Spatial and temporal distribution patterns and driving mechanisms of ciliate communities in the midstream and downstream reaches of the Lhasa River
(2.Laboratory of Tibetan Plateau Wetland and Watershed Ecosystem, College of Science, Tibet University, Lhasa 850000)
【Abstract】 Aims: As a high-altitude water area, the Lhasa River's aquatic ecosystem has a high research value due to its special environmental conditions. In recent years, studies on the high-altitude water area have gradually increased, but there are few studies on the community structure of ciliates in the Lhasa River. We conducted this study to explore the composition pattern, spatial and temporal diversity pattern, and maintenance mechanism of ciliate communities in the midstream and downstream reaches of the Lhasa River. Methods: Seventeen samples were collected from the middle and lower reaches of the Lhasa River in May 2015 and August 2015, and October 2016. In-vivo observation, Rugo's iodine solution fixation staining, and Wilbert's protein silver method were utilized for species identification. The spatial and temporal differences of community structure were analyzed by the Shannon diversity index, Margalef index, and richness. The interactions between ciliate groups were analyzed through co-occurrence network. The effects of physical and chemical factors on ciliate community structures were investigated using redundancy analysis (RDA). Results: There was no significant difference in the Shannon index between seasons and river segments. The richness and Margalef index were significantly different among the reaches. The correlation between nodes in the midstream and downstream of the co-occurrence network is primarily positive. Dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), and total dissolved salt (TDS) are the key factors affecting ciliate community structures. Conclusion: The ciliate community structures in the midstream and downstream of the Lhasa River exhibited no significant seasonal differences but significant spatial differences. At the class level, the interaction between ciliates was dominated by synergy, and there were complex interactions among different groups. On the whole, the interaction between ciliates was more complex in spring and simpler in summer. The community structures of ciliates in the midstream and downstream of the Lhasa River were influenced by several environmental factors.
【Keywords】 Lhasa River; ciliate; community structure; co-occurrence networks; spatial and temporal distribution;