Metal accumulation and rhizosphere microbial associations in Nymphaea lotus and Limnocharis flava from a natural wetland

Abstract

Wetlands are vital ecosystems that support nutrient cycling and water purification but are increasingly threatened by heavy metal contamination. This study evaluated the accumulation of Ni, As, Cd, Cr, Cu, and Zn in Nymphaea lotus L. and Limnocharis flava (L.) Buchenau and investigated their relationships with sediment properties and rhizosphere microbial communities in a natural wetland in central Thailand. Metal levels in plant tissues and sediments were quantified, and rhizosphere bacteria were characterized using 16S rRNA gene sequencing. N. lotus showed higher accumulation of Ni, As, Cd, and Cr, whereas L. flava preferentially accumulated Cu and Zn. Bioconcentration and bioaccumulation factors exceeded 1 for As and Zn in N. lotus and for Cu and Zn in L. flava, while translocation factors indicated efficient movement of Zn in N. lotus and of Cr, Cu, and Zn in L. flava. Strongly acidic sediments enhanced metal solubility and mobility. Microbial diversity was higher in L. flava roots, whereas diversity declined in N. lotus under elevated As and Cr. Both rhizospheres were dominated by Proteobacteria, with metal tolerant taxa enriched in contaminated zones. Both species are promising phytoremediation candidates for As, Cr, Zn, and Cu contaminated wetlands.