Precise and accurate retrospective geolocation of marine predators via their tissues’ isotopic composition relies on quality reference maps of relevant isotopic gradients (“isoscapes”). Additionally, a good working knowledge of any discrimination factors that may offset a marine predator’s isotopic composition from baseline isotopic values, as well as tissue specific retention rates, are imperative. We provide a critical assessment of inter-specific differences among marine predator-level isoscapes within the Indian Sector of the Southern Ocean. We combined fine-scale GPS tracking data and concurrent blood plasma δ13C and δ15N values of eight seabird species (three albatross, two giant petrel and three penguin species) breeding at Marion Island to produce species- and guild-specific isoscapes. Overall, our study revealed latitudinal spatial gradients in both δ13C and δ15N for far-ranging seabirds (albatrosses and giant petrels) as well as inshore-offshore gradients for near-ranging seabirds (penguins). However, at the species level, latitudinal spatial gradients were not reflected in the δ13C and δ15N isoscapes of two and three, respectively, of the five far-ranging species studied. It is therefore important when possible to estimate and apply species-specific isoscapes or have a good understanding of any factors and pathways affecting marine predators’ isotopic composition when estimating the foraging distribution of marine predators via their tissues’ stable isotope compositions. Using a multi-species approach, we provide evidence of large and regional scale systematic spatial variability of δ13C and δ15N at the base of the marine food web that propagates through trophic levels and is reflected in the isotopic composition of top predators’ tissues.

中文翻译：

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对印度洋南部海洋捕食者等景观的批判性评估。

通过其组织的同位素组成对海洋捕食者进行精确和准确的追溯地理定位依赖于相关同位素梯度（“isoscapes”）的质量参考图。此外，对可能从基线同位素值中抵消海洋捕食者的同位素组成以及组织特定保留率的任何歧视因素的良好工作知识是必不可少的。我们对南大洋印度区海洋捕食者级等景观之间的种间差异进行了批判性评估。我们结合了在马里恩岛繁殖的八种海鸟（三种信天翁、两种巨型海燕和三种企鹅）的精细 GPS 跟踪数据和同时血浆 δ13C 和 δ15N 值，以生成特定于物种和行会的等景图。总体，我们的研究揭示了远距离海鸟（信天翁和巨型海燕）的 δ13C 和 δ15N 纬度空间梯度以及近海海鸟（企鹅）的近海-近海梯度。然而，在物种水平上，纬度空间梯度并未反映在所研究的五个远距离物种的两个和三个的 δ13C 和 δ15N 等值景观中。因此，在通过其组织的稳定同位素组成估计海洋捕食者的觅食分布时，在可能的情况下估计和应用特定物种的等值图或充分了解影响海洋捕食者同位素组成的任何因素和途径是很重要的。采用多品种方法，