Devon Island Research Articles

A high resolution proxy-climate record from an arctic lake with annually-laminated sediments on Devon Island, Nunavut, Canada

Sediments from a 3 ha lake (75 °34.34′N, 89 °18.55′W) from the coastal region of northern Devon Island, Nunavut, Canada, contain discrete laminations in the deepest part of the basin. The laminations are varves as indicated by the correspondence between counts and thickness measurements of the couplets and 210Pb dating. A 14 cm core representing 150 years of sedimentation contained laminated couplets consisting of a lighter inorganic layer with a higher percentage of calcium and magnesium, alternating with fine darker bands, typically more cohesive, and comprising higher proportions of silica and carbon. A reddish oxidation zone with higher iron and aluminum frequently separates the laminations. The dark layer represents a biogenic component deposited in summer and is made cohesive by bacterial filaments among the other particles. The light inorganic layer represents clastic deposition from allochthonous sources. Deposition rates were relatively consistent through the core with an increase in varve thickness in the 1950s. Diatom concentrations in the sediments increased by two orders of magnitude in this century, with major increases in the 1920s and 1950s. The increase in varve thickness and diatom abundance coincides with an increase in summer melt percentage in an ice core from the Devon Island Ice Cap (Koerner, 1977). The relatively high sedimentation rate (0.15 cm yr-1) coupled with the consistency of deposition makes this lake a significant indicator for recent climate changes of the Canadian Arctic Archipelago.

Field Evidence for Wet-Based Ice Sheet Erosion from the South-Central Queen Elizabeth Islands, Northwest Territories, Canada

Glacial erosional features were studied in detail at three locations in the southcentral Queen Elizabeth Islands, Canada. Numerous striated bedrock outcrops, indicating ice flowing from the sea onto the coast, were discovered on BaillieHamilton Island, off the west coast of northern Devon Island. The consistency of obtained ice-flow directions indicates that thick, wet-based ice overrode the >200m-high island from northwest, west-northwest, and northeast, without topographic deflection. We conclude that this ice also flowed across the >300 m deep Queens and Wellington channels bordering Baillie-Hamilton Island. A similar conclusion was derived from striated bedrock outcrops on the northeast coast of North Kent Island, positioned between Devon and Ellesmere islands. Ice flowing from the northwest obliquely across Baillie-Hamilton and North Kent Islands, and from the northeast across Baillie-Hamilton Island, could not have emanated from local ice domes. Instead, these results are consistent with a large ice sheet covering the central and southern Queen Elizabeth Islands with an ice spreading center in the Norwegian Bay region. The timing of these events remains uncertain, but the degree of weathering of the striated outcrops indicates that both northwest and northeast ice-flow directions could be of late Wisconsinan age.

Nitrogen Mineralization, Nitrification, and Denitrification in a High Arctic Lowland Ecosystem, Devon Island, N.W.T., Canada

This study examined nitrogen (N) transformations in two sites at Truelove Lowland (Devon Island, NWT, Canada). The two sites (sedge meadow and willow/ herb hummocks) were located at the low end and midway along the beach ridgebasin topographic gradient typical of Truelove Lowland. Net N-mineralization and nitrification rates were measured using both field (late June through July) and laboratory incubations. Denitrification rates (July) were measured using the acetylene blockage technique. Natural abundance of 15N was analyzed in plant tissue and soils from both sites. Net N-mineralization rates in the field incubated cores were similar between the two sites, but were higher in the willow-herb hummock soils incubated in the laboratory. Nitrification and denitrification rates were significantly higher in the drier hummock site. Nitrogen stable isotope ratios (815N) from the hummock site were 1.82%o higher in soils, 1.20%o higher in moss, and 3.25%0 higher in Salix arctica leaves compared to ratios from the meadow site, consistent with the long-term enrichment of the 15N isotope in the hummock site resulting from higher nitrification and denitrification rates. Rates of nitrification along the beach ridge-basin gradient appear to be controlled primarily by differences in moisture, whereas denitrification rates are governed by nitrate concentration. Thus, topographic control of N transformations is both direct and indirect and is exerted on one, rather than multiple, points of the N cycle in this high arctic lowland ecosystem.

Nitrogen Mineralization, Nitrification, and Denitrification in a High Arctic Lowland Ecosystem, Devon Island, N.W.T., Canada

Nitrogen Mineralization, Nitrification, and Denitrification in a High Arctic Lowland Ecosystem, Devon Island, N.W.T., Canada

Quantitative Studies of Arctic Cod (<i>Boreogadus saida</i>) Schools: Important Energy Stores in the Arctic Food Web

Aggregations of Arctic cod (Boreogadus saida) in Allen Bay, on the southern coast of Cornwallis Island, Lancaster Sound were studied with fishery acoustics techniques in 1989 and 1990. Nonschooling fish were also examined in several Cornwallis and Devon Island bays. Although acoustic signal shading within the schools minimized abundance estimates (error may exceed 50%), measurements in 1989 indicated that two aggregations of adult Arctic cod together comprised at least 900 million individuals. Combined surface area of these two schools was 59 hectares, and total biomass was 30 715 tonnes (520 t/ha). Mean density in one school was 91 fish/cu m. In the other it was 307 fish/cu m, each fish occupying a space equivalent to about one body length cubed. A smaller school studied in the same location a year later had a mean density of 72 fish/cu m. Mean length of net-captured fish from that school was 18.7 cm (TL), and mean weight was 44.5 g. School surface area was about 4.6 hectares, and it contained an estimated 2835 t of biomass (616 t/ha). Given that significant concentrations of biomass occurred in this small portion of the Lancaster Sound region, we concluded that, in theory, sufficient biomass was sequestered in fish schools within the region to support energy flows through the food web. Acoustic measurements indicated that fish at a school edge were larger (target strength [TS] = -44.7 dB, equivalent size = 19.3 cm) than nonschooling fish elsewhere (TS = -53.4 dB, equivalent size = 8.4 cm). Zooplankton abundance near a school was markedly reduced. Near Cornwallis Island, where water temperatures throughout the water column were >-1.3 C, fish were scattered from surface to bottom. But near Devon Island, fish were common only in warmer surface waters (>2.0 C) above a marked thermocline at about 35 m, but not deeper, where water temperature was -1.5 C.

Plant Communities of Archaeological Sites, Abandoned Dwellings, and Trampled Tundra in the Eastern Canadian Arctic: A Multivariate Analysis

Arctic terrestrial ecosystems subjected to anthropogenic disturbance return to their original state only slowly, if at all. Investigations of abandoned settlements on three islands in the eastern Canadian Arctic Archipelago have detected striking similarities among contemporary and ancient human settlements with regard to their effects on tundra vegetation and soils. Ordination procedures using 240 quadrats showed the plant assemblages of Thule (ca. 800 B.P.) winter dwellings on northern Devon and southern Cornwallis Islands to be floristically similar to pedestrian-trampled meadows on northeast Baffin Island last used ca. 1969. Comparisons from the literature made with other North American sites in the Low Arctic reveal similar findings. The implication is that the depauperate flora of the Arctic has a limited number of species able to respond to disturbance, and that anthropogenically disturbed patches may be extremely persistent.

Thermal Maturity of Lower Paleozoic Sedimentary Successions in Arctic Canada

Mean maximum graptolite reflectance values from numerous sections in Arctic Canada range from 0.6% in Cornwallis Island and northwestern Devon Island to 4.7% in Ellesmere Island. We attribute this great lateral reflectance variation to differing burial depths of the graptolite-bearing strata beneath thick synorogenic siliciclastic covers. We attribute the low maturity of rocks in northern Cornwallis and eastern Bathurst islands to a maximum burial of about 2 km. Elsewhere, we used the paleogeographic location and proximity to the Ellesmerian overthrust wedge to interpret the measured reflectance values. In northern Ellesmere Island, where the highest graptolite reflectance values (4.7%) occur, as much as 9.6 km of synorogenic siliciclastics accumulated on a tectonically loaded carbonate shelf. Initial synorogenic siliciclastics encountered substantial submarine-to-basin relief, and thus about 2 km of sediment were deposited prior to the initiation of deposition on the adjacent drowned shelf. Also, the deep-water sequence probably was underlain by attenuated continental crust adjacent to the southeastward-advancing Ellesmerian overthrust wedge. Together, these factors caused deposition of as much as 7.6 km of sediment in western Melville Island and, as much as 9.6 km in northeastern Ellesmere Island. On the drowned shelf, synorogenic stratal thicknesses were less, a feature we attribu e to a thicker, more rigid crustal sequence and greater distance from the Ellesmerian tectonic loading. We expect liquid hydrocarbons to be generated from the organic matter in the shales in areas with a graptolite R0 maximum (GR0 max) of less than 1.7%. The presence of two types of solid bitumens having different reflectances, morphologies, and optical textures suggests that hydrocarbons were generated and migrated through the graptolite-bearing strata. We expect only gaseous hydrocarbons in areas where GR0 max exceeds 2.0% R0.

Rotifers from the Canadian high arctic (Devon Island, Northwest territories)

Rotifers from the Canadian high arctic (Devon Island, Northwest territories)

An Annotated List of Testate Amoebae Observed in the Arctic between the Longitudes 27° E and 168° W

Summary A geographic database is presented of the occurrence of the 220 testate amoebae taxa observed by the authors in the Arctic between the longitudes 27°E and 168°W. Visited and studied were localities in Svalbard (West Spitsbergen, Edgeoya, Barentsoya, Hopen, Bear Island), Jan Mayen, Greenland (Angmagssallik and Sondre Stromfjord region), Canada (Devon Island, Victoria Island), and Alaska (Barrow and Nome regions). The number of samples analysed was 1142. For each region, information is given on the occurrence of the taxa in different habitats. Browsing the data from other authors completes this protistological list with 71 taxa not seen by us, resulting thus in a total of 291 testate amoebae taxa known from the Arctic.

Balizoma and the new genera Aegrotocatellus and Perirehaedulus: Encrinurid trilobites from the Douro Formation (Siluiran, Ludlow) of the central Canadian Arctic

Species of two new genera of Encrinuridae occur in the Ludlow Douro Formation at Goodsir Creek, Cornwallis Island, Gamier Bay, Somerset Island, and Prince Alfred Bay, Devon Island. The encrinurine Aegrotocatellus n. gen. includes four highly autapomorphic species, and is most closely related to Balizoma Holloway, 1980. Separate taxa are recognized at low and high stratigraphic intervals at Goodsir Creek (the type species, Aegrotocatellus jaggeri n. gen. and sp., and Aegrotocatellus n. sp. A, respectively), at Gamier Bay (Aegrotocatellus n. sp. B), and at Prince Alfred Bay (Aegrotocatellus nankerphelgeorum n. gen. and sp.). Perirehaedulus n. gen. is a coronocephaline most closely related to the Chinese upper Llandovery taxon Kailia Chang, 1974. The type species, Perirehaedulus caprus (Thomas in Thomas and Narbonne, 1979) from Goodsir Creek, is distinct from P. richardsi n. gen. and sp. at Garnier Bay. The upper Wenlock–Ludlow range of Balizoma is extended into the Arctic by Balizoma aff. B. variolaris (Brongniart, 1822) from Homerian rocks of the Cape Phillips Formation near Abbott River, Cornwallis Island, and by Balizoma sp., from the late Ludlow Douro Formation at Goodsir Creek.

The Water Relations of Carex stans in Wet Sedge-Moss Tundra at a High Arctic Oasis, Devon Island, N.W.T., Canada

The Water Relations of <i>Carex stans</i> in Wet Sedge-Moss Tundra at a High Arctic Oasis, Devon Island, N.W.T., Canada

The Water Relations of Carex stans in Wet Sedge-Moss Tundra at a High Arctic Oasis, Devon Island, N.W.T., Canada

In the eastern Canadian High Arctic, wet sedge-moss tundras, dominated by Carex stans, are usually associated with oases where ameliorated physical conditions allow relatively high plant production. Although Carex stans occurs in water-saturated soils, low transpiration rates, stomatal conductances and leaf water potentials indicated that mild water stress was common in this species. Low transpiration rates under conditions of relatively high solar irradiance and air temperature resulted in leaf temperatures up to 10'C higher than that of the air. Trends in transpiration rate closely followed those in solar irradiance, air and leaf temperature and the leaf-to-air vapor pressure difference. Transpiration also exhibited significant positive correlations with soil temperature and wind speed. The maximum stomatal conductance in Carex stans (0.16 mol m-2 S-1) was considerably lower than maxima reported for polar semidesert graminoids; furthermore, the maximum rate in Carex was seldom achieved. Stomatal conductance showed strongest positive correlations with solar irradiance, leaf temperature, and leaf-toair temperature and vapor pressure differences, and showed a strong negative correlation to soil temperature at -10 cm. Carex leaf water potentials ranged from -0.65 to -2.26 MPa, suggesting a water status more characteristic of polar semidesert graminoids than those of wet tundra. Leaf water potential was most highly correlated with air temperature and air vapor pressure deficit. Several anomalous relationships between stomatal conductance and other variables were observed. For example, stomatal conductance did not respond to changes in leaf water potential, was insensitive to changes in air vapor pressure deficit and was positively correlated with the leaf-to-air vapor pressure difference when a negative correlation was expected. Water stress in Carex stans is hypothesized to result from low soil temperatures and poor soil aeration, characteristics of sedge-moss meadows which result from their waterlogged condition. Several studies have reported that productivity of wet graminoid tundra remains constant from year to year despite considerable annual variation in thermal inputs. We propose that in relatively warm summers, high arctic tundras dominated by Carex stans show no increased productivity due to greater instances of water stress and stomatal closure.

Factors Controlling Soil Development on a Sequence of Raised Beaches, Truelove Lowland, Devon Island, N.W.T., Canada

A random stratified sampling design was used on soils formed on the crests of a sequence of raised beaches in Truelove Lowland, Devon Island, N.W.T., to determine if time is the principal factor in soil development. Two hundred and eighty-eight bulk soil samples were collected from three depth intervals on 24 beaches; 14 soil properties were determined for each sample. An analysis of variance showed that most soil properties varied systematically and not by error or inherent random variations within and among beaches. Regression modelling and cluster analysis, however, revealed that soil development was discontinuous and not a direct function of time, while canonical discriminant analysis revealed that soil properties associated with parent material weathering were the principal discriminating variables. A random sample of the stone fraction revealed that, regardless of age, soils formed on beaches dominated by calcareous lithologies had developed a fine-textured and organic-rich solum, while the sola formed on beaches dominated by metamorphic and igneous lithologies are coarse textured and more poorly developed. Beach lithologies in Truelove Lowland appear to have been controlled by the lithology of adjacent rock outcrops that were progressively exposed to marine action at the time of coastal emergence. Consequently, parent material, not time, has been the principal factor influencing the degree of pedogenesis on this sequence of beaches.

Dacampia hookeri New to the American Arctic

The lichenicolous fungus Dacampia hookeri (Borrer) Massal. is reported new to the American Arctic from Devon Island, Northwest Territories.

Melt features in ice cores from Site J, southern Greenland: some implications for summer climate since AD 1550

Horizontal and vertical distributions of melt features (ice layers) were examined using two ice cores (206.6 and 101.5 m deep, 1 m apart) from Site J (66°51.9′ N, 46°15.9′W, 2030 m a.s.l.). The temperature at 10 m was −16.3°C. We observed 2804 melt features, with a total thickness of 30.32 m, in the 206.6 m core, corresponding to 16.4% by volume of the ice-equivalent core length. Horizontal distribution of melt features was examined by correlating melt-feature thicknesses in the two cores. The correlation coefficient was 0.71 (n = 514) for each melt feature in the two cores. It was maximum for data passed through 5 and 40 year low-pass filters. A significant relationship (P = 0.005, n = 36) was obtained for the vertical distribution of melt features and the June temperature on the west coast of Greenland (Jakobshavn). Using this, June temperatures at Jakobshavn since 1550 were estimated. There are three periods (1685-1705, 1835-70 and 1933-45) during which mean June temperatures clearly decreased, when they were estimated to he 0.1°, 0.4° and 0.2°C lower than the average for the whole period (1550-1989). The first two “cold” periods have been identified in melt features of the Dye 3 and Devon Island ice cores and in a tree-ring profile from Yukon Territory, Canada. Melt-feature percentages in the Site J ice core have increased since about 1945, probably reflecting summer-temperature warming on the ice sheet.

Melt features in ice cores from Site J, southern Greenland: some implications for summer climate since AD 1550

Horizontal and vertical distributions of melt features (ice layers) were examined using two ice cores (206.6 and 101.5 m deep, 1 m apart) from Site J (66°51.9′ N, 46°15.9′W, 2030 m a.s.l.). The temperature at 10 m was −16.3°C. We observed 2804 melt features, with a total thickness of 30.32 m, in the 206.6 m core, corresponding to 16.4% by volume of the ice-equivalent core length. Horizontal distribution of melt features was examined by correlating melt-feature thicknesses in the two cores. The correlation coefficient was 0.71 (n = 514) for each melt feature in the two cores. It was maximum for data passed through 5 and 40 year low-pass filters. A significant relationship (P = 0.005, n = 36) was obtained for the vertical distribution of melt features and the June temperature on the west coast of Greenland (Jakobshavn). Using this, June temperatures at Jakobshavn since 1550 were estimated. There are three periods (1685-1705, 1835-70 and 1933-45) during which mean June temperatures clearly decreased, when they were estimated to he 0.1°, 0.4° and 0.2°C lower than the average for the whole period (1550-1989). The first two “cold” periods have been identified in melt features of the Dye 3 and Devon Island ice cores and in a tree-ring profile from Yukon Territory, Canada. Melt-feature percentages in the Site J ice core have increased since about 1945, probably reflecting summer-temperature warming on the ice sheet.

Crustal thickness variations between the Greenland and Ellesmere Island margins determined from seismic refraction

Two densely sampled marine refraction lines were shot in northern Baffin Bay on the shelves of Devon and Ellesmere islands (North American plate) and Greenland (Greenland plate). A total of 11 ocean-bottom seismometers recorded the airgun signals. The processed data were analyzed by the use of ray tracing and amplitude modelling. Two-dimensional models were derived that reproduce the characteristics of the observed data. A 5 km deep sedimentary basin was identified on the south end of line 3. On both lines the crustal velocity has a range of 5.7–6.6 km/s. Midway along the line on the shelf of Devon and Ellesmere islands, the Moho shallows abruptly northward from 27 to 20 km. The thinned crust is not overlain by a sedimentary basin to compensate for the elevated Moho, suggesting this is not an extensional feature. The thickness of the crust adjacent to northwest Greenland increases from south (22 km) to north (37 km). The thickening occurs in two stages: a sharp increase in the depth to Moho northwest of the sedimentary basin followed by a gradual deepening to the end of the line. The thin crust on the shelf of Ellesmere Island is located adjacent to the thick crust of Greenland. Plate reconstructions based on regional magnetic anomalies and transform faults indicate that Greenland is a separate plate. The crustal structure revealed by seismic refraction and reflection profiles and the variations in the depth to Moho are consistent with the plate boundary occurring between the refraction lines.

The patterning of plant communities and edaphic factors along a high arctic coastline: implications for succession

Isostatic rebound and the periodic development of ice-push beach ridges have created topography suitable for development of biologically rich polar oases along the northeast coast of Devon Island, Canada. Distinct patterning of both plant communities and edaphic factors from coastal shoreline areas inland indicate primary succession with a directional species replacement At Rocky Point (emergent &lt; 2000 BP) biological development along the shore is initiated by marine algae that are invaded by cyanobacteria. These organic mats are colonized by Puccinellia on the shoreline of these brackish lagoons. Where the topography grades upslope, via concave areas, the toposequence from Puccinellia proceeds through Dupontia → Carex → Salix hummocks → cushion plant–lichen communities. In drier, convex areas Puccinellia proceeds through rosette-herb hummocks → cushion plant–lichen communities as a toposequence. Reduced levels of salinity and of nitrogen fixation upslope (from the shore) along with increased depth of organic soils and ability of soils to hold more soil water appear important in the conversion of Puccinellia- to Dupontia- to Carex-dominated meadows. This is the major chronosequence at Rocky Point and it is these Carex meadows that occupy most of the wetlands of Truelove Lowland. The Salix hummocks and cushion plant–lichen communities of all drier habitats resemble communities of similar species composition on the beach ridges of the lowland. Key words: arctic Canada, succession, plant communities, soil factors, polar oasis.

Nitrogen fixation and photosynthesis in high arctic forms of Nostoc commune

Nostoc commune, a colonial cyanobacterium, has been suggested as an important contributor of nitrogen to terrestrial ecosystems in the Canadian High Arctic, yet little is known about the ecophysiology of this organism in arctic environments. This study focused on the physiological performance of macroscopic colonies of N. commune found on Devon Island, N.W.T. The objectives were to examine the influence of temperature, colony morphology, and seasonal phenology on nitrogen fixation rates and the effects of light and temperature on photosynthesis. Maximum rates of acetylene reduction in N. commune (2119 nmol C2H4∙g−1∙h−1) were higher than those previously recorded for arctic N. commune but lower than values reported for temperate poulations. Depending on the time of the growing season, the temperature optimum for acetylene reduction varied from 15 °C to greater than 20 °C. Photosynthetic temperature optima did not occur below 20–25 °C (the highest temperatures measured). Light saturation of photosynthesis was reached at low levels of irradiance (100–150 μmol∙m−2∙s−1 PPFD). Acetylene reduction rates varied strongly with colony morphology. Thin, fragile, flattened colonies had higher rates than thicker, more resilient, flattened colonies or spherical colonies. Cold post-thaw temperatures appeared to delay the recovery of maximum nitrogen fixation rates for 2–3 weeks following the onset of the growing season. Compared with two other species of cyanobacteria present on Truelove Lowland (Gloeocapsa alpina and Gleotrichia sp.), N. commune had higher rates of nitrogen fixation. Key words: Nostoc commune, cyanobacteria, High Arctic, nitrogen fixation, photosynthesis.

On the Habitat Specificity of the Testate Amoebae Assemblages from Devon Island (NWT, Canadian Arctic), with the Description of a New Species: Difflugia ovalisina

Summary A classification analysis of samples from different habitats demonstrates the importance of some ubiquistic and cosmopolitic taxa in high arctic environments. The number of habitat specific assemblages was found to be rather low: only 6 out of 18 recognized assemblages could be linked to a specific habitat. These assemblages are: for the soils, the Plagiopyxis callida assemblage; for the moss habitats, the Assulina muscorum — Corythion dubium , and the Euglypha rotunda assemblages; for the aquatic habitats, the Trinema lineare and the Paraquadrula irregularis — P. penardi assemblages. A new species, Difflugia ovalisina , is described.