Some massive coral core slices reveal luminescent bands under ultraviolet light, which have been attributed to terrestrial humic acids in the skeleton. Coral luminescence has therefore been used to reconstruct past climate and hydrological variability. However, it has remained unresolved how closely coral luminescence at sub-annual resolution is related to terrestrial humic acid concentrations. This study presents a solution-based fluorescence method to quantify terrestrial humic substances in less than 4 mg of coral powder. The results show that in corals from Malaysia and Singapore, the luminescence green-to-blue ratio is correlated with skeletal concentrations of terrestrial humic substances ( R 2 > 0.40, p < 0.001) at two sites that are exposed to terrestrial dissolved organic matter from peatlands on Sumatra. In contrast, coral cores from two other sites located far from major terrestrial organic matter sources show lower green-to-blue values and no convincing correlation with fluorescence intensity of terrestrial humic substances in the skeleton. Abiogenic aragonite precipitation experiments with both terrestrial and marine organic matter sources confirmed that terrestrial humic substances are readily incorporated into aragonite, but not fluorescent organic matter from marine sources. The results of this study suggest that in coral cores with high luminescence green-to-blue ratios (> 0.6) and large downcore variability (range of ≥ 0.05), the green-to-blue ratio is strongly linked to variation in terrestrial humic substances. Coral cores therefore have the potential to reconstruct past variation in terrigenous dissolved organic carbon fluxes.

中文翻译：

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珊瑚骨骼的次年荧光测量：骨骼发光与陆地腐殖质类物质之间的关系

一些巨大的珊瑚核心切片在紫外线下显示出发光带，这归因于骨骼中的陆地腐植酸。因此，珊瑚发光已被用于重建过去的气候和水文变化。然而，在次年分辨率下珊瑚发光与陆地腐植酸浓度之间的关系仍未得到解决。本研究提出了一种基于溶液的荧光方法来量化少于 4 毫克珊瑚粉中的陆地腐殖质。结果表明，在马来西亚和新加坡的珊瑚中，发光绿蓝比与暴露于陆地溶解有机物的两个地点的陆地腐殖质的骨骼浓度（R 2 > 0.40，p < 0.001）相关。苏门答腊的泥炭地。相比之下，来自远离主要陆地有机物质来源的另外两个地点的珊瑚核心显示出较低的绿色到蓝色值，并且与骨骼中陆地腐殖质的荧光强度没有令人信服的相关性。陆地和海洋有机物质来源的非生物源文石沉淀实验证实，陆地腐殖质很容易结合到文石中，但不能将海洋来源的荧光有机物质结合到文石中。这项研究的结果表明，在具有高发光绿蓝比（> 0.6）和大的下核变异（范围≥ 0.05）的珊瑚核中，绿蓝比与陆地腐殖质的变化密切相关. 因此，珊瑚核有可能重建陆源溶解有机碳通量的过去变化。