中文摘要：

在浮游有孔虫壳体稳定同位素及Mg/Ca和Sr/Ca值的相关研究中,人们常因各种原因而选择不同粒径的壳体进行分析测试,而很少注意壳体大小可能导致研究结果的分歧。针对这一问题,本文分析了位于低纬度海区钻孔中不同粒径的Glo-bigerinoides ruber（白色,sensu stricto）和Pulleniatinaobliquiloculata壳体,结果表明G.ruber壳体的δ^13C值受壳体大小的影响最为强烈,表现为正相关关系,不同粒径壳体的δ^13C绝对平均差值可达0.48‰±0.12‰和0.25‰±0.09‰;P.obliquiloc-ulata〉400μm与315～400μm和250～315μm壳体Mg/Ca值的差异相当于1.8℃的海水温度;相对而言,G.ruberδ^18O和Mg/Ca值以及P.obliquiloculataδ^13C受壳体大小的影响较小,但它们的Sr/Ca值与壳体大小的关系不显著。本文推测,壳体大小相同时厚重的壳体可能成壳速度较快,相对优先吸收轻的同位素,且壳体Mg/Ca值可能更接近周围海水的水平。据此,本文认为较大个体P.obliquiloculata的壳体分泌可能与周围海水达到了平衡分馏。

英文摘要：

Planktonic foraminiferal shells of various sizes have been processed in the studies of measuring stable isotope and Mg/Ca and Sr/Ca ratios to reveal changes in the water profiles of palaeo-oceans.The potential influence of different shell sizes on measurement results is often being ignored.The objective of this study is to call attentions to this issue by investigating Globigerinoides ruber（white,s.s.）and Pulleniatina obliquiloculata shells of three different size.The shell samples were obtained from a sediment core from a low latitude ocean area.The results indicated that the δ^13C values of G.ruber are strongly affected by shell size with a positive and linear correlation.The δ^13C value difference is up to 0.48±0.12‰ among the shells of the different size.δ^18O and Mg/Ca values of G.ruber shells and δ^13C values of P.obliquiloculata shells are relatively not strongly affected by shell size,in contrast,the mean of Mg/Ca for P.obliquiloculata shells with size 〉400 μm is 0.4±0.31mmol/mol larger than those for 315~400 μm and 250~315 μm size fractions.The difference is equivalent to 1.8℃ when converted into temperature using species-specific equation of Anand et al.（2003）.This work showed no significant difference of Sr/Ca among different size fractions.According to the negative（positive）linear correlation of weight per shell with stable isotopes（Mg/Ca ratios）,it is implied that,with the same size,heavy shells calcify faster than light shells.That is to say that the heavy shells preferentially uptake lighter isotopes and have an Mg/Ca value close to that of seawater.In addition,it is concluded that larger shells of P.obliquiloculata possibly calcify in the condition of achieving equilibrium with ambient seawater.