Japanese Journal of Limnology (Rikusuigaku Zasshi)
Online ISSN : 1882-4897
Print ISSN : 0021-5104
ISSN-L : 0021-5104
Volume 31, Issue 1
Displaying 1-4 of 4 articles from this issue
  • Ken-ichi HIRAI
    1970 Volume 31 Issue 1 Pages 1-14
    Published: April 18, 1970
    Released on J-STAGE: October 16, 2009
    JOURNAL FREE ACCESS
    The species composition and population numbers of zooplankton and attached animals in littoral vegetation zone in Lake Biwa were investigated during spring and summer of 1966 and 1967.
    The plankters were collected with 0.5 liter cylindrical water sampler, and attached animals with vinyl-sack.
    In the Yamanoshita Bay where the investigation was carried out intensively, littoral vegetation developed was as follows : In the marginal zone there were emerged plants (Phragmites, Zizania and Carex), among which patches of sub-merged plants were observed. In the outer part, submerged plants, such as Elodea, Potamogeton, etc., developed widely.
    Much more numbers of species of zooplankton were found in the littoral zone than in the offshore area. In the former, abundant species were Chydorus sphaericus and Alona guttata, whereas Daphnia longispina and Conochilus unicornis in the latter.
    Between the littoral stations there was no remarkable difference in the total density of zooplankton, but the species composition was remarkably different each other : i.e., Eodiaptomus japonicus and Bosminopsis deitersi were numerous in open littotal area, whereas Chydorus sphaericus, Mesocyclops leuckarti, Euchlanis dilatata and Philodina roseola were numerous in vegetational belt.
    Zooplankters living in vegetational belt were divided into two types by their modes of life as follows : completely free-swimming species and species which sometimes attached on aquatic plants and swam freely in other times.
    In the latter type of species, much more number of individuals remained attached and only few individuals swam freely at least in the daytime. For instance, attached number of Chydorus sphaericus was 60-120 times higher than the swimming one per unit water column.
    The total population number of attached animals changed according to the vegetation type. Attached animals usually occurred more abundantly in Potamogeton belt than in Elodea belt, and much less in Phragmites belt than in the former two submerged plants area.
    It was observed that the changes in number of free-swimming animals at small open space between Potamogeton leaves were strictly parallel with that of attached ones on the submerged plant. In such area, attached animals will be supply-base for the planktonic ones.
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  • Michiyasu MORI
    1970 Volume 31 Issue 1 Pages 15-20
    Published: April 18, 1970
    Released on J-STAGE: October 16, 2009
    JOURNAL FREE ACCESS
    The caldera of Mt. Aso is divided by the central cone into two parts : Aso-Valley and Nango-Valley. Rice-fields are cultivated inside the slope of caldera at Kugino, on a sharp inclination of the mouth of caldera at Tateno, on a easy slope of central cone at Bochu, and at Narukawa midst the Plain of Aso-Valley. Phycological and ecological survey was carried out at these 4 stations.
    In these fields cultivated on the slope or inclination, water is supplied from the adjoining upper field and flows down into the lower. Desmid is scanty even the water is comparatively poor in chlor and calcium. On the other hand desmid occurs luxuriantly at Narukawa in spite of considerable amount of both minerals, because the water is stagnant. In comparison with alluvial lowland of Yatsushiro-Plain, Kumamoto Pref. and calcareous district of Hiraodai-Plateau, Fukuoka Pref., Narukawa is the poorest in desmid among these fields. At Hiraodai the water contains corresponding amount of calcium to Narukawa but less of chlor. The water of Narukawa is richer than the lowland both in chlor and calcium. At Bochu the amount of both minerals is exceedingly rich and desmid can hardly be encountered. Accordingly desmid in Mt. Aso is scanty in general and chlor is also related to the distribution of desmid. It has been hitherto remarked that Cosmarium or Closterium dominates in the water which is rich in minerals or organic matter. The association of desmid in the caldera of Mt. Aso is chiefly composed of Cosmarium and Closterium and in this meaning resembles to that of alluvial lowland.
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  • Kyuemon GOSE
    1970 Volume 31 Issue 1 Pages 21-26
    Published: April 18, 1970
    Released on J-STAGE: October 16, 2009
    JOURNAL FREE ACCESS
    1. Samples of Ephemera strigata larvae were taken monthly from May 1967 to June 1968 in the River Niu-gawa, Nara Prefecture to determine the production rate.
    2. Ephemera strigata has one generation in a year.
    3. The production rate was calculated after the formula proposed by Ricker (1946) and Allen (1949), B=KP. The rate was found to be ca. 4.25g/m2 in the pool of the river. The yearly turnover rate is 2.4.
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  • Yoshikazu NAGATA
    1970 Volume 31 Issue 1 Pages 27-35
    Published: April 18, 1970
    Released on J-STAGE: October 16, 2009
    JOURNAL FREE ACCESS
    1. The amount of depositing matter, or sediment, was measured by using two types of sediment-trap set up over the bottom at four stations with depths of 0.5 to 3.5m in an inshore area in the shallow southern basin of Lake Biwa in the period from May to November 1967.
    2. The apparatus designed for the present experiment employs a tray (16.8cm23.0cm×2.5cm) fixed aside to a glass bottle (5.2cm in diameter at the mouth).The sediments once settled down in the tray may be assumed to be exposed nearly as freely to the action of the movement, current or turbulence, of water as the sediments on the bottom of the lake are, and may be stirred up and taken away again, whereas the bottle is presumed to retain the whole sediment deposited in it.
    3. Amounts of sediments collected within 24 hours period in bottles, varying from 21.1 to 31881.8 g/m2/day, were always larger than corresponding amounts in trays, varying from 1.6 to 558.7 g/m2/day. Remarkable increase in the amount of sediment, both in bottles and in trays, is recorded with an increasing intensity of wind on the days. Sediments collected during longer periods of 15 to 39 days showed also relatively greater amounts in bottles than in trays.
    4. The ignition loss of sediments collected within 24 hours period both in bottles and in trays revealed a tendency of decreasing with an increasing intensity of wind. This tendency is not clear in the sediment trapped in longer periods.
    5. It is concluded that the sediment collected in the bottles contains a larger amount of matter which is stirred up from the bottom, in addition to the deposition originated from dead pelagic organisms.
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