Zooplankton functional groups in tropical reservoirs: discriminating traits and environmental drivers

Trait-based approaches are increasingly being used in aquatic ecology to elucidate how environmental conditions affect community assembly. However, studies of zooplankton from tropical regions are relatively rare. Our objective was to construct zooplankton trait-based functional groups (ZFG) to study tropical reservoirs that differ with respect to precipitation, eutrophication and hydrological operations. We selected and analysed zooplankton and associated environmental variables from four tropical reservoirs that were sampled during dry and rainy seasons for three years. Eight traits were evaluated to construct ZFGs using hierarchical clusters and classification trees. Six ZFGs were identified based on three non-redundant functional traits: habitat type, feeding and predatory escape response. Significant differences in the density and biomass of ZFGs were observed as indicated by regression models showing reservoir morphometry, hydrology, rainfall, and phytoplankton biomass as main environmental drivers. Our results highlight the usefulness of ZFG to monitoring programmes and for predicting zooplankton community changes in tropical reservoirs, allowing a greater understanding of plankton dynamics and ecosystems functioning.