分析软骨鱼类脊椎骨羟磷灰石结构中碳和氮稳定同位素时，不同样本制备技术对结果的影响。

Effect of sample preparation techniques for carbon and nitrogen stable isotope analysis of hydroxyapatite structures in the form of elasmobranch vertebral centra.

机构信息

Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, N9B 3P4, Canada.

出版信息

Rapid Commun Mass Spectrom. 2014 Mar 15;28(5):448-56. doi: 10.1002/rcm.6801.

DOI:10.1002/rcm.6801

PMID:24497282

Abstract

RATIONALE

Bulk stable isotope analysis (SIA) provides an important tool for the study of animal ecology. Elasmobranch vertebral centra can be serially sampled to obtain an isotopic history of an individual over ontogeny. The measured total δ(13)C value, however, may be misinterpreted due to the inclusion of the (13)C-rich inorganic portion. Hydrochloric acid (HCl) is commonly used to remove the inorganic portion of hydroxyapatite structures before undertaking SIA, but more recently ethylenediaminetetraacetic acid (EDTA) has been recommended for elasmobranch vertebrae. These acid treatments may introduce uncertainty on measured δ(13)C and δ(15)N values above instrument precision and the effect of small sample size remains untested for elasmobranch vertebrae.

METHODS

Using a non-dilution program on an isotope ratio mass spectrometer the minimum sample weight of vertebrae required to obtain accurate isotopic values was determined for three shark species: white (Carcharodon carcharias), tiger (Galeocerdo cuvier), and sand tiger (Carcharias taurus). To examine if acid treatment completely removes the inorganic component of the vertebrae or whether the technique introduces its own uncertainty on measured δ(13)C and δ(15)N values, vertebrae samples were analyzed untreated and following EDTA treatment.

RESULTS

The minimum sample weight required for accurate stable isotope values and the percentage sample yield following EDTA treatment varied within and among species. After EDTA treatment, white shark vertebrae were all enriched in (13)C and depleted in (15) N, tiger shark vertebrae showed both enrichment and depletion of (13)C and (15)N, and sand tiger shark vertebrae were all depleted in (13)C and (15)N.

CONCLUSIONS

EDTA treatment of elasmobranch vertebrae produces unpredictable effects (i.e. non-linear and non-correctable) among species in both the percentage sample yield and the measured δ(13)C and δ(15)N values. Prior to initiating a large-scale study, we strongly recommend investigating (i) the minimum weight of vertebral material required to obtain consistent isotopic values and (ii) the effects of EDTA treatment, specific to the study species and the isotope ratio mass spectrometer employed.

摘要

原理

批量稳定同位素分析（SIA）为动物生态学研究提供了重要工具。可以对鲨鱼的脊椎骨进行连续取样，以获得个体在整个发育过程中的同位素历史记录。然而，由于含有富含 13C 的无机部分，所测量的总δ（13）C 值可能会被误解。盐酸（HCl）通常用于在进行 SIA 之前去除羟磷灰石结构的无机部分，但最近推荐使用乙二胺四乙酸（EDTA）来处理鲨鱼的脊椎骨。这些酸处理方法可能会在仪器精度之上引入不确定的δ（13）C 和 δ（15）N 值，并且对于鲨鱼的脊椎骨，小样本量的影响仍未经过测试。

方法

使用同位素质谱仪上的非稀释程序，确定了三种鲨鱼（白鲨、虎鲨和灰鲭鲨）获得准确同位素值所需的最小脊椎骨样本重量。为了检查酸处理是否完全去除了脊椎骨的无机成分，或者该技术是否会在测量的δ（13）C 和 δ（15）N 值上引入自身的不确定性，对未经处理和经 EDTA 处理的脊椎骨样本进行了分析。

结果

准确的稳定同位素值所需的最小样本重量以及 EDTA 处理后的样本产量百分比在种内和种间有所不同。经 EDTA 处理后，白鲨的脊椎骨均富集了 13C，且 15N 减少；虎鲨的脊椎骨中同时出现了 13C 和 15N 的富集和减少；灰鲭鲨的脊椎骨均减少了 13C 和 15N。

结论

EDTA 处理鲨鱼的脊椎骨会在种间产生不可预测的影响（即非线性和不可纠正），不仅表现在样本产量百分比上，还表现在测量的δ（13）C 和 δ（15）N 值上。在开始大规模研究之前，我们强烈建议调查（i）获得一致同位素值所需的最小脊椎骨材料重量，以及（ii）针对研究物种和所使用的同位素质谱仪的 EDTA 处理效果。