Environmental and temporal variability of the aquatic macrophyte community in riverine environments in the southern Amazonia

Temporal variation in limnological characteristics favors an increase in aquatic macrophyte diversity in Neotropical riverine environments. We assessed temporal and environmental variability in the aquatic macrophyte community in riverine environments of the Tapajós river basin, southern Amazonia, Brazil. Hydroperiod, type of riverine environment, limnological variables, and surrounding woody vegetation were found to influence aquatic macrophyte richness, cover, and dry and fresh biomass. A total of 98 species from 68 genera and 40 families were recorded. The greatest observed richness in streams was during the dry period. Richness, cover, and biomass were greater in lagoons and rivers during rising water and flood hydroperiods. Amphibious and emergent species had higher biomass in flood and receding water hydroperiods. Higher richness, cover, and fresh biomass were mostly related to electrical conductivity. Suspended and dissolved solids reduced species richness in all environments. Greater tree abundance in the surrounding vegetation was associated with higher macrophyte richness in streams and with macrophyte cover and biomass in rivers. The aquatic macrophyte community in southern Amazonia is subject to variation in riverine ecosystem type, tree composition and structure in surrounding vegetation, hydroperiod (temporal variation), and limnological parameters (environmental/temporal variation).