Bacterial Community and Diversity of River Ecosystems on the Qinghai-Tibet Plateau Based on 16S rRNA Gene Sequencing

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In recent years, the ecosystems on the Qinghai-Tibet Plateau (QTP) have been facing a high risk of degradation due to the impacts of climate change and human activities. As one of the important components in river ecosystems, microbial communities can reflect the overall changes in the watershed and are regarded as indicators of the health of river ecosystems. In order to investigate the diversity and composition characteristics of bacterial communities in river ecosystems on the QTP, 65 samples were collected from the Yellow River, Yangtze River, Lancang River, Nujiang River, Yarlung Tsangpo River, and Qaidam Basin on the QTP in July 2021 and were analyzed using 16S rRNA high-throughput sequencing. The results showed that the detected bacterial communities covered 65 phyla and 1311 genera in total. Bacterial communities had high α-diversity indexes across the rivers, indicating that the bacterial richness and diversity in rivers on the QTP were at a high level. Among them, Chao and observed OTUs had significantly negative relationships with SRP/TP. The dominant phyla were Proteobacteria, Bacteroidota, Actinobacteriota, and Cyanobacteria. The dominant classes were γ-proteobacteria, Bacteroidia, and α-proteobacteria. The dominant genera were Flavobacterium and Limnohabitans. The results of principal coordinate analysis and permutational MANOVA suggested significant differences in bacterial community structure among the rivers on the QTP. Canonical correspondence analysis showed that the significant environmental variables associated with the variation in the bacterial communities were physicochemical properties of the river water, including conductivity, pH, dissolved silicon, and dissolved organic carbon, as well as watershed characteristics, including the average normalized differential vegetation index, average slope, cumulative water channel distance, catchment size, proportion of shrub area, and average elevation. Among them, conductivity had the strongest influence on bacteria distribution on the QTP. These results provide a database and information for understanding the composition characteristics of microbial communities on the QTP and identifying environmental factors influencing the diversity of bacteria communities.