Otoliths, calcium carbonate (CaCO3) ear stones of fish, contain a wealth of information about fish life and environmental history yet the CaCO3 polymorph form the otolith is made of is a critical, but seldom considered, piece of information during otolith analysis. Otolith trace element chemistry data increasingly informs management decisions, but recent work has shown that CaCO3 polymorphs—aragonite, vaterite, and calcite—can bear on incorporation of trace elements in a non-trivial way. Most fishes are thought to have otoliths of the aragonite CaCO3 form, but this construct is potentially outdated with many recent literature reports showing otherwise. Our study used previously unpublished neutron diffraction data and reports from published literature to address three objectives: (1) summarize the relative effects of otolith CaCO3 polymorphism on otolith microchemistry, (2) summarize reports of otolith polymorphs to gain a better understanding of the extent of non-aragonite otoliths among fishes, (3) outline future research needed to align interpretations of microchemistry with our current understanding of otolith polymorph diversity. We found that while aragonite otoliths are the most common, so are exceptions. For example, the ostensibly rare (among species) CaCO3 form vaterite was reported in at least some otoliths of 40% of the species surveyed. Our work suggests that examination of the CaCO3 polymorph composition of otoliths should become more common particularly in studies where results will or may be used to inform management decisions. Future research should work to attribute controls on otolith CaCO3 polymorph expression using a combination of -omics and material characterization approaches to enrich the life history and environmental information output from otoliths and increase our understanding of the assumptions made in otolith trace element chemistry studies.

中文翻译：

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耳石碳酸钙晶体结构多样性对微化学研究的意义

耳石，即鱼类的碳酸钙 (CaCO3) 耳石，包含有关鱼类生活和环境历史的丰富信息，但构成耳石的 CaCO3 多晶型物在耳石分析过程中是一个关键但很少被考虑的信息。耳石微量元素化学数据越来越多地为管理决策提供信息，但最近的工作表明，CaCO3 多晶型物——文石、球霰石和方解石——可以以一种非平凡的方式影响微量元素的掺入。大多数鱼类被认为具有文石 CaCO3 形式的耳石，但这种构造可能已经过时，许多最近的文献报告表明情况并非如此。我们的研究使用以前未发表的中子衍射数据和已发表文献中的报告来解决三个目标：(1) 总结耳石 CaCO3 多态性对耳石微化学的相对影响，(2) 总结耳石多形性的报告，以更好地了解鱼类中非文石耳石的范围，(3) 概述未来需要进行的研究以调整对耳石的解释微化学与我们目前对耳石多晶型多样性的理解。我们发现虽然文石耳石是最常见的，但例外也是如此。例如，至少有 40% 的被调查物种的耳石中报告了表面上罕见的（在物种中）CaCO3 形式的球霰石。我们的工作表明，对耳石的 CaCO3 多晶型组成的检查应该变得更加普遍，特别是在结果将或可能用于为管理决策提供信息的研究中。