Potential daming effect on biogeographical patterns of microbial eukaryotic communities along the upper Yangtze River

Large rivers are commonly regulated by damming, and the effects of such disruption on microbial eukaryotic community structure in freshwater river-reservoirs ecosystems with large cascade hydropower stations (LCHS) are probably uncharted in this respect. The aim of this study was to explore the biogeographical patterns within large cascade hydropower reservoirs under dam regulation and to uncover the major drivers structuring microbial eukaryotic communities. Microbial eukaryotic community assemblages along upper reaches of Yangtze River were analyzed using Illumina Miseq sequencing by comparing 24 sites. This approach revealed robust biogeographical patterns alongside the upper Yangtze River. Across all sites, microbial eukaryotic community communities were dominated by Cryptophyceae, Fungi and Alveolata, with these three kingdoms encompassing 52.36%, 24.34% and 15.26% of all sequences. Generally, the Shannon diversity was higher in the dry season than that in the flood season, varying from 0.60-3.83 in the flood season and 1.41-4.53 in the dry season. Principal coordinate analysis of the microbial eukaryotic taxa yielded a distinct biogeographical distribution pattern between different seasons and positions. Results suggested that ecological processes of element cycling and large dam disturbance are of prime importance in driving the assemblages of microbial eukaryotic communities.