中文摘要：

以星云湖为代表的云南大中型湖泊近年来受到多个环境压力的胁迫,出现水质持续恶化、环境功能降低、生态系统退化等问题。目前针对这些湖泊生态环境的研究主要集中于以富营养化为代表的单一环境胁迫,且以短期监测为主,因此有效的湖泊治理与生态修复急需评价多重环境压力的长期驱动过程与特征。本文围绕星云湖枝角类群落沉积物记录,开展了多指标（如色素、粒度等）的综合分析,并结合湖泊调查、历史资料和多变量统计方法对主要环境压力与长期生态响应模式进行了识别。结果表明：沉积物分析中共鉴定出枝角类10属16种,其中盘肠溞属与象鼻溞属占绝对优势;在1890年之前湖泊沉积物色素浓度稳定在较低水平,随后湖泊生产力缓慢上升且沉积物颗粒（〉63μm）增加;1980年初开始沉积物色素含量快速上升,耐污种C.sphaericus明显增加并成为绝对优势种;随着湖泊生产力水平的上升,枝角类生物量持续增加（R2=0.753,P〈0.001,n=33）,且枝角类群落出现显著变化（R2=0.953,P〈0.001,n=33）;同时,随着外来鱼类的引入和鱼类捕食压力的变化,象鼻溞生物量总体下降但个体大小变化不明显;营养水平的持续增加与水生植物的逐渐消亡,可能导致了枝角类物种趋于单一,底栖枝角类生物量总体下降。总之,星云湖枝角类群落结构与生物量在过去100年来出现了显著变化,湖泊富营养化与生产力的变化是主要驱动因子,同时外来鱼类的引入、水文条件及水生植物的变化也对枝角类群落产生了重要的影响。

英文摘要：

Xingyun Lake,a large and hypereutrophic lake in Southwest China,has experienced deterioration of water quality and degradation of ecosystem functioning during the past few decades. Despite the fact that this lake has suffered from multiple environmental stressors（ i.e. eutrophication,fish invasion and hydrological regulation）,few studies have examined their interactive roles in driving lake communities. Therefore,it is urgently needed to identify the pattern of multiple stressors in driving long-term ecosystem changes in Xingyun Lake. In combination with lake survey and historical data,we conducted multi-proxy analyses of sediment records for Xingyun Lake with a focus on cladoceran community. We identified 10 genera and 16 species of cladocerans from sediments,with taxa such as Chydorus and Bosmina generally dominating through the sediment cores. The concentration of Chl-a pigments remained consistently low before1890,but thereafter rose slowly and was concurrent with the increased proportion of sand particles（ 63 μm）. From 1980,the Chl-a level began to rise rapidly with increasing abundance of C. sphaericus which is known to tolerate high nutrient levels. Further analysis showed that total cladoceran production increased significantly with increased lake productivity（ R2= 0. 753,P 0.001,n = 33）,and primary production was also a significant driver of cladoceran community change（ R2= 0. 953,P 0. 001,n = 33）. In addition,changes in predation pressure associated with fish introduction have led to an obvious reduction of Bosmina production. The gradual loss of macrophytes due to eutrophication and water level fluctuation may have caused the decline or even decimation of benthic cladocerans. In all,cladoceran community in Xingyun Lake has experienced long-term changes over the past century with nutrient enrichment identified as the key environmental driver. Furthermore,we found evidence for the impacts from fish introduction,hydrological fluctuation and change in macrophytes. Our sediment evidence of