Abstract
Distributions of aquatic macrophyte species are commonly associated with water chemistry characteristics. However, other environmental factors that can lead to the occurrence of aquatic plants in lotic ecosystems, such as dynamic habitats linked to the surrounding landscape, have been underestimated. This study aims to evaluate landscape features that may influence the occurrence of species of euhydrophyte aquatic macrophytes in a tropical river basin. We assessed the occurrence of the following seven species: Egeria densa, Cabomba furcata, Potamogeton pusillus, Potamogeton polygonus, Utricularia foliosa, Pistia stratiotes and Salvinia molesta. We also measured environmental variables related to three spatial scales, local (limnological), channel and riparian landscape, along 25.5 Km of the Itanhaém River basin (São Paulo, Brazil). We found that local (limnological) and channel characteristics were important variables in determining the occurrence of aquatic macrophyte species while the landscape scale had little influence on species composition. Channel depth and margin slope were especially relevant abiotic variables in explaining the occurrence of four of the species but not P. pusillus, P. polygonus and U. foliosa. Our results highlight the importance of channel morphology for understanding aquatic plant occurrence and community composition in tropical rivers.
Highlights
Aquatic macrophytes occur in different types of aquatic ecosystem, but their distributions in lentic and lotic environments differ because of the distinct dynamics between these two habitats (Szoszkiewicz et al 2014)
Higher water nitrate concentration was related to C. furcata (Fig. 2A) and low water alkalinity was related to P. pusillus (Fig. 2B)
Deeper portion of the channel, steeper margins and lower sediment nitrogen concentration were related to C. furcata and deeper channel was related to Egeria densa, Pistia stratiotes and Salvinia molesta
Summary
Aquatic macrophytes occur in different types of aquatic ecosystem, but their distributions in lentic and lotic environments differ because of the distinct dynamics between these two habitats (Szoszkiewicz et al 2014). They are usually more abundant in lakes when compared to rivers, because of their higher water light incidence and low water flow (Bornette & Puijalon 2011). For instance, channel width and depth, and hydrological characteristics, like water current velocity, are important environmental factors in rivers that differentiate them from lakes
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