Efficacy of phytoremediation technology in decontaminating the toxic effluent released during recovery of metals from polymetallic sea nodules

Abstract

Efficacy of phytoremediation using two macrophytes Azolla pinnata and Lemna minor in decontaminating the toxic effluent released during recovery of metals from polymetallic sea nodules was analysed by applying fish bioassay. The economically important fish, L. rohita, was exposed to both, the Azolla-phytoremediated effluent (APE) and Lemna-phytoremediated effluent (LPE) for assessment of metal bioaccumulation (Fe, Mn, Zn, Cu, Pb, Cr and Cd) and alterations in biochemical (proteins, lipids, glycogen, cholesterol, AST (aspartate amino transferase), ALT (alanine amino transferase) and ALP (alkaline phosphatase) composition of various tissues. Accumulation of metals (e.g. Mn, Zn, Cu and Fe) decreased in most of the tissues exposed to both the phytoremediated effluents perhaps due to decontamination of metals by the two macrophytes. The significantly recovered concentrations of different biomolecules included glycogen, lipids, cholesterol and proteins. The activities of three marker enzymes (AST, ALT and ALP) in phytoremediated effluent-exposed fish also decreased due to lowering of the toxicity of the decontaminated effluents achieved by phytoremediation. The improvement in different biomolecules and reduction in metal concentration in the fish tissues were better in APE exposed fish. However, their concentrations in both the phytoremediated effluent-exposed fish failed to reach the levels of control fish. This study points towards the efficacy of phytoremediation in detoxification of metal-contaminated effluents often released following industrial activities.