentrations of TFM and (210)Pb.

Spatial and temporal distribution of soil organic carbon in nonsorted striped patterned ground of the High Arctic

The role of periglacial processes on soil carbon distribution is examined at a High Arctic site in northwest Greenland. A 16‐m trench dug across a series of nonsorted stripes at Thule Air Base revealed sand‐rich wedges underlying striped, vegetated troughs, and organic‐rich soil horizons buried at depth. The site has sparse prostrate vegetation and is estimated to contain 9.4 kg/m2 of soil organic carbon (SOC) in the active layer. The distribution of carbon is variable with nearly half (49%) stored in the sand wedges, which only account for 10% of the trench area. Additionally, 62% of the total SOC was found below 25 cm, highlighting the significant role of cryoturbation and physical redistribution of carbon in permafrost‐affected soils. Carbon in the active sand‐rich wedges dates from modern at the surface (65 ± 35 radiocarbon years) to 2695 ± 40 radiocarbon years at depth, and carbon turnover time appears to be ∼450 years. Buried organic horizons found at 50–70 cm depth have radiocarbon ages of 27,480–31,900 BP. A conceptual model is proposed in which the active sand wedges have developed in an approximately 30 ka surface containing buried soils preserved in permafrost or under a cold‐based glacier. As the ice retreated and soils warmed, soil development and active cryoturbation resumed forming nonsorted stripes in the modern surface.

Differences in cold and drought tolerance of high arctic and sub-arctic populations of Megaphorura arctica Tullberg 1876 (Onychiuridae: Collembola)

The springtail Megaphorura arctica (Onychiuridae: Collembola) inhabits the arctic and sub-arctic parts of the northern hemisphere where it on a seasonal basis will be exposed to severe cold and desiccating conditions. In the present study we compared how traits of stress resistance differed between two populations of M. arctica that were collected at a high arctic site (Spitsbergen) and a sub-arctic site (Akureyri, Iceland) with contrasting thermal environments. In addition we investigated how cold and desiccation affected the phospholipid fatty acid composition of M. arctica from Spitsbergen. The springtails from Spitsbergen were the most cold tolerant and this was linked to an almost three times higher level of trehalose accumulation during cryoprotective dehydration (15% and 5% of tissue dry weight in the Spitsbergen and Iceland populations, respectively). Although cryoprotective dehydration is intimately related to desiccation stress it was shown that M. arctica had a higher mortality when dehydrated over ice (−10 or −20 °C) than when dehydrated at temperatures above 1 °C. Thus, survival was lower after exposure to −10 °C than after exposure to a relative humidity of 91.2% RH at +1 °C although both treatments led to the same level of dehydration. Exposure to both cold (−10 and −20 °C) and desiccation at +1 °C caused significant changes in the phospholipid fatty acid composition with some similarities. These changes included a decrease in average chain length of the fatty acids due primarily to an increase in the phospholipid fatty acids 16:0 and a decrease in 18:3 and 20:4ω6.

An investigation of cadmium and lead from a High Arctic waste disposal site, Rsesolute Bay, Nunavut, Canada*

Heavy metal contamination in the High Arctic is a growing concern. Cadmium and lead are recognized by the Canadian Government as metals of concern but little research has been done on small point sources such as municipal waste disposal sites. In 2003 a study was conducted near Resolute, Nunavut, Canada (74°43′N, 95°55′W) to determine the extent of cadmium and lead leaching from a local dumpsite which lay adjacent to a large late-lying snowbed. Three transects (reaching ∼700 m in length) were established downslope from the waste site and water and soil samples were collected for metal analysis at regular intervals. Information on snowbed retreat, water table position, soil moisture conditions and frost table decline were also obtained. Cadmium levels in water samples exceeded government guidelines and along one transect increased with distance. Little lead in surface waters supports the notion that it does not travel easily in soil solution. Overall, soil cadmium and lead levels were low and did not exceed government guidelines. Some spatial patterns did emerge and can be linked to variations in water flow patterns, nearness to the dumpsite and ground cover conditions.

Parsimonious modelling of nutrient fluxes for a terrestrial ecosystem on Svalbard

MBL-MEL, a simple model of ecosystem biogeochemistry, is amended and applied to plant and soil C, 14N and 15N data for the summers of 2001–2003 from Brandalpynten, a maritime high Arctic site on Svalbard following the application of 15N (99 atom%) as 15NO3-N at or 15NH4-N at concentrations of 1 or 5 kg N ha−1. Variants of this Parent model are also developed to incorporate: temperature dependence into equations describing nutrient fluxes (Temp model); cryptogams (Cryp model); both features combined (CrypTemp model). Goodness-of-fit (GOF) statistics suggest that the addition of temperature-dependence improves the utility of models with and without cryptogams: the residual weighted sums of squares per data point were 5.69, 3.91, 4.31 and 3.93 for the Parent, Temp, Cryp and CrypTemp models respectively. The application of model selection criteria confirm that the addition of temperature-dependence also improves model generalisability. Across all models, the principal discrepancies between observation and prediction are associated with the inorganic soil 15N pool. We conclude that models in which fluxes are described using simple equations that can be augmented to include additional complexity, are an ideal starting point from which the relationship between GOF and model generalisability can be assessed.

Reconstruction of Summer Temperature for a Canadian High Arctic Site from Retrospective Analysis of the Dwarf Shrub, Cassiope tetragona

We used retrospective analysis of the widespread evergreen dwarf-shrub, Cassiope tetragona, to reconstruct average summer air temperature for Alexandra Fiord, Ellesmere Island, Canada. Retrospective analysis is a technique based on dendrochronological methods. In this study, chronologies are based on the morphological characteristics of the plant stems. Two growth and two reproduction chronologies, ranging from 80 to 118 years long, were developed from each of two populations at the High Arctic site. We used multiple regression models to develop a 100-year-long (1895–1994) reconstruction of July–September average air temperature that explained 45% of the climatic variance in the instrumental record. The reconstruction revealed an increase in summer temperature from ∼1905 to the early 1960s, a cooling trend from the mid-1960 to the 1970s, and an increase in temperature after 1980. These historical temperature patterns correspond well with those from other climate proxies from sites on Ellesmere and Devon Islands. As well, the similarity between our model and an arctic-wide proxy temperature time series suggests that the Cassiope-based reconstruction contains a large-scale temperature signal. There is great potential for the development of proxy climate data using Cassiope tetragona from sites throughout the Arctic.

Variation in baseline haematology of Northern Fulmars (Fulmarus glacialis) in the Canadian High Arctic

We present the normal baseline variation in haematology of 59 Northern Fulmars (Fulmarus glacialis) collected from two high arctic sites in Nunavut, Canada. We found no differences between males and females in any haematological variable, but leukocyte profiles differed between non-breeding and breeding birds and also between breeding birds at different colonies. Breeding birds also had higher thrombocyte counts than non-breeders. Given that the Arctic is experiencing significant environmental changes due to climate warming, reference haematological values from seabirds may prove useful in monitoring the impacts on arctic ecosystems.

Stratospheric Ozone Depletion: High Arctic Tundra Plant Growth on Svalbard is not Affected by Enhanced UV-B after 7 years of UV-B Supplementation in the Field

The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78 degrees N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996 and 2002. After 7 years of exposure to enhanced UV-B radiation, plant cover, density, morphological (leaf fresh and dry weight, leaf thickness, leaf area, reproductive and ecophysiological parameters leaf UV-B absorbance, leaf phenolic content, leaf water content) were not affected by enhanced UV-B radiation. DNA damage in the leaves was not increased with enhanced UV-B in Salix polaris and Cassiope tetragona. DNA damage in Salix polaris leaves was higher than in leaves of C. tetragona. The length of male gametophyte moss plants of Polytrichum hyperboreum was reduced with elevated UV-B as well as the number of Pedicularis hirsuta plants per plot, but the inflorescence length of Bistorta vivipara was not significantly affected. We discuss the possible causes of tolerance of tundra plants to UV-B (absence of response to enhanced UV-B) in terms of methodology (supplementation versus exclusion), ecophysiological adaptations to UV-B and the biogeographical history of polar plants.

Soil fauna communities and microbial respiration in high Arctic tundra soils at Zackenberg, Northeast Greenland

The soil fauna communities were described for three dominant vegetation types in a high arctic site at Zackenberg, Northeast Greenland. Soil samples were extracted to quantify the densities of mites, collembolans, enchytraeids, diptera larvae, nematodes and protozoa. Rates of microbial respiration were also assessed. Collembolans were found in highest densities in dry heath soil, about 130,000 individuals m−2, more than twice as high as in mesic heath soils. Enchytraeids, diptera larvae and nematodes were also more abundant in the dry heath soil than in mesic heath soils, whereas protozoan densities (naked amoeba and heterotrophic flagellates) were equal. Respiration rate of unamended soil was similar in soil from the three plots. However, a higher respiration rate increase in carbon + nutrient amended soil and the higher densities of soil fauna (with the exception of mites and protozoa) in dry heath compared to the mesic heath soils indicated a higher decomposition rate here.

Transitional occupations of southeastern Somerset Island, Nunavut

Four transitional period sites on Somerset Island compare closely with High Arctic sites attributed to Independence II. The four sites are situated at elevations between Pre-Dorset and Early Dorset occupations in the same area. The sites are described, with an emphasis on architectural characteristics. Vertical slab midpassage structures are present at all sites along with artifact assemblages containing shallowly side-notched bifaces, "cloven hoof" lance heads, a closed socket harpoon head, burin-like tools, narrow microblades, and needles with gouged eyes. Some sites also have exterior hearths and possible caches. Radiocarbon dates place the occupations within the transitional period (i.e. 800-500 B.C.). As during Independence II, the sites are of various size (three small ones and a large one), and are in association with polynyas.

Quantitative estimates of recent environmental changes in the Canadian High Arctic inferred from diatoms in lake and pond sediments

Diatoms were examined in three lacustrine sediment records from Alert, northern Ellesmere Island, and from Isachsen, Ellef Ringnes Island. Diatom assemblages changed markedly since the mid-19th century following relatively stable community composition that spanned centuries to millennia. Three different assemblages, primarily composed of Fragilaria pinnata, Diadesmis spp., or Pinnularia spp., dominated the pre-1850 period at the three sites, but were replaced with different, more diverse assemblages in recent sediments. These species shifts occurred in the mid- to late-19th century in the Isachsen sites, and in the mid- to late-20th century in our Alert site. This difference in timing appears to be a result of the different sensitivities of lakes and ponds to environmental change, rather than of site-specific chemical properties. Reconstructions of pH using diatom inference models indicated increases from 0.5 to 0.8 pH units at these sites over this period of assemblage change. The diatom-inferred pH record from Alert showed agreement with measured climate data from Alert over the last ∼30 years. These marked community changes suggest that these sensitive high arctic sites have recently crossed important ecological thresholds due to environmental change, most likely related to recent warming.

Diatom species-environment relationships and inference models from Isachsen, Ellef Ringnes Island, Canadian High Arctic

Surface sediment diatom assemblages were examined from 26 freshwater sites near Isachsen (78� 47¢ N, 103� 32¢ W), Ellef Ringnes Island, a region of diverse and atypical water chemistry for high arctic sites. One hundred and sixty eight diatom taxa were identified from these samples, over 50% of which had not previously been recorded in the Canadian High Arctic. Variations in diatom assemblages were related to changes in measured environmental variables using multivariate techniques. Canonical correspondence analysis (CCA) indicated that five variables contributed significantly to explaining patterns of diatom variation (i.e., COND, DIC, Mn, TPF, TPU). The first CCA axis (k ¼ 0.44) was primarily controlled by conductivity-related variables, while CCA axis 2 (k ¼ 0.21) was related to particulate concentrations. Diatom-based inference models were generated for the reconstruction of conductivity (RMSEPjack ¼ 0.32, r 2 jack ¼ 0.76) and pH (RMSEPjack ¼ 0.40, r 2 jack ¼ 0.69). The strengths of these models indicate that it will be possible to reliably infer past trends in conductivity and pH from diatom assemblages preserved in dated sediment cores from the Isachsen region.

Modelling the snow distribution at two high arctic sites at Svalbard, Norway, and at an alpine site in central Norway

In Arctic regions snow cover has a major influence on the environment both in a hydrological and ecological context. Due to strong winds and open terrain the snow is heavily redistributed and the snow depth is quite variable. This has a significant influence on the snow cover depletion and the duration of the melting season. In many ways these are important parameters in the climate change aspect. They influence the land surface albedo, the possibilities of greenhouse gas exchange and the length of the plant-growing season, the latter also being important for the arctic terrestrial fauna. The aim of this study is to test to what degree a numerical model is able to recreate an observed snow distribution in sites located in Svalbard and Norway. Snow depth frequency distribution, a snow depth rank order test and the location of snowdrifts and erosion areas were used as criteria for the model performance. SnowTran-3D is the model used in this study. In order to allow for occasions during the winter with milder climate and temperatures above freezing, a snow strengthening calculation was included in the model. The model result was compared to extensive observation datasets for each site and the sensitivity of the main model parameters to the model result was tested. For all three sites, the modelled snow depth frequency distribution was highly correlated to the observed distribution and the snowdrifts and erosion areas were located correspondingly by the model to those observed at the sites.

Limnological Characteristics of 22 Lakes and Ponds in the Haughton Crater Region of Devon Island, Nunavut, Canadian High Arctic

The physical and chemical limnological characteristics of 22 lakes and ponds in the remote region of Haughton Impact Crater, Devon Island, Nunavut, Canada, were explored. Our overall goals were to gather baseline information for use in climate and environmental change monitoring programs in the High Arctic as well as to compare these observations to other limnological surveys conducted in high-latitude regions. Study sites were alkaline (pHmean = 8.3), ultraoligotrophic (TPUmean = 3.7 μg L−1), and phosphorus limited. Major and minor ionic concentrations of most sites are comparable to other previously surveyed high arctic sites. Lakes and ponds in close contact with the impact-generated carbonate melt rocks associated with Haughton Crater were distinguished from the larger data set due to their elevated Mg2+, SO4 2−, Ba2+, Sr2+, and SiO2 concentrations. Selenite (CaSO4·2H2O) formations commonly associated with the lower levels of the carbonate melt sheets were identified as a likely source for the elevated SO4 2− concentrations in these sites. Principal Components Analysis separated sites along a conductivity and nutrient gradient on the primary and secondary axes, respectively. This study serves as a baseline for a long-term monitoring program in the Haughton Crater region.

Metabolic cold adaptation in arthropods: a smaller‐scale perspective

Metabolic cold adaptation in arthropods: a smaller‐scale perspective

Primary plant succession on recently deglaciated terrain in the Canadian High Arctic

AbstractAim Primary succession in a high arctic environment was examined to determine whether the patterns conform to models based on studies in temperate regions. The location also presented an unique opportunity to examine a well preserved pre‐Little Ice Age plant community and organically enriched palaeosol that are being released from the glacier along with the glacial and glaciofluvial sediments.Locations The main location was the recently deglaciated terrain of the Twin Glacier foreland at Alexandra Fjord, Ellesmere Island (79° N). The position of the glacier from air photos in 1959 and 1981, and periodic direct monitoring of the position of the terminus since 1980 provided good chronological control. Surveys of succession patterns were also conducted at four other sites in the Alexandra Fiord region of eastern central Ellesmere Island.Methods Vegetation cover of mosses and vascular plants (lichens were not present) was measured in 1994 and 1995 using a stratified random design. twinspan and canonical correspondence analysis were used together to examine successional vegetation patterns in relation to a set of environmental variables. Species richness, total vegetation cover, and a combined set of soil parameters (pH, organic matter content, moisture and fine substrate) were compared between the two principal soil types, palaeosol and glaciofluvial sediment.Results Terrain age accounted for most of the variation in species composition over the study area. The succession followed a directional‐replacement series with four main stages of dominance in at least 44 years: (1) mosses → (2) graminoid‐forb → (3) deciduous shrub‐moss → (4) evergreen dwarf‐shrub‐moss. There was little difference in species richness patterns over time on the palaeosol compared with the glaciofluvial sediment. However, total vegetation cover was significantly higher on palaeosol and there was a significant difference in a combined set of soil parameters between the two soil types, which indicates that palaeosol may provide conditions more favourable for establishment and growth.Main conclusions Directional‐replacement succession is possible in a high arctic oasis environment; however, this mode of succession is probably atypical of much more extensive high arctic environments such as polar deserts. Descriptive results from four other glacier forelands sampled in 1995 on east‐central Ellesmere Island showed directional succession with no species replacement at two sites and non‐directional succession without species replacement at another site. Primary succession in these high arctic sites is strongly controlled by local environmental conditions.

Resource allocation patterns in a forb and a sedge in two arctic environments—short‐term response to herbivory

The present work investigates C and N allocation patterns in two forage plants: a forb, Oxyria digyna, and a sedge, Eriophorum angustifolium, in subarctic Sweden and high arctic Canada. Short‐term changes in concentrations after simulated or natural herbivory (caused by Gynaephora groenlandica on Oxyria in the high arctic habitat) were also investigated. There were no clear differences in concentrations of C and N between the high arctic and subarctic sites in either species. In Oxyria of the subarctic habitat, the minimum N concentrations occurred at earlier phenological stages compared with plants in the high arctic habitat. Simulated herbivory increased the concentration of C in belowground tissues relative to those in control plants in Oxyria at the subarctic site, which may indicate increased allocation of non‐C compounds to the growing shoots or daughter ramets. Herbivory by Gynaephora groenlandica caterpillars increased the N concentrations of Oxyria both in aboveground and belowground tissues, possible indicating increased uptake of N in the high arctic habitat. Eriophorum did not show clear trends in concentrations relating to habitat, phenology or simulated herbivory. The difference between Oxyria and Eriophorum in their response to herbivory apparently resulted from contrasting growth habits between the species. Tiller death after reproduction and long leaf life span may be the main reasons for the lack of clear patterns in concentrations in Eriophorum. Compensation after herbivory may be attained by the early production of daughter tillers in Eriophorum instead of the regrowth of the damaged ramets, as in Oxyria. Monitoring the responses for only one season is apparently a too short time period in these long‐lived plants.