白洋淀近70年生态环境演化过程及影响因素

基于白洋淀北部沉积岩心210Pb和137Cs测年、重金属元素、营养元素、粒度和硅藻优势属种分析，结合水文、气候以及保定市和安新县社会经济统计资料，重建了白洋淀近70年以来的生态环境演化历史，并探讨了影响硅藻优势属种演替的主要驱动因素.结果表明:1960年之前，重金属和营养元素处于较低的水平，硅藻属种以Aulacoseira granulata为主，反映湖泊生态环境处于自然演化阶段；1960年前后，由于受到上游水文调控的影响，白洋淀TP和TN含量开始缓慢增加，富营养指示种Cyclotella meneghiniana明显增加；1960~1990年，TP和TN含量明显升高，反映快速农业化进程中营养物质输入增加，但重金属含量仍保持在较低的水平，硅藻属种以A.granulata和C.meneghiniana为优势组合；1990年以来，流域工农业活动的快速发展导致重金属和营养盐富集，尤其是2000年以后，重金属和营养盐富集进一步加剧，此时硅藻组合也发生了重大转变，由1990年前的A.granulata优势种转变为1990年后的C.meneghiniana优势种，重金属耐受种Nitzschia palea也自2000年以来开始持续增加.冗余分析表明沉积物重金属、TP、TN、温度、风速、入淀水量和水位是影响白洋淀近70年以来3个硅藻优势属种演替的显著因子，其中重金属和营养是硅藻组合演替的主要驱动因素，水文过程、温度和风速是硅藻组合演替的重要诱因. 

A 70 Year Sedimentary Record of Eco-Environment Changes in Baiyangdian Lake and Its Influencing Factors

Based on sedimentary proxies (i.e., 210Pb and 137Cs dating, heavy metal nutrient and elements, particle size and diatom dominant species) from sediment core in the northern part of Baiyangdian Lake and documentary date (i.e., hydrology, climate, economic and society statistic from Baoding city and Anxin county), this study reconstructed the eco-environment changes of Baiyangdian Lake during the past 70 years and discussed the main driving factors affecting the succession of dominant diatom species.The results showed heavy metals and nutrients were of lower levels, and the diatom was dominated by Aulacoseira granulate before 1960, which indicated that the lake ecology was in the stage of natural evolution.Around 1960, influenced by hydrological control upstream, TP and TN content in Baiyangdian Lake started to increase slowly, and the indicator species of eutrophication, Cyclotella meneghiniana, increased significantly.Between 1960 and 1990, TP and TN content rose significantly, indicating more nutrient input in the rapid process of agriculturalization, however, the content of heavy metals still remained at a lower level. The diatom assemblages were characterized by the codominance of A. granulate and C. meneghiniana. After 1990, accelerated industrial and agricultural activitiesenriched heavy metals and nutrients, especially after 2000, such enrichment became even more significant.At which point diatom assemblages went through material changes: the dominant species shifted from A. granulate before 1990 to C. meneghiniana after 1990; the heavy metal-tolerant species Nitzschia palea hasbeen on the rise since 2000. According to the redundancy analysis, heavy metals, TP, TN, temperature, wind speed, hydrological conditions were significant factors influencing the succession of three diatom dominant speciesover the past 70 years in Baiyangdian. Heavy metals and nutrients were most important factors on diatom succession. Meanwhile, hydrological conditions, temperature and wind speed also imposed on diatom succession.