The isoscape of particulate organic matters (POM) in the euphotic zone at the shelf of the East China Sea (ECS) is affected by hydrological interactions and biological activities. Based on the stable carbon and nitrogen isotope values (δ¹³C and δ¹⁵N) and C:N ratio of POM (0.7 to 50 μm) in the euphotic zone of the ECS from 2008 to 2018 with a total of 113 samples, we inferred their resources and then investigated what hydrographical and biological conditions determined these spatio-temporal variations through synoptic and intensive seasonal monitoring. The isotopic signatures (δ¹³C: −26.9 to −12.4 ‰, δ¹⁵N: −1.0 to 10.8 ‰) and C:N ratios (4.4 to 9.0) of euphotic POM varied within the range of values reported for marine phytoplankton, suggesting limited contribution of terrigenous POM to the shelf of the ECS. The δ¹³C values of POM increased with the increase of chlorophyll-a (chl-a) concentration at the depth of chl-a maximum and the δ¹⁵N values decreased near the Changjiang River plume and inner shelf with freshwater input and coastal upwelling in summer. This indicated that phytoplankton production was enhanced by high nutrient supply and warmer temperature. Besides, the δ¹⁵N values were higher under lower inorganic nitrogen nutrient concentrations, and were negatively correlated with POM C:N ratio (i.e., δ¹⁵N value was less negative with higher nitrogen content in POM). Such correlations may suggest the enhanced trophic interactions in microbial food chains in oligotrophic environments, where phagotrophic protists with high δ¹⁵N values could be included into the size fraction (0.7-50 μm) of POM. Based on our study, the spatial and temporal δ¹³C and δ¹⁵N isoscape of euphotic POM serves as an ecological indicator to infer primary production and plankton food web properties of the East China Sea.

东海陆架(ECS)富光区颗粒有机物(POM)等值景受水文相互作用和生物活动的影响。基于2008-2018年ECS光强区碳氮稳定同位素值（δ ¹³ C和δ ¹⁵ N）和POM的C:N比值（0.7-50 μm）共113个样品，我们推断他们的资源，然后通过天气和密集的季节性监测调查是什么水文和生物条件决定了这些时空变化。同位素特征（δ ¹³ C：-26.9 至 -12.4 ‰，δ ¹⁵N：-1.0 到 10.8 ‰) 和富光 POM 的 C:N 比（4.4 到 9.0）在海洋浮游植物报告的值范围内变化，表明陆源 POM 对 ECS 大陆架的贡献有限。的δ ¹³ POM的C值与叶绿素的增加而增加一（chl-一个）浓度在chl-的深度一个最大和δ ^15个N个值附近的大江羽流，并用淡水输入和沿海上升流内架下降在夏天。这表明高养分供应和温暖的温度提高了浮游植物的产量。此外，δ ¹⁵在较低无机氮养分浓度下，N 值较高，并且与 POM C:N 比呈负相关（即，δ ¹⁵ N 值在 POM 中氮含量较高时负性较小）。这种相关性可能表明在贫营养环境中微生物食物链中的营养相互作用增强，其中具有高 δ ¹⁵ N 值的吞噬原生生物可以包含在 POM 的尺寸分数（0.7-50 μm）中。基于我们的研究，富光 POM 的时空 δ ¹³ C 和 δ ¹⁵ N 等值景可作为推断东海初级生产和浮游生物食物网特性的生态指标。