Abstract:To understand species diversity and distribution of benthic diatoms in typical tropical rivers, the benthic diatoms were investigated seasonally in Jianjiang River, Guangdong Province. The results showed that there were 242 benthic diatoms, belonging to 52 genera and 10 families were detected from 19 sites and 4 times sampling. Navicula, Nitzschia and Gomphonema were the main dominant genera with high frequency and relative abundance. Three diatom diversity indexes of benthic diatom, such as richness, true Shannon-Wiener diversity index, and true Simpson diversity index, showed certain spatial distribution with increasing of river class, but there was no significance in season. Community dissimilarity of benthic diatoms decreased from class 1 to class 3 but increased in class 4. Structure of benthic diatoms showed clear temporal and spatial patterns by Two-Way PERMANOVA analysis. Rarefaction curve indicated that counting with 400 individuals for each sample would underestimate richness and diversity of benthic diatoms in the tropical river. These would establish the foundation for river health monitoring and water ecological conservation of Jianjiang River system.