浙江近岸泥质区百年来浮游植物生产力的变化及对环境的响应

Changes in phytoplankton productivity and impacts on environment in the Zhejiang coastal mud area during the last 100 years

在210Pb定年的基础上,对取自浙江沿岸泥质缺氧区的柱样沉积物开展了菜子甾醇、甲藻甾醇、长链烯酮等生物标志化合物分析,根据生物标志化合物含量及比例的分布特征,重建了泥质区110年来浮游植物生产力及群落结构变化。结果表明浙江近岸浮游植物生产力百年来呈上升趋势,自20世纪60年代开始上升,80年代以来有显著增加,浮游植物群落结构则均有甲藻比例上升、硅藻比例下降的趋势。研究认为,浙江沿岸泥质区百年来浮游植物生产力的提高与我国化肥施用量和长江氮的入海通量呈正相关,营养盐N∶P和N∶Si比值的增加导致浮游植物优势种由硅藻向甲藻的转变,说明自20世纪60年代,尤其是自20世纪80年代以来工农业快速发展、大型水利工程建设等人类活动是导致浙江沿岸泥质区海域浮游植物生产力提高及群落结构变化的主要因素。

A high resolution sediment core was selected in the Zhejiang coastal mud area, which was also located within the hypoxia area. The biomarkers, such as brassicasterol, dinosterol and Ca. 7-Alkenone were determined on the 210 Pb-dated sediment core. According to the vertical distribution of the biomarkers and ratios in the core sedi- ments, we reconstructed the changes in phytoplankton productivity and community structure over the last 110 years in the Zhejiang coastal region. The results indicated increased phytoplankton productivity during the last 100 years in the mud area. Phytoplankton productivity increased gradually starting in the 1960s and accelerated after the 1980s. The change of phytoplankton community structure showed an increasing relative contribution of dino- flagellates and a decreasing relative contribution of diatoms over the last 100 years. The increase in phytoplankton productivity in the Zhejiang coastal mud area corresponded to the increased use of fertilizer and nitrogen fluxes from the Changjiang River during the last 50 years. Meanwhile the succession of diatoms to dinoflagellates was probably caused by the increasing trends in N ＂ P and N .＂ Si ratios. We suggested that these variations were mainly caused by the increasing anthropogenic activities such as the industrialization, agricultural development and the construc- tion of darns since the 1960s and especially since the 1980s.