Effects of mining and reduced turnover of Ephemeroptera (Insecta) in streams of the Eastern Brazilian Amazon

Mining operations can cause environmental alterations that have a major impact on aquatic organisms. In the present study, we analyzed the effects of mining operations on the environmental heterogeneity of streams in the eastern Brazilian Amazon, and the beta diversity (and components) of the local communities of the order Ephemeroptera. We tested three hypotheses: (a) mining activities reduce the environmental variation of streams; (b) altered streams have lower beta diversity, and (c) environmental variables influence the genus richness and abundance of ephemeropterans. The ephemeropterans were sampled in the Carajas National Forest in the dry season over 3 years. Streams were sampled in areas near the extraction of iron ore (16) and in pristine environments (8). The beta diversity was estimated based on the occurrence and abundance approaches. We recorded 2259 individuals and 32 genera. The comparative assessment of environmental variables indicated that environments altered by mining have higher total manganese and iron concentrations than preserved environments. Environmental variables influenced ephemeropteran communities, and the analysis of the components of the beta diversity indicated a higher turnover of ephemeropterans in preserved streams, which implies that species substitution rates are higher in preserved streams than in altered streams. These results indicate that the substitution of species in preserved streams is limited spatially, probably linked to the sensitivity of the organisms to oscillations in the environmental variables occurring in impacted environments. Implications for insect conservation: The results indicated that possibly the changes brought about by mining activities restrict the turnover of species between the preserved and altered areas, and only species tolerant to these changes were established. Over time and with the advancement of mining activities may occur the local exclusion of the most sensitive species and homogenization of the composition formed by more tolerant and less relevant conservation species.