INTRODUCTION

The freshwater diatom flora of Indian subcontinent has been studied since the18^th century (Ehrenberg, 1845; Skvortzow, 1935; Gandhi, 1966 & 1998; Foged, 1976; Sarode and Kamat, 1984). Recently there are few reports of new species and combinations from India, particularly from biodiversity hotspots like the  - Himalayas and Western Ghats. Recently described species belong to the genera Achnanthidium (Wojtal et al., 2010; Jüttner et al., 2011), Cymbopleura (Van de Vijver et al., 2011), Gomphonema (Jüttner et al., 2004, Karthick et al., 2011a), Oricymba (Jüttner et al., 2010), Pleurosigma (Karthick and Kociolek, 2011), Surirella (Karthick et al., 2011b) and centric genera like Pleurosira and Spicaticribra (Karthick and Kociolek, 2011). Most of these studies report new taxa and combinations from samples collected at conservation reserves. In contrast, studies on the diatom floral diversity of wetlands in human dominated landscapes (anthropogenically impacted) are scarce.

In India taxa belonging to genus Nitzschia, Navicula, Cyclotella and Diadesmis are recorded as cosmopolitan, dominating in human impacted water bodies and thus are pollution tolerant taxa (Alakananda et al., 2011). The genus Nitzschia is less understood because of the complexity in identification and its wide ecological preferences. Members of the genus Nitzschia are generally recognized as cosmopolitan in distribution and many have wide species tolerances to ion and nutrient enriched aquatic ecosystems. Studies from tropics particularly in India (Humane et al, 2010, Sharma et al, 2011) focus on diatom distribution of various environments; but end up in identification of Nitzschia up to genus level. Examining the taxonomy and ecology of Nitzschia in wetlands near human habitation within the continent of India will provide more insights into documenting dominant species and their application in biomonitoring.

Bangalore with an urban dominated ecosystem in the southern regions of India harbors many wetlands since centuries which are unexplored for diatom distribution. These wetlands maintain a semi-arid climate containing numerous interconnected shallow wetlands that helps sustain water residence in the neighborhood. Most of the wetlands in peninsular India are less than 2000 years old, created during the Kings era to meet water requirements during the water scarce summer months (Buchanan, 1870; Kamath, 1980). Forty eight of these historically constructed wetlands were examined in an ongoing Aquatic Ecosystems Research in the region. During biomonitoring we observed and describe two new Nitzschia species from Thalghattapura and Begur wetlands within the region of Bangalore and represented autecological data on the water quality of their growing conditions.