摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f74-085

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f74-086

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f74-087

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The prime environmental contingency affecting Canadian limnologists and limnology during the next decade may be a deteriorating economic situation brought about by global demophoric (population × technology) growth. In such an event there would be strong pressure for a fusion of economic and ecological interests, and for organizational arrangements facilitating problem solving. As an adaptation of this fusion, arguments are presented for cooperative education in which students with different disciplinary backgrounds jointly conduct problem-oriented work.

ISSN:0706-652X    

DOI:10.1139/f74-088

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The history of Atlantic salmon (Salmo salar) runs of the Northwest Miramichi from 1950 to 1973 is reviewed. Decreases in these runs are related to degrading of ecological conditions in the river's rearing reaches as a result of adverse chemical conditions attributable to recent developments in forest management and to base metal mining. Diversion of indigenous adult stocks into other streams of the system as a result of pollution of the home stream by mining, pulpmill, and other human activities is examined and evaluated. Increase of commercial catches as a result of pollution-caused delay in the estuary of migrating adults is analyzed. Grave depletion of stocks as a result of the combined effects of these factors plus distant-water fishing is identified, as is incipient recovery of stocks when home-water commercial fishing was eliminated and pollution abatement measures were introduced to the river. A suppressing effect of heavy angling pressure on stock abundance when stocks are low is noted.

ISSN:0706-652X    

DOI:10.1139/f74-089

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Investigations into the vertical distribution of stream animals by means of a coring technique have demonstrated that they could be found many decimeters down in the gravel; a maximum of 17% was found in the top 5 cm.Sampling of arctic streams revealed that chironomid larvae comprised 70–80% of the numbers in the benthos and that their rate of drift did not vary with the time of day.Life history studies of stream invertebrates have demonstrated clear seasonal patterns in Canada. Work has been done on several mayflies and stone flies, some Chironomidae, and two species ofGammarus. Currently the life histories of the stone flies of southern Australia are being investigated in which the seasonality is much less marked.After the experimental application of the blackfly larvicide Methoxychlor to two rivers, a catastrophic drift of invertebrates occurred and larvicide residues were detected up to 8 wk after application.Work on the decomposition of autumn-shed leaves in water has included the responses to temperature and to additional nutrients (N and P). The effect of nutrient addition was to increase the amount of nitrogen in the leaf after incubation, but temperature affected only the rate of decomposition. Determination of the relative importance of bacteria and fungi in decomposition, was studied with use of antibiotics, and food preference ofGammarusfor several leaf species was determined.A considerable portion (up to 40%) of the autumn-shed leaf is water-soluble, and the way in which it is made available to stream animals was investigated. One process, its conversion into particles, appears to involve mechanisms similar to those found in soils, i.e. by formation of organic/metal complexes. Using infrared spectroscopy, attempts have been made to characterize the laboratory and field-produced particles. Field investigations have also demonstrated large-scale fluctuations, during only a few hours, of dissolved and particulate organic matter in the water.These findings are considered in relation to general stream ecology.

ISSN:0706-652X    

DOI:10.1139/f74-090

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Five oligotrophic lakes in Terra Nova National Park, Newfoundland, varying in mean depth (1.06–9.22 m), in water renewal rate (0.2–20.7 times per annum), in salinity (18.2–42.6 mg/liter), in total phosphorus (0.1–0.6 mg-at P/m3), and in chlorophyllaconcentration (0.5–3.2 mg/m3), were investigated for 17 mo in 1969 and 1970. Hypolimnetic oxygen deficits ranged between 111 and 217 mg O2per m2/day. Low levels of nutrients, reduced solar radiation, and low underwater light penetration, owing to excessive cloudiness and high water color, seriously limited planktonic primary production. The relation between primary production at optimum light, and water renewal per annum, appeared to be curvilinear when the rate of primary production began to decline above an optimum water renewal rate. The seasonal and annual variations in water color and salinity were dependent on the rate of water renewal, but other lakes on the catchment areas modified that relation. Winter road salting operations within the catchment area caused a considerable increase in salinity, total phosphorus concentration, and primary production in one lake. A new morphometric index which reflects the littoral effect on basin volume was proposed.

ISSN:0706-652X    

DOI:10.1139/f74-091

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Seasonal data for several physical and chemical variables in Char Lake are given. Annual cycles of major solutes are influenced primarily by freeze–thaw cycles. Concentrations of most substances are increased by freezing–out during the winter. Because the lake does not circulate during maximum spring meltwater flow, this freezing-out maintains concentrations in the lake above those in inflow streams.Concentrations of phosphorus and nitrogen in the lake are low throughout the year. Precipitation contains little phosphorus or nitrogen. Input of phosphorus and nitrogen are calculated to be 0.016 and 0.314 g/m2, respectively. Retention of nutrients by the lake is lower than in temperate regions, although still quite efficient.With the exception of silica, return of ions from the sediments during winter was found to be negligible.Disturbance of one inflow stream due to airstrip construction caused great increases in concentrations of nitrogen, silica, chloride, sulfate, and bicarbonate in the stream.

ISSN:0706-652X    

DOI:10.1139/f74-092

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Benthic photosynthesis and respiration was measured by in situ oxygen change and correlated with in situ radiation in ultraoligotrophic Char Lake Oat. 74°42′N). Photosynthesis by the moss and deep sediment zones was correlated with light but photosynthesis by the shallow rocky zone was not. Total benthic gross photosynthesis in Char Lake is 47.5 g O2m−2yr−1, or 80% of the total lake photosynthesis. Benthic respiration was 43.6 g O2m−2yr−1, in close agreement with the 40.1 g O2m−2yr−1derived from whole lake metabolism. Light input is strongly dependent on snow cover and extinction coefficient. Subsurface irradiance is 24% of the photosynthetically available surface radiation.

ISSN:0706-652X    

DOI:10.1139/f74-093

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Phytoplankton production of ultraoligotrophic Char Lake and polluted Meretta Lake Oat. 74°42′N; long. 94°50′W) were studied between 1969 and 1972. Phytoplankton production in Char Lake is approximately 4.1 g C m−2yr−1, making it the most oligotrophic lake on record. Photosynthesis takes place virtually the whole 9 mo the sun comes above the horizon. Changes in depth of maximum photosynthesis, in efficiency of low light utilization, and in optimal light flux resulted in a much more constant production rate than suggested by the light input, which is importantly affected by amount of snow cover. Phytoplankton in nearby sewage-polluted Meretta Lake averages 11.3 g C m−2yr−1, and chlorophyll concentrations are 20 times higher than in Char Lake. Nutrient deficiencies, especially of phosphorus, are almost certainly responsible for the low efficiency of light utilization and resulting low production in Char Lake. Benthic production is of major significance in both lakes.

ISSN:0706-652X    

DOI:10.1139/f74-094

出版商:NRC Research Press    

年代:1974

数据来源: NRC