The Southern Ocean is a very dynamic ecosystem comprising many fronts and interfrontal areas. Among the fronts, the Subtropical Front (STF) is a region of eddy activity exhibiting high spatial-temporal variability. The variability of food web structure in such a dynamic system and their influence on the plankton community structure is of great interest. The present study attempts to explain the variability of microzooplankton (MZP) mediation in the planktonic food web, using multi-disciplinary data collected along the zonal sections 40° S and 43° S in the STF during the austral summer 2012. Even though both zonal sections are in the STF, significant differences in the variability of their thermohaline structures were observed due to the presence of multiple mesoscale features (viz. cyclonic and anticyclonic eddies), leading to discrete environments within the STF. Our study highlights the concept of the classical food web in productive environments (cyclonic eddies), which is governed by the duration of such dynamic events. On the contrary, in the generally less productive anticyclonic eddies, the variability of trophic level interaction varies between the periphery and core regions of the eddies. The present study reveals the biological consequences of frequent mesoscale features in terms of the variability of food web structure. It also elucidates the trophic importance of MZP in the two contrasting environments within the STF.

南大洋是一个充满活力的生态系统，包含许多前沿和前沿区域。在这些锋线上，亚热带锋（STF）是一个涡流活动区域，表现出很高的时空变化性。食物网结构在这种动态系统中的可变性及其对浮游生物群落结构的影响引起人们极大的兴趣。本研究试图利用2012年南方夏季STF沿40°S和43°S纬向剖面收集的多学科数据来解释浮游食物网中的微浮游生物（MZP）介导性的变化。在STF中，由于存在多个中尺度特征（即旋风和反旋风涡流），观察到它们的热盐结构变异性存在显着差异，导致STF中存在离散的环境。我们的研究突出了在生产环境（旋风涡流）中经典食物网的概念，该概念由此类动态事件的持续时间决定。相反，在通常产量较低的反气旋涡流中，营养水平相互作用的变化性在涡流的外围和核心区域之间变化。本研究从食物网结构的可变性揭示了频繁的中尺度特征的生物学后果。它还阐明了STF内两个相反环境中MZP的营养重要性。在通常生产效率较低的反气旋涡流中，营养水平相互作用的变异性在涡流的外围和核心区域之间变化。本研究从食物网结构的可变性揭示了频繁的中尺度特征的生物学后果。它还阐明了STF内两个相反环境中MZP的营养重要性。在通常生产效率较低的反气旋涡流中，营养水平相互作用的变异性在涡流的外围和核心区域之间变化。本研究从食物网结构的可变性揭示了频繁的中尺度特征的生物学后果。它还阐明了STF内两个相反环境中MZP的营养重要性。