Collaborative Research: MSB: Impact of sea level rise on sedimentary nitrogen removal processes in tidal freshwater ecosystems

合作研究：MSB：海平面上升对潮汐淡水生态系统沉积氮去除过程的影响

• 批准号: 1020944
• 负责人: Bongkeun Song
• 金额: $ 50.02万
• 依托单位: University of North Carolina at Wilmington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-10-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1020944&HistoricalAwards=false
• 关键词: Collaborative; Research; MSB; Impact; sea

Tidal freshwater ecosystems such as rivers and estuaries are located at the interface between land and sea. These ecosystems provide important natural services including primary production, nutrient distribution and regulation, and waste management - services that are at risk due to climate change. Two aspects of climate change, sea level rise and lower precipitation in some watersheds, will shift the location of freshwater-saltwater mixing zones to upper rivers and continuously increase salinity intrusion into freshwater habitats. Sea level is predicted to rise up to 100 cm by 2100, and by itself can have multiple impacts on freshwater ecosystems, including direct toxic effects, habitat degradation and alteration of nutrient cycles. Salinity increases may also have significant effects on the nitrogen (N) dynamics of freshwater habitats. Nitrification (ammonia conversion to nitrate) and denitrification (nitrate conversion to dinitrogen) are key microbial processes controlling the intensity and duration of eutrophication caused by excess N loading. Salinity intrusion might diminish microbial N removal capacity in freshwater sediments as nitrification and denitrification are reduced due to substrate limitation and physiological inhibition. This could result in prolonged eutrophication and hypoxia at rivers and estuaries. Alternatively, anaerobic ammonium oxidation (anammox; ammonium and nitrite conversion to dinitrogen gas) may become a more important microbial N removal process and help recover N removal capacity in freshwater sediments since anammox bacteria can tolerate salinity increases. This project will study 1) the importance of anammox in tidal freshwater sediments, 2) the effects of salinity on freshwater anammox bacteria and the sedimentary N cycle, and 3) predictions of an alternative N removal pathway in sedimentary communities threatened by sea level rise. The proposed research will integrate molecular microbial techniques, chemical tracer methods and mathematical models to examine sedimentary N removal processes in the Cape Fear River and New River of North Carolina. This proposal will result in the following benefits and outcomes; 1) revealing the structures and activities of microbial communities involved in N removal processes in tidal freshwater sediments, 2) determining differential responses of sediment communities to seawater intrusion, 3) understanding the impacts of sea level rise on sedimentary N removal processes in freshwater ecosystems, 4) predicting a key microbial process for net N removal capacity of freshwater ecosystems experiencing sea level rise. This project will also provide an in-depth understanding of microbial responses in freshwater sediment communities under threat of sea level rise. Interdisciplinary approaches will provide insight into the linkages between community structure and activity as well as salinity effects on riverine sedimentary N cycling. Broader impacts will be manifested through diverse educational components, outreach, and improved research infrastructure at the University of North Carolina Wilmington (UNCW) and the University of Connecticut. Three PIs (microbial ecologist, biogeochemist and ecosystem modeler) will provide interdisciplinary training to at least three graduate students seeking a M.S. or Ph.D. degree. Additional educational impact will be accomplished both in the classrooms and through individual undergraduate research projects at the two institutions. Research experience for high school students will be achieved by including the project within the UNCW "Summer Ocean Ventures" and "Ocean17" programs. The high school students will participate in DNA analysis and mesocosm experiments. The PI will provide a lecture on the microbial nitrogen cycle to the students and design three days of laboratory and field courses to detect and measure denitrification during the Ocean 17 camp. The graduate students recruited for this proposed research will act as teaching assistants for the high school students. The program will culminate with a Summer Ventures Symposium where students will present their work. Outreach will be facilitated by partnering with a local citizens group (NC-Coastal Ocean Federation) to recruit volunteers to participate in sampling cruises and water monitoring program, and by using the existing UNCW "Planet Ocean" lecture series as a public platform to discuss coastal water resources issues and actions.

河流和河口等潮汐淡水生态系统位于陆地和海洋的交界处。这些生态系统提供重要的自然服务，包括初级生产、养分分配和调节以及废物管理——这些服务因气候变化而面临风险。海平面上升和部分流域降水量减少这两个方面的气候变化将使淡水-咸水混合区的位置向上游河流转移，并不断增加对淡水栖息地的盐分入侵。预计到 2100 年，海平面将上升 100 厘米，海平面本身就会对淡水生态系统产生多种影响，包括直接毒性影响、栖息地退化和营养循环的改变。盐度增加也可能对淡水栖息地的氮（N）动态产生重大影响。硝化作用（氨转化为硝酸盐）和反硝化作用（硝酸盐转化为二氮）是控制过量氮负荷引起的富营养化强度和持续时间的关键微生物过程。盐分入侵可能会降低淡水沉积物中微生物的脱氮能力，因为硝化作用和反硝化作用因底物限制和生理抑制而减少。这可能导致河流和河口长期富营养化和缺氧。或者，厌氧氨氧化（厌氧氨氧化；铵和亚硝酸盐转化为氮气）可能成为更重要的微生物脱氮过程，并有助于恢复淡水沉积物中的脱氮能力，因为厌氧氨氧化细菌可以忍受盐度增加。该项目将研究 1) 厌氧氨氧化在潮汐淡水沉积物中的重要性，2) 盐度对淡水厌氧氨氧化细菌和沉积氮循环的影响，以及 3) 受海平面上升威胁的沉积群落中替代氮去除途径的预测。拟议的研究将整合分子微生物技术、化学示踪方法和数学模型，以研究北卡罗来纳州开普菲尔河和新河的沉积氮去除过程。该提案将带来以下好处和成果； 1) 揭示潮汐淡水沉积物中参与氮去除过程的微生物群落的结构和活动，2) 确定沉积物群落对海水入侵的差异反应，3) 了解海平面上升对淡水生态系统中沉积氮去除过程的影响， 4）预测经历海平面上升的淡水生态系统净氮去除能力的关键微生物过程。该项目还将深入了解淡水沉积物群落在海平面上升威胁下的微生物反应。跨学科方法将深入了解群落结构和活动之间的联系以及盐度对河流沉积氮循环的影响。北卡罗莱纳州威尔明顿大学 (UNCW) 和康涅狄格大学的多元化教育内容、外展活动和改进的研究基础设施将体现出更广泛的影响。三位 PI（微生物生态学家、生物地球化学家和生态系统建模师）将为至少三名寻求硕士学位的研究生提供跨学科培训。或博士学位程度。额外的教育影响将通过两个机构的课堂和个人本科研究项目来实现。高中生的研究经验将通过将该项目纳入UNCW“夏季海洋创业”和“Ocean17”计划中来获得。高中生将参加DNA分析和中宇宙实验。 PI 将为学生们提供有关微生物氮循环的讲座，并设计为期三天的实验室和现场课程，以在 Ocean 17 训练营期间检测和测量反硝化作用。为这项拟议研究招募的研究生将担任高中生的助教。该计划将以夏季创业研讨会结束，学生将在会上展示他们的作品。将通过与当地公民团体（北卡罗来纳州沿海海洋联合会）合作招募志愿者参加采样巡航和水体监测项目，并利用现有的UNCW“行星海洋”系列讲座作为讨论沿海地区的公共平台来促进外展活动。水资源问题和行动。