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

海平面上升不仅使我们的海岸线上升，使我们的盐沼变得面目全非，而且还将海潮推向内陆，使它们席卷河流，席卷森林。这些淡水湿地因其生物多样性、美丽和它们为社会提供的其他服务而受到珍视，随着海平面上升，这些淡水湿地将从森林演变为沼泽，再演变为开放水域。未来几十年这种转变的速度尚不清楚，即使是沿海景观与河流之间相互作用的微小变化也可能导致对公共土地，私人财产以及流域和河口的环境管理产生非常不同的影响。社会将通过两种方式做好准备，更好地适应这些影响。首先，探索河流和河口的淤泥、淤泥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，将有助于确定这些湿地的主要变化将发生在哪里（以及何时）。第二，教育沿海居民了解他们的沿海景观正在发生变化的原因，并培训他们测量和监测这些变化，这将加强地方决策，使科学家和沿海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区悬浮沉积物的直接来源，特别是在河流洪水期间。这些测量将有助于回答众所周知的关于河流与河口连通性的挑战性问题，例如“在河流洪水期间，河流携带的颗粒进入河口多远，以及这些颗粒在盐水河口的悬浮沉积物中占多大比例？”这些问题的答案将揭示河流和河口影响的空间尺度以及颗粒运动的时间尺度。沉积物颗粒的近期来源将使用颗粒相关微生物群落的高通量DNA测序进行评估。这种技术的优点是，具有相同矿物学和化学成分的沉积物颗粒可以追溯到其最近的来源（淡水、潮汐淡水、底栖生物、湿地、盐水河口）。与颗粒相关的微生物DNA的天气调查沿沿着河流-河口过渡的两个支流的切萨皮克湾将解释实验室培养和混合实验的结果与悬浮泥沙从各种来源和水基质。沉积物混合的空间和时间模式将被概括和应用于预测美国东海岸淡水潮汐湿地的脆弱性。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

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.