Unplanned rapid urbanization due to globalisation and subsequent push for the industry-economic development in nineties have resulted in the increased stress on natural resources evident from the significant deterioration of urban wetlands/lakes in terms of quality and quantity, aquatic biodiversity, eco-aquatic processes, land use land cover (LULC) and micro-hydrological regimes (Ramachandra et al., 2006; Ramachandra, 2008; Martinuzzi et al., 2014). Untreated or partially treated industrial and domestic wastewater generated in urban locality taking advantage of the existing natural drains in the system of interconnected lakes. Sustained inflow of untreated sewage, though aided in maintaining the water levels, but has contributed to the nutrient enrichment rendering lakes vulnerable to blooms, frothing, foul odour with influx of wide spectrum of organics and inorganics, heavy metals (Timothy, 2000) and xenobiotics. The prime source of pollution is untreated domestic and industrial wastewater in the urban catchment (Ramachandra et al., 2006, 2013; 2017).

The interaction among the various physico-chemical components of abiotic environment has profound impact on the local microflora and on the primary productivity and treatment capability (Carta-Escobar et al., 2004) of urban wetlands. Bacteria (Paerl et al., 2003), algae (Mahapatra et al., 2011a) and the aquatic plants (Mahapatra et al., 2011b,c) play a major role in remediation and aid as bio-indicators indicating the health of wetlands. The physicochemical environment together with the abundance of the biological organisms decides the utility of the wetlands (lakes), whether it is fit for recreational, irrigational or potable purposes (Figueiredo et al., 2010). The presence of organics in water, due to inflow of untreated sewage and other high impact industrial toxicants alters the biotic community composition as the micro and macrophytes are sensitive to nutrients loads, various pollutants and alterations of the microenvironment. The changes in the community structure also affect the treatment potential (Kayombo et al., 2002; Tarlan et al., 2002; Kirkwood et al., 2003). The most tolerant and resistant micro flora constitute community assemblage, in urban wetlands with high influx of untreated domestic wastewaters loads (Timothy, 2000; Mahapatra et al., 2011a)/ treatment plant effluents (Mahapatra et al., 2013a,b; Mahapatra et al., 2014; Ramachandra et al., 2015), landfill leachate (Naveen et al., 2017) and industrial effluents (Veeresh et al., 2009; Ramachandra et al., 2012).

The changes in the microbial community structure have altered the metabolic flux flow, which alter the integrity of aquatic ecosystem impairing its functions. This necessitates understanding of all major ecological entities and their dynamics with the nutrient influx, mobilization and accumulations to address sustainability of the ecological processes. Advanced metagenomic techniques are presently being used for a detailed characterization of the eukaryotic and the prokaryotic community structures (Zarraonaindia et al. 2013). Such analyses provide insight to the bioprocesses that help in identifying the pollution pattern and impacts (Singh et al., 2009). However, these techniques are expensive and do not reveal either causal factors or the pollution status. The physico-chemical parameters and the microflora community structure form a complex data structure, and require multivariate analysis and data treatment for the evaluation of water quality and the impact on micro flora (Bernal et al., 2008) with changes in the spatiotemporal patterns. Evaluation of the ecological structure and status of wetlands, pattern recognitions for variability in species abundance and their turnover, and development of an easy assessment tool for management have been done for Dianchi Lake (Yang et al., 2010) and Baiyangdian Lake (Zhao et al., 2012) in China; Navisha Lake, Kenya, (Ndungu et al., 2014), Curtin Lake in Malaysia (Prasanna et al., 2012). The objective of this study is to understand the linkages of the seasonal dynamics in physico-chemical and microflora bioprocesses in two major lakes in Bangalore region and evaluate the treatment competency of wastewater fed lakes.