Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, United States of America.
Marine Science Institute, University of California, Santa Barbara, CA, United States of America.
PLoS One. 2022 Jan 5;17(1):e0249330. doi: 10.1371/journal.pone.0249330. eCollection 2022.
Salt marsh loss is projected to increase as sea-level rise accelerates with global climate change. Salt marsh loss occurs along both lateral creek and channel edges and in the marsh interior, when pannes expand and coalesce. Often, edge loss is attributed to erosive processes whereas dieback in the marsh interior is linked to excessive inundation or deposition of wrack, but remains poorly understood. We conducted a two-year field investigation in a central California estuary to identify key factors associated with panne contraction or expansion. Our study explored how an abundant burrowing crab, shown to have strong negative effects on marsh biomass near creek edges, affects panne dynamics. We also explored which physical panne attributes best predicted their dynamics. To our knowledge, ours is the first study of panne dynamics in a California marsh, despite how ubiquitous pannes are as a feature of marshes in the region and how often extensive marsh dieback occurs via panne expansion. Overall, we found that pannes contracted during the study period, but with variable rates of marsh recovery across pannes. Our model incorporating both physical and biological factors explained 86% of the variation in panne contraction. The model revealed a positive effect of crab activity, sediment accretion, and a composite of depth and elevation on panne contraction, and a negative effect of panne size and distance to nearest panne. The positive crab effects detected in pannes contrast with negative effects we detected near creek edges in a previous study, highlighting the context-dependence of top-down and bioturbation effects in marshes. As global change continues and the magnitude and frequency of disturbances increases, understanding the dynamics of marsh loss in the marsh interior as well as creek banks will be critical for the management of these coastal habitats.
随着全球气候变化导致海平面加速上升，盐沼的损失预计将会增加。盐沼的损失发生在侧向溪流和河道边缘以及盐沼内部，当洼地扩张和合并时。通常，边缘的损失归因于侵蚀过程，而盐沼内部的衰退则与过度淹没或碎屑物的沉积有关，但仍了解甚少。我们在加利福尼亚中部河口进行了为期两年的实地调查，以确定与洼地收缩或扩张相关的关键因素。我们的研究探讨了一种丰富的穴居蟹如何影响洼地动态，这种蟹被证明对溪流边缘附近的沼泽生物量有强烈的负面影响。我们还探讨了哪些物理洼地属性最能预测它们的动态。据我们所知，尽管洼地是该地区沼泽的普遍特征，并且通过洼地扩张经常发生广泛的沼泽衰退，但这是加利福尼亚沼泽洼地动态的首次研究。总体而言，我们发现洼地在研究期间收缩，但不同洼地的沼泽恢复速度不同。我们的模型结合了物理和生物因素，解释了 86%的洼地收缩变化。该模型揭示了蟹活动、沉积物堆积以及深度和海拔的综合因素对洼地收缩的积极影响，以及洼地大小和与最近洼地的距离的负面影响。在洼地中检测到的蟹的积极影响与我们在前一项研究中在溪流边缘检测到的负面影响形成对比，突出了沼泽中自上而下和生物扰动影响的背景依赖性。随着全球变化的继续和干扰的幅度和频率的增加，了解沼泽内部和溪流岸边的沼泽损失动态对于这些沿海栖息地的管理将至关重要。
