Diversity of Benthic Diatoms and Water Quality of the Mekong River Passing Through Ubon Ratchathani Province, Thailand

The study on the diversity of benthic diatoms and water quality in the Mekong River as it passes through Ubon Ratchathani, Thailand was carried out from February 2007 to January 2008. Samples were collected from 10 stations, which were situated in areas involving different geographical features and human activities. Three hundred and seven species of benthic diatoms were found. The majority of them were Gomphonema lagenula Kützing, Navicula rostellata Kützing, Nitzschia palea (Kützing) W. Smith, Luticola goeppertiana (Bleisch) D. G. Mann, Nitzschia liebetruthii Rabenhorst, Sellaphora pupula (Kützing) Mereschkowsky, Navicula erifuga Lange-Bertalot and Cymbella tumida (Brébisson) Van Heurck, respectively. The water quality was slightly different at each sampling site which was classified as moderate water quality (mesotrophic status). Ban Na Muang, Pak Seang Temple, Ban Ta Mui, Ban Na Sanarm, the location behind the Municipal Market and Wigittra Beach were all found to possess moderate water quality (mesotrophic status). Chang Mop Cataract, Ban Koom, Ban Dan and Ban Huay Phai were found to have moderate to polluted water quality (mesotrophic to eutrophic status). The Multivariate Statistical Package (MVSP) particularly Principal Correspondence Analysis (PCA), and the cluster analysis were used to determine the relationship between the water quality and the present of benthic diatoms, in terms of biomonitoring. It was found that Cymbella tumida Cymbella tumida (Brébisson) Van Heurck and Navicula erifuga Lange-Bertalot could be indicators of mesotrophic status, whereas Cymbella turgidula Grunow, Gomphonema clevei var. javanica Hustedt, Luticola goeppertiana (Bleisch) D. C. Mann, Nitzschia liebetruthii Rabenhorst and Nitzschia palea (Kützing) W. Smith could be indicator of the meso-eutrophic status.