Introduction

Microhabitats with complex interactions in the aquatic environment and influenced by physical and chemical factors (such as water depth, light availability and nutrients load), support diverse flora and fauna. Symbiotic association of submerged macrophytes with bacteria, blue green algae and diatoms provide heterogeneous habitats for microbial diversity (Tundisi & Matsumura-Tundisi, 2011). Spatio-temporal factors such as catchment land use, water inflow level, nutrients, ionic concentration, organic content, etc. influence macrophyte. Also, the habitat complexity and heterogeneity of an aquatic environment is influenced by macrophytes (Thomas & Cunha, 2010). Scheffer, 2004 compares the attached/littoral zone macrophyte floral diversity to aquatic forest whereas free floating/pelagic zone floral diversity as barren sand dune. Biomass production in macrophytes serves as food sources for grazing and detritivorous invertebrates (Esteves, 1998). Diatoms constitute a vital freshwater component, considering its function as primary food source for zooplanktons, macroinvertebrates and amphibians (Welsh and Ollivier, 1998; Skelly et al., 2002). They occupy submerged habitats of lakes and also grow on rocks in rivers and streams (Stenger-Kovács et al., 2007; Karthick et al., 2010; Uedeme-Naa et al., 2011). Diatom species preferences for particular substrata and microhabitats like stones (epilithic), sediments (epipelic, epipsammic), submerged plants (epiphytic) and fish guts hav been reported (Round, 1991; Rothfritz et al., 1997; Shirey et al., 2008; Alakananda et al., 2011). Synedra sp., Lemnicola sp. Cocconeis sp. and Cymbella sp. (epiphytic diatoms) favor growing on macrophytes like Wolffia sp., Lemna sp. and other submerged plants (Round, 1991; Hameed, 2003; Buczko 2007) due to the availability of higher concentrations of organic matter. Epiphytic diatoms and its abundance depend on microhabitats for the optimal growth of species (Muylaert et al., 2006) and hence are used as potential biological indicators of trophic status in several temperate streams (Kelly et al., 1998).  Organic content, nutrient availability and ions influence the distribution pattern of diatoms (Negro and Hoyos, 2005; Cantonati et al., 2009), but the role of macrophyte as microhabitat has not been explored in diatom ecological studies (Leira and Cantonati, 2008). Diatoms attached to macrophytes indicate the extent of urban stress such as nutrient run off, invasive species, etc. (King and Buckney, 2000). The investigation of epiphytic diatoms is indispensable for improvement of water quality and also to define urban stress in lakes (Uedeme-Naa et al., 2011).  Macrophytes perform an important ecological function of water purification by removing nutrients. Still their role is least understood by policy makers evident from the removal of shoreline aquatic plants, submerged macrophytes and wetlands while restoring urban lakes. The current study focuses on the vital associations of epiphytic diatoms and macrophytes in urban lakes of Bangalore region. The study provides restoration guidelines for Bangalore lakes.