ABSTRACT: Coastal marine ecosystems are very complex and composed of myriad organisms, including offshore, coastal, and migratory fish occupying diverse trophic positions (TPs) in food webs. The illustration of trophic hierarchy based on the TP and resource utilization of individual organisms remains challenging. In this study, we applied compound-specific isotope analysis of amino acids to estimate the TP and isotopic baseline (i.e. δ¹⁵N values of primary resources at the base of food webs) for 13 fish and 1 squid species in a coastal area of Sagami Bay, Japan, where a large diversity in the isotopic baseline is caused by an admixture of ocean currents and artificial nitrogen inputs. Our results indicate that the TP of fish and squid varies between 2.9 and 3.9 (i.e. omnivorous, carnivorous, and tertiary consumers), with low variation within individual species. Moreover, the δ¹⁵N values of phenylalanine revealed the diversity of isotopic baselines between and within species. Low values (7.8-10.3‰) and high values (18.6-19.2‰), with a small variation (1σ < 1.0‰), were found in 2 offshore species and 3 coastal species, respectively. In contrast, highly variable values (9.8-19.7‰), with large variation within species (1σ > 1.0‰), were found for the remaining 9 migratory species. These results represent evidence of differential trophic exploitation of habitats between offshore and coastal species, particularly among individuals of migratory species, that were all collected in a single area of Sagami Bay.

中文翻译：

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通过氨基酸的化合物特异性同位素分析观察沿海海鱼群落的营养等级

摘要：沿海海洋生态系统非常复杂，由多种生物组成，包括在食物网中占据不同营养位置（TP）的近海，沿海和coastal游鱼类。基于TP和单个生物体资源利用的营养层次说明仍然具有挑战性。在这项研究中，我们采用氨基酸的特定化合物的同位素分析来估计TP和同位素基线（即δ ¹⁵在日本相模湾沿海地区的13种鱼类和1种鱿鱼物种的食物网基础上的主要资源N值，在该地区，由于洋流和人工氮的混合，同位素基线的多样性很大。我们的结果表明，鱼和鱿鱼的总磷在2.9至3.9（即杂食，肉食和三级消费者）之间变化，而单个物种之间的变化很小。此外，δ ¹⁵苯丙氨酸的N值揭示了物种之间和物种内部同位素基线的多样性。在2个近海物种和3个沿海物种中分别发现低值（7.8-10.3‰）和高值（18.6-19.2‰），且变化较小（1σ<1.0‰）。相比之下，对于其余9个迁徙物种，发现了高度可变的值（9.8-19.7‰），且种内差异很大（1σ> 1.0‰）。这些结果表明在沿海和沿海物种之间，特别是在迁徙物种个体之间对栖息地进行了不同的营养开发利用，这些都收集在相模湾的一个地区。