长江口作为中国最大的河口,其沉积物记录了东亚季风演化及海陆变迁的丰富信息,是研究环境演化的理想区域.脂类生物标志物具有特定的生物来源,对外部环境变化响应敏感且具有较高的保存潜力,是一类重要的古环境代用指标.本研究在长江口横沙岛采集了一根40 m长的沉积柱样(HSD22),运用高效液相色谱质谱联用仪分析了微生物细胞膜脂的生物标志物——甘油二烷基甘油四醚(Glycerol Dialkyl Glycerol Tetraethers;GDGTs),计算了BIT(Branched Isoprenoid Tetraether)、MI(Methane Index)、RI-OH(the ring index of OH-GDGTs)等分子指标,着重对羟基化GDGTs(OH-GDGTs)指标进行了研究.对比前人研究结果后发现OH-GDGTs具有环境特异性,不同环境中的生物来源不同,导致化合物的变化趋势不同.基于OH-GDGTs温度指标,HSD22的三次沉积相变换分别对应全新世的早期偏冷、中期偏暖、晚期偏冷的气候模式.此外,OH-GDGTs还显示出指示盐度变化和甲烷活动的潜力,OH/ALL％指标可以有效反映河口区域淡水信号的变化,但该指标在非河口区的适用性还有待进一步验证.
Research on the environmental indication of OH-GDGTs to the Holocene Yangtze Estuary
The Yangtze River Estuary,the largest estuary in China,is an ideal area for studying environmental evo-lution because its sediments record abundant information of East Asian monsoon evolution and land-sea transition.Lipid biomarkers are an important class of paleoenvironmental proxies due to their specific biological origins,sen-sitive responses to external environmental changes,and high preservation potential.In this study,a 40-m-long sediment column(HSD22)was collected from the Yangtze River Estuary.High-performance liquid chromatogra-phy-mass spectrometry was used to analyze glycerol dialkyl glycerol tetraethers(GDGTs),a microbial membrane lipid biomarker.Molecular indexes such as branched isoprenoid tetraether index,methane index,and ring index of OH-GDGTs were calculated.This study found that the biological origin of OH-GDGTs varies across different en-vironments,resulting in distinct compositional trends.The three sedimentary facies transitions of core HSD22 cor-respond to the early,middle,and late Holocene periods,and the corresponding cold-warm-cold temperature trends are recorded based on the OH-GDGT temperature index.OH-GDGTs demonstrate potential in indicating salinity changes and methane activities.The OH/ALL％index can effectively reflect changes in freshwater signals in estu-ary areas;however,its applicability in non-estuary areas requires further verification.
Yangtze River EstuaryGDGTssalinitymethane
袁梦、肖文杰、年小美、张卫国、葛黄敏、许云平
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上海海洋大学海洋科学与生态环境学院,上海 201306
Department of Biology,HADAL & Nordcee,University of Southern Denmark,5230 Odense M,Denmark
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