Indicative significance of biogenic elements to eco-environmental changes in waters
沉积物生源要素对水体生态环境变化的指示意义

The increasing input of nutrients to lakes and estuaries by the anthropogenic activities has resulted in the aquatic eco-environment changes,such as the change of food chain,eutrophication and frequently seasonal hypoxia in bottom waters,which can be recorded in sediments.The biogenic elements and their stable isotopes in sediments are effective proxies to reflect the paleoproductivity and nutrient level in waters.The indicative significance of biogenic elements(C,N,P,Si) to the change of primary production,material sources and nutrient levels was reviewed in this paper.TOC,TN,δ13C,CaCO3 and BSi in sediments reflecting the content of organic matter and the growth of phytoplankton,can be used as effective proxies to indicate the primary production level.Source identification of organic matter by the differences of δ13C,δ15N and C/N values between different types of plants has important value to study the influence of anthropogenic activities on the aquatic environment and eutrophication.The increasing trend of TN,δ15N,TP and non-apatite phosphorus(NAIP) in sediments reflects the increasing input of terrestrial nitrogen and phosphorus to coastal waters.BSi can reflect the phytoplankton growth,and further indicate the Si concentration variations and eutrophication in waters.Biogenic elements are influenced by many factors in their deposition and burial,such as diagenesis and hydrodynamic conditions,which can disturb the sedimentary records of biogenic elements and then hinder the proper indication of environmental changes by these proxies.Consequently,in order to exactly understand the aquatic environmental changes,it is essential to comprehensively analyze the information of environmental changes provided by multiple biogenic element proxies and to fully consider the potential interference factors for the paleoenvironmental reconstructions.