选取长江口外赤潮多发区沉积物柱状样,在高分辨率测年基础上,通过有机碳、有机碳同位素(δ13C)、生物硅、绿素等多项指标的分析获得了调查海区古生产力的变化信息。并结合近几十年来营养盐浓度及组成结构的变化探讨了海洋浮游藻类组成结构的变化在海洋古环境中的记录。柱状样年代可追溯到20世纪40年代初。δ13C值在柱中的分布为-26.15×10-3~-19.5×10-3,表明有机碳为陆源与海生的混合。生物标志物在柱状样中的分布可大致分为三个阶段,50年代以前含量均较低;50年代至80年代含量均增加,表明海洋浮游藻类活动强烈且以硅藻为主,与此阶段长江口营养盐浓度迅速增加相对应;80年代以后,生物硅的含量下降至整个柱中最低水平,绿素有所降低,但高于50年代前的水平,而有机碳含量增加,表明在该时段硅藻生物量降低,其他藻类生物量有所增加,这与长江口营养盐氮盐持续增加而硅酸盐逐年降低、氮与磷的含量比值、磷与硅的含量比值迅速增大有关。沉积记录还表明此阶段陆源有机碳的贡献增强。 Based on the high-resolution dating, a series of sedimentary column samples of red tide-prone areas outside the Changjiang Estuary were selected to analyze the changes of paleoproductivity in the surveyed sea areas by analyzing a number of indicators such as organic carbon, organic carbon isotope (δ13C), biological silicon and chlorophyll information. In the light of changes of nutrient concentration and composition in recent decades, the changes of composition of marine phytoplankton in marine paleoenvironmental records were discussed. Columnar dating back to the early 1940s. The distribution of δ13C values ​​in the column is -26.15 × 10-3 ~ -19.5 × 10-3, indicating that the organic carbon is a mixture of terrestrial and marine. The distribution of biomarkers in columnar samples can be roughly divided into three stages, with low contents before 1950s. From the 1950s to the 1980s, the content of biomarkers increased, indicating that the marine planktonic algae are strongly active and dominated by diatoms. After the 1980s, the content of biosilica decreased to the lowest level in the whole column, and the chlorophyll decreased but was higher than the level before the 1950s, while the content of organic carbon increased. The biomass of diatoms decreased and the biomass of other algae increased with the continuous increase of nutrients and nitrogen in the Yangtze River estuary, the decrease of silicate, the ratio of nitrogen and phosphorus, and the rapid increase of the ratio of phosphorus to silicon. Sedimentary records also show that the contribution of terrestrial organic carbon at this stage is enhanced.