This paper reports on a study involving an estimate of the biomass of rotifers, cladocerans, and cyclopoid and calanoid copepods found in reservoirs in different trophic conditions, comparing and relating numerical density data and pointing out differences between the dry and rainy seasons. In terms of numerical densities, both reservoirs were dominated by rotifers, although cladocerans represented a higher biomass in the oligotrophic environment in both seasons. In the eutrophic environment, higher biomass values were found for cyclopoids during the dry season and for cladocerans during the rainy one. Different biomass patterns were observed relating to both the trophic conditions and the rainy and dry seasons.
biomass; zooplankton; trophic state; Alto Tietê Basin
