Collaborative Research: Cryptic nitrogen cycling in the anoxic subterranean estuary

合作研究：缺氧地下河口的隐氮循环

• 批准号: 1658135
• 负责人: Bongkeun Song
• 金额: $ 39万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658135&HistoricalAwards=false
• 关键词: Collaborative; Research; Cryptic; nitrogen; cycling

Nitrogen is an important nutrient that maintains high coastal ecosystem productivity. Yet excess nitrogen delivery can cause serious water quality deterioration including harmful algal blooms, fish kills, and oxygen free dead zones. Numerous nitrogen transformations regulate the balance between nitrogen delivery and nitrogen removal in coastal environments and the majority of these reactions occur in sediments where seawater passes through the subsurface and mixes with groundwater transported from uplands. This mixing zone, referred to as the subterranean estuary, is characterized by very different geochemistry than either the seawater above it or the groundwater below it. Thus, it has the potential to host a variety of unique reactions that affect nitrogen availability to the overlying water. Scientists from the College of William and Mary, Virginia Institute of Marine Science (VIMS), and the University of Connecticut (UConn) propose to examine the importance of a cryptic nitrogen cycle, a novel and potentially widespread nitrogen cycling process in the subterranean estuary. The cryptic nitrogen cycle comprises anoxic ammonium oxidation to nitrite (anoxic nitrification) coupled with anaerobic ammonium oxidation (anammox) or denitrification producing harmless dinitrogen gas. The proposed project represents highly transformative science because it has the potential to change the current paradigm detailing operation of the biogeochemical nitrogen cycle in anoxic environments. Occurrence of the cryptic nitrogen cycle would have broad implications for the nitrogen budget of terrestrial and groundwater systems and the coastal ocean. Characterization of the cryptic nitrogen cycle will allow us to better understand interactions among the nitrogen, metals, and sulfur cycles, and potential impacts of ongoing human modification of coastal environments. Educational contribution of this project focuses on graduate and undergraduate student training. Two graduate students at VIMS and UConn will receive interdisciplinary training in microbiology, molecular ecology, and biogeochemistry while several undergraduates recruited through the VIMS REU (Research Experience for Undergraduates) Program and the UConn marine science programs will also participate in the project. In addition, three summer undergraduate interns will be recruited from Hampton University, a historically Black college, and trained to enhance minority education and research in marine science. Public outreach will be achieved through popular venues such as VIMS Marine Science Day, and the VIMS After Hours Public Lecture Series at VIMS. Tobias at UConn also provides educational contributions and outreach efforts through the UConn Marine Scholars and Early College Experience programs and an exhibit at Mystic Aquarium.A cryptic nitrogen cycle is proposed as a new process coupling anoxic nitrification to microbial nitrogen removal pathways such as anammox and denitrification. Unlike anammox, which refers to the oxidation of ammonium by nitrite to form dinitrogen (N2) gas, anoxic nitrification occurs by oxidation of ammonium in the absence of oxygen using other common chemical oxidants such as metal oxides (namely, Fe and Mn) or sulfate, abundant in many marine and coastal systems. The thermodynamic favorability of these reactions relies on coupling nitrite formed via these oxidants with anammox or denitrification. Due to the coupling, nitrite will not accumulate or be measurable in anoxic marine systems. Thus, a cryptic N cycle responsible for nitrite production can occur as a novel N transforming process in anoxic environments, serve as a vital link to N2 production, and attenuate N loads discharging from a subterranean estuary (STE). Preliminary results from a STE in the York River Estuary located in Virginia showed substantial N2 production, representing removal of 50-75% of the fixed groundwater N, in ferruginous and sulfidic zones where neither nitrite nor nitrate were detectable. Stable isotope incubation experiments using the 15N tracer and molecular analysis of microbial communities suggest that coupled anoxic nitrification and anammox processes are the dominant N2 production pathways rather than canonical denitrification in the STE. Therefore, coupled anoxic nitrification-anammox in coastal groundwater may be a major unrecognized sink for fixed nitrogen at the land-sea interface. In addition to coastal groundwater, the cryptic N cycle has potential importance in anoxic zones and ocean basins. This proposal focuses on the STE because geochemical conditions there appear optimal for the proposed reactions to occur, and our preliminary data show strong evidence for a cryptic N cycle. The proposed work uses a combined geochemical, 15N isotope tracer and microbiological approach to evaluate environmental controls on the cryptic N cycle as well as to estimate its contribution to reduction of fixed N fluxes to the coastal ocean. Four approaches are proposed: (1) Field characterization of anoxic nitrification reactions and associated microbial communities in a subterranean estuary; (2) Laboratory incubation experiments to identify hotspots of the cryptic N cycle; (3) Controlled microcosm experiments to determine geochemical controls on anoxic nitrification; and (4) in situ assessment of anoxic nitrification to estimate the importance of the cryptic N cycle in a coastal aquifer.

氮是维持较高沿海生态系统生产率的重要养分。然而，过量的氮输送会导致严重的水质恶化，包括有害的藻华，杀死鱼类和无氧死区。许多氮转化调节沿海环境中氮的递送和去除氮之间的平衡，这些反应大多数发生在沉积物中，海水穿过地下并与从高地运输的地下水混合。该混合区（称为地下河口）的特征是地球化学与上方的海水或下方的地下水的特征非常不同。 因此，它有可能容纳各种影响氮对上层水的独特反应。 威廉和玛丽学院，弗吉尼亚海洋科学研究所（VIMS）和康涅狄格大学（UConn）的科学家提议研究一个神秘的氮循环的重要性，这是一种新颖且可能广泛的氮气循环过程，对地下河口。神秘的氮循环包括对亚硝酸盐（缺氧硝化）以及厌氧铵氧化（ANAMMOX）或硝化剂产生无害的二氮气的结合。提出的项目代表了高度变革性的科学，因为它具有改变生物地球化学氮循环在缺氧环境中的当前范式详细范围的操作。神秘的氮周期的发生将对陆地和地下水系统以及沿海海洋的氮预算具有广泛的影响。神秘的氮循环的表征将使我们能够更好地理解氮，金属和硫周期之间的相互作用，以及沿海环境正在进行的人类修饰的潜在影响。该项目的教育贡献着重于研究生和本科生培训。 VIMS和UCON的两名研究生将接受微生物学，分子生态学和生物地球化学的跨学科培训，而通过VIMS REU（本科生的研究经验）计划招募的几位大学生和UCONN Marine Science计划也将参与该项目。此外，将从历史悠久的黑人学院汉普顿大学招募三个夏季的本科实习生，并接受了培训，以增强海洋科学领域的少数族裔教育和研究。公众宣传将通过流行的场地（例如VIMS Marine Science Day）和VIMS公开演讲后的VIMS实现。 UConn的Tobias还通过UConn Marine学者和早期的大学体验计划以及在Mystic Aquarium上的展览提供教育贡献和外展工作。提出了一个隐秘的氮周期，作为一种新的过程，将无氧氮化耦合到微生物氮移除途径，例如An An Anmammammox和DenItrification。与Anammox不同，它指的是亚硝酸盐形成二氮（N2）气体的氧化，使用其他常见的化学氧化剂（例如金属氧化物（即FE和MN）（即FE和MN）或硫酸盐，在许多海上和沿海系统中，使用其他常见的化学氧化剂（例如，使用其他常见的化学氧化剂）在缺乏氧气的情况下通过氧化而发生缺氧硝化。这些反应的热力学有利性依赖于通过甲氧化物或硝化的这些氧化剂形成的亚硝酸盐偶联。由于耦合，在缺氧海洋系统中，亚硝酸盐不会累积或可测量。因此，在缺氧环境中，可以作为一种新的N转化过程，是与N2产生的重要联系，并减轻从地下河口（Ste）排出的N负载。位于弗吉尼亚州约克河河口的Ste的初步结果显示出大量的N2产量，代表在富铁酸盐和硫酸盐区域中均无法检测到固定地下水N的50-75％，在富铁酸盐和亚硫酸盐区域都无法检测到。使用15N示踪剂和微生物群落的分子分析的稳定同位素孵育实验表明，耦合的缺氧硝化和厌氧剂过程是主要的N2产生途径，而不是Ste中的典型硝化途径。 因此，沿海地下水中的缺氧 - 硝化 - 纳米毒素可能是土地海界面固定氮的主要未识别的水槽。除沿海地下水外，神秘的N周期在缺氧区和海盆中具有潜在的重要性。该提案的重点是Ste，因为该提出的反应发生似乎是最佳的，而我们的初步数据显示出了含糊的N周期的有力证据。拟议的工作使用了地球化学，15N同位素示踪剂和微生物学方法来评估神秘n周期的环境控制，并估计其对减少固定N通量对沿海海洋的贡献。提出了四种方法：（1）地下河口中缺氧硝化反应和相关微生物群落的现场表征； （2）实验室孵化实验，以鉴定神秘n周期的热点； （3）受控的缩影实验，以确定缺氧硝化的地球化学对照； （4）原位评估缺氧硝化，以估计沿海含水层中神秘n周期的重要性。

项目成果

Temporal and Spatial Variations in Subterranean Estuary Geochemical Gradients and Nutrient Cycling Rates: Impacts on Groundwater Nutrient Export to Estuaries

• DOI: 10.1029/2022jg007132
• 发表时间: 2023-05
• 期刊: Journal of Geophysical Research: Biogeosciences
• 作者: Stephanie J. Wilson;I. Anderson;B. Song;C. Tobias

Microbial nitrogen loss by coupled nitrification to denitrification and anammox in a permeable subterranean estuary at Gloucester Point, Virginia

弗吉尼亚州格洛斯特角可渗透的地下河口中硝化、反硝化和厌氧氨氧化耦合导致的微生物氮损失

• DOI: 10.1016/j.marpolbul.2021.112440
• 发表时间: 2021
• 期刊: Marine Pollution Bulletin
• 影响因子: 5.8
• 作者: Wu Jiapeng;Hong Yiguo;Wilson Stephanie J.;Song Bongkeun
• 通讯作者: Song Bongkeun

Determining chemical factors controlling abiotic codenitrification

确定控制非生物共硝化的化学因素

• DOI: 10.1021/acsearthsapcechem.0c00225
• 发表时间: 2021
• 期刊: ACS earth and space chemistry
• 影响因子: 3.4
• 作者: Wilson, Stephanie J;Song, Bongkeun;Phillips, Rebecca L.
• 通讯作者: Phillips, Rebecca L.