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  • 11
    Electronic Resource
    Electronic Resource
    Seasonal succession of phytoplankton in a large subarctic river (1979)
    Springer
    Hydrobiologia 67 (1979), S. 107-112 
    Details
    ISSN: 1573-5117
    Keywords: Chlamydomonas ; Diatoms ; Dinobryon ; Light ; Nutrients ; Phytoplankton ; Subarctic ; Succession ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The factors influencing the abundance of phytoplankton in the Yellowknife River, in the Canadian subarctic, were determined from collections made for 42 consecutive months from June 1975 to November 1978. The spring bloom of plankton occured during April of each year in response to changing light conditions. WhileChlamydomonas lapponica was dominant during this period, it was replaced during the early part of the summer by a rapid succession ofDinobryon species in whichD. cylindricum was followed byD. sociale and in turn byD. bavaricum andD. divergens. Although low nutrient levels permitted the development ofDinobryon during the summer, the abundance of diatoms was greatly limited by the concentrations of SiO2 (〈 0.1 g/m3). Algal densities began to decline in August and reached low overwintering levels by November. The absence of a fall bloom in densities was due to a combination of low temperatures and nutrient levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00126709
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  • 12
    Electronic Resource
    Electronic Resource
    Factors influencing the species composition, distribution and abundance of benthic invertebrates in the profundal zone of a eutrophic northern lake (1981)
    Springer
    Hydrobiologia 83 (1981), S. 505-510 
    Details
    ISSN: 1573-5117
    Keywords: benthos ; food ; oxygen ; algae ; subarctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factors influencing the species composition, distribution and abundance of benthic invertebrates were determined in a eutrophic subarctic lake from April 1978 to April 1979. Collections were made at five stations located at depths of 4 to 13 m. The largest populations of up to 5 × 103 animals m−2 were found in the deepest part of the lake. of the 24 species recorded in this area, the chironomidsProcladius denticulatus, Dicrotendipes modestus, Chironomus decorus andGlyptotendipes barbipes were most common. The strong development of benthos in the profundal zone was attributed to a consistently large supply of food and warm (4 °C) winter temperatures on bottom. Slightly smaller populations (up to 4 × 103 animals, m−2), composed of 19–23 species, occurred in shallower water, a reflection of lower (1.5 °C) winter temperatures. In the anoxic northern part of the lake, only 4–8 species were found in low numbers (400–1 000 animals m−2). This was likely due to low (〈5% saturation) oxygen levels in water and high organic content (18.5%) of the sediments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187047
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  • 13
    Electronic Resource
    Electronic Resource
    Influence of food availability and other factors on the composition, structure and density on a subarctic population of benthic invertebrates (1979)
    Springer
    Hydrobiologia 62 (1979), S. 215-223 
    Details
    ISSN: 1573-5117
    Keywords: Algae ; density ; depth ; feeding ; molluscs ; oligochaetes ; subarctic ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The factors influencing the composition, structure and density of benthic invertebrate communities in Yellowknife Bay in the Canadian subarctic were determined between June 1975 and April 1977. Attached algae, primarily Fragilaria vaucheriae, Fragilaria pinnata, Cymbella ventricosa and Cocconeis placentula were ingested in large numbers by several dominant species including the oligochaetes Rhyacodrilus sodalis, Lumbriculus variegatus and Limnodrilus claparendeianus and the mollusc Valvata sincera helicoidea. Although up to 7 × 105 cells/oligochaeta, representing 65% by volume of the gut contents, were recorded for littoral zone populations, specimens in the profundal zone contained 〈 7.5 × 104 cells in their guts. V. sincera helicoidea also ingested large numbers of attached algae (up to 2.3 × 104 cells/animal), these representing 15–18% by volume of the gut contents. Consequently, multiple regression analysis indicated that the availability of attached algae was the major factor influencing the benthic communities. While 31–64% of the population variability could be accounted for by this factor, other parameters such as phytoplankton availability, water depth, temperature, dissolved oxygen levels, total amount of food in the gut, and the organic content of the sediments had little if any direct effect on the benthic populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00043538
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  • 14
    Electronic Resource
    Electronic Resource
    Diversity and indicator species as measures of water pollution in a subarctic lake (1979)
    Springer
    Hydrobiologia 66 (1979), S. 73-80 
    Details
    ISSN: 1573-5117
    Keywords: Benthos ; Chironomids ; diversity ; heavy metals ; indicator species ; molluscs ; subarctic ; water pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Benthic invertebrates were collected from a subarctic lake during 1976 to assess the effectiveness of diversity indices and indicator species as measures of heavy metal pollution. Collections were made near an operating metal mine, where sediments were contaminated with high levels of arsenic (up to 2,500 mg/kg dry weight), mercury (500 µg/kg), lead (850 mg/kg), copper (750 mg/kg) and zinc (950 mg/kg). A total of 25 species and a diversity index of 2.4—2.9 were recorded in this heavily impacted area. Chironomids (Procladius denticulatus, Heterotrissocladius changi, Chironomus decorus) were most common in the sediments, followed in importance by molluscs (Pisidium casertanum) and oligochaetes (Lumbriculus variegatus). There were 23 and 25 species in the areas of moderate and negligible contamination, respectively. The diversity indices ranged from 2.4–2.6 and 2.4–2.8 and the main species were generally similar to those found in the heavily impacted area. While diversity indices and indicator species were therefore ineffective in monitoring metal contamination, the strong negative correlation between the concentration of metals and the abundance of benthic organisms provided a much more realistic assessment of the level of contamination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019142
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  • 15
    Electronic Resource
    Electronic Resource
    Zooplankton, and related phytoplankton cycles, in a eutrophic lake (1980)
    Springer
    Hydrobiologia 74 (1980), S. 99-104 
    Details
    ISSN: 1573-5117
    Keywords: algae ; cladocerans ; food ; predators ; rotifers ; temperature ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The seasonal cycles of zooplankton were determined for 18 consecutive months in a sewage-enriched lake in northern Canada and were related to algal availability and utilization, food consumption, temperature and the density of predators. Most of the common species (Daphnia pulex, Daphnia middenorffiana, Keratella cochlearis, Keratella quadrata, Polyarthra vulgaris) increased in abundance in May and June, reached a mid-summer maximum, and declined sharply in the fall. Phytoplankton densities increased sharply in May, peaked early in June and gradually decreased through the summer and fall. Since the quantity of algae in the guts remained constant during this period, algal availability and utilization had no direct impact on the seasonal cycles of any species. Furthermore, the amount of ingested material in D. pulex and D. middendorffiana was similar regardless of time of year, implying that the total quantity of food in the environment did not restrict development. Although temperature was the most important factor influencing variations in the densities of all species, predation by Cyclops spp. probably had little effect on the population dynamics of the fauna.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014560
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  • 16
    Electronic Resource
    Electronic Resource
    Some factors influencing the density of subarctic populations of Bosmina longirostris, Holopedium gibberum, Codonella cratera and Ceratium hirundinella (1977)
    Springer
    Hydrobiologia 56 (1977), S. 199-207 
    Details
    ISSN: 1573-5117
    Keywords: Bosmina ; Ceratium ; Codonella ; density ; food ; Holopedium ; light ; reproduction ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the density of 2 populations of Bosmina longirostris, Holopedium gibberum and Codonella cratera were correlated through multiple regression analyses with shifts in temperature, light, nannoplankton densities and seston weight. Sampling took place every 2 weeks between June 1975 and November 1976 in the Yellowknife River and Yellowknife Bay, both in the Canadian subarctic. Temperature was usually the main factor influencing all 3 species, accounting for up to 60% of the seasonal variability in B. longirostris, 37% in H. gibberum and 62% in Codonella cratera. Seston (the major food source) ranked second overall and in one instance accounted for 60% of density changes in B. longirostris. Nannoplankton were consumed in only small numbers and had little influence on densities. Light was of minor importance to all species. Temperature was also the main factor effecting reproduction and feeding in B. longirostris and H. gibberum (the only species studied). The simultaneous collections of Ceratium hirundinella made in the river and bay indicated that temperature accounted for 30–55% of the seasonal variability of this species, followed by light (4% and nutrients (3–4%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017506
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  • 17
    Electronic Resource
    Electronic Resource
    Some factors influencing the density of invertebrates near a sewage outfall (1978)
    Springer
    Hydrobiologia 61 (1978), S. 81-93 
    Details
    ISSN: 1573-5117
    Keywords: Algae ; benthos ; densities ; invertebrates ; plankton ; sewage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The factors influencing the density of benthic and planktonic invertebrates near a sewage outfall on Great Slave Lake in the Canadian subarctic were determined between June 1975 and May 1977. Densities were measured along 3 transects extending 500 m from the outfall and at 3 stations located 0.5–6.0 km from the outfall. Almost all benthic (Chironomus decorus, Procladius denticulatus, Polypedilum nebeculosum, Tanytarsus sp., Limnodrilus hoffmeisteri, Pontoporeia afftnis, Pisidium casternatum, Valvata sincera helicoidea) and planktonic (Keratella earlinae, Kellicottia longispina, Synchaeta stylata) species increased in abundance moving towards the sewage discharge point. Multiple regression analyses indicated that the elevated levels of algae and the total amount of food available in the environment had little if any influence on all species. Detritus and associated bacteria were the most important factors affecting densities and were probably the major food source for all species. Low winter oxygen levels (10–60% staturation), water depth and temperature had negligible effect on most species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019027
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  • 18
    Electronic Resource
    Electronic Resource
    Inter-species variability in the consumption of algae by oligochaetes (1981)
    Springer
    Hydrobiologia 83 (1981), S. 241-244 
    Details
    ISSN: 1573-5117
    Keywords: algae ; food ; oligochaetes ; subarctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The importance of algae in the diet of the oligochaetesArcteonais lomondi, Uncinais uncinata andLimnodrilus claparedeianus was determined from May 1978 to April 1979 in two lakes located in northern Canada. The lakes were small (130–157 ha), shallow, (〈15 m) and mesotrophic. During summer, algae accounted for up to 57–75% by volume of ingested matter inA. lomondi andU. uncinata depending on lake whereas in winter the corresponding range was 10–22%. Dominant algae found in the gut included the diatomsSurirella robusta, Diploneis puella, Amphora ovalis, Stephanodiscus astraea, Fragilaria construens andAchnanthes minutissima. Although the same taxa were ingested byL. claparedeianus, algae always represented 〈5% by volume of the gut contents. This possibly reflects subsurface feeding in an area where algae were rare. The length distribution of ingested diatoms, ranging from 9 to 250 μm, was similar regardless of species in both lakes. Hence, there was no partitioning of algal food resources among oligochaetes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00008272
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  • 19
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    Influence of water movements and other factors on distribution and transport of heavy metals in a shallow Bay (Canada) (1981)
    Springer
    Details
    Publication Date: 1981-11-01
    Print ISSN: 0090-4341
    Electronic ISSN: 1432-0703
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by Springer
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  • 20
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    Distribution of heavy metals and radionuclides in sediments, water, and fish in an area of Great Bear Lake contaminated with mine wastes (1981)
    Springer
    Details
    Publication Date: 1981-01-01
    Print ISSN: 0090-4341
    Electronic ISSN: 1432-0703
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by Springer
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