Plankton studies in a lacustrine environment : I. Preliminary data on zooplankton ecology of Broa Reservoir

Weekly zooplankton samples were taken during the period February, 1972 to January, 1973 at station III in a shallow and turbulent tropical reservoir (Broa Reservoir, São Carlos, São Paulo, State-Brazil). The samples were taken by plankton standard net with 68 μ mesh size, and collected through the horizontal hawls during 3 min. Rotifera was the most abundant group with 77.6%; Cladocera 13.6%, and Copepoda 8.7% (adult and naupliae stages). Other forms like Chaoborus larvae and some worms occurred sporadically. The seasonal fluctuation of the total zooplankton was very irregular in warm and rainy season and more stable in the dry and cold season. The composition of the zooplankton and its patterns of seasonal variation for eutrophic and oligotrophic aquatic ecosystems, in tropical regions, may differ significantly from temperate waters.