The geochemistry of the calcium carbonates of marine organisms is an excellent proxy for reconstruction of the paleoceanographic history. However, previous studies of hypercalcified demosponges (sclerosponges) are considerably fewer than those of corals, foraminifers, and bivalves. Here, we investigated stable oxygen (δ¹⁸O) and carbon (δ¹³C) isotopes and minor and trace element (Mg, Sr, Ba, Pb, and U) to Ca ratios of 36 living sclerosponges (Astrosclera willeyana) collected from Kume Island in the Ryukyu Islands, southwestern Japan, to evaluate the utility of geochemistry as a paleoenvironmental proxy. The δ¹⁸O, δ¹³C, and Sr/Ca deviations of the coevally precipitated skeleton were extremely small and almost constant at all skeletal portions, strongly suggesting that within-skeletal variations in the chemical components are negligibly small for non-symbiotic sclerosponges. Mean δ¹⁸O, δ¹³C, and Sr/Ca values (N = 36), falling within a quite narrow range, showed no significant evidence for intraspecific (inter-specimen) variations in the sclerosponges. The sclerosponges δ¹⁸O and δ¹³C were consistent with those of the aragonites precipitated in isotopic equilibrium with seawater at the growth site. The sclerosponge Sr/Ca was close to that of inorganically precipitated aragonite, and the estimated partition coefficient of 1.1 (almost unity) is identical to previously reported values for different species (Ceratoporella nicholsoni). Consequently, these results suggest that A. willeyana sclerosponge, having little vital effects on the geochemistry, is a robust indicator of paleocean environments (seawater δ¹⁸O, temperature, and dissolved inorganic carbon δ¹³C). Further, our evaluation study documents that sclerosponges living in deeper ocean environments can support the reconstruction of spatial and vertical paleoceanographic changes in conjunction with coral proxy records. The sclerosponge U/Ca showed little within-skeletal and intraspecific variations, but the heterogeneity and individual difference of the Mg/Ca, Ba/Ca, and Pb/Ca were relatively large, the reasons of which still remain unresolved.

中文翻译：

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评价地球化学记录作为超钙化demo石天蛾中的古环境代用物

海洋生物碳酸钙的地球化学是重建古海洋史的极好代表。但是，先前对钙化过高的脱脂海绵（硬骨海绵）的研究远少于珊瑚，有孔虫和双壳类动物的研究。这里，我们调查稳定氧（δ ¹⁸ O）和碳（δ ¹³ C）同位素和次要和微量元素（镁，锶，钡，铅，和U）与Ca的36个居住硬海绵（比率Astrosclera willeyana从久米收集）日本西南部琉球群岛上的一个小岛，用于评估地球化学作为古环境代用物的效用。的δ ¹⁸ O，δ ¹³凹处沉淀的骨架的C和Sr / Ca偏差极小，并且在所有骨骼部分都几乎恒定，这强烈表明，对于非共生的硬化反应，化学成分的骨骼内变化很小，可以忽略不计。平均δ ¹⁸ O，δ ¹³ C，和Sr /钙值（Ñ在硬海绵= 36），落在很窄范围内时，表现出对种内（检测体间）没有显著证据变化。所述硬海绵δ ¹⁸ O和δ ¹³C与在生长位点处与海水同位素平衡沉淀的文石的碳相符。硬化海绵Sr / Ca与无机沉淀文石的Sr / Ca接近，并且估计的分配系数1.1（几乎为1）与先前报道的不同物种（Ceratoporella nicholsoni）的值相同。因此，这些结果表明，A. willeyana硬海绵，具有在地球化学小重要作用，是古海洋环境的稳健指示符（海水δ ¹⁸ O，温度和溶解的无机碳δ ¹³C）。此外，我们的评估研究文件还表明，生活在更深海洋环境中的硬海绵菌可以与珊瑚代理记录一起支持重建空间和垂直古海洋学变化。硬化海绵体U / Ca几乎没有骨骼内和种内变异，但Mg / Ca，Ba / Ca和Pb / Ca的异质性和个体差异较大，其原因仍未解决。