Diatoms and Water Quality Indices in Thamirabarani River help Environmental Impact Assessment of stretch between Naranammalpuram and Punnakayal, Tamil Nadu, India

The present study reports the occurrence of diatom taxa, their distribution and ecology in Thamirabarani River between the study areas Naranammalpuram and Punnakayal, covering the districts of Tirunelveli and Thoothukudiin Tamil Nadu, India. The study employs diatoms collected from 10 different locations in the Thamirabarani River to monitor its quality. A total of 40 diatom taxa belonging to 20 genera were recorded in the study area. The dominant presence of diatom taxa, such as Aulacoseira ambigua, Cocconeis placentula, Cyclotella meneghiniana, Cymbella tropica, Discostella stelligera, Gyrosigma acuminatum, Navicula cryptonella, Nitzschia amphibia, Planothidium lanceolatum, Staurosirella pinnata, and the water quality index values (29–48) recorded at sites 1 to 7 indicate oligotrophic due to good flow of water. The abundant of diatom taxa, such as Diadesmis confervacea, Gomphonema parvulum, Nitzschia palea and Pinnularia gibba, were recorded at sites 8–10, and the water quality indices (100–110) indicate eutrophication attributable to less flow of water, high dispersion of cremation ashes (the casting ceremony) and anthropogenic activities. Particularly, locations around Punnakayal are most polluted due to the dumping of fish wastes as well as stagnant water.