Studies on the Bottom Fauna of Seven Lakes of North Japan
Japanese Journal of Limnology (Rikusuigaku Zasshi)
1. Lakes Towada-ko, Tazawa-ko, Inawasiro-ko, Akimoto-ko, Onogawa-ko, Hibara-ko and Numazawanuma were investigated in 1972 and 1973 in regard to their bottom fauna. The results obtained were compared with the data by MIYADI during the years from 1928 to 1932. They are shown in Table 14 . 2. Lake Towada-ko : Micropsectra sp. (A), a characteristic species of oligotrophic lakes, is dominant in the profundal zone deeper than 300 meters. This lake belongs to an oligotrophic Tanytarsus (=Micropsectra)
... lake. 3. Lake Tazawa-ko : No macroscopic animals occurred on the bottom deeper than 400 meters. The profundal zone of this lake is azoic. In the littoral zone some kinds of chironomids were found, though not abundant. 4. Lake Inawasiro-ko : Tubifex sp, is the dominant species in the profundal zone. Chironomus bathophilus occurred on the zone shallower than 40 meters. 5. Lake Akimoto-ko : Tubifex sp. and C. plumosus, though not abundant, occurred in the profundal zone. This lake belongs to a mesotrophic Plumosus lake. 6. Lake Onogawa-ko : Corethra (=Chaoborus) sp., C. plumosus and Tubifex sp. were found in the profundal zone where dissolved oxygen was absent in the summer stagnation period. 7. Lake Hibara-ko : At present C. bathophilus occurs instead of C. plumosus which was the dominant species of the bottom fauna at the time of MIYADI's investigation. 8. Lake Numazawa-numa : T, genuinus and Sergentia sp., which were abundant in the profundal zone in 1930, do not occur at present ; only Tubifex sp, occurs there.