珊瑚骨骼生长与地球化学组成

Coral skeletogenesis and its influence on skeletal geochemistry

造礁珊瑚对环境变化极为敏感,在气候变化与人类活动的多重胁迫下,全球珊瑚礁在近几十年急剧退化。然而,也正是这种环境敏感性使得珊瑚具有记录海水物理化学条件变化的能力,成为研究海洋气候环境变化的重要载体。珊瑚骨骼中的Sr/Ca、Li/Mg、B/Ca、Ba/Ca、δO以及δB等地球化学指标,被广泛应用于重建海水温度、降雨、pH值、陆源输入以及上升流等环境信息。但需要注意的是,珊瑚骨骼的地球化学组成受控于环境变化的同时,也受到珊瑚及共生虫黄藻的生命过程即所谓的“生命效应”的影响。因此,厘清“生命效应”对珊瑚骨骼地球化学组成和环境记录重建的影响,对于准确重建海洋气候环境变化至关重要。本文系统回顾了近三十年来常用的珊瑚地球化学指标,对其原理及存在的“生命效应”进行总结,并归纳了团块状造礁珊瑚的生长模式、骨骼三维结构与微结构特征,及其同珊瑚地球化学替代指标间的关联。结合对珊瑚生长与“生命效应”的理解,以及对珊瑚微区地球化学信号的解读,本文进一步阐述了珊瑚生长对地球化学信号的影响。

Coral reefs have degraded rapidly due to climate change and anthropogenic activities. The vulnerability and sensitivity of corals to environmental changes make them unique archives for climate variability. The geochemical proxies, such as Sr/Ca, Li/Mg, B/Ca, Ba/Ca, δO, and δB, in coral skeletons are widely used to reconstruct paleo-environment changes, such as temperature, precipitation, pH, terrestrial input, and upwelling;however,geochemical signals within coral skeletons are also affected by biological processes, that is, the “vital effects”. Therefore,understanding the underlying mechanisms of these “vital effects” and the associated impacts on geochemical proxies is crucial for accurateenvironmental reconstruction. In this study, we systematically reviewed coral-based geochemical proxies and the related “vital effects”. Furthermore, in combination with the skeletogenesis and in-situ geochemical analyses, we summarized the influence of coral growth on skeletal geochemistry.