ABSTRACT: Accelerated sea-level rise poses a significant threat to coastal habitats, such as salt marshes, which provide critical ecosystem services. Persistence of salt marshes with rising sea levels relies, in part, on vertical accretion. Ecogeomorphic models emphasize the role of plant production in vertical accretion via sediment trapping and belowground organic matter contribution. Thus, changes in plant production can influence saltmarsh persistence with sea-level rise. However, models of marsh accretion do not consider animal-mediated changes in plant production. We tested how 2 marsh crabs, Minuca pugnax and Sesarma reticulatum, which have contrasting effects (facilitation vs. herbivory) on Spartina alterniflora production, may indirectly influence sediment deposition and belowground production, through observational surveys and field manipulation. Minuca facilitated Spartina biomass in some marshes, but not sediment deposition, and had no effect on belowground organic matter contribution, suggesting that in isolation, Minuca has little indirect impact on saltmarsh geomorphic processes. Sesarma reduced Spartina biomass; however, sediment deposition increased, contrary to ecogeomorphic models, likely due to sediment resuspension by Minuca. When Minuca and Sesarma co-occur, the effect on Spartina production and sediment deposition depended on the amount of grazing. When Sesarma grazing is low, Minuca facilitates Spartina growth and mitigates the effect of grazing. However, when Sesarma grazing is high and vegetation is removed, Minuca can resuspend sediment through bioturbation, suggesting the net effect of these species may depend on their relative abundance. This study demonstrates that the effects of plant-animal interactions on marsh resilience against sea-level rise are context dependent.

中文翻译：

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生态相互作用在盐沼地貌过程中的作用

摘要：加速的海平面上升对提供重要生态系统服务的盐沼等沿海生境构成了重大威胁。随着海平面上升，盐沼的持久性部分取决于垂直积聚。生态地貌模型强调了通过沉积物捕集和地下有机物贡献在垂直增生中植物生产的作用。因此，植物的变化 生产会随着海平面上升而影响盐沼的持久性。但是，沼泽增生模型没有考虑动物介导的植物生产变化。我们通过观察调查和野外操作，测试了对互花米草生产具有对比作用（促进与草食）的2种沼泽蟹，Minuca pugnax和Sesarma reticulatum如何间接影响沉积物沉积和地下生产。麦卢卡（Minuca）在某些沼泽中促进了斯巴蒂纳（Spartina）生物量，但没有沉积物沉积，和 对地下有机物的贡献没有影响，这表明，单独地，Minuca对盐沼地貌过程没有间接影响。Sesarma减少了Spartina的生物量；但是，与生态地貌模型相反，沉积物沉积增加了，这可能是由于Minuca重新悬浮了沉积物所致。当米奴卡（Minuca）和塞萨尔玛（Sesarma）并存时，对斯巴蒂娜（Spartina）产量和沉积物沉积的影响取决于放牧量。当Sesarma放牧量低时，Minuca会促进Spartina的生长并减轻放牧的影响。但是，当塞萨玛高放牧和植被被清除后，Minuca可以通过生物扰动使沉积物重新悬浮，这表明这些物种的净效应可能取决于它们的相对丰度。这项研究表明，植物-动物相互作用对沼泽抵抗海平面上升的抵抗力是取决于环境的。