Within the world’s oceans, regionally distinct ecological niches develop due to differences in water temperature, nutrients, food availability, predation and light intensity. This results in differences in the vertical dispersion of planktonic foraminifera on the global scale. Understanding the controls on these modern-day distributions is important when using these organisms for paleoceanographic reconstructions. As such, this study constrains modern depth habitats for the northern equatorial Indian Ocean, for 14 planktonic foraminiferal species (G. ruber, G. elongatus, G. pyramidalis, G. rubescens, T. sacculifer, G. siphonifera, G. glutinata, N. dutertrei, G. bulloides, G. ungulata, P. obliquiloculata, G. menardii, G. hexagonus,G. scitula) using stable isotopicsignatures (δ18O and δ13C) and Mg/Ca ratios. We evaluatetwo aspects of inferred depth habitats: (1) the significance of the apparentcalcification depth (ACD) calculation method/equations and (2) regionalspecies-specific ACD controls. Through a comparison with five global,(sub)tropical studies we found the choice of applied equation andδ18Osw significant and an important consideration whencomparing with the published literature. The ACDs of the surface mixed layer andthermocline species show a tight clustering between 73–109 m water depthcoinciding with the deep chlorophyll maximum (DCM). Furthermore, the ACDs forthe sub-thermocline species are positioned relative to secondary peaks in thelocal primary production. We surmise that food source plays a key role in therelative living depths for the majority of the investigated planktonicforaminifera within this oligotrophic environment of the Maldives and elsewherein the tropical oceans.
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机译：在全球海洋中，由于水温，养分，食物供应，捕食和光照强度的差异，形成了区域不同的生态位。这导致浮游有孔虫在全球范围内的垂直扩散差异。在将这些生物用于古海洋重建时，了解这些现代分布的控制非常重要。因此，本研究限制了北赤道印度洋的现代深度生境，包括14种浮游有孔虫物种（G. ruber，G。elongatus，G。pyramidalis，G。rubescens，T。sacculifer，G。siphonifera，G。glutinata， N. dutertrei， G 。 bulloides ， G 。 ungulata ， P 。< em> obliquiloculata ， G ， menardii ， G ， hexagonus ， G 。 scitula ）使用稳定的同位素签名（δ 18 O和δ 13 C）和Mg / Ca比。我们评估推断深度生境的两个方面：（1）表观生境的意义钙化深度（ACD）的计算方法/方程式和（2）区域特定物种的ACD对照。与五个全球比较（亚热带）研究中，我们找到了应用方程式的选择，并且δ 18 Osw的显着性和重要考虑因素与已发表的文献进行比较。表面混合层的ACD和跃层物种在水深73-109 m之间显示出紧密的聚集与深层叶绿素最大值（DCM）一致。此外，ACD亚热线菌种相对于当地的初级生产。我们推测食物来源在大多数被调查浮游生物的相对生活深度在马尔代夫和其他地方的贫营养环境中的有孔虫在热带海洋中。
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