Hot springs are some of the most special environments on Earth. Many prokaryotic and eukaryotic microbes have been found to live in this environment. The Himalayan geothermal belt (HGB) has numerous hot springs spread across the area. Comprehensive research using molecular techniques to investigate eukaryotic microorganisms is still lacking; investigating the composition and diversity of eukaryotic microorganisms such as protists in the hot spring ecosystems will not only provide critical information on the adaptations of protists to extreme conditions, but could also give valuable contributions to the global knowledge of biogeographic diversity. In this study, we used high-throughput sequencing to illuminate the diversity and composition pattern of protist communities in 41 geothermal springs across the HGB on the Tibetan Plateau. A total of 1238 amplicon sequence variants (ASVs) of protists were identified in the hot springs of the HGB. In general, Cercozoa was the phylum with the highest richness, and Bacillariophyta was the phylum with the highest relative abundance in protists. Based on the occurrence of protist ASVs, most of them are rare. A high variation in protist diversity was found in the hot springs of the HGB. The high variation in protist diversity may be due to the different in environmental conditions of these hot springs. Temperature, salinity, and pH are the most important environmental factors that affect the protist communities in the surface sediments of the hot springs in the HGB. In summary, this study provides the first comprehensive study of the composition and diversity of protists in the hot springs of the HGB and facilitates our understanding of the adaptation of protists in these extreme habitats.

The middle reaches of the Yarlung Zangbo River are a hot zone of the Alpine Water System and its ecological environment is diverse but vulnerable. We systematically examined and detailed the phytoplankton community’s composition, spatial-temporal dynamics, and driving factors in this area. A total of 224 samples from 28 sampling sites across wet and dry seasons were analyzed. The results showed that: (1) the community structure of the main stream is more complex and stable than that of the tributaries; (2) the number of species, average cell abundance, and average biomass in the main stream were higher than those in the tributaries; (3) TN, TUR, WT, and pH were the main influencing factors for the difference in the phytoplankton community’s structure between the main stream and the tributaries; (4) the phytoplankton community had a closer structure, higher connectivity, stronger resistance to environmental disturbance, and higher stability in the main stream, while those in the tributaries had higher interspecific synergy; and (5) the phytoplankton community’s assembly process in the main stream was mainly influenced by random processes and was mainly driven by dispersal limitation in the middle reaches of the Yarlung Zangbo River.