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Volume 8, Issue 2
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Kikuya MASIKO1938 Volume 8 Issue 2 Pages 45-52
Published: July 10, 1938
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSLake Osoresan, or Usoriko, Aomori Prefecture. is well known for its strong acidity (pH ca 3-4), the fauna and flora met with in it are consequently limited. The phytoplankton is generally poor through all seasons. The zooplankton is, however, found in great abundance, being dominated by a certain species from year to year.
The fact that the dominant species in this lake vary according to year deserves special comments. A cladoceran, Eimocephalus vetualus (O. F. Müller), which dominated until 1933 showed a marked decrease in 1934, remaining so during 1935-1936. Chydorue aphaeriew O. F. Müller, too, showed a similar change. A copepod, Cyclops fuecue Jurine, on the contrary, showed a marked increase in later years. As to the' explanation of such a change the writer recalls the fact that in 1931 and 1932 the lake water showed but little stagnation, while in 1935-1936 the stratification was very distinct.
The vertical distribution and diurnal migration were studied using wing pump. On June 2829th, bulk of the nauplius and juvenile of C. fuseue inhabited the thermoeline through a day, though slight nocturnal and twilight migration were likely to occur. Contrasted with the above case C. fuacus, on August 4-5 th, tended to migrate nocturnally, though majority of nauplius remained in the hypolimnion. A rotifer, Brachionus uroeolaria O. F. Müller, mainly inhabited the surface layer. As regards the last two species the layer of maximun population sank deeper in in the early morning. This may be considered as being due to the heavy rain of that morning.View full abstractDownload PDF (309K) -
Yosine HADA, Yosiaki KUSUKI1938 Volume 8 Issue 2 Pages 53-67
Published: July 10, 1938
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSLake Toyoni is a single lake found in the Hidaka ranges which are very steep and non-volcanic. This lake which is situated on the north-eastern slope of Alt. Toyoni was probably made by slide damming a deep dale, judging from the heap of stones of the lake-shore. This is a small but deep, heart-shaped lake with the longest axis of about 300 m and the greatest depth of 18.55m, and has neither inlet nor an outlet. Our hydrobiological observations and collections were made on September 12, 1936, and the following results were obtained.
The thermal and chemical stratifications were observed, but the definite thermocline could not be found on account of slight stir of the surface layer by wind, though the matalimnion was distinct in the layer of 10-13 m. Dissolved oxygen was in the super-saturated condition in the epilimnion, but suddenly decreased in the metalimnion, then diminished in the upper layer of the hypolimnion and finally disappeared in the deep layer lying to the bottom. Free carbon dioxide and bicarbonate increased in the hypolimnion, and a remarkable increase of iron and pnosphate was also observed. Nitrate, nitrite and ammonia were detected only from water of the hypolimnion, while chloride and silicate gradually increased with the increase of depth. As the amounts of dissolved salts except silicate are very poor, this lake apparently belongs to a lake of the oligotrophic type.
We could not see any aquatic vegatation on the stone and rocky shore of this lake. Only a species, of fish, rainbow trout, propagates, it was transferred from other lake in 1929. Two forms of Copepoda, four kinds of Cladocera, seven species of Rotatoria, two Testacea, and larvae of aquatic insects and a mite were detected as the zooplankters from the material. Of them, Acanthodiaptomus pacificus var. yamaaaa-ceasis Brehm was most frequently found in off-shore plankton, but near the shore Alonaella excisa (Fischer) most abundant. In the phytoplankton algae were very poor, but two species of Dinoflagellata were exceedingly abunadant in the hypolimnion. The biological characteristics of this lake are as follows : the first is the vegatable bareness of the lake-shore, the second the richness of the flagellata as well as the scantiness of diatoms in spite of plentiful supply of dissolved silicate, the third the differences in the number and the composition of plankton between the central part and shore part, and the last the presence of the living Crustacea in the deep layer lacking in dissolved oxygen.View full abstractDownload PDF (1385K) -
Shinkichi YOSHIMURA, Tosio WADA1938 Volume 8 Issue 2 Pages 68-78
Published: July 10, 1938
Released on J-STAGE: March 04, 2010
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Hisanao YAMAGUCHI1938 Volume 8 Issue 2 Pages 79-83
Published: July 10, 1938
Released on J-STAGE: June 12, 2009
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Sin-itiro KAMBARA1938 Volume 8 Issue 2 Pages 84-95
Published: July 10, 1938
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSDownload PDF (403K)
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