Benthic algae including benthic diatoms are one of the most vital primary producers in riverine ecosystems, and their spatial distribution and assemblage structure respond sensitively to various environmental variables. Thus, benthic diatoms have been widely used as indicators of water quality in riverine systems.

The upper Han River in the Yangtze River basin is the water source area of China’s South-to-North Water Transfer Project which will transfer water to the North China Plain including Beijing and Tianjin for domestic, industrial and irrigational use. The good water quality and ecosystem health of the river are the guarantee of this project’s social and economic efficiency. Dr. TAN  Xiang under the supervision of Professor ZHANG Quanfa  from Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden studied benthic diatoms and applied them to water quality assessment  in the upper Han River, a subtropical river with a length of 925 km in China.

Canonical correspondence analysis indicated that spatial patterns of diatom assemblages could be primarily explained by dissolved organic carbon, pH, major ions, and flow velocity. Two-way indicator species analysis based on the diatom assemblages grouped the sampling sites into those from mainstream and tributaries. There were also significant differences in the Shannon-Wiener diversity index, evenness index, species richness, and diatom indices between the mainstream and tributary sites, and the mainstream were evaluated as mesotrophic and the tributaries were categorized as oligo-mesotrophic using diatom indices in the upper Han River. Lower water quality in the mainstream led to the dominance of pollution tolerant species such as Eolimna subminuscula, while tributaries were characterized by Achnanthidium pyrenaicum and A. subatomus. The research demonstrates the applicability of diatom indices for water quality and ecohealth assessment in subtropical rivers.
The research was funded by the National Natural Science Foundation of China (nos. 31200354, 31130010), the National Key Technology R&D Program of China (2012BAC06B03), and the QCQS Biotechnology Fund (GJHZ1243). Theresults were published in Clean-Soil, Air, Water. (DOI: 10.1002/clen.201200152.) entitled "Spatial pattern of benthic diatoms and water quality assessment using diaotm indices in a subtropical river, China.”
Article link: http://onlinelibrary.wiley.com/doi/10.1002/clen.201200152/pdf