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Volume 39, Issue 1
Displaying 1-6 of 6 articles from this issue
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Norizumi KITAGAWA1978 Volume 39 Issue 1 Pages 1-8
Published: January 30, 1978
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSA classification of Japanese lakes was made with special references to the hypolimnetic oxygen and the benthonic fauna in the profundal regions. The following characteristic benthonic animals were selected as the indicator species for classifying lakes : Micropsectra sp. A, Calopsectra sp. J and Spaniotoma sp. B were for stenoxybiontic; Chironomus bathophilus and Sergentia sp. B for mesoxybiontic; Chironomus plumosus and Chaoborus sp. for euroxybiontic. Tubifex sp. was also used as an indicator species of the lakes without chironomid or chaoborid larvae. According to the difference in the dissolved oxygen content in the hypolimnion for the summer stagnation period, oligotrophic, mesotrophic and eutrophic lakes were respectively defined as lakes where hypolimnetic oxygen content was more than 50% in saturation, less than 50% but more than 10%, and less than 10%.
Taking the distribution of indicator species into account, fifty lakes in Japan were classified into the 4 types and 14 classes shown in Table 2.View full abstractDownload PDF (1264K) -
Yoko YAMAMOTO1978 Volume 39 Issue 1 Pages 9-14
Published: January 30, 1978
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSThe detection of biological agents responsible for the deterioration of the blooms of blue-green algae in lakes was attempted by the soft-agar overlayer technique. One ml of algal suspension and a measured volume of sample were added into about 2ml of melted 0.8% agar cooled to 45°C-48°C, and the mixture was poured over the surface of a hardened layer of modified Detmer medium containing 1.5% agar. After the upper layer solidified the plate was incubated at 25°C to 30°C in the light of 3000 lux to 5000 lux. After 10 days incubation, plaques on agar plates were counted. Most of the agents detected by this technique were amoebae, bacteria and fungi. Especially, development of large plaques was accompanied by amoebae.View full abstractDownload PDF (1170K) -
Motomu NIKAIDO1978 Volume 39 Issue 1 Pages 15-21
Published: January 30, 1978
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSStudies on the ratios of organic carbon to nitrogen (C/N ratios) in the core sediments from Lake Kojima were conducted in relation to both the changes of C/N ratios and the relative mineralization rates of organic carbon and nitrogen with the incubation experiments.
Both the organic carbon and organic nitrogen decreased with the core depth, whereas the C/N ratios markedly increased with same.
In the incubation experiments of sediment samples, the amount of mineralized organic carbon was larger than that of the organic nitrogen, but the mineralization percentage of organic nitrogen based on the initial amount of organic nitrogen in the sediment samples was higher than that of the organic carbon. This fact suggests that the organic nitrogen was more rapidly mineralized than the organic carbon, and that the vertical profiles of C/N ratios in the core samples resulted from the difference between the relative mineralization rates of the organic elements. This phenomenon was also discussed from the viewpoint of the processes of methane production in the lake sediments.View full abstractDownload PDF (1013K) -
Jun SHIMADA, Isamu KAYANE, Tadashi TANAKA1978 Volume 39 Issue 1 Pages 22-28
Published: January 30, 1978
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSTo investigate the transport mechanism of solutes in soil water in the unsaturated zone, collection of soil water samples having different matric potential is necessary. Three methods originally developed for the purpose of measuring matric suction, i. e., the centrifuging, the pressure membrane, and the vapor pressure depression methods, were used to extract soil water samples under different matric potentials. The time to attain an equilibrium between the pressure of soil water and a given matric suction (pF 3.0 or 4.2) was much faster by the centrifuging method than by the pressure membrane method. The soil water sample with matric potential of pF 4.2-6.8 was extracted by the vapor pressure depression method under the regulated temperature of 110°C (Fig.5). By combining these three methods, three soil water samples having different matric potential ranges were collected from each soil sample with satisfactory accuracy.View full abstractDownload PDF (894K) -
Coefficients of Vertical Thermal DiffusivityNorihisa IMASATO, Hideaki KUNISHI1978 Volume 39 Issue 1 Pages 29-36
Published: January 30, 1978
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSMeasurements of air and water temperature had been carried out at Lake Yogo from January, 1969 to January, 1970. Using these continuous records, characteristics of the seasonal variation in limnological conditions in Lake Yogo are described. Coefficients of vertical thermal diffusivity, Kz, are evaluated for 6 layers of water with time scales from a day to a month. Ignoring the absorption of solar radiation in evaluation of thermal diffusivity, coefficient Kz becomes about 10% larger. In the period when lake water is stratified, coefficient Kz in the upper layer is larger than in the lower one, namely about 0.2 cm2/sec in 3m layer and about 0.04 cm2/sec in 7m layer. It is shown that, the larger the vertical gradient of water temperature is, the smaller the coefficient Kz is, and that the value of Kz is about 0.08 cm2/sec at ∂T/∂z=1.0°C/m and about 0.5 cm2/sec at ∂T/∂z=0.1°C/m.View full abstractDownload PDF (1113K) -
Monthly Variations of Heat BudgetNorihisa IMASATO, Hideaki KUNISHI, Yoshiaki TOBA, Kenji HONDA1978 Volume 39 Issue 1 Pages 37-43
Published: January 30, 1978
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSThe heat budget at Lake Yogo was studied using the daily averaged values of wind speed, vapour pressure, air temperature and surface water temperature observed at Lake Yogo from August 1969 to January 1970. The monthly averaged values of latent heat, QE, transferred from the lake to the atmosphere were large in August-November and those of sensible heat, QH, were large in October-November. Adopting the constant value 1.1×10-3 as the bulk transfer coefficients CE and CH for evaporation and sensible heat, the estimated values of the absorbed net radiative energy, QR, were found to be considerably smaller than the observed values of QR. When these bulk transfer coefficients are changed as wind speed and temperature difference between surface water temperature and air temperature according to KONDO (1975), the estimated values of QR are found to be in satisfactory agreement with the observed values.View full abstractDownload PDF (1068K)
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