The structure of the pelagic food web is a key issue to understand the variability in C and N fluxes in the ocean. The trophic structure of the hyperiid amphipods and its spatial variation in the subtropical area of the Southeast Pacific was studied based on C and N isotope composition. Zooplankton were collected off northern and Central-southern Chile during September-November 2016 at the coastal zone and in oceanic areas. Measurements of δ¹⁵N and δ¹³C of individual hyperiids were used to estimate the trophic position for each species, and to assess the community isotopic niche for 3 pre-defined areas: the coastal upwelling (eutrophic) zone, the coastal transition (mesotrophic) zone and the oceanic (oligotrophic) zone, as well as three depth layers. Our results showed different assemblages of species among the 3 zones, but also a large overlap between the isotopic niche for all zones and depth layers. In the mesotrophic zone there was a noticeable increase in the trophic position of individual species. The trophic diversity of hyperiids over the study region was relatively high, including primary consumers, omnivores and carnivorous feeders, and was associated with the changes in productivity across zones. However, carnivory was more prevalent in the mesotrophic zone and in the mesopelagic (500–1000 m) layer. We suggest that such variations reflect both the biogeochemical processes controlling the productivity in each zone, and the life-traits of individual species.

远洋食物网的结构是了解海洋中C和N通量变化的关键问题。基于C和N同位素组成，研究了东南太平洋亚热带地区双节肢动物的营养结构及其空间变异。浮游动物于2016年9月至11月在智利北部和中南部的沿海地区和海洋区域采集。的δ测量¹⁵ N和δ ¹³单个双曲线的C用于估计每个物种的营养位置，并评估3个预定义区域的群落同位素生态位：沿海上升流（富营养）区，沿海过渡（中营养）区和海洋（贫营养区）区域以及三个深度层。我们的结果表明，三个区域之间的物种组合不同，但所有区域和深度层的同位素生态位之间都存在较大的重叠。在中营养区，单个物种的营养位置显着增加。研究区域中双节律的营养多样性相对较高，包括主要消费者，杂食动物和肉食动物，并且与整个地区生产力的变化有关。然而，食肉动物在中营养层和中古生界（500-1000 m）层中更为普遍。我们建议，这种变化既反映了控制每个区域生产力的生物地球化学过程，又反映了单个物种的生命特征。