Japanese Journal of Limnology (Rikusuigaku Zasshi)
Online ISSN : 1882-4897
Print ISSN : 0021-5104
ISSN-L : 0021-5104
Volume 60, Issue 2
Displaying 1-9 of 9 articles from this issue
  • Masami NAKANISHI, Tatsuki SEKINO, Takashi KIMOTO, Ryohei TSUDA, Michio ...
    1999 Volume 60 Issue 2 Pages 125-137
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
    The vertical distribution of chlorophyll differed in. its pattern between September 1993 when monthly precipitation was 200-350 mm in July and August (similar to an average year) and September 1994 when it was well below the average (8-50mm). Chlorophyll was more abundant in the epilimnion in 1993, while in 1994 it was less in the mixed layer but instead showed a peak in the thermocline. Algal biomass decreased in the mixed layer due to the absence of nutrients from river water under drought conditions in September 1994. As a result, light intensity sufficient for photosynthesis could penetrate into the thermocline. Nutrients available for algae were supplied by physical and chemical processes from the hypolimnion and/or from turbid water transported from the shore-bottom into the thermocline.The subsurface chlorophyll maximum seems to have been formed by in situ growth of algae in the thermocline relatively rich in nutrients under sufficient light conditions.
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  • Kentaro NOZAKI
    1999 Volume 60 Issue 2 Pages 139-157
    Published: June 01, 1999
    Released on J-STAGE: December 11, 2009
    JOURNAL FREE ACCESS
    Seasonal variations in the biomass and species composition of benthic and planktonic algal communities were investigated from June 1994 to April 1996 in a littoral zone with gravel in the north basin of Lake Biwa. Seasonal fluctuations in biomass were mainly brought about by the rise and fall of a filamentous green alga (FGA) Spirogyra sp. in the benthic algal community, together with Closterium aciculare, Staurastrum dorsidentiferum and Gomphosphaeria lacustris in the planktonic algal community. Comparing the benthic with the planktonic algal biomass, the former made up over 90% of the total algal biomass. This result suggests that the benthic algal community contributes highly to primary production in the littoral zone. There were extraordinary differences in the vertical-distribution pattern and lightextinction coefficient between the FGA and sessile algae (benthic algae except FGA) forming the benthic algal community, thus dividing it into two components : FGA, and sessile algal communities. From the viewpoint of the productive structure of the algal community in the littoral zone, we propose that the community should be regarded as a three-component structure of planktonic, FGA, and sessile algal communities.
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  • Tomiko ITO
    1999 Volume 60 Issue 2 Pages 159-175
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
    The life history of a net-spinning caddisfly, Parapsyche shikotsuensis was studied in a headwater stream, a tributary of Ichankoppe Creek, Eniwa, Hokkaido, northern Japan, 1994-1996. This species is univoltine with an early and mid-summer adult period. Females deposit eggs either above- or underwater on cobbles and wood debris. Early instar larvae appear in August, and almost all of them develop to fifth instar by December. Larvae grow and develop even in winter. Larvae live on riffles, wood debris and the submerged leaves and stems of living riparian plants. Second, third and fifth instar larvae were found at a relatively high density in riffles. Gut contents of larvae are mostly composed of animal fragments (55-95%) and vascular plant fragments (5-45%). The animal-fragment frequency in the guts was relatively low in fourth instar larvae and in October. Moreover, a comparison among the same instar larvae collected in different months showed that animal-fragment frequency was low in October for third, fourth and fifth instar larvae.
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  • Kazuyo NAGAOSA, Kazuko MORIKAWA
    1999 Volume 60 Issue 2 Pages 177-184
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
    Fluctuations in the density of heterotrophic bacteria, an acridin orange direct count (AODC) and environmental factors were studied every two weeks from March 1993 to October 1994 at the urban spring Masugata in the upper reaches of the Nogawa River in Tokyo, Japan. Although water temperature was a constant at 16°C throughout the year, the density of heterotropic bacteria in water fluctuated between 2.6×10 and 1.6×103 CFU ml-1, and the density of AODC ranged from 1.8×103 to 5.5×104 count ml-1. These fluctuation patterns of bacterial density did not follow seasonal changes. Different fluctuation patterns were observed between the density of heterotrophic bacteria and that of AODC, and the values of the density of AODC were 2 to 3 orders of magnitude higher than those of heterotrophic bacteria. Annual changes in the density of heterotropic bacteria appeared to be affected by the rainfall. The fluctuations in AODC and the concentration of NO3--N had a significant positive correlation (p<0.01). Nitrifying bacteria were not detected, and the density of proteolytic bacteria, deaminating bacteria and nitrate reducer were lower than that of heterotropic bacteria.
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  • Yanwen FENG, Norio OGURA, Zongwei FENG
    1999 Volume 60 Issue 2 Pages 185-200
    Published: June 01, 1999
    Released on J-STAGE: December 11, 2009
    JOURNAL FREE ACCESS
    The present studies were carried out in order to explore the current status of air pollution, chemical composition of precipitation, and element budgets at two small watersheds of Shisanling, Beijing suburb and Hakyuchi, Tokyo suburb, during June 1995-May 1996.
    The results showed that annual average pH values of rainfall were 6.7 at Shisanling and 4.7 at Hakyuchi, and that the chemical compositions of precipitation were different between Shisanling and Hakyuchi. The concentration of sulphate was 325μeq l-1, which alone contributed over 70% to the anion total at Shisanling, while the concentration of nitrate was 46.5μeq l-1, which accounted for 38% of the anion total at Hakyuchi. This status indicated that air pollution was classified as sulphuric and nitric acid types, respectively. Concerning the element budget at the Shisanling watershed, total ions (F-, Cl-, NO2--N, NO3--N, SO42--S, Na+, K+, Ca2+, Mg2+, H+, NH4+-N) accumulated, but at the Hakyuchi watershed, Na+, Mg2+ and F- were discharged, and other ions such as SO42--S, NO3--N, Cl-, K+, Ca2+ and NH4+-N accumulated. The F- budget was remarkably different ; about 81% of the input accumulated at Shisanling, and 105% of the input was discharged at Hakyuchi. F- should significantly higher toxicity to plants than that of other acidic substances. If F- deposition remains at the recent level in Shisanling area continually, there will be possible future on the effects ecosystem.
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  • Akihiro TUJI, Chiharu KARASAKI, Yukihiro KOHMATSU, Toshiya YAMAMOTO, K ...
    1999 Volume 60 Issue 2 Pages 201-213
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
    This work is based on the water quality, attached diatom assemblages and water plant community of Naka-ikemi marsh, Tsuruga, Fukui, Japan. Samples were collected from about 50 stations in this marsh from 6 February to 5 September 1997. Using factor analysis, the first axis made by calcium-magnesium hardness and pH was found. This axis was strongly related to the attached diatom assemblages and water plant community. The second axis was characterized by oxidation and reduction. This axis was related to water plants, but not to diatom assemblages. These results clarify the importance of the water quality on the conservation of marsh vegetation.
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  • Atsuko KADONO, Yasuhiro TAKEMON, Mutsunori TOKESHI
    1999 Volume 60 Issue 2 Pages 215-222
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
    A set of field experiments was conducted in the Takami River, a tributary of the Yoshino River in Nara Prefecture, to assess differences in mobility among invertebrate taxa.
    Four experimental designs (drift nets, fall traps, colonization trays with or without gaps) plus a core sampler were used to sample invertebrates and to compare their taxonomic composition. Taxonomic composition was significantly different for all pairwise comparisons of samples except for colonization trays with and without gaps. In terms of the abundance of different taxa, five sampling methods revealed some notable differences. There were more non-chironomid dipterans and less Acarina in drift nets, more Trichoptera and Chironominae in fall traps, more Tanypodinae in colonization trays, and more Ephemeroptera and fewer non-chironomid dipterans in the natural substrate. Consideration was given to the behavioural characteristics of different taxa and to the possibility of interspecific interactions which may have contributed to the observed differences in colonization pattern.
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  • Shuichi ENDOH, Shuhei YAMASHITA, Motoko KAWAKAMI, Yasuaki OKUMURA
    1999 Volume 60 Issue 2 Pages 223-228
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
    Water temperature has increased rapidly over the last decade in Lake Biwa, undoubtedly due to global warming. Deep water has warmed significantly following a succession of mild winters in recent years. The minimum temperature is formed by the overturn in winter and is conserved in the deep water throughout the stratification period in monomictic lakes such as Lake Biwa. This warming of the lake water and the weakening of the overturn in winter should seriously affect the metabolism and ecosystem in the lake.
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  • 1999 Volume 60 Issue 2 Pages 235-243
    Published: June 01, 1999
    Released on J-STAGE: June 12, 2009
    JOURNAL FREE ACCESS
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