Zooplankton species indicate water quality and land use changes in Amazonian streams and ponds

In the face of multiple, co-varying environmental threats, measuring anthropogenic impacts and species responses to them is essential for developing biomonitoring programs and for biodiversity conservation. One way of investigating species responses to different conditions is through indicator species indexes. In this context, we investigated zooplankton species indicators of system type (stream or pond), and the most responsive zooplankton indicators of land use changes (pasture and forest) and water quality (oxygen, pH, temperature, and conductivity) within each system type. We studied 221 sites (162 streams and 59 ponds) across one region of Acre state and seven regions of Pará state, Brazil. We sampled zooplankton and physical and chemical variables at each site and determined land use through digital image processing. We recorded 190 taxa (112 Rotifera, 57 Cladocera, and 21 Copepoda). Thirteen species were pond indicators but none were stream indicators. Several species were indicators of land use and water quality in streams; for example, Disparalona tenuispina indicated highly forested streams and Alonella clathratula and Nicsmirnovius pagii indicated high pasture levels. In ponds, Ephemeroporus barroisi and Lecane doryssa indicated moderate pasture levels and no species indicated forested ponds. Temperature, pH, conductivity, and oxygen were the main drivers of species richness. Our results demonstrate that species-specific responses, rather than assemblage-level patterns, offer insights into the ecological status of these aquatic systems. Furthermore, landscape variables, such as forest and pasture cover, influence the selection of specific zooplankton species in streams but not in ponds. However, forested ponds had the highest species richness. Finally, we highlight the role of certain zooplankton species as sensitive bioindicators of ecosystem health. • Measuring anthropogenic impacts and species responses to them is essential for developing biomonitoring programs. • We studied zooplankton, water quality, and land use in 221 sites across a diverse landscape in the Amazon. • We recorded 190 taxa: 30 were pond indicators and none were stream indicators. • Cladoceran species were indicators of forested or pastured streams, and several zoolankton species indicated water quality. • Species-specific responses offered the most insight into the ecological status of these aquatic systems.