Microcosm investigation on differential potential of free floating azolla macrophytes for phytoremediation of P-controlled water eutrophication

Eutrophication is caused by an over enrichment of aquatic ecosystems with nutrients, principally with chronic release of phosphorus (P) from point and non-point sources, leading to nuisance algal blooms, anoxic events, impaired water quality and stubborn environmental issues. Aquatic macrophytes display an efficient phytosequestration of inorganics in plant parts due to their non-degradable nature. Serial microcosm experiments were conducted to estimate differential phytoremdiation ability of A. japonica, A. pinnata, and A. hybrid to remove P from different P-eutrophicated solutions under different incubation periods. Azolla plants showed substantial P-removal efficiency from P-eutrophicated solutions, and removed P-amounts were significantly correlated with P-accumulated in plant biomass. About 1-fold decrease in solution pH might be ascribed to H⁺-efflux. Plants without P-hunger showed lower P-removal rates compared to P-hunger plants. A. japonica displayed highest P-removal efficiency in different experiments. From these kinetic experiments, it is plausible to conclude that phytoaccumulation was the possible mechanism for P-removal, and due to fast growth, high tolerance and accumulation ability, free floating Azolla might be the best candidate among macrophytes to combat P-driven eutrophication. results obtained will not only provide information to environmental managers to mitigate P-eutrophication but will also provide data base to scientists for their future ventures.