LAKE ENVIRONMENTAL CHARACTERISTICS RECOREDED BY ISOTOPES IN SEDIMENTS OF DAPU AREA IN LAKE TAIHU: LAKE ENVIRONMENTAL CHARACTERISTICS RECOREDED BY ISOTOPES IN SEDIMENTS OF DAPU AREA IN LAKE TAIHU

Through the determinations of δ13C,δ15N,total organic C,total N,total P in sediments of Dapu area in the Taihu Lake,this paper analyzed the eutrophication process of this area.The results showed that δ13C,δ15N in sediments had a significant change in patferns with the water evolution from low nutrition to eutrophication.Before 1950s,primary productivity of the lake was low and the water environment was good.Moreover,the impact of human activities was weak,and the lake sediments record showed a high value of δ13C and low values of δ15N,TOC,TN,TP.In 1990s,the lake environment changed significantly and the primary productivity increased substantially.As the result,the water environment deteriorated and the nutrition level increased rapidly resulting in eutrophication.Accordingly,the value of δ13C decreased rapidly,but δ15N increased,and the correlation showed significant reverse(R=-0.81).However,the correlation between δ13C and δ15N was significantly positive(R=0.96).This phenomenon reflected that the isotopic elements of different lakes responded differently to environmental changes,and the eutrophication patterns of grass-type lake and algae-type lake were initially established.