Small hydropower dam alters the functional structure of macroinvertebrate assemblages in a Neotropical savanna river

Hydropower dams and their reservoirs are major disturbances affecting riverine ecosystems worldwide. However, most existing knowledge comes from large hydropower systems. We evaluated the upstream and downstream effects of a small run-of-river hydropower dam on the functional structure of benthic macroinvertebrate assemblages in a Neotropical savanna river. We found that functional originality and divergence were significantly higher near the dam site. In contrast, functional dispersion was higher at free-flowing sites upstream and downstream of the dam. Sites near the dam had greater proportions of univoltine organisms with spherical and low-flexibility bodies. On the other hand, free-flowing sites had increased proportions of multivoltine organisms with flattened bodies and flexible. The macroinvertebrate assemblages at all sites were mainly homogeneous and composed functionally generalist taxa. This study enhances our understanding of the environmental effects of small run-of-river dams on benthic macroinvertebrates, emphasizing the usefulness of functional characteristics for those assessments.