Longitudinal distribution of microcrustacean biomass in three tropical reservoirs (Paraná State, Brazil)

ABSTRACT. This study evaluated the biomass distribution of microcrustaceans in three subtropical reservoirs in Brazil and the relationship among these distributions and some limnological variables in the reservoirs. The hypothesis was that the microcrustacean biomass is distributed according to Marzolf´s third model, proposed in 1990 for zooplankton density in tropical reservoirs. The planktonic microcrustacean biomass ranged from 261.5 mg DW m-3 (Iraí reservoir, transition zone, dry season) to 0.03 mg DW m-3 (Segredo reservoir, fluvial zone, wet season). The highest biomass values were registered in the transition zone, but this longitudinal variation was not significant. The total biomass was related to the trophic state of each reservoir, and a higher difference was observed among the reservoirs than within them. The longitudinal biomass distribution was also related with the longitudinal distribution of chlorophyll-a and showed the same pattern described in Marzolf´s third model. In this way, the results suggested that this model developed for density zooplankton could be employed for the longitudinal distribution of zooplankton biomass in the studied reservoirs. Key words: zooplankton, biomass, longitudinal distribution, tropical reservoirs