Collaborative Research: Quantifying the effects of different nitrogen forms on marsh resilience to environmental change

合作研究：量化不同氮形式对沼泽适应环境变化的能力的影响

• 批准号: 2203323
• 负责人: Anne Giblin
• 金额: $ 35.07万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2203323&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; effects; different

Nitrogen delivery from watersheds to the coast harms aquatic ecosystems, including the formation of dead zones where oxygen concentrations drop below levels that can support most aquatic life. Salt marshes provide an important line of defense against nutrient pollution by intercepting watershed nitrogen before it enters estuaries. This nitrogen can enhance the growth of marsh plants, much as fertilizers enhance growth in gardens. However, some forms of nitrogen can also be used by microbes, who use it as a substitute for oxygen to decompose plant organic matter in low-oxygen sediments. Understanding which of these two outcomes of nitrogen delivery is most likely to occur is important to the environment. If marsh plants take up that nitrogen and grow larger, this will cause the marsh to gain elevation by trapping more sediment and adding more plant material to the sediments. This process will increase salt marsh resilience to sea-level rise. However, if marsh microbes can outcompete marsh plants for the added nitrogen, then it could enhance sediment decomposition and reduce the ability of marshes to keep up with rising sea levels. The results of this research will help predict how marshes will respond to sea-level rise in coastal systems that experience large inputs of land-derived nitrogen, helping to create more resilient coastal communities. This research also supports workforce development through training across multiple levels of education (high school, undergraduate, and graduate), in particular for people from historically marginalized groups. To understand how nitrogen speciation and plant genetic diversity affect the ability of salt marshes to keep pace with sea-level rise, this research has three goals: quantify how environmental nitrogen availability alters responses of the coupled plant-microbe system, determine how these responses vary under different flooding regimes, and assess how different populations of cordgrass respond to different nitrogen sources. To address our first goal, we are conducting paired plot-level nutrient enrichment experiments in two locations along the eastern US coast where nitrate and ammonium will be added at a range of concentrations for two years. We are measuring the effects of nitrogen addition on marsh plants, microbes, and carbon and nitrogen cycling. To address our second goal, we are performing experiments at both locations, where nitrogen form is crossed with elevation to assess how variation in elevation alters the responses of the plant and microbial communities to different forms of nitrogen. These experiments are purposefully designed so that results can be used in a new generation of the Marsh Equilibrium Model that incorporates how future nitrogen inputs will alter the capacity of marshes to keep pace with sea-level rise. Lastly, greenhouse nitrogen uptake experiments are providing essential data on population-specific uptake rates of both nitrogen forms in the absence of sediment microbes. Taken together, this research mechanistically addresses how different forms of nitrogen and plant genetic variation affect marsh ability to store carbon and keep pace with sea-level rise. This information is being incorporated into a modeling framework that allows resource managers to predict how marshes will respond to the combined effects of nutrient enrichment and sea-level rise.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.

从流域到海岸的氮递送会损害水生生态系统，包括形成死区，其中氧气浓度下降到水平以下可以支持大多数水生寿命。盐沼在进入河口之前拦截水分氮，为营养污染提供了重要的防御方法。这种氮可以增强沼泽植物的生长，就像肥料增强花园的生长一样。但是，微生物也可以使用某些形式的氮，他们将其用作低氧沉积物中分解植物有机物的氧气的替代品。了解氮递送的这两个结果中的哪一个对环境很重要。如果沼泽植物占据了氮并生长更大，这将通过捕获更多沉积物并在沉积物中添加更多植物材料来使沼泽升高。这个过程将增加盐沼对海平面上升的弹性。但是，如果沼泽微生物能够胜过增加氮的沼泽植物，那么它可以增强沉积物的分解并降低沼泽的能力，以跟上海平面上升。这项研究的结果将有助于预测沼泽将如何应对沿海系统的海平面上升，这些沿海系统经历了大量的土地衍生氮投入，从而有助于建立更多有韧性的沿海社区。这项研究还通过跨多个教育（高中，本科和毕业生）的培训，特别是对历史上边缘化的群体的人们进行培训，以支持劳动力的发展。为了了解氮的形态和植物遗传多样性如何影响盐沼泽与海平面上升的能力，这项研究具有三个目标：量化环境氮的可用性如何改变耦合植物 - 微生物系统的反应，确定这些反应在不同的洪水方面在不同的洪水方面变化，并评估不同山脉的不同人口源代表不同的NITORN NITORGENT。为了解决我们的第一个目标，我们正在美国东部海岸的两个地点进行配对的情节养分富集实验，在那里硝酸盐和铵将在两年内以一系列浓度添加。我们正在测量添加氮对沼泽植物，微生物以及碳和氮循环的影响。为了解决我们的第二个目标，我们在两个位置进行了实验，在两个位置，氮形式越过高度，以评估海拔的变化如何改变植物和微生物群落对不同形式的氮的反应。这些实验是有目的地设计的，因此可以将结果用于新一代的沼泽平衡模型，该模型结合了未来的氮输入方式将改变沼泽的能力，以保持与海平面上升的步伐。最后，在没有沉积物微生物的情况下，温室氮摄取实验提供了两种氮形式的人口特异性摄取率的重要数据。综上所述，这项研究从机械上讲述了不同形式的氮和植物遗传变异如何影响沼泽储存碳的能力，并与海平面上升保持同步。该信息已被整合到一个建模框架中，该框架使资源经理能够预测沼泽将如何应对养分富集和海平面上升的综合影响。该奖项反映了NSF的法定任务，并认为使用基金会的知识分子优点和更广泛的影响审查标准，被认为值得通过评估来获得支持。