【Title】HOLOCENE BIOMARKER RECORDS ON THE NORTHERN BERING SEA SLOPE AND THEIR PALEOENVIRONMENTAL IMPLIMATIONS
phytoplankton and primary productivity;
igh-carbon Alkane input and terrestrial vegetation structure;
【摘要】 本文通过白令海北部陆坡区B2-9站位沉积物柱样高分辨率的生物标志物（菜子甾醇、甲藻甾醇、长链烯酮、nC30-diol）提取和分析，获得了近一万年来浮游植物群落和初级生产力、高碳烷烃输入与陆源植被变化等相关记录，研究结果显示，全新世以来表层浮游植物和初级生产力都经历了“高-低-高”的变化过程，并具有明显的阶段性，可能受控于陆架坡折处海冰的分布、上层海洋营养盐供应和全新世气候与环境的变迁；浮游植物群落结构较为稳定，硅藻是初级生产力的主要贡献者，甲藻次之，颗石藻和黄绿藻比前两者低了一个数量级，硅藻与甲藻之间具有明显的竞争关系，前者明显占据优势，是白令海有机碳汇的主要贡献者；正构烷烃总量分别在7.8 ka B.P.，6.7 ka B.P.和5.4 ka B.P.经历了三次阶梯状的下降过程，并呈现出四个相对稳定的阶段，其主要受控于早全新世海平面上升以及周边陆地植被源区的气候与环境变化；正构烷烃分子组合特征显示其来自陆地高等植物、且陆源植被结构较为稳定，木本植物占据优势；单体碳同位素研究表明正构烷烃的主碳峰为nC27，对烷烃总量的贡献最大，可能与当时陆源繁盛的木本植物及输入有关，含量较高的nC23则可能主要来源于北半球沿海广泛分布的一类沉水植物。
【Abstract】Variations in phytoplankton community and primary productivity, terrestrial high-carbon n-alkanes input and vegetation change in their source during the last 9.6 ka B.P. are investigated based on high-resolution biomarker (brassicasterol, dinosterol,nC37-alkenone,nC30-diol) extraction and measurement at Site B2-9 from the northern Bering Sea Slope. The researched results show that surface phytoplankton and primary productivity appeared obviously periodic change from high to low and again to high during the Holocene, which might be controlled by the sea-ice extension on the shelf-break, the nutrient supplement in sea surface and climate change. Diatoms were the greatest contributor to primary productivity, in turn followed by dinoflagellates, coccolithophores and eustigmatophytes, which indicate lower order of magnitude than two formers in the steady phytoplankton community. In the clear competitive relationship between diatoms and dinoflagellates, the former toke the obviously advantage and made the main contribution to organic carbon sinks in the Bering Sea. Furthermore, stepwise total n-alkanes dropped quickly at 7.8 ka B.P., 6.7 ka B.P. and 5.4 ka B.P., respectively, showing four relatively stable stages, which might be controlled by sea-level rise during early Holocene and environmental change of terrestrial vegetation source of surrounding the Bering Sea. The molecular parameters indicate that n-alkanes were originated from terrestrial higher plant with stable vegetation structure, and then woody plant dominated in this kind of combination. Mono-carbon isotopic results denote that thenC27content was the main carbon peak and dominated in total n-alkanes, which might be related to the prosperous woody plants from vegetation source and their spatial distribution. HighernC23content may be mainly derived from the submerged plants which widely distributed along coastal areas in Northern Hemisphere.