Spatial and temporal taxonomic and functional beta diversity of macroinvertebrate assemblages along a tropical dammed river

Abstract

Tropical freshwater ecosystems are essential for supporting biodiversity and providing crucial ecosystem services. However, these ecosystems face increasing threats from human activities, including the construction of hydropower dams. We investigated how the spatial and temporal taxonomic and functional β-diversity of aquatic macroinvertebrate assemblages varied above and below the Pandeiros River Dam, which is the first dam planned for decommissioning in South America. Integrating spatial and temporal perspectives is essential for understanding ecological community dynamics. We evaluated macroinvertebrate assemblages at eight sites over a period of 6 years, spanning five rainy and dry seasons. Our results revealed that turnover was the predominant component of taxonomic β-diversity spatially and temporally, whereas nestedness exerted a substantial role in shaping functional β-diversity. In addition, we observed higher values of taxonomic temporal β-diversity (TBI) compared with functional TBI. Finally, β-diversity decreased temporally. This study provides: (1) valuable knowledge regarding the spatial and temporal dynamics of the dammed Pandeiros River macroinvertebrate assemblages, as well as those of similar run-of-river dam/reservoir systems; (2) a foundation for the biological effects in case the dam is decommissioned; and (3) increased understanding of temporal assemblage dynamics. By shedding light on the spatial and temporal dynamics in dammed ecosystems, our research serves as a foundation for future monitoring and conservation efforts in tropical freshwater rivers, including how they may respond to dam breaching or removal.