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

合作研究：湿地地貌因海平面上升而发生的生物物理变化

• 批准号: 1131393
• 负责人: Duncan FitzGerald
• 金额: $ 34.13万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1131393&HistoricalAwards=false
• 关键词: Collaborative; Research; Biophysical; alteration; wetland

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.

合作研究：湿地地貌对海平面上升的生物物理变化我们的目标是研究盐沼潮沟网络的演变，因为它们响应海平面上升。我们已经记录了快速增长的小溪，在整个南大西洋湾的沿海沼泽和世界各地的类似沼泽中，每年以1-2米的速度切入沼泽。了解驱动这些排水网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，这项研究将研究潮汐流动和沉积物侵蚀的物理学，同时也将探讨沼泽植物和动物（如螃蟹）对这些过程的重大影响。通过野外测量、围隔实验和数值模拟相结合的方法，我们将1）评估溪流泥沙侵蚀的物理机制，包括流速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以促进溪流生长的假设; 3）建立了河流演变的数值模型，探讨了植被类型、动物密度、潮差和泥沙供应等参数对河流形态演变的重要性。该模型将帮助我们整合我们的观察结果，并在一系列条件下概括我们的发现。盐沼为人类提供了宝贵的生态系统服务，但这些富有成效的栖息地在全球范围内受到海平面加速上升的威胁。了解海平面上升对湿地物理结构的影响对于预测湿地生态系统的响应和海岸线的大尺度形态响应都是至关重要的。水位上升对沼泽的影响取决于物理和生物过程之间的复杂反馈，对这一问题的初步研究集中在水深和沼泽高程之间的相互作用，这影响了沉积物沉积和植物生长。最近，越来越多的注意力被导向小溪网络的演变方式，因为它们在每个潮汐周期中必须在更高的海平面输送更大体积的水。小溪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，因为小溪形态影响了输送到沼泽表面的水和沉积物的量，以及沼泽的排水，因此，沼泽被水淹没的时间长度。反过来，沼泽的扩张和排水影响着这个生态环境中动植物的健康。小溪网络应对海平面上升的能力部分取决于沼泽表面侵蚀的难易程度，这取决于沉积物类型和与植物群和动物群相关的稳定或松动。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对海岸保护和盐沼演变感兴趣的人产生影响。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。