热带西太平洋250ka来浮游有孔虫G.sacculifer壳体质量变化特征及控制机理

SHELL WEIGHT CHANGES OF PLANKTONIC FORAMINIFERA G.sacculifer FROM THE TROPICAL WESTERN PACIFIC DURING THE LAST 250 ka AND CONTROLLING MECHANISMS

作为新兴的海水CO2-3替代性指标,浮游有孔虫壳体质量对于海洋碳循环研究具有重要意义。测定了热带西太平洋WP7孔250ka以来表层浮游有孔虫G.sacculifer壳体质量。除了在MIS1和MIS4期外,壳体质量显示冰期重、间冰期轻的旋回特征,响应大气pCO2变化,表明大气pCO2变化是该海域浮游有孔虫壳体质量变化的主控因素。研究结果表明MIS4期间壳体质量异常低值可能是该时期加强的上升流和CaCO3溶解事件共同导致。温度与营养盐浓度并不是壳体质量异常的主要原因,共生体则可能是影响因素。G.sacculifer壳体质量与大气pCO2整体上良好的反相关关系表明其可以作为可靠的表层海水CO2-3替代性指标。

As a new proxy to reconstruct sea water [CO3^2 ] in the past, shell weight of planktonic foraminifera can provide clues to revealing ocean carbon cycle. Shell weights of G. sacculifer measured from a tropical western Pacific sediment core WP7 during the last 250 ka show higher values in glacial periods and lower values in interglacial periods responding to changes in CO2 concentrations in the Antarctic Ice Core of Vostok, except in MIS1 and MIS4. Hence, shell weight variations in this sea area are mainly controlled by the CO2 concentration in atmosphere. As a result of intensified upwelling and carbonate dissolution, shell weights have reduced during MIS4. Shell weights also can be affected by coexisting symbionts, but not the changes in temperature and surface nutrient levels. Shell weights of G. sacculifer exhibit a generally inverse relationship with CO2 concentrations, and thus they can be used as a reliable proxy to trace variations in [CO3^2 ] of surface water.