Study area and Methods

Bangalore is located at 12.95º N and 77.57º E with an altitude of 920 metres a.m.s.l. The annual precipitation is 924m and temperature varying from ~15 °C during winter months (January) to ~36 °C in hot summer months (April/May). Bangalore is delineated into four watersheds, namely the  Hebbal, Koramangala, Challaghatta and Vrishabhavathi valleys with more than 70 interconnected lakes. During the last decade, lakes located at Ulsoor, Hebbal, Lalbhag were restored, but eutrophication persists. Five lakes viz., Ulsoor, Kothanur, Ramasandra, Kommaghatta and Yelahanka were studied considering different habitats and also water quality. Water and diatoms from submerged plants were sampled simultaneously for 6 months (December 2010- March 2011). Kommaghatta lake was sampled during pre and post restoration to study the effects of restoration on lake biodiversity. Lists of lakes along with the code used in the text are mentioned in Table 1. Analysis of pH, Electric Conductivity, Total Dissolved Solids, Dissolved Oxygen and water temperature was performed onsite. Biological oxygen demand, Chemical oxygen demand and chlorides were analyzed following APHA (1985) in Aquatic ecology laboratory at Centre for Ecological Sciences, Indian Institute of Science, Bangalore. Diatom samples were collected, cleaned, process in acid and slides were prepared following standard protocol (Karthick et al., 2010)  and identified following standard diatom literatures. Statistical analysis was performed using PAST 2.16 (Hammer et al., 2001).