Dams disrupt the longitudinal gradient and decrease the natural connectivity of lotic systems and change the physical, chemical, and biological compartments of the river environment. Here, we investigated the effects of damming and seasonal variation in environmental conditions and richness, density, taxonomic and functional beta diversity patterns of phytoplankton, through dry and rainy seasons (of 2011 and 2012), among four zones (upriver, reservoir, dam, downriver) of the Tucuruí dam (Tocantins River sub-basin, eastern Amazon, Brazil). Species were quantified and classified into three functional traits (size class, floating, life form) used to estimate functional beta diversity. We showed that water transparency was higher in the dam, and dry periods presented higher total phosphorus. Our results also demonstrated that the dam promotes species turnover between zones and seasonal periods and that the functional morphological groups respond to local limnological conditions. However, the dam led to a reduction in functional beta diversity—functional homogenization—of phytoplankton species, mainly downstream. We demonstrated that the dam is promoting unfavorable conditions and reducing the environmental heterogeneity, leading to a significant loss of functional traits variation between phytoplankton communities, which compromises the ecosystem processes provided by phytoplankton.

大坝破坏了纵向坡度，降低了水处理系统的自然连通性，并改变了河流环境的物理，化学和生物区室。在这里，我们调查了干旱和雨季（2011年和2012年）在四个区域（上游，水库，大坝，图卢里大坝（巴西东亚马孙东部Tocantins河次流域）的下游。物种被量化并分为三个功能性状（大小分类，漂浮性，生命形式），用于估计功能性β多样性。我们发现大坝的水透明度更高，而干旱期的总磷更高。我们的研究结果还表明，该水坝促进了区域和季节之间的物种更新，并且功能形态群对当地的气候条件做出了响应。但是，大坝导致浮游植物种类（主要是下游）的功能性β多样性（功能性均质化）降低。我们证明了大坝正在促进不利条件并减少环境异质性，导致浮游植物群落之间的功能性状变异显着丧失，从而损害了浮游植物提供的生态系统过程。主要是下游。我们证明了大坝正在促进不利条件并减少环境异质性，导致浮游植物群落之间的功能性状变异显着丧失，从而损害了浮游植物提供的生态系统过程。主要是下游。我们证明了大坝正在促进不利条件并减少环境异质性，导致浮游植物群落之间的功能性状变异显着丧失，从而损害了浮游植物提供的生态系统过程。