Japanese Journal of Limnology (Rikusuigaku Zasshi)
Online ISSN : 1882-4897
Print ISSN : 0021-5104
ISSN-L : 0021-5104
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Volume 53, Issue 1
Displaying 1-10 of 10 articles from this issue
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  • Potamoplanktonic Diatoms in the Nagara River
    Flora, Population Dynamics and Influences on Water Quality
    Tetuo MURAKAMI, Chiaki ISAJI, Nobuo KURODA, Kyoji YOSHIDA, Hiroki HAGA
    1992 Volume 53 Issue 1 Pages 1-12
    Published: January 29, 1992
    Released on J-STAGE: December 11, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.1
    JOURNAL FREE ACCESS
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    The fluctuations of drift diatom assemblage and water quality in the lower reaches of the Nagara river part of a river system without large reservoirs, were surveyed monthly from March 1990 to February 1991. In August 1990, large planktonic diatom standing crops were recorded near the river mouth. Dominant species were Cyclotella atomus and C. meneghiniana (Bacillariophyta: Centrales). Judging from the patterns of algal distribution in the stream and of diurnal fluctuation of both flora and the standing crops associated with tidal movement, the major portion of diatom assemblage is considered to be autochthonous potamoplankton which reproduce in the main stream.
    Current velocity was an important controlling factor in flora and standing crops of potamoplanktonic diatoms. Maximal standing crops were recorded when precipitation in the catchment was low. After considerable precipitation, the relative abundance of exfoliated periphytic diatoms and pheo-pigment content increased.
    In August, when the chlorophyll a concentration increased to a peak value of 32.6 μg⋅l-1, BOD reached the maximum, 3.9 mg⋅l-1 at the lower reaches of the river, and both inorganic nitrogen and phosphorus registered lower values than in the upper stream.
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  • Population Dynamics and Cyclomorphosis of Bosmina longirostris in Lake Yunoko
    Takayuki HANAZATO
    1992 Volume 53 Issue 1 Pages 13-25
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.13
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    Population dynamics and cyclomorphosis of the cladoceran Bosmina longirostris were investigated in Lake Yunoko.
    The Bosmina population showed a marked decline in density in midsummer. Food limitation was considered to be the most probable cause of the decline. Food limitation for the Bosmina population might be promoted by competition with Daphnia longispina, which established a dense population in summer.
    B. longirostris showed a marked cyclomorphosis; they reduced the antennule length and mucro length in summer but recovered them in fall. The presence of predator Cyclops sp., seemed to be a major cause inducing the cyclomorphosis, since a significant positive correlation was obtained between the predator's density and the lengths of the proturberant structures.
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  • CaCO3-Inclusions of Macromonas sp. Blooming at an Upper Boundary of the H2S Layer of Lake Kaiike
    Michiro MATSUYAMA
    1992 Volume 53 Issue 1 Pages 27-33
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.27
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    Two large-celled bacterial species, Macromonas sp. and Chromatium sp., bloom at an upper boundary of the H2S layer in Lake Kaiike throughout the year (bacterial plate). Large pearl white refractile inclusions of Macromonas sp., which were composed of CaCO3, disappeared from the cells when the bacterial plate sample was acidified below a pH 6.3. But, as soon as the pH was returned to an initial level (8.5), these cells rapidly deposited them again, indicating that CaCO3 deposition is one of the essential activities in maintaining cell integrity. The inclusions also disappeared with exposure of live bacteria to a H2S solution. It was suggested that Macromonas sp. inhabits the H2S boundary using CaCO3-inclusions as protection from environmental H2S.
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  • Population Dynamics and Diel Changes in Vertical Distribution of the Cladoceran Holopedium gibberum and bosmina logirostris in Lake Ozenuma
    Takayuki HANAZATO, Seiichi NOHARA
    1992 Volume 53 Issue 1 Pages 35-45
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.35
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    Population dynamics of two cladoceran species, Holopedium gibberum and Bosmina longirostris, in Lake Ozenuma were studied during ice-free seasons in 1987 and 1988, and diel changes in vertical distribution of the two populations were investigated in summer. Both species were distributed in the whole water column during July-October, and showed no marked diel vertical migration. The population parameters(density, biomass, %adult, egg ratio, birth rate) were relatively stable. Fish predation pressure seemed high among the H. gibberum population, since mean body length and minimum reproductive length of the animals were markedly smaller in Lake Ozenuma than those reported in other fish-scarce lakes.
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  • Morphology and Variation of Daphnia galeata SARS from Lake Biwa and Lake Kizaki in Japan
    Susumu TANAKA
    1992 Volume 53 Issue 1 Pages 47-54
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.47
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    In Japan Daphnia galeata SARS has been confused for a long time with Daphnia hyalina or Daphnia longispina due to the confusion in Europe where the three species originally described. In this paper, the Daphnia species from Lake Biwa and Lake Kizaki, which has been assigned various scientific names, are confirmed as Daphnia galeata SARS, 1863, based on the determinative key proposed by FLOBNER and KRAUS (1986), and their morphology and morphological variations are described.
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  • Seasonal Succession and Vertical Distribution of Zooplankton in Lake Ozenuma
    Takayuki HANAZATO, Seiichi NOHARA
    1992 Volume 53 Issue 1 Pages 55-63
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.55
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    Seasonal succession and vertical distribution of zooplankton in the central region of Lake Ozenuma were studied during icefree seasons in 1987 and 1988. Rotifers were more abundant in density than cladocerans. Copepods were rare. The most dominant species were Polyarthra trigla in Rotifera and Bosmina longirostris in Cladocera. In biomass, however, cladocerans usually surpassed rotifers, and the cladoceran Holopedium gibberum took the highest percentage of the total zooplankton biomass. Some zooplankton species were found commonly throughout the study period, whereas others appeared irregularly. It seems that, in recent years, rotifers have become more abundant in the lake.
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  • Decomposition Activity and Nutrient Regeneration Rates in the Hypolimnion of the North Basin of Lake Biwa
    Toshihiro MIYAJIMA
    1992 Volume 53 Issue 1 Pages 65-73
    Published: January 29, 1992
    Released on J-STAGE: December 11, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.65
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    In the course of a recent survey on nutrient dynamics in the north basin of Lake Biwa, an abundant accumulation of nitrate was observed in the hypolimnion during the stagnation period, and the regeneration rate of nitrogen in the hypolimnion was estimated to be 40.5 mmol⋅m-2⋅mon-1. However, it was calculated on the basis of oxygen consumption that the C : N ratio of organic matter mineralized within the hypolimnion should'have been 19-21, which suggested a low regeneration efficiency of nitrogen relative to carbon. Dissolved phosphate was found to be accumulated in small concentrations near the bottom, but the regeneration rate of phosphate was very low (0.22 mmol⋅m-2⋅mon-1), and the activity of hypolimnetic biota seemed to contribute hardly at all to phosphorus recycling in this basin. Possible factors determining the regeneration efficiency of nutrients are discussed in relation to the physiological properties of the hypolimnetic microbial metabolism.
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  • Marked Variation in Lacustrine N2O Accumulation Level and Its Mechanism
    Muneoki YOH
    1992 Volume 53 Issue 1 Pages 75-81
    Published: January 29, 1992
    Released on J-STAGE: December 11, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.75
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    Compilation of N2O accumulation data in the low-oxygen zone of Lake Kizaki revealed a marked variation in the maximum N2O concentrations observed, ranging from 0.17 to 26.5 ug atomN⋅1-1. The N2O accumulation level differed noticeably from year to year: from less than 0.6, ug atomN⋅1-1 in 1983 and 1988, to more than 2.4 pg atomN⋅1-1 in three other years. The maximum N2O concentrattion was correlated with its relative peak position in the low-oxygen zone, with the smaller peak at the "shallower" layer, the larger peak at the "deeper" layer. It was inferred from the N20, NO3- and O2 profile characteristics that the shift in N2O production-consumption balance during the denitrification process may be responsible for such a wide variation in N2O accumulation level and that organic matter availability in the hypolimnion may play a key role in this phenomenon.
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  • Proceedings of the Society
    1992 Volume 53 Issue 1 Pages 95-101
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.95
    JOURNAL FREE ACCESS
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  • Proceedings of the Society
    1992 Volume 53 Issue 1 Pages 103-109
    Published: January 29, 1992
    Released on J-STAGE: June 12, 2009
    DOIhttps://doi.org/10.3739/rikusui.53.103
    JOURNAL FREE ACCESS
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