PLANKTONIC DIATOMS AS INDICATORS OF WATER QUALITY IN THE DONG NAI RIVER, VIETNAMThanh-Luu Pham
Planktonic diatom assemblages were investigated as potential biological indicators in the Dong Nai River (DNR), Vietnam. Diatom and water samples were taken in dry and wet season at fifteen stations spread out across two land-use categories: rural upstream and urban downstream along the DNR. Physico-chemical variables and planktonic diatom metrics of abundance, taxa richness (S), Shannon Wiener diversity index (H), Simpsons diversity index (D) and biological diatom index (BDI) were used in the determination of water quality and ecological conditions of the river. Canonical correspondence analysis (CCA) was performed to investigate the main environmental factors structuring planktonic diatom communities. A total of 47 taxa belonging to 26 genera of planktonic diatom were identified. One-way ANOVA showed that water physical and chemical variables were significantly different (p < 0.05) between rural upstream and urban downstream sites. Planktonic diatom metrics indicated that water quality in the DNR varied between moderate to low status, while water quality was classified in to A2 class based on the physico-chemical variables according to The Vietnamese national technical regulations for surface water quality. CCA and Monte Carlo permutation tests demonstrated that the planktonic diatom community structure was determined by a variety of factors including physico-chemical variables and urbanization. In this study, the BDI was applied for the first time for water quality assessment in Vietnam. The results demonstrated that the composition of planktonic diatom assemblages was sensitive to the trophic status and potentially useful tool for surface water quality monitoring and ecological state assessment.
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