Diatom Assemblages in The Natural, Impounded And Regulated Sections of The Tons River (Uttarakhand)

Abstract

The purpose of the study is to examine the difference in diatom community, assemblages and their diversity with respect to the natural and regulated section of montane river Tons (Yamuna basin) in Himalaya. Diatom samples were collected at 4 stations from upstream to downstream; TR1 to TR4 at regular monthly basis and preserved in 4% formaldehyde solution. The permanent mounts were prepared in naphrax and examined for recording the flora under the bright field using Nikon Japan 80i trinuclear research microscope. The number of diatom taxa decreased from natural to regulated section. The continuity was impaired in this stretch as only 42 of 116 species and 14 of 24 genera occurred at all the stations. The species richness was highest in the natural upstream section TR 1(96 from 21 genera). It declined at TR2 (59 species-18 genera) and increased mildly at TR3 (63 species-15 genera) and TR4 (69 species,15 genera). Four genera (Denticula, Hantzschia, Hippodonta and Adlafia) were totally absent in downstream section. Didymosphenia and Melosira were recorded only at the dam location, exhibiting restricted distribution. Dominant taxa varied and amounted to 4 taxa for TR1 and TR2, only 2 taxa for TR3. No diatom taxon was at dominant at TR 4. Cymbella was recorded as the most species rich genera. Species richness decreased from TR1 to TR4. Consequently, the assemblages differed in natural, impounded and regulated sections of the Tons R.Vast variations in the flora, species richness and assemblages suggest a severe impact on the Tons R. ecosystem.