Cornwallis Island Research Articles

UPPER WENLOCK CERATOIKISCIDAE (RADIOLARIA) FROM THE CAPE PHILLIPS FORMATION, ARCTIC CANADA

Abstract Taxa belonging to the Ceratoikiscidae are described in detail from two measured sections of Member C of the Cape Phillips Formation exposed along Rookery Creek, Cornwallis Island, Arctic Canada. The sections encompass uppermost Sheinwoodian (top lower Wenlock) to the base of the Gorstian (base Ludlow) and are dated by graptolites assigned to the Cyrtograptus perneri–Monograptus opimus Zone (upper Sheinwoodian), the Cyrtograptus lundgreni Zone (lower Homerian), and the Colonograptus praedeubeli–Colonograptus deubeli Zone (upper Homerian). Radiolarians are found in great abundance throughout the lower Homerian, allowing for the establishment of the first appearance of the genus Helenifore Ormiston and Nazarov. Helenifore is emended to accommodate the Silurian species H. quadrispina n. sp. and H. speciosus (Furutani 1990). One new genus, Kappaforma, including the new species, K. insecta, is described, as is the new species H. quadrispina. Ceratoikiscum octapleura Renz and C. armiger Furutani are syn...

Evaluating diatom community composition in the absence of marked limnological gradients in the high Arctic: a surface sediment calibration set from Cornwallis Island (Nunavut, Canada)

Fossil diatom assemblages preserved within the sedimentary record in Arctic lakes provide the potential to reconstruct past changes in important limnological variables. During the summers of 1992 and 1993, we examined previously unstudied freshwater ecosystems on Cornwallis Island, Arctic Canada, with the specific objectives of (1) documenting the limnology and modern diatom assemblages from this region, and (2) determining which environmental variables most influence diatom species distributions. The Cornwallis Island study sites displayed the least amount of variance in measured water chemistry variables in comparison to nearly all of our labs’ previous freshwater surveys in the Arctic. The small limnological gradients precluded the development of a statistically robust diatom inference model, but perhaps more importantly, allowed us to explore variations in diatom composition in the absence of marked variations in water chemistry. Diatom species turnover was minimal, with the most common diatom taxa being Achnanthidium minutissima, Nitzschia perminuta, N. frustulum, with lesser percent abundances of Chaemaepinnularia soehrensis, Navicula chiarae, Psammothidium marginulata, and A. kryophila. A small number of study sites differed from the majority with respect to water chemistry (e.g., coastal sites with high specific conductivities) and habitat availability (e.g., ephemeral ponds with extensive moss habitats), and these sites had markedly different diatom assemblages. These data reinforce previous observations that water chemistry and other climate-related factors are the primary environmental controls influencing diatom distributions at high latitudes.

Structural geology and Zn-Pb mineral occurrences of northeastern Cornwallis Island: implications for exploration of the Cornwallis Fold Belt, northern Nunavut

Abstract The Stuart River and Caribou Lake areas of northeastern Cornwallis Island, Nunavut are dominated by Middle Ordovician to Upper Silurian carbonate and shale, and Lower to upper Middle Devonian carbonate and sandstone. These units have been thrust faulted and have undergone multiple phases of folding. Four deformational events are recognized. D1 develops NNW-SSE trending F1 folds and associated thrusts in Ordovician and Silurian strata. D1 is correlative with movement on the Boothia Uplift (Late Silurian-Early Devonian). D2 develops F2 folds and west-directed thrust faults that are co-axial with F1 but affect late Middle Devonian and older strata. D3 exhibits east-west trending F3 folds and is correlated with the Ellesmerian Orogeny (Late Devonian to Early Carboniferous). F3 folds re-fold F1/F2 folds creating interference patterns at a variety of scales. D4 is defined by northwest-southeast trending F4 folds. F4 folds overprint F1/F2 folds, and are unaffected when axial surfaces of F3 are crossed. D4 may possibly be associated with the Paleogene Eurekan Orogeny. Hydrothermal dolomite and Zn-Pb mineralization are strongly controlled by pre-exisiting structures. Specifically, they correlate most commonly with thrusts (preferentially east-directed thrusts) and along the hinge surface traces of regional F3 folds.

Mercury distribution, partitioning and speciation in coastal vs. inland High Arctic snow

Atmospheric mercury deposition on snow at springtime has been reported in polar regions, potentially posing a threat to coastal and inland ecosystems receiving meltwaters. However, the post-depositional fate of Hg in snow is not well known, and no data are available on Hg partitioning in polar snow. During snowmelt, we conducted a survey of Hg concentrations, partitioning and speciation in surface snow and at depth, over sea ice and over land along a 100 km transect across Cornwallis Island, NU, Canada. Total Hg concentrations [THg] in surface snow were low (less than 20 pmol L −1) and were significantly higher in marine vs. inland environments. Particulate Hg in surface snow represented up to 90% of total Hg over sea ice and up to 59% over land. At depth, [THg] at the snow/sea ice interface (up to 300 pmol L −1) were two orders of magnitude higher than at the snow/lake ice interface (ca. 2.5 pmol L −1). Integrated snow columns, sampled over sea-ice and over land, showed that particulate Hg was mostly bound to particles ranging from 0.45 to 2.7 μm. Moreover, melting snowpacks over sea ice and over lake ice contribute to increase [THg] at the water/ice interfaces. This study indicates that, at the onset of snowmelt, most of the Hg in snow is in particulate form, particularly over sea ice. Low Hg levels in surface snow suggest that Hg deposited through early spring deposition events is partly lost to the atmosphere from the snowpack before snowmelt. The sea ice/snow interface may constitute a site for Hg accumulation, however. Further understanding of the cycling of mercury at the sea ice/snow and sea ice/seawater interfaces is thus warranted to fully understand how mercury enters the arctic food webs.

Perfluoroalkyl Contaminants in the Canadian Arctic: Evidence of Atmospheric Transport and Local Contamination

Perfluorosulfonates (PFSAs) and perfluorocarboxylates (PFCAs) have been hypothesized to reach remote locations such as the Canadian Arctic either indirectly as volatile precursor chemicals that undergo atmospheric transport and subsequent degradation, or directly via oceanic and atmospheric transport of the PFSAs and PFCAs themselves. Water, sediment, and air samples were collected from three Arctic lakes (Amituk, Char, and Resolute) on Cornwallis Island, Nunavut, Canada. Samples were analyzed for PFSAs and PFCAs, precursor chemicals including the fluorotelomer alcohols (FTOHs) and polyfluorinated sulfonamides (FSAs), and precursor degradation products such as the fluorotelomer unsaturated carboxylates (FTUCAs). PFSAs and PFCAs were detected in water and sediment of all three Arctic lakes (concentrations ranged from nondetect to 69 ng/L and nondetect to 85 ng/g dry weight, respectively). FTOHs and FSAs were observed in air samples (mean concentrations ranged from 2.8 to 29 pg/m3), and confirm that volatile precursors are reaching Arctic latitudes. The observation of degradation products, including FTUCAs observed in sediment and atmospheric particles, and N-ethyl perfluorooctanesulfonamide (NEtFOSA) and perfluorooctanesulfonamide (PFOSA) in air samples, indicate that degradation of the FTOHs and FSAs is occurring in the Arctic environment. PFSAs and PFCAs were also observed on atmospheric particles (mean concentrations ranged from < 0.1 to 5.9 pg/m3). In addition, results of this study also indicate that local perfluoroalkyl contamination of Resolute Lake, which is located downstream of an airport wastewater input, has occurred.

BIOGEOCHEMICAL TOXICITY AND PHYTOTOXICITY OF NITROGENOUS COMPOUNDS IN A VARIETY OF ARCTIC SOILS

Ammonium nitrate (NH(4)NO(3)) is a common water pollutant associated with many industrial and municipal activities. One solution to reduce exposure of sensitive aquatic systems to nitrogenous compounds is to atomize (atmospherically disperse in fine particles) contaminated water over the Arctic tundra, which will reduce nitrogen loading to surface water. The toxicity of ammonium nitrate to Arctic soils, however, is poorly understood. In the present study, we characterized the biogeochemical toxicity and phytotoxicity of ammonium nitrate solutions in four different Arctic soils and in a temperate soil. Soil was exposed to a range of ammonium nitrate concentrations over a 90-d period. Dose responses of carbon mineralization, nitrification, and phytotoxicity endpoints were estimated. In addition to direct toxicity, the effect of ammonium nitrate on ecosystem resilience was investigated by dosing nitrogen-impacted soils with boric acid. Ammonium nitrate had no effect on carbon mineralization activity and only affected nitrification in one soil, a polar desert soil from Cornwallis Island, Northwest Territories, Canada. In contrast, ammonium nitrate applications (43 mmol N/L soil water) significantly impaired seedling emergence, root length, and shoot length of northern wheatgrass (Elymus lanceolatus). Concentrations of ammonium nitrate in soil water that inhibited plant parameters by 20% varied between 43 and 280 mmol N/L soil water, which corresponds to 2,100 to 15,801 mg/L of ammonium nitrate in the application water. Arctic soils were more resistant to ammonium nitrate toxicity compared with the temperate soil under these study conditions. It is not clear, however, if this represents a general trend for all polar soils, and because nitrogen is an essential macronutrient, nitrogenous toxicity likely should be considered as a special case for soil toxicity.

The Centre of the World: Robert McGhee’s Inter-Connected Actic

Centre of World: Robert McGhee's Inter-Connected Actic Last Imaginary Place: A Human History of Arctic World. By Robert McGhee. Toronto: Key Porter Books; Gatineau, QC: Canadian Museum of Civilization, 2004. 296 pp. $39.95 (hardcover). ISBN 1-55263-637-2. Ian MacRae As those who have researched in far North will know, Polar Continental Shelf Project (PCSP), from its base in resettled community of Resolute Bay (Qaussittuq) on Cornwallis Island, provides much of ground and air support for field work in Canadian High Arctic. PCSP control room can be a high-stress and high-stakes place, where Twin Otters and helicopters are deployed across thousands of kilometres of formidable terrain under fickle and often treacherous conditions. One afternoon a few years ago I was at PCSP, checking weather on Ellesmere Island, waiting to fly out to Alexandra Fiord, and as I waited I couldn't help but overhear station's chief operator who, in between firing off directions and co-ordinates to far-off pilots and ground crews into his headset-umbilicus, busily moving people and fuel and gear across Arctic archipelago, was humming old Janis Joplin tune, Me and Bobby McGee. Robert McGhee was out there somewhere, he told me, digging through a pile of old bones. It was not a slight but an homage, one that should serve as introduction enough for an eminent Canadian archaeologist, curator of Arctic Archeology at Canadian Museum of Civilization, and for his latest book-length work, Last Imaginary Place: A Human History of Arctic World (2004). If they are singing about you at PCSP, then this is good enough for me. Last Imaginary Place is a book that is truly circumpolar in scope and articulation. A compendium of some 35 years of thinking and travelling and working in Arctic, it has feel of a summarizing effort, one that treats deep patterns of climate and language and flows of goods and people across top of world. Its structure is episodic, with each of 12 chapters treating a specific region and time (the first two more generally than rest), such that entire Arctic region is covered. chapters are only loosely linked into an overall thesis, which slowly emerges as evidence accumulates, that Inuit are not a timeless, isolated, primeval people, but are our contemporaries, alive in this same historical time. Along with other northern peoples, asserts McGhee, Inuit are active participants in globalized flows of resources and economy, and are well prepared and equally willing today to manage their relationships with modern world, as indeed they always have been: The small nations of north have histories as long and as complex as those of more southerly peoples, a fact that archaeologists are continually and surprisingly demonstrating (McGhee 2004, 41). establish a baseline for his argument, McGhee reaches back to beginnings of Homo erectus in Africa, and moves forward through warming and cooling events that have impacted human and animal migrations throughout time. He traces Western perceptions of Arctic in ancient Greek thought, apocryphal escapades of Irish monk St. Brendan, Norse and their societies in Iceland and Greenland, Basque whalers and French fur traders, and English and vanity of their follies in a frozen world. Inuit shamanism and beauty, security and comfort (35) of Arctic life for hunting peoples are considered, as are European voyagers such as Thomas Hearne (who wins some respect travelling overland with Dene) and Martin Frobisher (who, mining for gold on a bleak Arctic island, gains little). Peary and Cook and their race to pole are taken up, with emphasis on support of Inughuit, local Inuit of northwestern Greenland, unsung Sherpas of north. McGhee is clear in his conclusion that Arctic has largely served as a foil, a blank screen for West to project its fears of death and imaginings of paradise: To most southerners, says McGhee, the Arctic remains what it was to their counterparts centuries and perhaps even millennia ago: ultimate otherworld (19). …

Hypolithic Colonization of Opaque Rocks in the Arctic and Antarctic Polar Desert

The colonization of the underside of rocks normally requires that the material is sufficiently translucent to allow the penetration of photosynthetically active radiation. We examined the underside of 950 opaque rocks in sixteen locations in the Arctic for hypolithic colonization by photosynthetic microorganisms. Greater than 90% of rocks were colonized. The mean width of the bands of colonization was 3.1 ± 1.9 cm on Devon Island, and 3.0 ± 1.6 cm on Cornwallis Island. The width of the bands of colonization was less in the interior of frost-sorted polygons compared to their edges (in the arctic location, 0.7 ± 0.8 and 3.6 ± 1.4 cm in the interior and at the edges, respectively), suggesting the importance of frost sorting in enhancing the penetration of light around the edges of rocks to their undersides, and thus allowing colonization by photosynthetic organisms. We observed a similar pattern of colonization in antarctic polygons. The hypolithic habitat provides protection from environmental extremes. We show that within the hypolithic habitat organisms are protected from UV radiation. From radiolabeled carbon uptake measurements we estimate the productivity of the arctic communities to be approximately 0.8 g m−2 a−1, potentially as high as above-ground productivity. We discuss the potential implications of climate change for these communities.

Carbon isotope chemostratigraphy of the Llandovery in Arctic Canada: Implications for global correlation and sea-level change

Stratigraphic and δ13C data from the Rhuddanian to lower Telychian succession on Cornwallis Island, Arctic Canada show evidence of a significant positive δ13C excursion in the upper Aeronian and weak positive shifts in the mid-Rhuddanian and uppermost Rhuddanian—lower Aeronian. The lower and upper Aeronian levels coincide with times of continental glaciation in Gondwana and these can be correlated with events recorded in the δ13C records from Dob's Linn (Scotland), Anticosti Island (Quebec), and Estonia. In most instances in the C-isotope records appear to coincide closely with local sea-level changes. The available data suggest that the global environmental impact of the late Aeronian glaciation was greater than that of the early Aeronian event. The data support the hypothesis that changes in degree of carbonate platform exposure and weathering resulting from of a combination of local and global (glacioeustatic) sea-level changes (particularly sea-level fall) were an important controlling factor in the generation of positive δ13C excursions in this time interval. These changes shifted the isotope value of the C-weathering flux entering shelf seas, which in turn resulted in positive δ13C excursions of varying magnitudes in shelf and deep basinal settings. These varied regionally in magnitude in close correspondence with differences in local sea-level histories.

Recent Summer Climate Recorded in Complex Varved Sediments, Nicolay Lake, Cornwall Island, Nunavut, Canada

The recent (1950–1996) varve record from the proximal sediments in Nicolay Lake, Cornwall Island, Nunavut, Canada (77°46′ N, 94°40′ W) contains distinct subannual rhythmites. Deposition of these subannual rhythmites is due primarily to nival snow melt, with additional sedimentary units resulting from major summer precipitation and subaqueous mass wasting events. In order to evaluate the potential hydroclimatic signal contained in the varves from the unglacierized catchment, the nival deposition record was estimated by delineating the initial subannual rhythmite within each varve. When the record is split into temporal segments based on two phases that exhibit different sediment deposition patterns in the lake, the nival rhythmites are significantly correlated to annual cumulative melting degree days (MDD) from the nearest weather station Isachsen (78°47′ N, 103°32′ W) (1950–1962 AD and 1963–1977 AD with r = 0.55 and r = 0.82, respectively). A similar analysis with data from Resolute (74°43′ N, 94°59′ W) yields slightly weaker correlations (1950–1962 AD, r = 0.60; 1963–1994, r = 0.59). The strong positive correlation with both the Isachsen and Resolute thermal records suggests that the paleoclimatic signal in the sediments reflects regional climate conditions. Notably, the signal is strongest when the entire melt season is considered; weaker correlations with instrumental weather records are associated with comparisons limited to the peak melt or early season melt periods. We attribute this to the ongoing supply of snowmelt through the season in this polar region and the availability of sediment for transport throughout the melt season. These results indicate that a high resolution hydroclimatic signal is present in the sediments from Nicolay Lake and can be used for paleoclimate reconstruction provided sedimentary depositional controls are taken into account.

HAPLOTAENIATUMIDAE AND INANIGUTTIDAE (RADIOLARIA) FROM THE LOWER SILURIAN OF THE CAPE PHILLIPS FORMATION, CORNWALLIS ISLAND, NUNAVUT, CANADA

Radiolaria of the families Haplotaeniatumidae Won, Blodgett, and Nestor, 2002 and Inaniguttidae Nazarov and Ormiston, 1984 were recovered from the Llandovery and lower Wenlock of the Cape Phillips Formation on Cornwallis Island, Nunavut, Canada. Three new species of haplotaeniatumids are described. Haplotaeniatum fissura n. sp. is diagnosed by a densely constructed outer layer around a less dense interior; Haplotaeniatum nunavutensis n. sp. has small, circular pores separated by wide lattice bars; and Orbiculopylorum granti n. sp. possesses robust external spines. Haplotaeniatumids described in open nomenclature are Haplotaeniatum labyrintheum?, Haplotaeniatum aff. cathenatum, Haplotaeniatum cf. raneatela, Haplotaeniatum species A, Orbiculopylorum aff. adobensis, Orbiculopylorum cf. marginatum and Orbiculopylorum species A. Gyrosphaera Noble and Maletz, 2000 is synonymized with Haplotaeniatum. The Inaniguttidae are assigned to Plussatispila n. gen. The genus is diagnosed by two, well-spaced lattice shells and at least seven main spines; additional shells may be present. Plussatispila magnilimax n. sp. has a total of four shells, and P. cornwallisensis n. sp. a total of three. Plussatispila delicata n. sp. has only the two fundamental shells of the genus and is slightly more delicate than the other inaniguttids. Plussatispila pellicia n. sp. possesses weakly developed spines and may have additional irregular layers.

The paradox of the global standard Late Ordovician–Early Silurian sea level curve: Evidence from conodont community analysis from both Canadian Arctic and Appalachian margins

Relative sea level fluctuations in the Late Ordovician–Early Silurian were largely driven by Gondwana deglaciation, three possible short-lived ice readvances, and the closure of the Iapetus Ocean. This study establishes and compares sea level events on the Canadian Arctic and Appalachian margins of Laurentia based on the pattern of conodont communities, and demonstrates that sea level events were not synchronous on the two margins. Conodont data were compared for a) the Arctic margin from the Cape Phillips Formation (Richmondian, Upper Ordovician through lower Sheinwoodian, Lower Silurian), Cornwallis Island, Canadian Arctic Islands, and b) the Appalachian margin from the upper Ellis Bay, Becscie, Merrimack, Gun River, Jupiter and Chicotte formations (Richmondian, Upper Ordovician, Rhuddanian, Aeronian, and most of Telychian, Lower Silurian), Anticosti Island, Quebec. The pattern of Late Ordovician–Early Silurian conodont communities is established based on three cluster analyses on conodonts from Cornwallis Island (4967 specimens representing 54 species from 77 samples, Cape Phillips Formation) and Anticosti Island (1980 specimens representing 21 species from 25 samples, upper Ellis Bay Formation; 24,839 specimens representing 42 species from 123 samples, Becscie, Merrimack, Gun River, Jupiter and Chicotte formations). Overall, the sea level curves inferred from the distribution of the conodont communities from Cornwallis and Anticosti exhibit gradual and rapid oscillating patterns, respectively. Specifically, during the time interval of the latest Ordovician and the Early Silurian (Rhuddanian), the sea level behaved differently in these two regions: 1) during the latest Ordovician, conodont community changes show the different patterns in the two regions, which reflects a transgression on Cornwallis, but a regression on Anticosti; 2) during the earliest Rhuddanian, similar conodont communities arose in both regions, but they indicate a regression on Cornwallis and a transgression on Anticosti; 3) in the early Rhuddanian, these communities were replaced by a deeper water community on Cornwallis and a shallower water community on Anticosti, which suggest a transgression on Cornwallis and a regression on Anticosti; 4) a highstand drove out almost all conodonts from Anticosti by the end of Rhuddanian, which is not seen on Cornwallis; 5) a deep-water conodont community remained almost unchanged on Cornwallis from the late Rhuddanian to the early Aeronian, whereas a shallow water conodont community returned to Anticosti in the early Aeronian. However, the sea level dropped on both Cornwallis and Anticosti during the late Telychian, and the sea level curves show a similar pattern. The difference in the sea level pattern during the late Richmondian, Rhuddanian and Aeronian on both the northern and southern margins of Laurentia reflected by conodont communities is supported by the studies on Quaternary glaciation/deglaciation events, where the melting of an ice sheet was accompanied by sea level change but with variable regional isostatic effects that do not generate a uniform global eustatic signal.

Distribution of Chironomidae (Insecta: Diptera) Head Capsules in Recent Sediments of Canadian Arctic Lakes

Thirty-two taxa of chironomid larvae were collected from the sediments of 50 lakes from across the Canadian Arctic Islands. Most chironomid taxa living in the Arctic have wide distributions, with only one taxon, Abiskomyia, showing a clear geographic limitation in this region. Many of these taxa have habitat preferences, among which lake morphometry, pH, nutrients and temperature are important. Due to the complex environmental patterns in the Arctic, lakes in both the northern and southern portion of the Canadian Arctic Archipelago have warmer temperatures and the chironomid assemblages of these two regions resemble each other more than those of the intervening central islands. Chironomid diversity is lowest in the central arctic islands, primarily Devon and Cornwallis Island, where the combination of low nutrients and cold temperatures provide the most severe environment for chironomid survival.

Total and methyl mercury patterns in Arctic snow during springtime at Resolute, Nunavut, Canada

Patterns of gaseous elemental mercury (GEM) were monitored at 20 and 150 cm above the snowpack near Resolute Bay, Cornwallis Island, Nunavut, Canada near the Upper Air Station of Environment Canada (74°42′N, 94°58′W) from 7 May (day 127) to 12 June (day 163) 2003. At this time of year there was 24 h daylight but still a strong diel change in solar radiation. Daily patterns of GEM-tracked solar radiation with a lag of about 2 h and the GEM gradient between these two heights showed the direction of flux. In addition to the previously established autocatalytic reactions involving halogens where reactive gaseous mercury and fine particulate mercury result in direct deposition to the snow, both diffusion to and volatilization from the snow occurred on a regular basis. Total mercury (THg) in the snowpack increased to near 30 ng L −1 following 8 d of atmospheric mercury depletion then decreased to values near 1 ng L −1. Losses from the snow could not be accounted for in melt water as stream runoff values were also low. In other words, most of the mercury associated with increased levels in snow was volatilized back to the atmosphere either directly from the snow or from the water surfaces. However, using accepted mass transport coefficients, the flux appeared low and other mechanisms are suggested. In contrast to THg, methyl mercury (MeHg) in the snow reached values near 140 pg L −1 but also declined to less than detection limit (10 pg L −1) with the onset of warmer temperatures. MeHg in stream runoff water was similar to maximal values seen in the snow. This observation is consistent with the view that MeHg came in the snowfall or was deposited to the snow pack rather than produced in the snow. In contrast, much of the THg associated with mercury depletion events was volatilized back to the atmosphere.

Spatial and temporal trends of mercury and other metals in landlocked char from lakes in the Canadian Arctic archipelago

Spatial and temporal trends of mercury (Hg) and 22 other elements were examined in landlocked Arctic char ( Salvelinus alpinus) from six lakes in the Canadian Arctic (Char, Resolute and North Lakes, and Amituk Lake on Cornwallis Island, Sapphire Lake on Devon Island and Boomerang Lake on Somerset Island). The objectives of the study were to compare recent concentrations of Hg and other metals in char with older data from Amituk, Resolute and Char Lakes, in order to examine temporal trends as well as to investigate factors influencing spatial trends in contaminant levels such as lake characteristics, trophic position, size and age of the fish. Geometric mean Hg concentrations in dorsal muscle ranged from 0.147 μg/g wet weight (ww) in Resolute Lake to 1.52 μg/g ww in Amituk Lake for samples collected over the period 1999–2003. Char from Amituk Lake also had significantly higher selenium (Se). Mercury in char from Resolute Lake was strongly correlated with fish length, weight, and age, as well as with thallium, lead and Se. In 5 of 6 lakes, Hg concentrations were correlated with stable nitrogen isotope ratios ( δ 15N) and larger char were feeding at a higher trophic level presumably due to feeding on smaller char. Weight adjusted mean Hg concentrations in char from Amituk Lake, and unadjusted geometric means in Char Lake and Resolute Lakes, did not show any statistically significant increase from the early 1990s to 2003. However, small sample sizes from 1999–2003 for fish < 1000 g limited the power of this comparison in Char and Amituk Lakes. In Resolute Lake char, manganese, strontium and zinc showed consistent decreases from 1997 or 1999 to 2003 while nickel generally increased over the 6 year period. Differences in char trophic level inferred from δ 15N values best explained the higher concentrations of Hg in Amituk Lake compared to the other lakes.

Early Silurian (Wenlockian) δ13C profiles from the Cape Phillips Formation, Arctic Canada and their relation to biotic events

Geochemical data from the Cape Phillips Formation, Arctic Canada, are examined in association with three Silurian biotic crises in the graptolite community; the early Wenlockian Ireviken, mid Wenlockian Cyrtograptus lundgreni, and end Wenlockian Colonograptus ludensis extinction events. Positive δ13Corg excursions are associated with the Ireviken and C. lundgreni events, but not the Co. ludensis Event. The Ireviken and C. lundgreni excursions are recognized worldwide and are herein interpreted to be the result of carbonate weathering in response to eustatic sea-level drop. The C. lundgreni excursion is of greater magnitude in the more proximal basin margin section at Abbott River, Cornwallis Island, and is explained by the amplification of a more strongly positive δ13C signature in shallower parts of an epeiric basin during increased exposure and weathering of the carbonate shelf. Excursion C5, within the C. praedeubeli – C. deubeli Zone, is also of regional significance, as it occurs in both the Abbott River section and Twilight Creek section on Bathurst Island, and is also recognized in Estonia, Poland, and England. Excursion C6 is recognized in the Gorstian Stage, yet its regional significance remains equivocal. There is a reasonable general agreement between the shape of the δ13Corg and δ13Ccarb curves, yet the δ13Ccarb curve is largely a record of detrital carbonate derived from the shelf. The δ13Corg curve represents extraction of dissolved inorganic carbon by plankton and thus is more indicative of ambient paleoceanographic conditions. These data are valuable in that they provide a detailed secular marine δ13C curve for the Wenlockian of Arctic Canada from relatively unaltered sections of varying facies whose ages are well constrained by graptolite biostratigraphy.

Late Dorset architecture on Little Cornwallis Island, Nunavut

Late Dorset dwellings from two sites on Little Cornwallis Island (Nunavut) illustrate the diversity of architectural forms from this period. Ten architectural features are described. They include five tent rings, ascribed to warm season occupations, and five rectangular semi-subterranean houses with axial features, including one exceptionally well-preserved example, ascribed to cold season occupations. Variations in size, number of hearths, and construction techniques are examined and the use of both types of structures to house multiple nuclear families is suggested.

Hydrochemistry and mercury cycling in a High Arctic watershed

Mass budgets for total mercury, major ions and nutrients were calculated for Amituk Lake, located on Cornwallis Island, Nunavut, Canada. Total mercury in two distinct snowpacks averaged 1.25 and 4.21 ng L −1; the discharge-weighted concentration of influent streams averaged 0.76 ng L −1. The recent and pre-industrial Hg T fluxes in atmospheric deposition to the catchment were estimated to be 0.57 and 0.23 μg m −2 but through retention within the catchment and/or re-volatilization from the melting snowpack, these decreased by 69% in the lake inflow. The spring freshet was the prime conduit for transporting Hg T into Amituk Lake. Because of limited mixing of surface runoff with the lake water column during snowmelt, 59% of the Hg T input was directly discharged through the outflow, 16% entered the lake water column where concentrations increased from 0.23 to 0.33 ng L −1 from June to August and 25% was deposited to the bottom sediments producing a sediment Hg T flux of 3.1 μg m −2.

Recolonization of soft-sediment ice scours on an exposed Arctic coast

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 286:21-42 (2005) - doi:10.3354/meps286021 Recolonization of soft-sediment ice scours on an exposed Arctic coast Kathleen E. Conlan1,*, Rikk G. Kvitek2,3 1Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, Ontario K1P 6P4, Canada2Moss Landing Marine Laboratories, PO Box 450, Moss Landing, California 95039, USA3Present address: Earth System Science and Policy Institute, California State University Monterey Bay, 100 Campus Center, Seaside, California 93955, USA *Email: kconlan@mus-nature.ca ABSTRACT: Ice scour is the most disruptive and widespread physical disturbance that naturally affects the coastal benthos in polar waters, where it creates a mosaic of disturbances in various stages of recolonization. The purpose of this study was to (1) determine the timing and sequence of biotic recovery following ice scour disturbance of soft sediment and (2) test the general hypothesis that ice scour increases biotic diversity in high-latitude benthic communities. The study area was a 6.6 km length of Barrow Strait along the exposed coast of Cornwallis Island in High Arctic Canada. Core-collected (0.0075 m2) macrofauna (≥0.5 mm) inhabiting 19 scours at 12 to 28 m depth were sampled during open water in August of 1991 to 1996 and again in 1999. We repeat-sampled 2 scours for 6 summers, 3 scours for 3 summers, and 2 for 2 summers, while the other 12 scours were sampled once. Sampling was severely limited by availability of open water which was constrained by frequent invasion of the study area by drift ice. Young ice scours were refugia for the dorvilleid polychaete Ophryotrocha spatula. Its numbers declined precipitously as the scours aged. Other early colonists maintained or increased their abundance. Most of the later colonists significantly increased in abundance as the scours aged despite the presence of the early colonists. Abundance, biomass and species richness increased progressively with scour ageing but did not significantly exceed that in the unscoured community. Thus, although the scours differed from the unscoured reference community in species composition, they were not havens for species-rich or highly different assemblages (at least not among core-collected macrofauna). Recolonization of ice scours ≤9 yr old fitted a linear model. Assuming that further colonization would continue to be linear, the 2 scours monitored the longest had achieved 65 to 84% recolonization by Ages 8 to 9. The unscoured reference community was significantly more diverse, massive and abundant where disturbance was a chronic but infrequent occurrence, compared to where it was protected from ice scour by an offshore rise. Thus, ice scour appears to have a positive effect on the benthos of this coast. KEY WORDS: Ice scour · Recolonization · Disturbance · Benthos · Arctic Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 286. Online publication date: February 02, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Modeling arctic snow distribution and melt at the 1 km grid scale*

Snow accumulation, re-distribution and melt are important hydrological considerations in the Arctic. This study presents a model of the late-winter snow cover and the ensuing snowmelt in a High Arctic environment at a scale of 1 km. Indexing is used to spread the snow data from a lowland weather station to various terrain units over a 16×13 km2 target area east of Resolute, Cornwallis Island, Canada. Meteorological variables measured at this base station are spatially extended by field derived empirical relationships for the computation of melt at various terrain units using the energy balance approach. These melt rates are weighted by the fractional coverage of various terrain unit within each 1×1 km2 cell. The snow distribution pattern is obtained daily and model performance was tested by comparing observed and computed dates of melt and the radiation balance over snow. The simulated snow pattern compared favourably with the snow cover imaged by LANDSAT. Daily changes in the probability distribution of snow water equivalent over the target area was examined and snow depletion curves were derived. They describe sub-grid variability over an area and our results point to several assumptions that should be scrutinized in sub-grid parameterization of snow distribution.