Abstract
Experimental studies using four enclosures each containing pond waters of 2.9 m3 in volume were performed to analyse the effects of nutrients and zooplankton on succession of the phytoplankton community. Nutrient enrichment at the beginning of the experiment produced marked increases in chlorophyll-a concentration and algal cell density, followed by a sharp decrease in algal abundance in the later half of the experiment. Three patterns of algal population growth (Types I, II and III) were observed under a regime of decreasing nutrient concentrations. Population development of Simocephalus vetulus (cladocera), which were added to the enclosures accelerated declines in the algae of Types I and II. Species-specific differences in algal nutrient utilization efficiency and a considerable decrease in nutrient concentrations caused by phytoplankton growth were major factors in determining successional changes in phytoklankton of the three growth types.
