为探究西北干旱区内陆河流域水生态系统时空演变规律，2017年7月对黑河甘肃段进行了浮游植物的采样调查，并收集1981、1997、2008年浮游植物夏季调查数据，分析黑河上中下游浮游植物物种、生物多样性和优势种等群落结构的演变特征，同时提出生物活动力指标以表征河流生物的活动能力和活跃程度。结果表明：在空间分布上，黑河中游在各年份都具有最为丰富稳定的浮游植物群落结构，物种数（61属）、生物多样性指数（2.87）和生物活动力指数（0.194万cells·hm^-2）均高于上下游。在时间尺度上，上游浮游植物群落变得持续丰富；中游从1981年持续衰落到2008年后出现反转并快速恢复到2017年更为丰富和活跃的水平；下游则呈现出持续衰落的态势。以1981年为基准，黑河中游水域面积到2010年减小5.2%，浮游植物生物活动力降低了16.5%，到2017年水域面积增加1.2%，浮游植物生物活动力增加了4.3%。黑河浮游植物对流域天然湿地及水域的变化具有强烈的敏感性和依赖性，浮游植物演变特征与湿地水域面积变化趋势一致。

In order to investigate the temporal and spatial evolution of the aquatic ecosystem in northwest inland river basin， phytoplankton of Gansu section of Heihe River was investigated in July 2017. And phytoplankton datas in 1981， 1997 and 2008 were collected to analyze the evolutionary characteristics of phytoplankton species， biodiversity and dominant species in the upstream， midstream and downstream of the Heihe River at different periods. At the same time， Bioactivity index was proposed to characterize the activity of river organisms. The results showed that the midstream of Heihe River has the most abundant and stable phytoplankton community structure in each year， and its species （61 genera）， biodiversity （2.87）， and bioactivity index （0.194 million cells·hm^-2） were higher than those of upstream and downstream. On the time scale， the upstream phytoplankton community continued to be abundant. The midstream continued to decline from 1981 to 2008， and then quickly reversed to a richer and more active level in 2017. The downstream showed a continuous decline. Based on 1981， the water area of midstream of Heihe River decreased by 5.2%， and phytoplankton biological activity decreased by 16.5% in 2010. Water area increased by 1.2%， and phytoplankton biological activity increased by 4.3% in 2017. Phytoplankton in Heihe River basin has strong sensitivity and dependence on changes in its natural wetlands and waters. The evolution of phytoplankton community structure was consistent with the change of wetland water area.