Phenolic Content of Aquatic Macrophytes of the Middle Paraná River Floodplain

Abstract

Phenolic compounds (PC) of aquatic macrophytes are involved in relevant ecological interactions and ecosystems functions. However, they have been scarcely evaluated in tropical and subtropical floodplains, where hydrological connectivity could be a related variable due to its effects on environmental conditions. Accordingly, we analysed the foliar phenolic content of 16 common aquatic macrophyte species that are native to the subtropical floodplain of the Middle Paraná River to evaluate 1) intraspecific variability in relation with the hydrological connectivity of floodplain habitats; 2) differences among the main life forms occurring in the floodplain; and 3) PC release and production of chromophoric dissolved organic matter (CDOM) from leaves belonging to species characterized by different PC content. No species showed significant differences in PC between individuals collected in connected and isolated habitats. However, emergent macrophytes showed a higher PC content than free-floating macrophytes, which could be related with their higher frequency in isolated habitats. In this regard, biotic interactions, nutrient limitation, and water stress are known to be stronger in isolated habitats, which could favour the establishment of phenolic-rich species due to the beneficial functions of PC under these conditions. Finally, PC release and CDOM production were larger in phenolic-rich species, with the highest values for Ludwigia peploides. The high PC content of L. peploides could have important implications for the functioning of the Middle Paraná floodplain, where it is one of the most conspicuous macrophyte species; and could be involved in the major ecological problems that it causes outside its native distribution range.