Slurry pipeline effects on Amazonian streams and Odonata communities

Abstract Mining activities have substantially altered Amazonian watercourses. Odonata are sensitive to environmental changes and efficient bioindicators because they are highly responsive to conditions in riparian and aquatic habitats. Therefore, our objectives were to assess the changes associated with a slurry pipeline on Amazonian streams and to determine whether those changes altered Odonata assemblage structure. We also sought to determine which environmental variables most influenced regional Odonata diversity and the degree to which those variables differed between pipeline and control sites. We collected 769 adult odonates from which we derived biodiversity variables (richness, abundance, composition) and measured 245 environmental variables in 48 stream sites located in the Belém endemic center, northeastern Amazonia. We found that the slurry pipeline altered the Amazonian stream environments, including changes in acidity and water speed. The main impacts identified were related to stream damming. These effects significantly affected Zygoptera abundances and Anisoptera species composition. We suggest that the moderate impacts highlighted probably reflect the history of widespread human exploitation in the region, which likely filtered out the more sensitive Zygoptera species. Consequently, the remaining communities exhibit only a weak response to the environmental differences detected in our study. Implications for insect conservation Our results show that slurry pipeline-associated infrastructure can alter Amazonian stream habitats by partially impounding and increasing sedimentation, reducing Zygoptera abundance and shifting Anisoptera community composition. We recommend limiting sediment inputs from access roads, improving hydrological monitoring, ensuring adequate culvert design and maintenance, and implementing long-term bioindicator monitoring to reduce cumulative losses of Amazonian freshwater diversity.