Little information about biodiversity patterns in high-elevation aquatic systems has been gathered, even though these patterns are important for understanding the impacts of human activities. The source region of the Yangtze River, a typical alpine zone with vulnerable and sensitive ecosystems, was selected. Phytoplankton, which play a critical functional role as freshwater primary producers, serve as an important ecological indicator of aquatic systems. Here, systematic surveys on the water environment and phytoplankton were carried out to examine how the phytoplankton community varies with elevation based on hypothesized structural equation models (SEMs) in 10 typical rivers of the Yangtze River source region in March and October 2018. In total, 58 species of phytoplankton belonging to 28 genera were identified. The relationship between species abundance and elevation for phytoplankton showed unimodal elevational patterns. The results of the SEMs showed that all studied aspects affecting the phytoplankton community were directly or indirectly associated with elevation. The synergistic effects of human activities and basic environmental factors (terrestrial productivity and slope gradient) were the drivers affecting the phytoplankton community in the Yangtze River source region. Climate, topography, human activities and other factors are significantly different with changes in elevation, resulting in significant differences in the structure of aquatic communities at different elevations. Human activities were the major drivers affecting the phytoplankton community along the elevational gradient. As the elevation decreased, the disturbances to aquatic ecosystems caused by human activities intensified in the study area.

中文翻译：

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地方地理因素共同驱动长江源区浮游植物海拔格局

尽管这些模式对于理解人类活动的影响很重要，但关于高海拔水生系统生物多样性模式的信息很少。长江源区是典型的高寒带，生态系统脆弱敏感。浮游植物作为淡水初级生产者发挥着重要的功能作用，是水生系统的重要生态指标。在此，基于2018年3月和2018年10月长江源区10条典型河流的假设结构方程模型（SEMs），对水环境和浮游植物进行系统调查，研究浮游植物群落如何随海拔变化。共鉴定出浮游植物28属58种。浮游植物物种丰度与海拔的关系显示出单峰海拔模式。SEM 的结果表明，影响浮游植物群落的所有研究方面都与海拔直接或间接相关。人类活动与基本环境因素（陆地生产力和坡度）的协同作用是影响长江源区浮游植物群落的驱动因素。气候、地形、人类活动等因素随海拔变化显着不同，导致不同海拔水生群落结构存在显着差异。人类活动是影响沿海拔梯度浮游植物群落的主要驱动因素。随着海拔的降低，