Summary

Diatoms comprise a ubiquitous, photosynthetic and distinctive group of essentially unicellular algae. They are more specific in their preference and tolerance of environmental conditions than most other aquatic biota and have long been recognised as excellent indicators of ecological status of water bodies. This study documents the diatom flora of six urban wetlands of Coimbatore city, examines benthic diatom assemblages across different habitats and investigates pollution status based on diatom composition.  96 Species belonging to 34 genera were recorded and out of them 27 species were dominant. The dominant species that are cosmopolitan include Cyclotella meneghiniana, Nitzschia sp., Sellaphora pupula, Gomphonema parvulum and Navicula sp. Singanallur wetland and Noyyal river stretches are characterised by pollution tolerant species with low diatom diversity. Diatom assemblages indicate wetlands; Vedapatti, Perur and Sundakamuthur are moderately polluted, while Pallapalayam, Noyyal River and Singanallur wetlands are heavily polluted.

Keywords: Urban wetlands, pollution indicators, diatom-indices, diatom assemblages, Cyclotella, Coimbatore.