On the Plankton of Lake Hakamagata and Lake Ushikata, Aomori Prefecture, Japan

Lake Hakamagata (depth 4.5M) and Lake Ushikata (depth 4.0M) which situated in close locality in Nishitsugaru Country of Aom ori Prefecture have been observed limnologically, laying stress on the study of the plankton. The vertical distribution of water temperature showed an apparent stratification, though the difference between the surface and the bottom was not more than 2.0°C. The percentage sauration of the oxygen of surface was 95.4% in the former and 93.6% in the latter, while those of the bottom were 44.6% and 73.2% respectively. Such a oxygen relation suggested the greater abundance of the plankton in the former lake than in the latter lake. The species of the plankton of both lakes are much alike in general appearance except that in the former lake Microcystis aeruginosa vegetated extravagantly. It is also notable that Eurytemora affinis (copepoda), Attheya Zacharisi and Rhizosolenia longiseta (diatoms) which are not always common in other lakes were common to both lakes.