美国索诺玛州立大学Hughes Brent B.团队近日的研究表明，顶级捕食者的复苏减缓了沿海生态系统的地貌衰退。这一研究成果发表在2024年1月31日出版的国际学术期刊《自然》上。

研究人员结合观测和实验数据，揭示了美国河口海獭的重新定居，其定居产生了一个营养级联，促进了沿海湿地植物的生物量增加，抑制了沼泽边缘的侵蚀(否则这一过程会导致栖息地和生态系统服务的严重丧失)。研究几十年来对Elkhorn Slough河口的监测表明，该系统中存在自上而下的控制，尽管系统中的物理压力(即营养负荷、海平面上升和潮汐变化)持续增加，盐沼边缘的侵蚀通常随着海獭数量的增加而减缓。

研究人员在5条沼泽小溪中进行的捕食者排除实验表明，海獭抑制了穴居蟹的数量，这是一种自上而下的效应，它既增加了沼泽边缘的强度，又减少了沼泽的侵蚀。多溪调查比较了海獭定居前后的沼泽溪流，证实了楔石海獭、穴居蟹和沼泽溪流之间存在相互作用，证明了捕食者控制生态系统边缘过程的空间普遍性：在海獭重新定居水平较高的溪流中，穴居蟹的密度和边缘侵蚀明显下降。这些结果表明，营养退化可能是沿海湿地丧失的一个强大但未得到充分认识的因素，并表明恢复顶级捕食者有助于重建地貌稳定性。

据介绍，人们认为，顶级掠食者的恢复对植被生态系统及其地貌具有级联效应，但这方面的证据仍然存在相关性和存在激烈的争论。

附：英文原文

Title: Top-predator recovery abates geomorphic decline of a coastal ecosystem

Author: Hughes, Brent B., Beheshti, Kathryn M., Tinker, M. Tim, Angelini, Christine, Endris, Charlie, Murai, Lee, Anderson, Sean C., Espinosa, Sarah, Staedler, Michelle, Tomoleoni, Joseph A., Sanchez, Madeline, Silliman, Brian R.

Issue&Volume: 2024-01-31

Abstract: The recovery of top predators is thought to have cascading effects on vegetated ecosystems and their geomorphology, but the evidence for this remains correlational and intensely debated. Here we combine observational and experimental data to reveal that recolonization of sea otters in a US estuary generates a trophic cascade that facilitates coastal wetland plant biomass and suppresses the erosion of marsh edges—a process that otherwise leads to the severe loss of habitats and ecosystem services. Monitoring of the Elkhorn Slough estuary over several decades suggested top-down control in the system, because the erosion of salt marsh edges has generally slowed with increasing sea otter abundance, despite the consistently increasing physical stress in the system (that is, nutrient loading, sea-level rise and tidal scour). Predator-exclusion experiments in five marsh creeks revealed that sea otters suppress the abundance of burrowing crabs, a top-down effect that cascades to both increase marsh edge strength and reduce marsh erosion. Multi-creek surveys comparing marsh creeks pre- and post-sea otter colonization confirmed the presence of an interaction between the keystone sea otter, burrowing crabs and marsh creeks, demonstrating the spatial generality of predator control of ecosystem edge processes: densities of burrowing crabs and edge erosion have declined markedly in creeks that have high levels of sea otter recolonization. These results show that trophic downgrading could be a strong but underappreciated contributor to the loss of coastal wetlands, and suggest that restoring top predators can help to re-establish geomorphic stability.

DOI: 10.1038/s41586-023-06959-9

Source: https://www.nature.com/articles/s41586-023-06959-9