Planktonic foraminiferal δ¹⁸O values and apparent calcification depths of core-top samples along an east-west transect across the tropical Atlantic/Caribbean@en

D18O values of nine tropical-subtropical planktonic foraminiferal species with different preferential habitat depths collected from 62 core-top samples along an east-west transect across the tropical Atlantic/Caribbean were used to test the applicability of interspecific d18O gradients for reconstructions of tropical upper ocean stratification. In general, the d18O difference (Delta d18O) between intermediate- and shallow-dwelling species decreases, and Delta d18O between deep and intermediate dwellers increases with increasing thermocline depth towards the west. The statistical significance of regional differences in Delta d18O highlights Delta d18O between the intermediate dwellers (in particular Globorotalia scitula and Globorotalia tumida) and the shallow dweller Globigerinoides ruber pink, as well as Delta d18O between the deep dwellers Globorotalia crassaformis or Globorotalia truncatulinoides dextral and intermediate dwellers as most sensitive to changes in tropical Atlantic thermocline depth. Based on the observed regional variations in interspecific Delta d18O, we propose a multispecies stratification index \"STRAtrop\" = (d18Ointermediate - d18Oshallow) / (d18Odeep - d18Oshallow) for the tropical ocean. Statistically significant differences in STRAtrop values between the E-Atlantic and the Caribbean suggest that this index may be a useful tool to monitor variations in tropical upper ocean stratification in the geological record.本研究采集了横跨热带大西洋/加勒比海的东西向断面62个表层沉积物岩芯样品中的9种不同优选栖息水深的热带-亚热带浮游有孔虫（planktonic foraminifera）的δ18O值，用以检验种间δ18O梯度在热带上层海洋层化重建中的适用性。总体而言，随着向西温跃层深度逐渐增加，中间栖息水层与浅栖有孔虫之间的δ18O差值（Δδ18O）呈降低趋势，而深栖与中间栖息水层有孔虫之间的Δδ18O则呈升高趋势。种间Δδ18O的区域差异具有统计学显著性，其中中间栖居种（尤以光滑抱球虫Globorotalia scitula与肥胖抱球虫Globorotalia tumida为代表）与浅栖种粉红色红拟抱球虫Globigerinoides ruber pink之间的Δδ18O，以及深栖种厚壁抱球虫Globorotalia crassaformis或右旋截圆抱球虫Globorotalia truncatulinoides dextral与中间栖居种之间的Δδ18O，对热带大西洋温跃层深度变化最为敏感。基于观测到的种间Δδ18O区域差异，我们提出适用于热带海洋的多物种层化指数"STRAtrop" = (中间栖居种δ18O值 - 浅栖种δ18O值) / (深栖种δ18O值 - 浅栖种δ18O值)。东大西洋与加勒比海区域的STRAtrop值存在统计学显著差异，这表明该指数可作为一种有效工具，用于监测地质记录中的热带上层海洋层化变化。