中文摘要：

以长江中下游典型草型湖泊龙感湖为研究对象,借助生物指标（沉积物表层硅藻）,通过硅藻分析、DCA分析、聚类分析以及硅藻属种指示的湖泊营养特征分析,探究龙感湖沉积物表层硅藻属种分类、影响硅藻的潜在环境梯度、表层沉积硅藻属种的空间分布特征以及分析表层沉积硅藻属种指示的湖泊营养特征。研究表明：龙感湖表层沉积硅藻属种分布存在空间差异;表层硅藻属种的分布主要由第一轴的环境因子所解释,反映的样点的排列受第一轴的控制,第二轴反映的环境意义不显著;龙感湖硅藻组合是以富营养的浮游种为优势,已经接近富营养态,以半浮游种Aulancoseira granulata为最大优势种,而Aulancoseira granulata在中营养湖泊中占绝对优势。主要出现在富营养湖泊中能较好指示富营养化的浮游、半浮游种Cyclotella atoms和C.meneghiniana、Aulacoseira alpigea、Cyclostephanos dubius、Stephanodiscus parvus、S.hantzschii出现在龙感湖内;以浮游种为优势种的东部湖区比以附生底栖种为优势种的西部湖区富营养化更严重,研究以期为湖泊治理提供一定的理论依据。

英文摘要：

In this study,we took the middle and lower reaches of the Yangtze river typical grass type lake dragon lake as the research object,used biological index（surface layer sediment diatom）,through the analysis of the diatoms,DCA analysis,clustering analysis and the lake nutrient characteristics analysis of diatom species,to explore the classification of dragon lake sediment surface diatom species,the potential environmental gradient of influencing diatom,the space distribution features of surface sediment diatom taxa,and analyzed the lake nutrient characteristics which surface sediment diatom taxa instruct.Research shows that dragon lake surface sediment diatom taxa had space differences in distribution.Surface of diatom taxa distribution was mainly explained by the first axis of environmental factors,reflecting the arrangement of the sample under the control of the first axis.The environmental significance reflected by the second axis was not significant.Rich nutrition of phytoplankton species was dominant species in dragon lake diatom combination.Dragon lake is close to eutrophic state.Half planktonic species Aulancoseira granulate is the biggest dominant species,and Aulancoseira granulate has absolute advantage in moderate nutrition lake.Floating and half floating kind of Cyclotella atoms and C.eneghiniana,Aulacoseita alpigea,Cyclostephanos dubius,Stephanodiscus parvus,S.hantzschii, which are eutrophication phytoplankton species that mainly occur in eutrophic lakes and can better indicate eutrophication appeared in Dragon lake.Phytoplankton species as the dominant species of east lake area than pick benthic species as the dominant species of west lake area in lake eutrophication is more serious.This study is looking forward to providing theoretical basis to the governance in the lakes wetlands.