Seasonal changes in horizontal distribution of algal picoplankton in Lake Biwa with special reference to water temperature, nutrient levels and heterotrophic flagellates

Abstract

Seasonal changes in the horizontal distributions of algal picoplankton (APP) were examined in relation to those of heterotrophic flagellates and some environmental factors at 8 sampling stations covering both the northern and southern basins of Lake Biwa from June 1992 to March 1993. Water temperature and nutrient levels differed little among these stations. Horizontal distribution of APP was variable during the summer and fall. There was a consistent trend in the changing pattern of APP density at each station : cell density of APP at all stations was highest in August and low during the winter. Horizontal distributions of both flagellates and APP were changeable during the summer and fall. However, we could not find a seasonal trend in the changing pattern of flagellate density at each station.