Environmental controls on nitrogen cycling in coastal sediments

沿海沉积物中氮循环的环境控制

• 批准号: RGPIN-2016-05410
• 负责人: Algar, Christopher
• 金额: $ 1.82万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=643731
• 关键词: Environmental; controls; nitrogen; cycling; coastal

Human activity is currently altering global elemental cycles to an unprecedented degree. For example, the invention of the Haber Bosch process, and with it, the ability to make fertilizer from atmospheric nitrogen, has greatly increased dissolved nitrogen (nitrate, nitrite, and ammonium) inputs to coastal waters. Because nitrogen is often a limiting nutrient in aquatic systems, the resulting increase in primary production and subsequent organic matter deposition can lead to O2 depletion at depth. This phenomenon, termed eutrophication, can induce harmful algal blooms (HABs) or the development of anoxic “dead zones”. If we are to effectively manage our costal resources, we must be able to understand and predict the impact of this nutrient loading. Such an understanding requires numerical models that can accurately simulate physical, chemical, and biological processes. Unfortunately, a major source of uncertainty in these biogeochemical models is a lack of knowledge as to how the microbial communities that catalyze many biogeochemical processes will respond to environmental perturbations. Two reasons for this are: 1) the lack of an explicit representation of the microbial communities carrying out the relevant processes, and 2) a lack of understanding of the fundamental principles controlling the organization of microbial communities. ***My research attempts to address this weakness by seeking to improve the representation of microbial processes in biogeochemical models. This will be investigated by studying nitrogen cycling in coastal sediments in the context of three interrelated themes. Theme I will examine nitrogen cycling dynamics in response to the changes in nutrient and carbon loading in two different coastal systems; 1) Bedford Basin, Halifax NS, and 2) sediments underlying salmonid aquaculture farms along the southern coast of Nova Scotia. Aquaculture operations alter carbon and nutrient inputs to sediments and so provide an ideal “natural laboratory”, to study these effects. Theme II will examine the theory of Maximum Entropy Production (MEP) as a principle of ecosystem organization. This theory from non-equilibrium thermodynamics states that ecosystems will organize to dissipate gradients in free energy by the fastest allowable pathway. Theme III will work on improving the representation of (meta)genomic data in biogeochemical models. Over the last 10 years, the application of genomic sequencing to environmental systems has provided an unprecedented view into the diversity and functional potential of microbial communities, however biogeochemical models are not yet formulated in a way to take advantage of these data. ***Through these three themes, this research will strengthen our ability to predict the impacts of coastal nutrient loading, therefore improving our ability to manage our coastal resources. **

人类活动目前正在以前所未有的程度改变全球元素循环。例如，Haber Bosch工艺的发明，以及随之而来的从大气氮中制造肥料的能力，极大地增加了沿海水域的溶解氮(硝酸盐、亚硝酸盐和铵)的输入。由于氮通常是水生系统中的一种限制性营养物质，因此初级生产力的增加和随后的有机物沉积可能会导致深海氧气的枯竭。这种现象被称为富营养化，可导致有害的藻华(HAB)或形成缺氧的“死区”。如果我们要有效地管理我们的沿海资源，我们必须能够理解和预测这种营养负荷的影响。这样的理解需要能够准确模拟物理、化学和生物过程的数值模型。不幸的是，这些生物地球化学模型中的一个主要不确定性来源是缺乏关于催化许多生物地球化学过程的微生物群落将如何响应环境扰动的知识。出现这种情况的两个原因是：1)缺乏执行相关过程的微生物群落的明确代表；2)缺乏对控制微生物群落组织的基本原则的了解。*我的研究试图通过改善微生物过程在生物地球化学模型中的表现来解决这一弱点。将通过在三个相互关联的主题范围内研究沿海沉积物中的氮循环来研究这一点。主题I将研究两个不同沿海系统的氮循环动态，以响应营养和碳负荷的变化：1)贝德福德盆地、哈利法克斯NS和2)新斯科舍省南部沿海鲑鱼养殖场的底层沉积物。水产养殖作业改变了对沉积物的碳和营养输入，因此提供了一个理想的“自然实验室”来研究这些影响。主题二将考察作为生态系统组织原则的最大熵生产(MEP)理论。这一来自非平衡热力学的理论指出，生态系统将以最快的允许路径组织起来，以耗散自由能的梯度。主题三将致力于改进生物地球化学模型中(元)基因组数据的表示。在过去的10年里，基因组测序在环境系统中的应用为微生物群落的多样性和功能潜力提供了前所未有的视角，但生物地球化学模型尚未以利用这些数据的方式建立。*通过这三个主题，这项研究将加强我们预测沿海营养物质负荷影响的能力，从而提高我们管理沿海资源的能力。**