Conclusion

Samples collected from six wetlands of Coimbatore, records 27 dominant species of 96 Species belonging to 34 genera. 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 that Vedapatti, Perur and Sundakamuthur wetlands are moderately polluted, while Pallapalayam, Noyyal River and Singanallur wetlands are heavily polluted. In these wetlands distribution of Cyclotella was determined by high electrolyte conductivity and Gomphonema and Nitzschia were distributed in all pH and conductivity ranges, where Fragilaria is restricted to neutral alkaline pH and moderate electrolytic waters. With respect to habitat preference epiphytic, epilithic and episammic habitats contained 50%, 10.4%, and 7.2% of taxa unique to that habitat. Diatom indices reveal that water quality of the sampled wetlands are moderate (mesotrophic) to heavily polluted (eutrophic).