The accumulation of heavy metals (Fe, Mn, Zn, Cu, Cr, Ni, Pb, Cd) and biogenic elements (P, S, K, Ca, Na) in leaves has been studied in macrophytes of different ecological groups growing in small water bodies of St. Petersburg. The ecogeological and biogeochemical role of macrophytes in the water-aquatic plants-bottom sediments system and their contribution to the stability of aquatic ecosystem functioning under conditions of a megalopolis are considered. Prospects for using macrophytes for bioindication and phytoremediation of polluted aquatic ecosystems are discussed.