Caught Between Macrophytes and Human Impact: Zooplankton Facing Multiple Stressors in Tropical Waters

Abstract

Tropical freshwater systems host diverse and functionally important zooplankton communities that are increasingly threatened by multiple stressors. Here, we assessed how land-use disturbance, local environmental conditions and macrophyte structure influence zooplankton richness, abundance and composition in Amazonian ponds and streams. Across 68 sites in Pará State, Brazil, we found that zooplankton composition differed significantly between system types (pond and stream), although richness and abundance were comparable. Landscape disturbance (mining and pasture) and riparian forest cover reduced zooplankton diversity—especially copepods and cladocerans—while macrophyte richness and abundance increased total and group-specific richness and abundance. High temperatures positively affected total zooplankton and rotifer diversity, whereas oxygen negatively affected copepods. These results reveal that both anthropogenic and habitat-related factors shape tropical zooplankton communities in complex, group-specific ways. Maintaining macrophyte-rich habitats and riparian vegetation may mitigate biodiversity loss and sustain ecosystem functioning in tropical freshwater systems under increasing human pressures.