To explore the bacterioplankton community structure in the Yangtze River basin, water samples were collected from 177 sampling sites, including the source to the estuary along the mainstream of the Yangtze River, eight primary tributaries, and several lakes and reservoirs. The 16S rRNA genes were used to explore the bacterioplankton communities based on single molecule real-time sequencing, with the aim to study the diversity and community characteristics in a border sampling area and higher species annotation accuracy. Based on α-diversity analysis, the river area had higher species richness than that of the lake/reservoir area, resulting in these two areas having different bacterioplankton community diversities. Based on the β diversity analysis, the bacterioplankton showed different community compositions between the river and lake/reservoir areas; temperature was the key environmental factor for the river area, and pH was the key environmental factor for the lake/reservoir area. In order to study the influence of different bacterioplankton communities, this study further investigated the species, function, and community differences between the river and lake/reservoir areas. The results were as follows:for the river area, the eutrophication level gradually increased from west to east along the mainstream of the Yangtze River, resulting in a gradually increased relative abundance of specific species. The lake/reservoir area had a higher risk of cyanobacteria bloom, and the opportunistic pathogen had a high relative abundance in the Danjiangkou Reservoir, indicating a higher ecological risk. For species composition, the river and lake/reservoir areas shared most OTUs (84%); however, some uncultured bacteria showed a high relative abundance in the Yangtze River, meaning the bacterioplankton of the Yangtze River basin still requires further study. In general, the river and lake/reservoir shared most species; however, the different bacterioplankton diversity, community composition, and enriched species made the river and lake/reservoir have different key environmental factors, and they also showed differences in ecological functions.
Keywords: 16S rRNA; Yangtze River basin; bacterioplankton; metabarcoding; single molecule real-time sequencing.