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Volume 36, Issue 2
Displaying 1-5 of 5 articles from this issue
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Norihito SATO1975 Volume 36 Issue 2 Pages 33-47
Published: April 30, 1975
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSIn this paper the author tried to know the changes of the river bed in the Oyodo River in the Outer Zone of Southwest Japan. The results of this survey are summarized as follows :
1) Judging from the records of the mean low water level, it can be recognized that since about 1960 the river bed has considerably lowered due to human activities.
2) As to the lowest heights of the river bed, the quantity of degradation in the lower reaches of the Oyodo River since about 1960 as much as in its upper reaches since about 1955 has become increased remarkably. These facts are also recognized in the changes of the mean heights of the river bed and in the annual fluctuations of the amount of deposition or scouring in the river bed.
3) The author was able to point out that there was something. to be directly proportional between the variations of the mean low water level and those of the mean heights of the river bed.
4) Regarding the causes of the degradation of this river bed since about 1955 or 1960, it can be : considered that the effect of gravel mining in the river bed. Moreover, the tractional load which is washed away to the lower reaches becomes decreased due to the construction of sand catch dams.
5) If it had not been for the human activities, for example the gravel mining etc., the annual vertical variations of this river bed would have shown as follows :
Lower reaches : +0.83±1 cm/y.
Upper reaches : +0.74±1 cm/y.View full abstractDownload PDF (2151K) -
Norizumi KITAGAWA1975 Volume 36 Issue 2 Pages 48-54
Published: April 30, 1975
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESS1. Lakes Shikotsu-ko, Kuttara-ko, Toya-ko, Hangetsu-ko and Oshima O-numa were investigated in 1972 and 1973 in regard to the bottom fauna.
2. In Lake Shikotsu-ko, only Tubifex sp. occurred in the profundal zone deeper than 350 meters. Some kinds of chironomid larvae were found in the littoral zone. The dissolved oxygen is rich throughout the layers of water.
3. In Lake Kuttara-ko, no macroscopic animals were found in the zone deeper than 138 meters. Tubifex sp. and Procladius sp. (F) occurred in the zone shallower than there, though not abundant. Transparency was 18 meters. This is the highest value of the nine lakes in Hokkaido investigated by the author.
4. In Lake Tuya ko, some kinds of chironomid larvae were found in the littoral zone, but not in the profundal zone. Tubifex sp, occurred widely all over the bottom.
5. In Lake Hangetsu-ko, no macroscopic animals were found on all over the bottom. The deoxygenated layer extends for several meters at the deepest zone.
6. In Lake Oshima 0-puma, C. plumosus is dominant in the profundal zone. This lake is a mesotrophic Plumosus lake.View full abstractDownload PDF (978K) -
Nobutada NAKAMOTO1975 Volume 36 Issue 2 Pages 55-64
Published: April 30, 1975
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSA long-lived, heavy freshwater red tide of Pyridinium occurred in a newly built water supply reservoir, between late February and late May, 1972 and 1973, starting and spreading from the entrance region. The densities of the alga reached at least 9.3 x 104 cells per ml and at least 2, 700 μg chlorophyll- a per liter at a wind drift. The red tide is attributed to the increase of solar radiation, the hardness of water and the sewage drains from towns and croplands. The water mass containing a dense algal bloom was an excellent receiver of the solar radiation. This flagellate acted as an accumulater of nutrients at the entrance region of the reservoir.View full abstractDownload PDF (1485K) -
Setuko KOBAYASHI, Osamu UDAGAWA1975 Volume 36 Issue 2 Pages 65-75
Published: April 30, 1975
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSVertical distribution was studied regarding the chlorophyll degradation product (phaeophytin), organic carbon, organic nitrogen and ignition loss in sediments of Lake Tega-numa.
The content of phaeophytin was lager in the upper layers and remarkably decreased with core depth. The correlation was obtained between organic carbon and ignition loss, organic nitrogen and ignition loss, and, organic carbon and organic nitrogen. The values of the carbon/nitrogen ratio in sediments was 10-16 in the upper layers and 16-29 in the deeper layers. In the upper layers the correlation was observed between the carbon/nitrogen ratio and the contents of phaeophytin.
The origin of organic substances in sediments of Lake Tega-numa is inferred phytoplankton in the upper layers and undecomposed plant in the deeper layers.View full abstractDownload PDF (1374K) -
Tomiko ITO1975 Volume 36 Issue 2 Pages 76-77
Published: April 30, 1975
Released on J-STAGE: October 21, 2009
JOURNAL FREE ACCESSDownload PDF (212K)
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