Rotifer fecundity in relation to components of microbial food web in a eutrophic reservoir

Abstract

The relationship among rotifers and their potential food sources such as bacteria, heterotrophic nanoflagelates and algae were examined in the eutrophic Řimov reservoir. The egg ratio of five rotifer species (Polyarthra spp., Keratella cochlearis, K. quadrata, Kellicottia longispina and Synchaeta spp.) was estimated and related to the concentration of food particles. Generally, the highest egg ratio was found during the spring time, before the clear water phase, although the densities of some species reached their highest numbers in summer. All investigated food sources were found to have a significant relationship to rotifer egg ratio. The fecundity of all species, except Synchaeta, depend on chlorophyll-a. The Monod curve of food-fecundity relationship reflects that K. cochlearis and P. dolichoptera have high affinities to lower concentrations of chl-a. This is in contrast to K. longispina and K. quadrata, which maximized their egg ratio under higher food concentrations. The two components of the microbial food web (bacterial carbon and HNF) were correlated with fecundity but only for K. cochlearis. The seasonal differences in food-fecundity relationships for K. cochlearis andK. longispina indicated that there might be differential food preferences of these two species during the season.