海洋生态与环境科学重点实验室知识库

科学认识鱼类耳石中微量元素的沉积机制及其与水环境中主要环境因子的关系是基于耳石微化学方法重新构建鱼类生活史并反演其生活履历的重要前提。本研究以褐牙鲆（Paralichthys olivaceus）仔稚鱼为研究对象，通过实验生态学方法研究了耳石中微化学元素沉积水平与鱼类早期生活过程中所经历的水环境中微量元素浓度的关系，并探讨了水温及个体生长因素对耳石中微量元素沉积的影响；旨在从基础生态学角度解析褐牙鲆仔稚鱼耳石中微量元素沉积机制及关键影响因子，为构建解决鱼类群体判别、生活史重建和基于种群的渔业资源管理等鱼类生态学问题的耳石微化学分析技术提供基础性理论支持。

传统的耳石沉积机制研究多以单一元素为研究对象，往往忽略其他元素浓度变化的潜在影响。本研究以Sr、Ba为代表性元素，探讨了在褐牙鲆耳石中目标元素沉积过程中的目标元素浓度的主导效应及与其他元素的潜在交互效应。研究发现，Sr、Ba在耳石中的沉积量分别与水环境中Sr、Ba的浓度变化显著正相关。Sr的沉积效率高于Ba，且二者的沉积效率均随水环境中元素浓度升高而降低。水环境中Sr的浓度升高对Ba在耳石中的沉积有较小抑制作用，而Ba的浓度变化对Sr在耳石中的沉积基本无影响。Sr浓度升高对Ba沉积的抑制效应可能是源于水环境中Sr的浓度远高于Ba的浓度，使Sr在与耳石结合的过程中具备更强的竞争能力。因此，在耳石微化学的实际应用中不仅需要考虑目标元素在水环境中的浓度，更需要考虑可能对目标元素沉积产生竞争或促进作用的其他水化学元素浓度，才能更为准确地追溯鱼类个体的水化学履历。

本研究主要针对同一环境条件下出现的生长差异对耳石中微量元素沉积的潜在影响，并发现这种生长差异对Sr、Ba在褐牙鲆仔稚鱼耳石中的沉积过程无明显作用。自然环境中，相同的环境条件下的同世代鱼类个体往往具有相同的生活史，相同年龄个体的耳石微化学特征能够代表其同世代群体所经历的水环境变化。

本研究发现，水温升高能够显著促进褐牙鲆仔稚鱼耳石中Sr的沉积，高水温下Sr在耳石中的沉积量及沉积速率均显著高于低水温条件。同时，微量元素沉积过程中的水温效应远小于元素浓度效应，不同水温下Sr在耳石中的沉积量与水环境中Sr的浓度表现为显著的线性正相关。水温变化能够影响Sr在褐牙鲆仔稚鱼耳石中沉积量的大小，故褐牙鲆仔稚鱼耳石中微量元素沉积具备良好的反演温度史的能力。

总体而言，褐牙鲆仔稚鱼耳石中的微量元素沉积能够良好地反映周围水化学及温度变化，具备反演自身生活史的能力。但在具体应用过程中，一方面应该考虑目标元素以外的其他元素浓度变动所带来的潜在影响，另一方面应该考虑个体生长发育水平差异可能带来的沉积效应差别。全面了解不同环境因子对耳石中微量元素沉积的影响能够更好地获取耳石中微量元素的沉积机制，为鱼类生活史重建、种群判别以及基于种群的渔业资源管理等应用提供科学依据。

An understanding of the effects of aquatic environmental factors on elemental incorporation into otoliths is fundamental for reconstructing life and environmental histories of fish using microchemistry analysis. The present study set a series of experiments to explore the relationships between otolith elemental incorporation and ambient water elemental concentrations, growth or water temperature in larval-juvenile flounder Paralichthys olivaceus. This study aimed to explain the mechanism of otolith elemental incorporation and provided fundamental support to address issues of fish ecology, such as stock discrimination, reconstruction of life history and resource management of the flounder.

In this study, the relative or interactive effects of water elements (strontium Sr and barium Ba) on otolith elemental incorporation in larval-juvenile flounder were investigated. The results revealed that the otolith incorporation of Sr and Ba were positively dependent on the concentrations of elements in water. Sr was incorporated into otoliths more efficiently than Ba, and the partition efficiency (D_Me) of both elements decreased with increasing water elemental concentrations. Increasing Sr concentrations in water appeared to negatively affect the incorporation of Ba into otoliths rather than facilitate it as previously reported in fish reared in freshwater. The Ba concentrations in water did not influence the otolith incorporation of Sr, which agreed with the findings in other fish species. The negative effects of Sr concentrations on the otolith incorporation of Ba may be caused by the difference between elemental concentrations in freshwater and seawater. Generally, Sr concentrations in freshwater are lower than in seawater, while Ba concentrations in freshwater are pretty higher than in seawater. It is essential to cautiously address the interactive effects of multiple elements in the environment on otolith elemental incorporation when applying otolith microchemistry to fish ecology studies.

This study mainly investigated the potential effects of growth under the same environmental conditions, but did not detect a significant effect of growth on otolith incorporation of either Sr or Ba in larval-juvenile flounder.

This study found that the increase of water temperature could effectively promote the incorporation as well as the incorporation efficiency of Sr. The otolith incorporation of Sr was positively dependent on ambient Sr concentrations at each water temperature. It appeared that the otolith elemental incorporation of Sr was closely related to the ambient elemental concentration that fish experienced, suggesting that Sr could be used as an elemental fingerprinter to reconstruct the life and environmental histories of the flounder during the early life stage in nature.

Overall, the otolith elemental incorporation in the flounder at early life stage could effectively reflect the chemistry of the environment, which means the elemental fingerprinting could be used to construct early life history of the flounder. Additionally, the interactive elemental effects as well as the somatic growth on the otolith incorporation of a target element should be cautiously considered and addressed when these experimental results are applied in field work, such as stock identification and life history construction.