中文摘要：

近几十年来,以大型湖泊为代表的云南部分湖泊受人类活动的持续影响出现了生态环境的明显变化.洱海作为云南面积第2大淡水湖泊,经历了多重环境压力（富营养化、外来鱼类引入、水生植被退化等）的影响.在湖泊现代监测数据面临时段较短、缺乏连续记录的背景下,湖泊沉积物的连续记录可以提供湖泊生态环境变化的长期历史并可用于生态响应模式的识别.以目前处于富营养水平的洱海为研究对象,应用湖泊沉积物记录进行多指标分析,探讨多重环境压力影响下洱海枝角类群落的长期变化特征以及影响因素,并与已有研究成果和现代监测数据进行对比,探讨了枝角类群落对环境压力响应的空间差异性.通过分析沉积物枝角类记录,重建了近百年来洱海枝角类群落的变化历史,结果表明过去100年来,枝角类的生物量总体呈增加趋势,尤其从1990年左右开始,象鼻溞生物量显著增加,物种相对组成出现明显变化（如Bosmina longispina被B.longirostris取代）.同时象鼻溞的生物量、壳长与触角长度在1990s初期有明显降低的趋势,与同期外来鱼类（如银鱼）引种成功的时间一致.限制性聚类分析结果表明,枝角类群落结构的变化有3个主要阶段：1990s以前,底栖枝角类为群落的主要组成;1990—2000年左右,浮游枝角类（以象鼻溞为主）在枝角类群落结构中的比例迅速增加;从2000年以后,枝角类群落组成以浮游枝角类为主.同时,枝角类数据的主成分（PCA）分析显示,仅有PCA主轴1呈现显著的变化且解释了群落结构变化的61.64%,进一步分析表明水生植被变化可能是驱动枝角类变化的主要环境梯度,如底栖枝角类生物量减少响应了湖泊水生植被的退化.与已有研究对比表明,浅水湖区沉积物记录的枝角类生物量在1970s急剧增加与1980s急剧降低等现象并没有被深水区的沉积物记录所反映,指示了?

英文摘要：

Obvious environment changes have occurred in some lakes of Yunnan Province due to intensifying human impacts over the past decades,especially in large lakes. Lake Erhai is the second largest lake in the Yunnan by surface area,which experienced the pressures of multiple environmental stressors（ e. g. eutrophication,fish invasion and macrophyte degradation）. The application of lake sediment records enables us to reconstruct the long-term changes of lake environment and ecosystem dynamics in situation of less monitoring data. Here multi-proxy analyses of lake sediments were conducted from a short sediment core in the south and shal-low basin of Lake Erhai,which are currently eutrophic. We aimed to recognize the long-term variations and driving factors of cladoceran community,and to test for whether spatial heterogeneity exists in community responses through a comparison with monitoring data and previous results from the deep basin of Lake Erhai. Our results showed that cladoceran production showed an overall increasing trend in the past century,and since 1990 s bosminid production increased significantly with a general trend of the oligotrophic taxon of Bosmina longispina replaced by B. longirostris. In addition,bosminid production and the body size（ i. e. carapace and antennule length） displayed a decrease during early 1990 s,were in good correspondence with the period when the population of the exotic noodlefish was well established. Based on the constrained cluster analysis,the historical changes of cladoceran community were characterized by three distinct phases： littoral cladocerans were dominant before the 1990 s and the relative abundance of pelagic cladocerans increased rapidly from the 1990 s before the pelagic cladocerans became predominant during early 2000 s. The principal component analysis showed that the environmental gradient associated with macrophyte coverage accounted for 61. 64% of the total variance in the cladoceran community. Compared with previous studies,we observed that the increa