濠の植物性〓の季節的消長

抄録

Diatomaceae: As were the cases observed by other authors, diatoms among phytoplankton were most predominated in the spring-time. However, in the present case their maximum abundance appeared comparatively early, namely on March 11, 1932 and their number was 16, 020 per 10c.c. holding 95, 6% of the total individuals of phytoplankton and the surface temperature being 10, 3°c at 13h. of that day. The second annual maximum occurred on Dec. 5, 1931. counting 1, 320 per 10c.c. and 89, 2%. The number of important species observed during the time of May 1931-April 1932, were in all 16 belonging to the genera, Synedra, Melosira, Fragilaria, Asterionella etc. The first two of them were the main genera in the spring outburst, and the maximum growth of Melosira, counting 5, 650 on March 26, occurred a little later (about 15 days) than that of Synedra. Asterionella was found in a moderate number in the high winter. On the whole, the quantity of diatoms was found more at the bottom layer than at the surface.
Chlorophyceae: This group was fairly less in quantity compared with diatoms. Its maximum growth appeared on May 26 counting 830 and the water temperature showing about 20°c. Scenedesmus was the representative among 15 species observed.
Cyanophyceae: 4 species were found out. Clathrocystis occurred in summer, especially on June 9, counting 1, 850 per 10c.c. at the surface layer and 600 at the bottom. Aphanocapsa was found more or less in the spring-time.