The ecology of leptocephali remains poorly known but they appear to feed on marine snow that can vary spatially and temporally according to the food web dynamics. This study provided new information about the position of leptocephali within the functional structure of microbial plankton and other food web components of the western South Pacific (WSP) region at a large geographic scale including the New Caledonia, Fiji, and Samoa islands. The hydrographic structure varied with latitude, and nutrient levels were generally low but somewhat variable. Stable isotopic signatures were examined in relation to the 3 current zones of the eastward flowing South Equatorial Countercurrent (SECC; north), the westward South Equatorial Current (SEC; mid-latitudes), and the eastward South Tropical Countercurrent (STCC; south), and all zones were found to be primarily based on a heterotrophic planktonic functioning that were co-limited by inorganic nitrogen and phosphorus, with biomasses of planktonic groups varying with depth. Isotopic signatures of leptocephali were compared to the signatures of other mesozoplankton, micronekton, and Trichodesmium components of the food web, and in relation to the signatures of particulate organic matter (POM) that varied among the 3 collection depths. The isotopic signatures of six taxa of leptocephali, other taxonomic groups and POM showed interesting variability according to latitude and among some stations. The presence of Trichodesmium at the surface in the STCC zone influenced the isotopic signatures of POM and thus the signatures of leptocephali. The signatures of leptocephali were therefore linked with the overall food web and were consistent with the larvae feeding on marine snow components of POM. The two apparent groups of leptocephali with different isotopic signatures that have also been observed in other oceanic areas may be explained by feeding behavior at different depths or on different types of marine snow.

中文翻译：

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南太平洋西部三个洋流带中细头菌的微生物功能结构和稳定同位素变化

leptocephali 的生态学仍然知之甚少，但它们似乎以海洋雪为食，海洋雪会根据食物网动态在空间和时间上发生变化。这项研究提供了关于在大地理范围内，包括新喀里多尼亚、斐济和萨摩亚群岛在内的西南太平洋 (WSP) 地区的微生物浮游生物和其他食物网成分的功能结构中，钩端虫的位置的新信息。水文结构随纬度变化，营养水平普遍较低，但有些变化。研究了与向东流动的南赤道逆流（SECC；北）、西向的南赤道流（SEC；中纬度）和向东的南热带逆流（STCC；南）的 3 个流带相关的稳定同位素特征，并且发现所有区域主要基于异养浮游功能，受无机氮和磷的共同限制，浮游群体的生物量随深度而变化。将钩端虫的同位素特征与食物网的其他中浮游生物、微型浮游生物和毛藻成分的特征进行了比较，并与在 3 个收集深度之间变化的颗粒有机物 (POM) 的特征进行了比较。根据纬度和某些站点，六种钩端动物、其他分类群和 POM 的同位素特征显示出有趣的变异性。STCC 区表面存在的木霉影响了 POM 的同位素特征，从而影响了细头虫的特征。因此，leptocephali 的特征与整个食物网有关，并且与以 POM 的海洋雪成分为食的幼虫一致。在其他海洋区域也观察到的具有不同同位素特征的两组明显的细头鱼可以通过不同深度或不同类型的海洋雪的摄食行为来解释。