ZOOPLANKTON OF LAKE HAZEN, ELLESMERE ISLAND, AND A NEARBY POND, WITH SPECIAL REFERENCE TO THE COPEPOD CYCLOPS SCUTIFER SARS

1964 ◽  
Vol 42 (4) ◽  
pp. 613-629 ◽  
Author(s):  
I. A. McLaren
Keyword(s):  
Special Reference ◽  
Standing Crop ◽  
Dry Weight ◽  
High Arctic ◽  
Ellesmere Island ◽  
Arctic Lakes ◽  
Net Production ◽  
Daphnia Middendorffiana ◽  
Ice Conditions ◽  
Cyclops Scutifer

Zooplankton was studied in the large, high-arctic Lake Hazen and in a small nearby pond. Primary (O2) production in Lake Hazen may have occurred largely before the ice began to melt, but was unmeasurable in summer. Primary production in the pond was about the same as in other small arctic lakes, Cyclops scutifer was overwhelmingly dominant in Lake Hazen. C. scutifer and Daphnia middendorffiana were commonest in the pond. C, scutifer is annual in Scandinavia, often with coexisting spring-born and fall-born generations. On Ellesmere Island the pond appears to contain alternating annual and biennial generations, whereas the species is strictly biennial in Lake Hazen. Numbers of C. scutifer in Lake Hazen were greatly reduced as a result of summer ice conditions between 1958 and 1961, while the rotifer Keratella hiemalis increased. Estimated mean standing crop (96 mg/m2) and net production (1.0 mg/m2 day) in dry weight ol C. scutifer in Lake Hazen during the summer of 1958 were extremely low. In early August the crop of this species in the pond was abont the same as in Lake Hazen, but net production was sonic 15 times as large, and other zooplankters added considerably to crop and production of the pond.

Chrysophycean stomatocysts from the postglacial sediments of a High Arctic lake

1988 ◽  
Vol 66 (6) ◽  
pp. 1117-1128 ◽  
Author(s):  
Katharine E. Duff ◽  
John P. Smol
Keyword(s):  
Species Composition ◽  
Light Microscopy ◽  
High Arctic ◽  
Ellesmere Island ◽  
Arctic Lakes ◽  
Ecological Research ◽  
Stratigraphic Analysis ◽  
Morphological Detail ◽  
Electron And Light Microscopy ◽  
Scanning Electron

Twenty-six chrysophycean stomatocyst morphotypes were described from the postglacial sediments of a small, rock basin lake near Baird Inlet, Ellesmere Island. Scanning electron and light microscopy were used to classify the stomatocysts, following the guidelines of the International Statospore Working Group. None of the stomatocysts could be related with certainty to the chrysophyte species that produced them, but sufficient morphological detail is present in most of the stomatocysts to allow for taxonomic differentiation. A stratigraphic analysis of the dominant stomatocyst morphotypes revealed that chrysophyte species composition changed most markedly during the lake's early development but then remained relatively constant. This study demonstrated that chrysophycean stomatocysts provide useful paleoecological information in High Arctic lakes, but further taxonomic and ecological research is required to fully exploit these microfossils.

scholarly journals Dispersal limitation and climate-related environmental gradients structure microcrustacean composition in freshwater lakes, Ellesmere Island, Canada

2008 ◽  
Vol 65 (9) ◽  
pp. 1905-1918 ◽  
Author(s):  
Angela L. Strecker ◽  
Rebecca Milne ◽  
Shelley E. Arnott
Keyword(s):  
Species Richness ◽  
Environmental Change ◽  
Community Composition ◽  
Environmental Gradients ◽  
Negative Relationship ◽  
Ellesmere Island ◽  
Arctic Lakes ◽  
The Arctic ◽  
Arctic Ecosystems ◽  
Daphnia Middendorffiana

Dramatic environmental change is expected in the Arctic, yet little is known about the occurrence and community composition of microcrustaceans in Arctic lakes and how this will be influenced by future environmental change. We sampled and calculated relative abundances of microcrustacean species in 54 lakes on Ellesmere Island, Canada. New species records on Ellesmere Island included Daphnia umbra , Tachidius discipes , and Artemeopsis stefanssoni . Daphnia middendorffiana/tenebrosa was the most common taxon and often dominated microcrustacean assemblages, likely a result of its pigmentation, which offers resistance to ultraviolet radiation. Species richness was positively associated with nutrients, dissolved organic carbon (DOC), temperature, calcium, and conductivity and negatively affected by elevation. In contrast to most findings in temperate systems, we detected a negative relationship between species richness and surface area. Community composition was influenced by DOC, nutrients, and elevation but was also related to spatial variables, suggesting that spatial gradients in environmental conditions and dispersal are important drivers of differences among sites. Arctic ecosystems are expected to change rapidly in the coming years because of climate change and ozone thinning, and we expect that associated changes in DOC, temperature, and nutrients will affect microcrustacean species richness and distribution throughout the landscape.

Effects of fertilization on three tundra plant communities of a polar desert oasis

1986 ◽  
Vol 64 (11) ◽  
pp. 2502-2507 ◽  
Author(s):  
G. H. R. Henry ◽  
B. Freedman ◽  
J. Svoboda
Keyword(s):  
Plant Communities ◽  
High Arctic ◽  
Ellesmere Island ◽  
Nutrient Addition ◽  
The Arctic ◽  
Arctic Ecosystems ◽  
Polar Desert ◽  
Net Production ◽  
Dwarf Shrubs ◽  
Desert Oasis

Three plant communities studied at a high arctic oasis on Ellesmere Island responded to nutrient addition. Response to nitrogen was greatest in the driest community and weaker in the more mesic and wet-mesic communities. Nutrient addition resulted in (i) increased inflorescence densities of dicotyledonous and certain graminoid species; (ii) increased tiller densities of wet sedge species; and (iii) increased net production of graminoids and forbs at high rates of application, and in some dwarf shrubs at lower rates. These results parallel those of studies at lower latitudes in the Arctic, and support the hypothesis that arctic ecosystems are typically oligotrophic.

Standing crop and net production of sedge meadows of an ungrazed polar desert oasis

1990 ◽  
Vol 68 (12) ◽  
pp. 2660-2667 ◽  
Author(s):  
G. H. R. Henry ◽  
J. Svoboda ◽  
B. Freedman
Keyword(s):  
Standing Crop ◽  
Growth Period ◽  
High Arctic ◽  
Climatic Conditions ◽  
Large Herbivores ◽  
Net Production ◽  
Carex Aquatilis ◽  
Eriophorum Angustifolium ◽  
Desert Oasis ◽  
Sedge Meadows

Standing crop and net production were measured in sedge meadow communities of a coastal lowland at Alexandra Fiord, Ellesmere Island (79°N), a high arctic oasis. The meadows are dominated by Carex aquatilis stans, Carex membranacea, and Eriophorum angustifolium triste. Dwarf shrubs (Dryas integrifolia and Salix arctica) are also important constituents. Total standing crop ranged from 1400 to 3200 g/m2 and was largely (50–80%) composed of attached dead matter. The accumulation of litter and dead roots and rhizomes is attributed to low rates of decomposition, and to a lack of grazing by large herbivores such as muskox. Net production (100–200 g/m2) was similar to more southerly tundra meadows, emphasizing the oasis-like nature of this high arctic location. Furthermore, net production did not vary significantly among sites or years. The consistent net production was due to similar edaphic and climatic conditions, the concentration of biomass belowground, and the apparently fixed growth period of arctic sedges. Key words: sedge meadows, high arctic, net production, standing crop, Carex.

scholarly journals Assessing the utility of sulfur isotope values for understanding mercury concentrations in water and biota from high Arctic lakes

2019 ◽  
Vol 5 (2) ◽  
pp. 90-106 ◽  
Author(s):  
Gretchen L. Lescord ◽  
Meredith G. Clayden ◽  
Karen A. Kidd ◽  
Jane L. Kirk ◽  
Xiaowa Wang ◽  
...  
Keyword(s):  
Food Webs ◽  
Total Mercury ◽  
Nitrogen Isotopes ◽  
Sulfur Isotopes ◽  
High Arctic ◽  
Arctic Lakes ◽  
Carbon And Nitrogen ◽  
Resolute Bay ◽  
Aquatic Food ◽  
Globally Stable

Methylmercury (MeHg) biomagnifies through aquatic food webs resulting in elevated concentrations in fish globally. Stable carbon and nitrogen isotopes are frequently used to determine dietary sources of MeHg and to model its biomagnification. However, given the strong links between MeHg and sulfur cycling, we investigated whether sulfur isotopes (δ34S) would improve our understanding of MeHg concentrations ([MeHg]) in Arctic lacustrine food webs. Delta34S values and total mercury (THg) or MeHg were measured in water, sediments, and biota from six lakes near Resolute Bay, NU, Canada. In two lakes impacted by historical eutrophication, aqueous sulfate δ34S was ∼8‰ more positive than sedimentary δ34S, suggestive of bacterial sulfate reduction in the sediment. In addition, aqueous δ34S showed a significant positive relationship with aqueous [MeHg] across lakes. Within taxa across lakes, [THg] in Arctic char muscle and [MeHg] in their main prey, chironomids, were positively related to their δ34S values across lakes, but inconsistent relationships were found across entire food webs among lakes. Across lakes, nitrogen isotopes were better predictors of biotic [THg] and [MeHg] than δ34S within this dataset. Our results suggest some linkages between Hg and S biogeochemistry in high Arctic lakes, which is an important consideration given anticipated climate-mediated changes in nutrient cycling.

scholarly journals Climate and permafrost effects on the chemistry and ecosystems of High Arctic Lakes

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
K. E. Roberts ◽  
S. F. Lamoureux ◽  
T. K. Kyser ◽  
D. C. G. Muir ◽  
M. J. Lafrenière ◽  
...  
Keyword(s):  
High Arctic ◽  
Arctic Lakes

Limnology of high arctic ponds (Cape Herschel, Ellesmere Island, N. W. T.)

1994 ◽  
Vol 131 (4) ◽  
pp. 401-434
Author(s):  
Marianne S. V. Douglas ◽  
John P. Smol
Keyword(s):  
High Arctic ◽  
Ellesmere Island ◽  
Arctic Ponds

An analysis of the stability of thawing slopes, Ellesmere Island, Nunavut, Canada

2000 ◽  
Vol 37 (2) ◽  
pp. 449-462 ◽  
Author(s):  
Charles Harris ◽  
Antoni G Lewkowicz
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Active Layer ◽  
Factor Of Safety ◽  
High Arctic ◽  
Ellesmere Island ◽  
Sensitivity Analyses ◽  
Pore Water Pressures ◽  
Hot Weather ◽  
The Stability

Active-layer detachment slides are locally common on Fosheim Peninsula, Ellesmere Island, where permafrost is continuous, the active layer is 0.5-0.75 m thick, and summer temperatures are unusually high in comparison with much of the Canadian High Arctic. In this paper we report pore-water pressures at the base of the active layer, recorded in situ on two slopes in late July and early August 1995. These data form the basis for slope stability analyses based on effective stress conditions. During fieldwork, the factor of safety within an old detachment slide on a slope at Hot Weather Creek was slightly greater than unity. At "Big Slide Creek," on a slope showing no evidence of earlier detachment failures, the factor of safety was less than unity on a steep basal slope section but greater than unity elsewhere. In the upper slope, pore-water pressures were only just subcritical. Sensitivity analyses demonstrate that the stability of the shallow active layer is strongly influenced by changes in soil shear strength. Possible mechanisms for reduction in shear strength through time include weathering of soils and gradual increases in basal active layer ice content. However, we suggest here that soil shearing during annual gelifluction movements is most likely to progressively reduce shear strengths at the base of the active layer from peak values to close to residual, facilitating the triggering of active-layer detachment failures.Key words: detachment slides, Ellesmere Island, pore-water pressures, gelifluction.

Energy Flow and Secondary Production of the Amphipods Hyalella azteca and Crangonyx richmondensis occidentalis in Marion Lake, British Columbia

1971 ◽  
Vol 28 (5) ◽  
pp. 711-726 ◽  
Author(s):  
Jack A. Mathias
Keyword(s):  
Population Growth ◽  
Energy Flow ◽  
Standing Crop ◽  
Production Efficiency ◽  
Hyalella Azteca ◽  
Growth Efficiency ◽  
Ecological Efficiency ◽  
Net Production ◽  
Annual Basis ◽  
Predator System

The Hyalella azteca population in Marion Lake, B.C., assimilated and produced about three times as much energy as did the Crangonyx richmondensis occidentalis population from May 1966 to May 1967, but during the summer the energy flow of H. azteca was four times, and production was five times, that of C. r. occidentalis.Hyalella azteca was abundant at a depth of 1.0 m (mean summer standing crop, 1952 animals/m2), but was rare (75 animals/m2) at depths greater than 2.5 m. Growth, molting, respiration, and hence energy flow rates decreased with depth, due (in part) to lower ambient temperatures in deeper water. On an annual basis, a mean standing crop of 1.1 kcal/m2 of H. azteca assimilated 18.1 kcal/m2, respired 13.5 kcal/m2, and used 4.6 kcal/m2 in production of growth, molts, and eggs. Approximately two-thirds of the annual energy flow was completed between June and October. On an annual basis, the ecological efficiency of an H. azteca-predator system was in the range 2.5–12.5%, the net production efficiency was 25%, and the net population growth efficiency was 16%.The mean summer density of C. r. occidentalis remained constant with depth (about 283 animals/m2). Annual energy flow and production were not appreciably affected by lower temperatures in deeper water. On an annual basis, a mean standing crop of 0.7 kcal/m2 assimilated 6.5 kcal/m2, respired 5.2 kcal/m2, and used 1.4 kcal/m2 in production. Crangonyx r. occidentalis energy flow was fairly constant throughout the year. The ecological efficiency of a C. r. occidentalis-predator system was in the range 2–10.5%, the net production efficiency was 21%, and the population growth efficiency was 17% on an annual basis.

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