摘要:

The diurnal and annual locomotory activity cycles of four brown trout confined in separate cages on the bed of Windermere and fed artificially from the lake surface are described. The annual activity curves were very similar, the fish being less active during the winter than in the summer with maximum activity occurring in June and again in August. The diurnal activity patterns were also very similar with a sharp rise in activity at dawn each day after an inactive night, the increased activity being maintained throughout the light period and falling rapidly at dusk.Two of the fish were fed daily at irregular times and two were fed automatically every 2 hr. The similarity of the activity patterns of these four fish and also the similarity to the patterns of unfed fish described in a previous paper suggests that light and not food is the prime stimulus to locomotory activity in brown trout.

ISSN:0706-652X    

DOI:10.1139/f64-011

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

An apparatus is described for exposing phytoplankton cultures to 64 different combinations of light and temperature. The light was of a known spectral energy resembling sunlight after passage through a few metres of clear coastal sea water and was measured in the energy units of cals/cm2/min (langlies/min or ly/min). The temperature range used varied in each experiment, the range of illumination was from about 0.005 to 0.4 ly/min, the latter being equivalent to bright summer sunlight at a depth of only a few metres in the sea.The growth of five bacteria-free cultures,Dunaliella tertiolecta,Amphidinium carteri,Monochrysis lutheri,Skeletonema costatumandThalassiosira nordenskiöldiiwas followed for a period of 3–5 days using a cycle of 16 hr illumination and 8 hr of darkness every 24 hr. Growth was measured by counting cell numbers and the rate constants for cell division were evaluated at standard times.The resulting growth-response curves are reported and discussed in relation to their ecological significance. Except forT.nordenskiöldiicell division was relatively insensitive to temperature over a range exceeding 10 °C. Cell division showed a "stress" response, the growth rate being more susceptible to extremes of illumination when the cells were near to the extremes of temperature for a given species and to extremes of both temperature and light if the chemical nature of the medium was unsatisfactory. At optimum temperatures there was no inhibition of cell division at intensities of 0.4 ly/min of photosynthetically active light.

ISSN:0706-652X    

DOI:10.1139/f64-012

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

An apparatus is described in which the constant for exponential algal growth has been determined as a function of light at controlled temperature. Studies were made of bacteria-free cultures ofSkeletonema costatumandDunaliella tertiolectagrown at the optimum temperature for cell division in media with and without adequate nitrate and phosphate. Less complete studies were made of the behaviour ofMonochrysis lutheriandAmphidinium carteri. In all experiments the growth constants were determined at known light intensities, expressed in the energy units, langlies/minute, using light of a known spectral distribution similar to sunlight shining through a few metres of coastal sea water.Growth constants were determined for the following processes: increase of cellular carbon, chlorophyllsa,borc, carotenoids, cell numbers and photosynthesis measured both by oxygen evolution (net and gross) and by the uptake of C-14 labelled carbonate.The rate of maximum photosynthesis occurred when the illumination reached about 0.1 ly/min and little or no light inhibition occurred when the intensity was increased to as high as 0.4 ly/min. Respiration was about 10% of maximum gross photosynthesis. This fraction increased when cells were nitrogen deficient but decreased in phosphate deficient cultures because a phosphate shortage inhibited respiration more severely than photosynthesis.Gross photosynthesis at low light intensities was proportional to thetotal number of moleculesof all plant pigments added together, irrespective of species or of culturing conditions. By contrast, the rate of maximum gross photosynthesis was poorly related to pigment composition, the best correspondence being with the amount of chlorophyllain the cultures.The uptake rate of C-14 varied with time. There was an apparent "leakage" of labelled organic matter which eventually reached a near-equilibrium with14CO2uptake, after which the C-14 method measured the production of particulate carbon but not necessarily net or gross photosynthesis. The rate of particulate carbon production was the same as that of cell division but about 40% less than net photosynthesis in cultures ofSkeletonema. Agreement between C-14 rates and net photosynthesis was better in cool-white fluorescent light than in the imitation submarine sunlight used in this work. At high light intensities there was apparently no excretion fromDunaliella"shade" cells but when these became changed to "sun" cells they behaved more likeSkeletonema.Various observations are recorded of the effect of growth conditions on cell composition, especially with regard to pigments.The relatively low C-14 rates found withSkeletonema costatummay be explicablein partby an abnormally low counting efficiency for this species even when present as a "weightless" source but the problem requires further study.

ISSN:0706-652X    

DOI:10.1139/f64-013

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

Temperature and salinity have been used to characterize the surface water bodies of the oceanic eastern North Atlantic and coastal waters of Britain. Species of plankton have been entered on temperature-salinity diagrams and it has been demonstrated that each is related in a characteristic manner to one or more of the water bodies, or their extended influences in mixtures. This relationship is maintained by each species regardless of seasonal temperature fluctuations of the water bodies, and within the available salinity variations. Species may be present concurrently in oceanic water of one temperature and oceanic-coastal water of a different, lower temperature. Increases and decreases in numbers of a species occur within the limits of these water bodies. These factors are regarded as demonstrating, for the area investigated, that species' occurrences and distributions may not be dependent on temperature and salinity.Discontinuities occur in the distribution of species, chiefly at boundary zones between different water bodies. These arise because some species may cross the boundary zone into another water, while other species of similar origin do not (or cannot).An hypothesis is proposed to explain these features. Unspecified properties are postulated for those water bodies which are contributing to mixed waters in the area studied. The relationships of the species are regarded as being regulated by their tolerances towards the properties; and occurrences and distributions of the species are discussed relative to the presence of the properties. It is considered that the species' reactions to the properties provide a reasonable basis on which to explain the relationships to the waters in the area, their apparent independence of seasonal temperature changes, and the species' distribution.

ISSN:0706-652X    

DOI:10.1139/f64-014

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f64-015

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f64-016

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f64-017

出版商:NRC Research Press    

年代:1964

数据来源: NRC

摘要:

not available

ISSN:0706-652X    

DOI:10.1139/f64-018

出版商:NRC Research Press    

年代:1964

数据来源: NRC