Introduction

Wetlands are transition zones that play a major role in nutrient dynamics and act as natural filters. The interaction of man with wetlands during the last few decades has been a concern largely due to rapid population growth accompanied by intensified industrial, commercial and residential development, further leading to wetland pollution by domestic, industrial wastewaters and agricultural runoff (Ramachandra et al. 2018). Wetland plant (macrophyte) communities constitute some of the most highly productive ecosystems in the world (Mitsch and Gosselink 2000).

Phytoremediation is the use of living green plants for in situ risk reduction of contaminated soil, sludge, sediments, and ground water through contaminant removal, degradation, or containment (U.S. Environmental Protection Agency 1998). The basis of phytoremediation is that plants may extract nutrients, including metals, from soil and water. Earlier studies highlight the phytoremediation and bio-monitoring ability of macrophytes. Galal and Farahat

(2015) evaluated the nutrient (N, P, and K) and metal (Cu, Zn, Mn, Pb, Cd, and Ni) remediation ability of Pistia stratiotes. Remediation potential of soil and water (contaminated with Ca, Cr, Cu, Pb, Zn, Mn, and Fe) by ten regional wetland species was studied by Chatterjee et al. (2011). Bioaccumulation and bioremediation capability of Phragmites australis to Fe, Al, Mn, Zn, As, Cu, Cr, Pb, Ni, Co, V, and Cd was reported by Esmaeilzadeh et al. (2016). Rana and Maiti (2018) reported metal bioaccumulation ability of Colocasia esculenta, Scirpus grossus and Typha latifolia.

Metals such as Pb, Cd, Cr, Zn, and Cu are one of the most significant pollutants in lake ecosystems due to their environmental persistence, toxicity, and capacity to bioaccumulate and biomagnify in food webs (Yang et al. 2014). Under certain circumstances they can be further transformed into more toxic compounds (Chen et al. 2010). Metals may enter aquatic ecosystems in the dissolved or particulate phase from domestic, industrial, or agricultural runoff, as well as from atmospheric deposition (Ahmed et al. 2015). Metals released into aquatic systems are generally bound to particulate matter, which eventually settle and become incorporated into sediments. Surface sediment therefore is the most important reservoir or sink of metals and other pollutants in aquatic environments (Kejian et al. 2008). Analyses of spatial and temporal distribution of metals in wetlands are useful to recognize degradation processes and trace sources of pollutants for environmental assessment and management. Bottom sediments, water bodies, plants, and other organisms in polluted wetlands contain metals and their concentrations fluctuate from year to year (Govindasamy et al. 2011). Objectives of the current research are to assess the metal [cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn)] concentrations in sediments and accumulation strategies in macrophytes of Varthur Lake, Bangalore, using bioconcentration and translocation factors.