OCE-PRF The impact of nitrogen loading and sea level rise on subsurface green house gas cycling and carbon sequestration in coastal salt marsh ecosystems

概述：盐沼在气候反馈系统中起着重要作用。盐沼是有效的碳掩埋和排放温室气体。在预测的气候变化下，海平面上升可能会改变这些系统的碳埋藏能力。在这些系统中，营养负荷是一个额外的外部压力源，可能会影响碳和温室气体的循环。在这个项目中，他将与美国地质调查局的Kevin D. Kroeger博士一起研究海平面上升和氮富集对盐沼中温室气体和碳的地下循环的影响。这位研究员计划在盐沼系统内安装一个监测井的网络，监测氮的富集和淹没水平，并在两年内每月收集溶解碳和氮的样本。此外，她还将在每月的采样中，通过安装亲水、透气性油管连接到气体分析仪，量化这些盐沼沉积物中地下温室气体的产生。将对盐沼地下和沼泽外的孔隙水通量进行测量，以确定这些成分流入河口水域并最终流入沿海海洋的通量。该研究地点位于海平面上升热点，因此是确定过去25年来海平面上升速度加快如何改变盐沼中碳埋藏的理想地点。沉积物岩心将从经历一系列氮负荷和海水淹没水平的地点收集，以合成盐沼碳埋藏随时间对这两个压力源（营养物富集和海平面上升）的响应。本研究结果将有助于进一步了解气候对盐沼生态系统服务的潜在影响。知识价值：地球将面临二氧化碳含量高的未来，潜在的气候影响将通过温度升高和海平面上升在全球沿海生态系统中产生共鸣。沿海地区的人口增长通过营养丰富给生态系统带来了更大的压力。盐沼是高碳埋藏区，因此它们的碳储存潜力引起了科学界和决策碳补救的利益相关者的兴趣。然而，气候变化对盐沼生态系统的直接影响尚不清楚，但可能是巨大的。除了储存碳的能力外，盐沼生态系统还产生和排放温室气体，如甲烷和一氧化二氮。该项目的研究结果将有助于确定在气候变化面前，盐沼中的碳埋藏是否具有弹性，以及温室气体排放的净影响是否会减少或抵消盐沼作为碳汇的价值。更广泛的影响：该项目与一个更大的已建立项目协同作用，该项目评估地表温室气体逃逸和盐沼生态系统跨氮负荷梯度的横向碳通量。该项目的一个关键组成部分是利用协作学习将科学成果转化为政策制定者和其他对盐沼生态系统服务经济学感兴趣的人可用的产品。有了这个框架，这项工作的结果将直接与有关盐沼的沿海政策决定联系起来。此外，扩大参与教育机会是该项目的重要组成部分。第二季将有一名来自伍兹霍尔教育合作项目的本科生参加。学生将在这个项目的框架内进行原创性的研究，并参加一个全国性的会议来展示他们的研究成果。该研究员还将在整个项目期间担任瓦奎特湾国家河口研究保护区妇女科学计划的讲师和导师。该项目允许7-9年级的年轻女性在保护区河口研究的背景下探索科学。

Overview: Salt marshes play a significant role in the climate feedback system. Salt marshes are efficient at carbon burial and emit greenhouse gases. Under predicted climate change, sea level rise will potentially alter the carbon burial capacity of these systems. Nutrient loading is an additional external stressor in these systems which may impact carbon and greenhouse gas cycling. In this project, the fellow will study the impact of sea level rise and nitrogen enrichment on subsurface cycling of greenhouse gases and carbon in salt marshes with Kevin D. Kroeger, PhD at the United States Geological Survey. The fellow plans to install a network of observing wells within a salt marsh system across nitrogen enrichment and inundation levels, and collect samples monthly for two years for dissolved carbon and nitrogen. In addition, she will quantify subsurface production of greenhouse gases in these salt marsh sediments with an installation of hydrophilic, gas permeable tubing attached to gas analyzers during the same monthly sampling. Measurements will be taken of porewater flux both within the salt marsh subsurface and out of the marsh to determine fluxes of these constituents to receiving estuarine waters and ultimately the coastal ocean. The study site exists in a sea level rise hot spot and, therefore, an ideal location to determine how enhanced rates of sea level rise over the past twenty-five years have changed carbon burial in salt marshes. Sediment cores will be collected from sites that undergo a range of nitrogen loadings and seawater inundation levels to synthesize the salt marsh carbon burial response through time to these two stressors (nutrient enrichment and sea level rise). Results from this study will further understanding of the potential climate impacts on the ecosystem services of salt marshes. Intellectual Merit: The earth is faced with a high CO2 future, with potential climate impacts resonating through global coastal ecosystems via increasing temperatures and rising sea level. Population growth in coastal regions places added stress on ecosystems via nutrient enrichment. Salt marshes are regions of high carbon burial, and as such their carbon storage potential is of interest to both the scientific community and to stakeholders making decisions about carbon remediation. The direct impact of climate change on salt marsh ecosystems is unknown, however, potentially significant. In addition to their ability to store carbon, salt marsh ecosystems also produce and emit greenhouse gases, such as methane and nitrous oxide. Research results from this project will help to determine if carbon burial in salt marshes will be resilient in the face of climate change and if the net impacts of greenhouse gas emissions will reduce or negate the value of salt marshes as a carbon sink. Broader Impacts: This project is synergistic with a larger established project evaluating surface greenhouse gas evasion and lateral carbon fluxes from salt marsh ecosystems across a gradient of nitrogen loading. A key component of this project is to use collaborative learning to transform the scientific results into useable products for policy makers and others interested in the economics of salt marsh ecosystem services. With this framework in place, the results of this work will be directly linked to coastal policy decisions regarding salt marshes. In addition, broadening participation educational opportunities are a significant component of this project. The second field season will include participation of an undergraduate student from the Woods Hole Partnership in Education Program. The student will conduct original research within the framework of this project and attend a national conference to present the findings of their research. The fellow will also serve as a lecturer and mentor in the Waquoit Bay National Estuarine Research Reserve Women in Science Program throughout the project. This program allows young women in grades 7-9 to explore science in the context of estuarine research at the Reserve.