Temperature Drives Macrophyte Species Composition in Streams and Ponds of Marajó Island, Brazilian Amazon

Changes in the landscape surrounding aquatic systems can alter the physical and chemical properties of water, leading to shifts in species composition and ecosystem services. Aquatic macrophytes are among the biological groups affected by local and landscape changes. In this study, we investigate the species richness and beta diversity of macrophytes in streams and ponds under different land uses in Marajó Island, Pará, Brazil. Sampling was conducted in 36 ponds and 26 streams in October 2022 and June 2023. Limnological variables were measured at each sampling site using a multiparameter probe, and land use was determined using satellite images. We recorded 120 species belonging to 38 families. In streams, 89 species were recorded (74% of the total species sampled), and in the lakes, 85 species were recorded (71%). There was no significant difference in macrophyte species richness between ponds and streams; however, macrophyte species composition differed between these systems, with exclusive species in each system. Dissolved oxygen, pH, and conductivity showed substantial variation among sites but were not associated with macrophyte composition or richness; only temperature was associated with species composition. Our findings highlight the great diversity of macrophyte species and the importance of conserving different water bodies to maintain biodiversity. Future studies should incorporate flood pulse dynamics and connectivity to enhance understanding of the factors shaping macrophyte species and to inform the development of effective conservation strategies.