Assembleias de Ephemeroptera (Insecta) em riachos de cabeceirano bioma Cerrado

Abstract

Different anthropogenic land uses have threaten biodiversity in rivers and streams, especially at tropical developing countries, due of their higher rates of changes of land uses. Sensitive organisms have been used for monitoring the effects of those conversions in aquatic systems. The benthic macroinvertebrates community is commonly used as bioindicators of ecosystem health, because a decreased of sensitive organisms is observed while tolerant ones prevalence, in streams under anthropogenic disturbances pressure. We aim to (1) inventory the mayfly fauna in streams in the Cerrado biome, (2) evaluate the effect of anthropogenic disturbances in headwater streams on the structure of mayfly assemblies (richness, abundance and taxonomic composition) and (3) to test its viability as bioindicators. We hypothesized that streams exposed to multiple human disturbance affect negatively the structure of Ephemeroptera assemblies. Eighty stream sites were sampled in the upper Araguari and São Francisco river basins, and the exposure to human disturbances was measured at local (stream bed and riparian vegetation) and catchment scales (% of land uses). An Integrate Disturbance Index was used to differentiate streams in least and most disturbed conditions. The Araguari basin includes least and most disturbed streams when compared to streams of upper São Francisco basin. The richness and abundance of mayflies nymphs were higher in streams of upper São Francisco river basin [35 genera (11.38 ± 5.42) and 12,533 nymphs (313.33 ± 356.71)] compared to upper Araguari river basin [30 genera (6.73 ± 8.84) and 3,291 nymphs (130.64 ± 82.28)]. The exposure to human disturbance in watershed scale, negatively influenced the richness only in the upper Araguari river basin, where agriculture and pastures activities occur. Only in this basin were found genera that indicates least disturbed streams [Aturbina, Cloeodes (Baetidae), Farrodes, Miroculis and Ulmeritoides (Leptophlebiidae)]. The composition of the assemblies differed significantly in richness and abundance between the least and most disturbed conditions only in streams of the upper Araguari river basin. The results suggest that the mayflies are indicators of streams in good environmental conditions, being more sensitive to disturbances in the catchment scale, and that basins with high exposure to anthropogenic disturbances have different assemblies, both in composition and abundance of sensitive organisms.