Does the structure of riparian vegetation affect the diversity of macrophytes in eastern amazonian streams?

Streams are among the most diverse aquatic ecosystems on the planet and help to structure different biological groups. Although streams are influenced by several environmental factors, riparian vegetation is especially important. Human activities have affected riparian zones, which consequently impact organisms such as aquatic macrophytes. Thus, here, we assessed the effects of the vegetation type in riparian zones on the diversity of aquatic macrophytes in eastern Amazonian streams. We sampled macrophytes across a stretch measuring 150 m in 17 streams. The riparian zone was characterized into: canopy, understory, and low-growing vegetation layer. The proportions in all categories were visually estimated, corresponding to semi-quantitative data. Our results show that the composition of riparian vegetation affects the macrophyte community. The richness of macrophyte species had a positive relationship with low-growing vegetation, showing that this vegetation type may favor the establishment of macrophytes on the streams. Low-growing vegetation cover and herbaceous cover positively affected macrophyte composition. The dominance of low-growing herbs indicated the presence of pioneer species in anthropized sites and the low shade levels provided by low-growing herbs, along with other factors, favored the occurrence of macrophytes in streams. Therefore, our results reinforce the assumption that aquatic macrophytes are affected by shade levels, and can be good indicators of altered environments.