Physical, Chemical and Plankton Observations of the Brackish Water Lake Jusangata in the Winter of 1949.

Abstract

Limnological and planktological observations were made on Jusangata, a brackish water lake of an area of 20.9km², in Aomori Prefecture, in January of 1949. The temperature of water was higher (5.6°C) at the stations near the outlet and became low (0.5°C) in the innermost part where there was covered with ice 8-10°cm thick. The pH-value was 8.25 at the stations where chlorine content was more than 10‰. The lake is oligohaline in winter, while in summer months it is polyhaline in its entire area. The plankters occurred in this season are as many as 90 species, of which 55 are phytoplankters and the remaining 35 zooplankters. Of the phytoplankters, the diatoms are the most abundant. The brackish water species of Copepoda such as Limnocalanus sinensis and Pseudodiaptomus inopinus were found in the area different from their range in summer.