Sediment Record Of Subfossil Chironomid Assemblages In The Ecosystem Evolution Of Typical Lakes In The Jianghan Lake Group

Jianghan plain is one of the most concentrated and typical areas of lake distribution in China.It is of great significance to understand the lake environment and ecological evolution in the area.In this paper,32 lakes of Jianghan Lake Group were selected as the research object,and the fossil chironomid head capsules as major proxy.This study introduces the application of chironomids paleoecology techniques in reconstructing the historical,ecological characters of lake ecosystems,which will provide essential information for the management of wide range types of wetland.A total of 58 species of 35 genera of Chironomidae were identified in the sediments of the Jianghan Lake Group.Among them,27 genera and 41 species were found in the modern environment(surface sediments).The reference environment identified 21 genera and 28 species.Mesotrophic and macrophyte-related species Paratanytarsus penicillatus,Microchironomus tener,Cricotopus sylvestris,Polypedilum nubifer,Dicrotendipes nervosus,Procladius etc,were most abundant in the reference samples suggesting that levels of water TP were relatively low(50-60 ?g/L TP).And lake ecological environment is better,while aquatic vegetation coverage is high.Eutrophic-and pollution-tolerate species Chironomus plumosus,Microchironomus tabarui,Tanypus,Propsilocerus akamusi,Procladius etc,were more abundant in the modern samples.The results of DCA sequencing showed that the ecological conditions of Jianghu Lake group were all deviated from the reference environment,and the adjustment of Chironomidae in the reference environment changed to the eutrophic species.The DCA sequencing analysis reflected the nutrition of Jianghan Lake group for nearly one hundred years.The gradient of the lake showed that the nutrient level of the lake was gradually increasing.Donghu Lake,Zhongxiangnan Lake,Ci Lake,Tangxun Lake,Daye Lake,Zhangdu Lake,Wanghu Lake,Zhupo Lake,Taibai Lake,Baoan Lake,Houhu Lake,Luhu Lake,evolved from mesotrophic and macrophyte-related species to the eutrophic-and pollution-tolerate species.Cehu Lake,Baoxie Lake,Hanyangdong Lake,Huama Lake,Niulang Lake,Chidong Lake,Yuni Lake,Haikou Lake,Hanyangxi Lake,eutrophic-and macrophyte-related species live together.Yanxi Lake,Changhu Lake,Liangzi Lake,Niushan Lake,Futou Lake,Dongxicha Lake,Honghu Lake,Xiliang Lake,Yaer Lake,Sanshan Lake,Yezhu Lake,Chironomus populations are the same in the reference environment and in the modern environment.P.penicillatus and C.sylvestris were most abundant in these lakes.The increase of nutrient level,the destruction of aquatic vegetation and the connectivity of sudden factors such as the connection of rivers and lakes and the stocking of herbivorous fish are the main factors of the Chironomidae changes.