Benthic megafauna in deep-sea ecosystems with and without methane seeps in the South China Sea were quantified during 2013–2016. In total, more than 190 taxa were identified. Stable isotopic analyses (δ¹³C, δ¹⁵N) on the tissues of these megafauna were used to provide complementary data to reveal their trophic relationships. Ecopath models were constructed to show the flow of matter within deep-sea ecosystems. There were four integer trophic levels in both deep-sea models. Most of the omnivory indices of the megafauna in the models were small, indicating the specialized diet niches of the megafauna. The mixed trophic impact results showed that both models were top-down controlled. Seep-associated king crabs were the keystone group in the seep model. These crabs not only transferred energy from lower trophic levels to top predators but also linked energy from seeps to neighboring deep-sea ecosystems. However, the low number of trophic connections between the seep animals and neighboring deep-sea communities indicates the uniqueness of the seep ecosystems in the deep sea. All the biomass, matter flow and trophic transfer efficiency values were higher in the seep model than in the model without seeps. The higher overhead/capacity ratio in the seep model than in the model without seeps suggests that the former model was more resilient to perturbations than the latter model. Although the net primary production and matter flow in the seep model were lower than those in the shallow-sea models, the models had comparable values of biomass excluding detritus. The relatively high system omnivory indices and low matter cycling of both deep-sea models indicate that these models were more mature than the shallow-sea models. Collectively, our deep-sea models combined with other models suggest that deep-sea ecosystems are characterized by slow dynamics and high environmental stability. This study reports the first Ecopath model for methane seep ecosystems, which may serve as a basis for potential anthropogenic impact assessment and ecosystem-based management.

2013-2016年期间，对南海有无甲烷渗漏的深海生态系统中的底栖大型动物进行了量化。总共确定了190多个分类单元。稳定同位素分析（δ ¹³ C，δ ¹⁵N）在这些大型动物的组织上被用来提供补充数据，以揭示它们的营养关系。构建了生态路径模型以显示深海生态系统中的物质流。两种深海模型都具有四个整数营养级。在模型中，大多数大型动物的杂食性指标都很小，表明大型动物的特殊饮食优势。混合的营养影响结果表明，两个模型都是自上而下控制的。与渗透有关的帝王蟹是渗透模型中的基石群。这些螃蟹不仅将能量从较低的营养水平转移到顶级捕食者，而且还将能量从渗漏转移到邻近的深海生态系统。然而，渗水动物与邻近的深海群落之间的营养联系数量很少，这表明了深海渗水生态系统的独特性。在渗流模型中，所有生物量，物质流量和营养传递效率值均高于无渗流模型。与没有渗漏的模型相比，渗漏模型的开销/容量比率更高，这表明前者的模型比后者的模型更能抵抗干扰。尽管渗流模型的净初级生产量和物质流量低于浅海模型，但除碎屑外，这些模型的生物量具有可比性。两个深海模型相对较高的系统杂食指数和低物质循环表明，这些模型比浅海模型更成熟。总的来说，我们的深海模型与其他模型的结合表明，深海生态系统的特点是动力学缓慢且环境稳定性高。这项研究报告了第一个甲烷渗透生态系统的生态路径模型，该模型可作为潜在的人为影响评估和基于生态系统的管理的基础。