Understanding the ecological interactions that enhance the resilience of threatened ecosystems is essential in assuring their conservation and restoration. Top-down trophic interactions can increase resilience to bottom-up nutrient enrichment, however, as many seagrass ecosystems are threatened by both eutrophication and trophic modifications, understanding how these processes interact is important. Using a combination of approaches, we explored how bottom-up and top-down processes, acting individually or in conjunction, can affect eelgrass meadows and associated communities in the northern Baltic Sea. Field surveys along with fish diet and stable isotope analyses revealed that the eelgrass trophic network included two main top predatory fish species, each of which feeds on a separate group of invertebrate mesograzers (crustaceans or gastropods). Mesograzer abundance in the study area was high, and capable of mitigating the effects of increased algal biomass that resulted from experimental nutrient enrichment in the field. When crustacean mesograzers were experimentally excluded, gastropod mesograzers were able to compensate and limit the effects of nutrient enrichment on eelgrass biomass and growth. Our results suggest that top-down processes (i.e., suppression of algae by different mesograzer groups) may ensure eelgrass resilience to nutrient enrichment in the northern Baltic Sea, and the existence of multiple trophic pathways can provide additional resilience in the face of trophic modifications. However, the future resilience of these meadows is likely threatened by additional local stressors and global environmental change. Understanding the trophic links and interactions that ensure resilience is essential for managing and conserving these important ecosystems and the services they provide.

中文翻译：

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食物网相互作用在促进咸水鳗草（Zostera marina）生态系统中营养丰富的恢复力中的作用

了解增强受威胁生态系统复原力的生态相互作用对于确保它们的保护和恢复至关重要。自上而下的营养相互作用可以提高自下而上营养丰富的恢复能力，但是，由于许多海草生态系统受到富营养化和营养变化的威胁，因此了解这些过程如何相互作用很重要。我们结合使用多种方法，探索了自下而上和自上而下的过程，单独或联合行动，如何影响波罗的海北部的鳗草草甸和相关社区。实地调查以及鱼类饮食和稳定同位素分析表明，鳗草营养网络包括两种主要的顶级掠食性鱼类，每种鱼类都以单独的无脊椎动物中食草动物群（甲壳类动物或腹足类动物）为食。研究区中食草动物的丰度很高，并且能够减轻因田间实验营养丰富而导致的藻类生物量增加的影响。当甲壳类中食草动物在实验中被排除在外时，腹足动物中食草动物能够补偿和限制养分富集对鳗草生物量和生长的影响。我们的研究结果表明，自上而下的过程（即，不同中食草动物群体对藻类的抑制）可以确保鳗草对波罗的海北部养分富集的恢复能力，并且多种营养途径的存在可以在面临营养变化时提供额外的恢复能力。然而，这些草地的未来恢复能力可能会受到额外的当地压力源和全球环境变化的威胁。