Environmental factors affect macrophyte diversity on Amazonian aquatic ecosystems inserted in an anthropogenic landscape

Land use is considered one of the most serious drivers of biodiversity change. Aquatic macrophytes are sensitive to changes occurring within their physical habitat and respond at different scales to the effects of land use. Our main objective was to evaluate the effects of multiple land uses on macrophyte diversity. For that, we surveyed aquatic macrophyte richness and cover, in addition to local (water parameters and canopy cover) and landscape (land use and land cover) environmental variables. We evaluated 30 aquatic ecosystems and the results showed canopy cover was negatively correlated with temperature and land use gradient, indicating this parameter reflects land use change within sites. Species richness was affected negatively by canopy cover. Forest cover loss could change macrophyte microhabitats, increasing light resources that favor species that otherwise would not be able to occur there. Species composition was related negatively with canopy cover and water turbidity, and positively related to pH. Three species were selected as indicators of change in canopy cover, which reflects land use change within the sites. Land use change favors mostly emergent and amphibious species, and some species belonging to other life-forms that show adaptations and niche requirements that are benefited by it. Macrophyte communities could be experiencing succession, in which the appearance of invasive species could be the onset of a reduction in diversity as land use consequences become abrasive. We recommend different aspects of macrophyte communities (e.g. species richness, composition, life-form diversity, presence of invasive species, and taxon-specific niche requirements) to be considered when creating indexes of integrity, and when making management decisions regarding the preservation of Amazonian freshwater ecosystems, due to their great potential as indicators, and in order to maintain overall aquatic biodiversity.