Aquatic Macrophytes Metal and Nutrient Concentration Variations, with Implication for Phytoremediation Potential in a Subtropical River System

Human activities have resulted in an increase in metal pollution within aquatic ecosystems, with most of these metals ending up being taken by macrophytes. Thus, these macrophytes provide an opportunity to study metal pollution dynamics and the role that macrophytes play in potentially translocating and accumulating these metals. Here, we studied three macrophyte species, namely Phragmites australis, Schoenoplectus corymbosus, and Typha capensis, and assessed their potential to be utilized in the phytoremediation of metals in an Austral subtropical river across three seasons. We measured P, K, Ca, Mg, B, Fe, Zn, Cu, and Mn concentrations in macrophyte roots, stems, and leaves, and we further quantified the metal bioconcentration factor (BCF). The N, Ca, and Mg concentrations were generally high in P. australis leaves across all seasons. In general, high Na, Mg, and Ca concentrations were observed in T. capensis across seasons. The bioconcentration factor (BCF) values were generally low (<1) in most macrophyte parts for most metals during the cool-dry season, with the exception of Na, which had high BCF values > 1 (i.e., accumulators) across the different macrophyte parts. We found that P. australis and S. corymbosus have the potential to accumulate metals such as B, Na, Mg, Ca, and N and also have high phytoremediation potential for the studied metals. We found that the studied macrophytes were good at phytoremediation within the river system; however, for any treatment of polluted systems, it is better to use a combination of different macrophytes, as some were better at translocating certain metals than others.