MATERIAL AND METHOD

Bangalore is located in the Deccan plateau, toward the south east of Karnataka state extending from 12°49’5”N to 13°8’32”N in latitude and 77°27’29” E to 77°47’2”E in longitude (Figure 1). Spatially Bangalore urban area has spatially increased from 69 sq.km (1901), 161 sq.km (1981), 221 sq.km (2001) to 741 sq.km (2006, Greater Bangalore). The undulating terrain in the region facilitated the creation of a large

number of tanks in the past, providing for the traditional uses of irrigation, drinking, fishing and washing (Ramachandra et al., 2017). This led to Bangalore having hundreds of such water bodies through the centuries. There were 1452 water bodies in 1800 in the current spatial extent of Bangalore (741 sq.km). A large number of water bodies (locally called lakes or tanks) in the city had ameliorated the local climate, and maintained a good water balance in the neighbourhood. The undulating topography, featured by a series of valleys radiating from a ridge, forms three major watersheds, namely the Hebbal Valley, Vrishabhavathi Valley and the Koramangala and Challaghatta Valleys (Figure 1). These form important drainage courses for the interconnected lake system which carries storm water beyond the city limits. Bangalore, being a part of peninsular India, had the tradition of storing this water in these man-made water bodies which were used in dry periods. Today, untreated sewage is also let into these storm water streams which progressively converge into these water bodies and results in a) algal bloom b) proliferation of exotic aquatic weeds and macrophytes c) large scale fish kill due to asphyxia (zero dissolved oxygen levels) and d) frothing due to P enrichment (Ramachandra et al.,2017).

The present study was conducted at Jakkur Wetland (Figure 1) in Hebbal valley and is situated at North East of Bengaluru. It spreads across 3 (Jakkur, Agrahara and Sampigehalli) villages and covers an area of 157.8 Acres. It consists 10 MLD sewage treatment plant near the inlet followed by manmade wetland through which both treated and partially treated water enters the lake (Figure 2).

Fig. 1. Study area- Jakkur Lake (marked in red circle)

FFig. 2. Sampling locations in the Jakkur wetlands

Macrophytes samples were collected from inlets and outlets of Jakkur wetlands in triplicates through quadrat sampling method (0.5 m2 area) every week. Plant species were identified based on morphological keys using the standard taxonomic literatures Cook (1996) and were stored in polythene bags. These samples were washed with distilled water to remove periphyton and sediments and later samples were dried at 600C until constant weight. The dry weights of samples were noted and biomass is expressed as kg/dry weight.

Dried plant samples were pulverised using mortar and pestle, sieved (1 mm) to get fine powders and labelled properly. Later 0.5 g of samples were acid digested APHA (1995) and analysed for six heavy metals viz., cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) with reagent blanks and suitable standards using AAS - Atomic Absorption Spectrophotometer (GBC Avanta version 1.31). Elemental carbon (C) and nitrogen (N) were estimated using CHN analyser. Total Phosphorus was analyzed according to the standard protocol; Tandon (1993) after digesting samples using HNO₃:H₂SO₄:HClO₄