Collaborative Research: Biophysical alteration of wetland geomorphology in response to rising sea level

合作研究：海平面上升对湿地地貌生物物理变化的响应我们的目标是研究盐沼潮汐溪网络对海平面上升的响应。我们已经记录了在整个南大西洋湾的沿海沼泽和世界各地类似的环境中，快速增长的小溪，以每年1-2米的速度切入沼泽。了解驱动这些排水网络演变的机制对于预测不同条件下沼泽对海平面上升的反应至关重要。这项研究将考察潮汐流和沉积物侵蚀的物理特性，同时也将考虑沼泽动植物（如螃蟹）对这些过程的重大影响。利用野外测量、中尺度实验和数值模拟相结合的方法，我们将1)评估河流中泥沙侵蚀的物理机制，包括入流速度的变化和改变沼泽土壤强度的过程；2)验证螃蟹通过挖洞和移除稳定植被来松动泥沙，从而促进河流生长的假设；3)建立了河川演化的数值模型，考察了植被类型、动物密度、潮差和泥沙供给等不同参数对河川形态演化的重要性。该模型将帮助我们整合我们的观察结果，并在一系列条件下推广我们的发现。盐沼为人类提供了宝贵的生态系统服务，但这些生产栖息地受到全球海平面加速上升的威胁。了解海平面上升对沼泽物理结构的影响，对于预测沼泽生态系统的响应和更大规模的海岸线形态响应至关重要。水位上升对沼泽的影响取决于物理和生物过程之间复杂的反馈。对这一问题的初步研究主要集中在水深和沼泽高程之间的相互作用，它们影响沉积物沉积和植物生长。最近，越来越多的人开始关注河网的演变方式，因为它们在海平面较高的潮汐周期中必须输送大量的水。河流网络的演变是沼泽对海平面上升的反应的一个关键组成部分，因为河流形态影响到输送到沼泽表面的水和沉积物的数量，以及沼泽的排水，因此，沼泽浸水的时间长度。反过来，沼泽的洪水和排水影响着这个生态重要环境中动植物的健康。河网对海平面上升作出反应的能力，在一定程度上取决于侵蚀沼泽表面的难易程度，这取决于沉积物类型，以及与动植物有关的不稳定或松动。揭示地质学和生物学之间的联系将对地质学、生态学和气候学领域以及那些对海岸保护和盐沼演变感兴趣的领域产生影响。该项目将开发一种新的建模工具来检查沼泽对海平面上升的反应，这将广泛适用于美国和全球的许多盐沼。

Collaborative Research: Biophysical alteration of wetland geomorphology inresponse to rising sea levelOur objective is to examine the evolution of networks of tidal creeks in salt marshes asthey respond to rising sea level. We have documented rapidly growing creeks, incising into themarsh at 1-2 m per year, in coastal marshes throughout the South Atlantic Bight and in similarenvironments worldwide. Understanding the mechanisms driving the evolution of these drainagenetworks is crucial for predicting marsh responses to sea level rise under different conditions.The study will examine the physics of tidal flows and sediment erosion, while also consideringthe significant impact of marsh plants and animals (e.g. crabs) on these processes. Using acombination of field measurements, mesocosm experiments, and numerical modeling, we will 1)evaluate the physical mechanisms underlying sediment erosion in creeks, including variation inflow speed and processes changing the strength of the marsh soils, 2) test the hypotheses thatcrabs facilitate growth of creeks by loosening sediment through burrowing and removingstabilizing vegetation; and that hydrological conditions at creek heads are preferred by crabs, and3) develop a numerical model of creek evolution to test the importance of different parameterssuch as vegetation type, faunal density, tidal range and sediment supply on the morphologicalevolution of creeks. The model will help us to integrate our observations and generalize ourfindings over a range of conditions.Salt marshes provide valuable ecosystem services to humanity, but these productive habitats arethreatened globally by accelerating sea-level rise. Understanding the impact of sea-level rise onthe physical structure of a marsh is crucial to predicting both the response of marsh ecosystemsand the larger-scale morphological response of the coastline. The impact of increasing waterlevels on marshes depends on complex feedbacks between physical and biological processes.Initial studies of this issue focused on interactions between water depth and marsh elevation,which affect sediment deposition and plant growth. Recently, increasing attention is beingdirected towards the manner in which creek networks evolve as they respond to the largervolume of water they must convey during each tidal cycle at higher sea levels. The evolution ofcreek networks is a critical component of marsh response to sea-level rise, because creekmorphology affects the amount of water and sediment delivered to the marsh surface, and thedrainage of the marsh, and thus, the length of time the marsh is waterlogged. In turn, the floodingand drainage of the marsh influences the health of plants and animals in this ecologically vitalenvironment. The ability of creek networks to respond to increasing sea levels depends, in part,on how easy it is to erode the marsh surface, which depends on both sediment type, and onstabilization or loosening associated with flora and fauna. Uncovering the linkages betweengeology and biology will have bearing on the fields of geology, ecology and climatology, as wellas those interested in coastal protection and salt marsh evolution. The project will develop a newmodeling tool to examine response of marshes to sea-level rise, which will be broadly applicableto many salt marshes in the U.S. and globally.