Mg/Ca, Ba/Ca, Mg vs. S and fluorescence measured with EMPA, CRM and LA-ICP-MS in a bamboo coral from the Blake Plateau@en

Assessing the physicochemical variability of the deeper ocean is currently hampered by limited instrumental time series and proxy records. Bamboo corals (Isididae) form a cosmopolitan family of calcitic deep sea corals that could fill this information gap via geochemical information recorded in their skeletons. Here we evaluate the suitability of high-resolution chemical imaging of bamboo coral skeletons for temperature and nutrient reconstruction. The applied elemental mapping techniques allow to verify the suitability of the chosen transect on the sample section for paleo-reconstructions and enhance the statistical precision of the reconstruction. We measured Mg/Ca via electron microprobe at 1 μm resolution and Ba/Ca via laser ablation ICP-MS at 35 μm resolution in a historic specimen of Keratoisis grayi from the Blake Plateau off Eastern Florida. Long-term growth temperatures of 7.1 ± 3.4 °C (2SD) that are in agreement with recent ambient temperature range can be reconstructed from Mg/Ca ratios provided that anomalously Mg-enriched structural features around the central axis and isolated features related to tissue attachment are avoided for reconstruction. Skeletal Ba/Ca measurements reflect mean seawater barium [Ba]SW concentrations […]当前，对深海物理化学变异性（physicochemical variability）的评估受限于有限的仪器观测时间序列与代用记录（proxy records）。竹珊瑚（Bamboo corals）隶属于竹珊瑚科（Isididae），该科是一类广布的钙质深海珊瑚类群，可通过其骨骼记录的地球化学信息填补上述信息空白。本研究评估了竹珊瑚骨骼的高分辨率化学成像技术（high-resolution chemical imaging）在温度与营养盐重建中的适用性。所采用的元素成像技术（elemental mapping techniques）可验证样品切片上所选测线（transect）用于古环境重建（paleo-reconstructions）的合理性，并提升重建结果的统计精度。本研究针对采自佛罗里达东部外海布莱克高原（Blake Plateau）的一枚陈年Keratoisis grayi标本，以1微米分辨率通过电子探针微区分析（electron microprobe）测定Mg/Ca比值，并以35微米分辨率通过激光剥蚀电感耦合等离子体质谱（laser ablation ICP-MS）测定Ba/Ca比值。若在重建过程中避开中轴线周围异常富镁的结构特征以及与组织附着相关的孤立结构，则可通过Mg/Ca比值重建出7.1±3.4℃（2倍标准差，2SD）的长期生长温度，该结果与当前周边海域的温度范围相符。骨骼Ba/Ca比值可反映海水平均钡浓度([Ba]SW)……