Stable isotopic record of planktonic foraminifera of the Pacific Ocean

We determined the d18O and d13C of individual Globigerinoides ruber and Pulleniatina obliquiloculata from sediment traps located from 5°N to 12°S along 140°W in the Pacific Ocean to evaluate the effects of varying [CO3=] on shell d18O and d13C. Variations in the offset between shell d13C and d13CDIC (Dd13Cs-DIC) are attributed to differences in [CO3]2-, temperature, and shell size between sample sites. When Dd13Cs-DIC of G. ruber was corrected for variations in [CO3]2- using the experimental slope of Bijma et al. (1998), the residual Dd13Cs-DIC was correlated with mixed layer temperature (+0.10±0.04 per mil °C**-1). The slope of this temperature effect is consistent with experimental results. In P. obliquiloculata, Dd13Cs-DIC and temperature were strongly anticorrelated (−0.14±0.03 per mil C**-1). We are unable to separate the influences of [CO3]2- and temperature in this species without independent experimental data. Correcting for [CO3]2- variability on d18Os of G. ruber improves the accuracy of estimated sea surface temperatures.

本研究对太平洋沿140°W经线、北纬5°至南纬12°海域布设的沉积物捕获器中的单个红拟抱球虫（Globigerinoides ruber）与斜室普林虫（Pulleniatina obliquiloculata）的氧同位素d¹⁸O（d18O）与碳同位素d¹³C（d13C）进行测定，以评估碳酸根离子浓度[CO₃²⁻]（[CO3=]）变化对壳体d¹⁸O与d¹³C的影响。壳体d¹³C与溶解无机碳d¹³C（d13CDIC）的差值Dd13Cs-DIC（Dd13Cs-DIC）的变化，可归因于采样位点间碳酸根离子浓度、温度及壳体尺寸的差异。利用Bijma等人1998年的实验斜率对红拟抱球虫的Dd13Cs-DIC进行碳酸根离子浓度变化校正后，剩余的Dd13Cs-DIC与混合层温度呈显著相关关系（+0.10±0.04 ‰·℃⁻¹），该温度效应斜率与实验结果一致。对于斜室普林虫，Dd13Cs-DIC与温度呈显著负相关（−0.14±0.03 ‰·℃⁻¹）。若无独立实验数据支撑，本研究无法区分该物种壳体的碳酸根离子浓度与温度对Dd13Cs-DIC的影响。对红拟抱球虫壳体d¹⁸O进行碳酸根离子浓度变异性校正，可提升海表温度估算的精度。