PDF(Pubmed)
Abstract：
Quantifying the tropic position (TP) of an animal species is key to understanding its ecosystem function. While both bulk and compound-specific analyses of stable isotopes are widely used for this purpose, few studies have assessed the consistency between and within such approaches. Champsocephalus gunnari is a specialist teleost that predates almost exclusively on Antarctic krill Euphausia superba. This well-known and nearly constant trophic relationship makes C. gunnari particularly suitable for assessing consistency between TP methods under field conditions. In the present work, we produced and compared TP estimates for C. gunnari and its main prey using a standard bulk and two amino acid-specific stable isotope approaches (CSI-AA). One based on the difference between glutamate and phenylalanine (TPGlx-Phe), and the other on the proline-phenylalanine difference (TPPro-Phe). To do that, samples from C. gunnari, E. superba and four other pelagic invertebrate and fish species, all potential prey for C.gunnari, were collected off the South Orkney Islands between January and March 2019, analyzed using standard isotopic ratio mass spectrometry methods and interpreted following a Bayesian approach. Median estimates (CI95%) for C. gunnari were similar between TPbulk (3.6; CI95%: 3.0-4.8) and TPGlx-Phe(3.4; CI95%:3.2-3.6), and lower for TPPro-Phe (3.1; CI95%:3.0-3.3). TP differences between C. gunnari and E. superba were 1.4, 1.1 and 1.2, all compatible with expectations from the monospecific diet of this predator (ΔTP=1). While these results suggest greater accuracy for Glx-Phe and Pro-Phe, differences observed between both CSI-AA approaches suggests these methods may require further validation before becoming a standard tool for trophic ecology.
摘要：
量化动物物种的热带位置（TP）是了解其生态系统功能的关键。虽然稳定同位素的批量和特定于化合物的分析被广泛用于此目的，很少有研究评估这些方法之间和内部的一致性。Champsocephalusgunnari是一种专业的硬骨鱼，几乎完全早于南极磷虾Euphausiasuperba。这种众所周知且几乎恒定的营养关系使C.gunnari特别适合于在现场条件下评估TP方法之间的一致性。在目前的工作中,我们使用标准的散装和两种氨基酸特异性稳定同位素方法（CSI-AA）产生并比较了C.gunnari及其主要猎物的TP估计值。一种基于谷氨酸和苯丙氨酸之间的差异（TPGlx-Phe），和其他关于脯氨酸-苯丙氨酸的差异(TPPro-Phe)。要做到这一点，C.Gunnari的样本,E.Superba和其他四种中上层无脊椎动物和鱼类，所有C.gunnari潜在的猎物,于2019年1月至3月在南奥克尼群岛附近收集，使用标准同位素比质谱方法进行分析，并按照贝叶斯方法进行解释。对于C.gunnari的中位数估计（CI95％）在TPbulk（3.6；CI95％：3.0-4.8）和TPGlx-Phe（3.4；CI95％：3.2-3.6）之间相似，TPPro-Phe较低（3.1；CI95%：3.0-3.3）。C.gunnari和E.superba之间的TP差异分别为1.4、1.1和1.2，均符合该捕食者单一饮食的预期（ΔTP=1）。虽然这些结果表明Glx-Phe和Pro-Phe的准确性更高，两种CSI-AA方法之间观察到的差异表明，在成为营养生态学的标准工具之前，这些方法可能需要进一步验证。
