Resolving Sediment Connectivity between Rivers and Estuaries by Tracking Particles with their Microbial Genetic Signature

海平面上升不仅攀升了我们的海岸线，塑造了我们的盐沼，还将海潮推到了遥远的内陆，在那里它们席卷了河流，滚滚穿过边缘的森林。这些淡水湿地因其生物多样性、美观和为社会提供的其他服务而备受珍视，随着海平面的上升，它们将从森林演变为沼泽，再演变为开阔水域。未来几十年这种转变的速度尚不清楚，即使沿海景观与河流之间的相互作用发生微小变化，也可能会对公共土地、私有财产以及流域和河口的环境管理产生非常不同的影响。通过两种方式的准备，社会将更好地适应这些影响。首先，探索来自河流和河口的泥沙和沙子的沉降如何建立潮汐湿地的海拔，特别是潮汐最上游的湿地，将有助于准确地确定这些湿地将在哪里(以及可能何时)发生重大变化。第二，教育沿海居民了解他们的海岸景观为什么正在变化，并培训他们测量和监测这些变化，这将加强当地的决策，并使科学家和海岸管理人员能够更准确地针对环境保护。该项目将测量河口河流潮汐和盐碱地地区的悬浮泥沙的直接来源，特别是在河流洪水期间。这些测量将有助于回答关于河流与其河口的连通性的臭名昭著的具有挑战性的问题，例如“在河流洪水期间，河流携带的颗粒进入河口的距离有多远，以及这些颗粒在盐碱地河口的悬浮泥沙中所占的比例？”这些答案将揭示颗粒运动的时间尺度以及河流和河口影响的空间尺度。将使用与颗粒相关的微生物群落的高通量DNA测序来评估最近沉积物颗粒的来源。这项技术的优点是，具有相同矿物学和化学成分的沉积物颗粒可以追溯到它们的最新来源(淡水、潮汐淡水、底栖生物、湿地、盐碱河口)。对切萨皮克湾两条支流河流-河口过渡过程中与颗粒相关的微生物DNA的天气调查将使用实验室培养和与来自不同来源的悬浮沉积物和水基质的混合实验的结果来解释。泥沙混合的空间和时间模式将被概括并应用于预测美国东海岸淡水潮汐湿地的脆弱性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Sea level rise is not only climbing our coastline and sculpting our saltmarshes, it is also pushing ocean tides far inland where they sweep up rivers and roll across their fringing forests. Treasured for their biodiversity, beauty, and other services they provide society, these freshwater wetlands will evolve from forest to marsh to open water as sea level rises. The pace of this transition over the coming decades isn’t yet known, and it is likely that even small changes in the interaction between coastal landscapes and their rivers will lead to very different impacts affecting public lands, private property, and environmental management of watersheds and estuaries. Society will be better positioned to adapt to these impacts by preparing in two ways. First, exploring how the settling of mud, silt, and sand from rivers and estuaries builds the elevation of tidal wetlands, especially wetlands at the farthest upstream reach of tides, will help pinpoint where (and possibly when) major changes to these wetlands will occur. Second, educating coastal populations on why their coastal landscapes are changing and training them to measure and monitor these changes will strengthen local decision-making and empower scientists and coastal managers to more precisely target environmental protections.This project will measure the immediate source of suspended sediment in the fluvial tidal and saline zones of estuaries, particularly during river floods. These measurements will help answer notoriously challenging questions about the connectivity of rivers with their estuaries, such as “how far do river-borne particles travel into estuaries during river floods, and what proportion of the suspended sediment do these particles comprise in the saline estuary?” The answers will reveal as much about the time scale of particle movements as the spatial scales of river and estuarine influence. The recent origin of sediment particles will be assessed using high throughput DNA sequencing of the particle-associated microbial community. The advantage of this technique is that sediment particles of identical mineralogy and chemical composition can be traced to their most recent source (freshwater, tidal freshwater, benthic, wetland, saline estuary). Synoptic surveys of particle-associated microbial DNA along the riverine-estuarine transition of two tributaries of the Chesapeake Bay will be interpreted using results from laboratory incubation and mixing experiments with suspended sediment from various sources and water matrices. The spatial and temporal patterns of sediment mixing will be generalized and applied to predict vulnerability of freshwater tidal wetlands on the US east coast.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.