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

合作研究：湿地地貌的生物物理变化对海平面上升的响应我们的目标是研究盐沼中潮沟网络的演变，因为它们对海平面上升做出了反应。我们记录了在整个南大西洋海湾的沿海沼泽和世界各地类似环境中快速增长的小溪，以每年1-2米的速度切入沼泽。了解这些水系演变的机制对于预测不同条件下沼泽对海平面上升的响应至关重要。这项研究将研究潮汐流动和泥沙侵蚀的物理学，同时也考虑沼泽动植物(如螃蟹)对这些过程的重大影响。我们将结合现场测量、中观实验和数值模拟，1)评估小溪泥沙侵蚀的物理机制，包括变化的流入速度和改变沼泽土壤强度的过程；2)检验蟹通过挖洞和移除稳定植被来疏松泥沙以促进小溪生长的假设；以及河头的水文条件是螃蟹所喜好的；3)建立小溪演变的数值模型，以检验不同参数如植被类型、动物密度、潮差和泥沙供应对小溪形态演变的重要性。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，但这些生产性栖息地因海平面加速上升而在全球范围内受到威胁。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海岸线更大范围的形态响应都是至关重要的。水位上升对沼泽的影响依赖于物理和生物过程之间的复杂反馈，最初的研究集中在水深和沼泽高程之间的相互作用，影响泥沙沉积和植物生长。最近，人们越来越多地关注小溪网络的演变方式，因为它们在海平面较高的每个潮汐周期中必须输送更多的水。小溪网络的演变是沼泽对海平面上升响应的关键组成部分，因为小溪形态影响向沼泽表面输送的水和沉积物的量，以及湿地的排水，从而影响沼泽受涝的时间长度。反过来，沼泽的泛滥和排水影响了这种生态环境中动植物的健康。小溪网络对海平面上升作出反应的能力，部分取决于侵蚀沼泽表面的难易程度，这既取决于沉积物类型，也取决于与动植物有关的稳定或松动。揭示地质学和生物学之间的联系将关系到地质学、生态学和气候学领域，以及那些对海岸保护和盐沼进化感兴趣的人。该项目将开发一种新的建模工具来研究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.