Primary Production in Lake Kasumigaura, 1981-1985

Abstract

The seasonal succession of phytoplankton was investigated from 1978 to 1985 and the primary production was examined from 1981 to 1985 in Lake Kasumigaura. A large bloom of Microcystis spp. was observed every summer. Synedra rumpens and S. acus dominated in spring, and Melosira granulata, Coscinodiscus lacustris, Cyclotella spp., and/or Chrysochromulina sp. dominated in autumn and winter. Exceptionally large blooms of Closterium aciculare and Oscillatoria agardhii were observed in spring of 1979 and in autumn of 1982, respectively. The gross primary production correlated significantly with the water temperature, the solar radiation, and the chlorophyll a concentration, but not with the nutrient concentrations by multiple regression analysis. Therefore the nutrients were not limiting factors for the primary production in this lake. The annual gross primary production at a center of this lake ranged from 483 to 734 gC·m–2·yr–1, which was intermediate among the values reported in other lakes with Microcystis bloom. © 1987, The Japanese Society of Limnology. All rights reserved.