Oxygen and carbon isotope ratios for six planktonic foraminifer species from different water depth, Ontong-Java Plateau, Pacific (Table 2)

Stable isotope analyses and scanning electron micrographs have been carried out on six planktonic forminifera species, Pulleniatina obliquiloculata, Globorotalia tumida, Sphaeroidinella dehiscens, Globigerinoides ruber, Globigerinoides sacculifer and Globigerinoides quadrilobatus from eleven box-cores taken at increasing depths in the equatorial Ontong-Java Plateau (Pacific). This allows us to describe the way dissolution affects the microstructures of the tests of the different species and to quantify the changes of isotopic composition. We may conclude that: 1) dissolution effects on test morphology and stable isotope compositions are species dependent, species with a similar habitat showing a similar trend; 2) the shallow water, thin-shelled species are the first to disappear: scanning electron microscope (SEM) work shows alteration of outer layers. Deep water, thick-shelled species are present in all samples: SEM work shows breakdown and disparition of inner layers; 3) for all species there is a similar trend towards increasing delta18O values with increasing water depths and increasing dissolution. This effect may be as high as 0.6 ? per thousand meters for Globorotalia tumida; 4) below the lysocline, around 3500 m, it appears that 13C/12C ratios slightly increase towards equilibrium values for thick shelled species: G. tumida, P. obliquiloculata and S. dehiscens. 14C dates and isotope stratigraphy of two box-cores show that all samples are recent in age, and exclude upward mixing of glacial deposits as an important factor.研究针对采自太平洋赤道翁通-爪哇海台沿深度梯度获取的11个箱式岩心（box-cores）中的6种浮游有孔虫（planktonic forminifera）——包括Pulleniatina obliquiloculata、Globorotalia tumida、Sphaeroidinella dehiscens、Globigerinoides ruber、Globigerinoides sacculifer及Globigerinoides quadrilobatus——开展了稳定同位素分析（Stable isotope analyses）与扫描电子显微成像分析（scanning electron micrographs）。本研究借此阐明溶解作用对不同物种壳体微观结构的影响机制，并定量分析同位素组成的变化特征。据此可得到如下结论： 1) 壳体形态与稳定同位素组成的溶解效应具有物种特异性，栖息环境相似的物种表现出相近的变化趋势； 2) 浅水环境下的薄壳物种最先因溶解作用消失：扫描电子显微镜（scanning electron microscope, SEM）分析显示其外层结构发生蚀变；深水厚壳物种在所有样品中均有留存，扫描电镜分析可见其内层结构发生破坏与消失； 3) 所有物种均呈现出随水深增加与溶解作用增强，δ¹⁸O值升高的相似趋势。对于Globorotalia tumida，该效应最高可达每千米0.6‰； 4) 在约3500米的溶跃层（lysocline）之下，厚壳物种（G. tumida、P. obliquiloculata与S. dehiscens）的¹³C/¹²C比值向平衡值小幅升高。 对两个箱式岩心的¹⁴C测年（14C dates）与同位素地层学（isotope stratigraphy）分析结果表明，所有样品均为近代沉积，排除了冰期沉积物（glacial deposits）向上混合作为重要影响因素的可能。