Collaborative Research: Linking Hydrogeomorphology And Denitrification in the Tidal Freshwater Region of Coastal Streams

AbstractTobias et al.？合作研究：连接水文地貌和反硝化作用在沿海河流的潮汐淡水区？近几十年来，土地利用的变化和人口密度的增加加快了陆地来源的营养物质（特别是氮）向水生生物群落的输送速度。 人类现在贡献更多的活性氮（N）的水和生物圈比所有其他自然氮源的总和。 水生生境的反应则是令人讨厌的藻华、物种组成的变化、对鳍和贝类资源的影响以及有害的经济后果。 随着溪流和河流趋于氮饱和，越来越多的氮污染被输出到沿海边缘，在那里它促进了缺氧事件的严重性和持续时间的扩大。 通过整个水生连续体（如溪流，河流和河口）的N的命运和运输的理解是必要的，以确定特别容易受到N输入的区域，以及那些作为热点的N去除。 控制N反应性的水文和化学机制的知识为指导养分管理策略和提高这些环境的自然能力以衰减N负荷提供了基础。 反硝化作用的测量，代表氮的绝对衰减的唯一机制，已被广泛的水生生态类型的研究。 然而，水生连续体中的一个特殊部分，潮汐淡水河流和溪流，一般都逃避了调查。 连接高地溪流和河流的河口，我们认为，潮汐淡水溪流具有独特的水文，地貌和化学反应，优化氮去除相对于任何其他组成部分的水生连续体。 此外，我们建议，增强N去除可以产生在非潮汐系统简单地通过诱导准潮汐水文制度（即通过产生一个有节奏的上升和下降的水位）。调查人员建议将联合收割机广泛的水化学监测工作在美国东南部沿海平原流与一个独特的一系列化学示踪剂的研究，和流建模。 所有工程均应在自然和水文条件下就地进行。 潮汐流是美国东南部的主要水生特征，拟议的工作将有助于确定在多大程度上，他们是一个热点的N去除在广泛的地理scales.The研究代表了联邦学术伙伴关系，将提供一个更好的理解如何在流域营养负荷转化为生态系统响应沿着大陆边缘。 这种性质的工作是必不可少的，以改善人类干扰和/或恢复影响的栖息地响应的预测，评估水生栖息地的弹性，完善营养负荷的监管目标。 水文学和化学如何相互作用，以调节N处理的机制图片提供了重要的基础，开发简单的低成本技术，增强自然N衰减，从而改善水质。 这项工作的更广泛影响包括广泛的教育内容、公共宣传和技术转让的潜力。 研究活动直接纳入学术课程，研究人员将指导高中和本科生，培训研究生，并为传统上代表性不足的群体提供机会。 这项工作所取得的水质恢复技术进步将传播给县、州和联邦各级的资源管理人员。总之，这一努力有助于加强对水产资源的管理。

AbstractTobias et al.?Collaborative Research: Linking hydrogeomorphology and denitrification in the tidal freshwater region of coastal stream?In recent decades, changes in land use and increasing population density have accelerated the delivery rates of nutrients (particularly nitrogen) from terrestrial sources to aquatic biomes. Humans now contribute more reactive nitrogen (N) to the hydro- and biospheres than all other natural N sources combined. Aquatic habitats have in turn responded with nuisance algal blooms, changes in species composition, impacts on fin and shellfish resources, and deleterious economic consequences. As streams and rivers trend closer towards nitrogen saturation, increasing amounts of nitrogen pollution are exported to the coastal margins where it promotes expanded severity and duration of hypoxic events. An understanding of the fate and transport of N through the entire aquatic continuum (e.g. streams, rivers and estuaries) is necessary for identifying zones that are particularly susceptible to N inputs, and those that act as hot spots for N removal. Knowledge of the hydrologic and chemical mechanisms controlling N reactivity provides the foundation for guiding nutrient management strategies and for enhancing the natural capacity of these environments to attenuate N loads. Measurement of denitrification, the only mechanism that represents absolute attenuation of nitrogen, has been examined across a wide range of aquatic ecotypes. However, one particular segment of the aquatic continuum, tidal freshwater rivers and streams, has generally escaped inquiry. Connecting upland streams and rivers to estuaries, we suggest that tidal freshwater streams possess unique hydrology, geomorphology, and chemical reactivity that optimize for N removal relative to any other component of the aquatic continuum. Further, we propose that enhanced N removal can be generated in non tidal systems simply by inducing a quasi-tidal hydrologic regime (i.e. by generating a rhythmic rise and fall in water level). Investigators propose to combine extensive hydro-chemical monitoring efforts in Coastal Plain streams in the Southeastern U.S. with a unique series of chemical tracer studies, and stream modeling. All work is to be conducted in situ under natural and hydrologically-manipulated conditions. Tidal streams are dominant aquatic features of the Southeastern US, and the proposed work will help to determine the extent to which they are a hotspot for N removal on broad geographic scales.The research represents a federal-academic partnership that will provide a better understanding of how nutrient loading in watersheds translates into ecosystem response along continental margins. Work of this nature is essential for improving predictions of habitat response to human perturbation and/or restoration effects, assessing resiliency of aquatic habitats, refining regulatory targets for nutrient loading. The mechanistic picture of how hydrology and chemistry interact to regulate N processing provides the critical foundation for developing simple low-cost technologies that enchance natural N attenuation and thereby improve water quality. Broader impacts of the work include extensive educational components, public outreach, and the potential for technology transfer. Research activities are integrated directly into academic curricula, investigators will mentor high school and undergraduate students, train graduate students, and provide opportunities for traditionally underrepresented groups. Technological advancements in water quality restoration resulting from this work will be disseminated to resource managers at the county, state, and federal levels. In total this effort facilitates enhanced stewardship of aquatic resources.