The Zooplankton of Ösbysjön, Djursholm. I. Seasonal and Vertical Distribution of the Species

Abstract

The zooplankton of Osbysjon was studied from 1957-1959, with quantitative samples being taken for a year (autumn of 1957 to autumn of 1958). An annotated list of the protozoans, rotifers, cladocerans, copepods and Acarina is given. There is a great oxygen deficit during the winter, and at that time the zooplankton is reduced radically, both qualitatively and quantitatively. In spring, when the water again is oxygenated, various species of rotifers and crustaceans appear one by one, reach a peak, then decline. The distribution of species between summer and winter is discussed briefly, and comparisons are made with the rotifers previously reported in Lake Glan by Carlin (1943), the only previous thorough Scandinavian study. Core samples from the bottom were examined. Bosmina longirostris has occurred in Osbysjon since it was isolated from the Baltic.