Abstract
We assessed the combined impacts on the community of small-sized herbivorous zooplankton using mesocosms, in which their populations were exposed to copepod Mesocyclops pehpeiensis predation and/or food shortage. The densities of the small-sized zooplankton were depressed in the tanks with M. pehpeiensis and a low algal density, probably because the prey populations were unable to compensate for the population loss by copepod predation. In contrast, most of the herbivorous zooplankton, especially rotifers, established large populations, despite their exposure to predation in the tanks with high algal density. This might be due to their high reproductivity under the conditions. In addition, the release from competitive pressure by cladocerans, whose populations were suppressed by intensive predation by M. pehpeiensis, would be favorable for the rotifers. Our experimental findings may explain the herbivorous zooplankton community structure in the shallow eutrophic lakes inhabited by abundant copepods. The results may become valuable information for reducing biological interference with rotifers within zooplankton assemblages, leading to effective use of the animals for water treatment systems.
