Collaborative Research: Microbial Regulation of Greenhouse Gas N2O Emission from Intertidal Oyster Reefs

合作研究：潮间带牡蛎礁温室气体 N2O 排放的微生物调控

• 批准号: 1233372
• 负责人: Craig Tobias
• 金额: $ 22.58万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1233372&HistoricalAwards=false
• 关键词: Collaborative; Research; Microbial; Regulation; Greenhouse

Intellectual Merit: Oyster reefs are biogeochemical hot spots and prominent estuarine habitats that provide disproportionate ecological function. Suspension-feeding eastern oysters, Crassostrea virginica, are capable of improving water quality and diminishing eutrophication by filtering nutrients and particles from the water and depositing them in the sediments. Remineralization of these deposits may enhance sedimentary denitrification that facilitates nitrogen removal in tidal estuaries. However, the scientific underpinning of oyster reef function has been challenged in various studies. In addition, recent studies of filter feeding invertebrates reported the production of nitrous oxide (N2O), a greenhouse gas, as an end product of incomplete denitrification by gut microbes. C. virginica could be another source of N2O flux from intertidal habitats. Preliminary work indicated substantial N2O production from individual oysters. The estimated N2O production from high density oyster reefs may exceed the N2O flux measured from some estuaries. With the new discovery of N2O emission and uncertainty regarding eutrophication control, the ecological value of oyster reef restoration may become equivocal. This project will quantify N2O fluxes to understand the factors controlling N2O emission from oyster reefs. Sedimentary N processes will be examined to develop an oyster reef N model to estimate N2O emission from tidal creek estuaries relative to other N cycling processes. The PIs hypothesize that intertidal oyster reefs are a substantial source of N2O emission from estuarine ecosystems and the magnitude of emission may be linked to water quality. If substantial N2O flux from oyster reefs is validated, ecological benefits of oyster reef restoration should be reevaluated. This interdisciplinary research team includes a microbial ecologist, a biogeochemist, an ecologist and an ecosystem modeler. They will utilize stable isotope and molecular microbiological techniques to quantify oyster N2O production, elucidate microbial sources of N2O emission from oysters and sediments, and estimate seasonal variation of N2O fluxes from oyster reefs. Measurements from this study will be integrated into a coupled oyster bioenergetics-sediment biogeochemistry model to compare system level rates of N cycling on oyster reefs as a function of oyster density and water quality. Modeling results will be used to assess the relative trade-­offs of oyster restoration associated with N cycling. They expect to deliver the following end products:1) estimation of annual N2O flux from oyster reefs as an additional source of greenhouse gases from estuaries, 2) a better understanding of the environmental and microbial factors influencing N2O and N2 fluxes in tidal estuaries, 3) transformative knowledge for the effect of oyster restoration on water quality enhancement and ecosystem function, 4) direct guidance for oyster restoration projects whose goals include water quality enhancement, and 5) a modeling tool for use in research and restoration planning. Broader impacts will be manifested through diverse educational components and outreach. Four principal investigators will provide interdisciplinary training to at least three graduate students seeking a M.S. or Ph.D. Additional educational impacts will be accomplished both in the classroom and through individual undergraduate research projects. The inter-­institutional group will provide semester long undergraduate field experiences based on this study. The project will provide research experience for high school students in which they participate in oyster incubation experiments and monitor N2O production. The ecological model will be translated into a user-­friendly, online tool for use by other scientists, restoration managers, and educators, and develop related outreach material. Data from the project will be used as problem sets in a "Isotope Biogeochemistry and Reaction and Transport" course. A commitment to underrepresented groups in the sciences will be realized at the graduate level through a Graduate Scholarship in Marine Sciences for Women and Underrepresented Groups.

学术成就：牡蛎礁是地球化学的热点和重要的河口生境，提供了不成比例的生态功能。以悬浮物为食的东方牡蛎Crassostrea virginica能够通过过滤水中的营养物质和颗粒并将其沉积在沉积物中来改善水质和减少富营养化。这些沉积物的再矿化作用可能会增强沉积物的反硝化作用，从而促进潮汐河口的氮去除。然而，牡蛎礁功能的科学基础在各种研究中受到挑战。此外，最近对滤食性无脊椎动物的研究报告了一氧化二氮（N2O）的产生，这是一种温室气体，是肠道微生物不完全脱氮的最终产物。C. virginica可能是潮间带生境N2O通量的另一个来源。初步工作表明，个别牡蛎产生大量N2O。高密度牡蛎礁的N2O排放量可能超过某些河口的N2O通量。随着N2O排放的新发现和对富营养化控制的不确定性，牡蛎礁恢复的生态价值可能变得不确定。该项目将量化N2 O通量，以了解控制牡蛎礁N2 O排放的因素。沉积N过程将检查牡蛎礁N模型估计N2O排放潮沟河口相对于其他N循环过程。PI假设潮间带牡蛎礁是河口生态系统N2O排放的重要来源，排放量可能与水质有关。如果牡蛎礁的N2O排放通量得到验证，牡蛎礁恢复的生态效益应重新评估。这个跨学科的研究团队包括一名微生物生态学家，一名微生物地球化学家，一名生态学家和一名生态系统建模师。他们将利用稳定同位素和分子微生物学技术来量化牡蛎N2O的产生，阐明牡蛎和沉积物中N2O排放的微生物来源，并估计牡蛎礁N2O通量的季节变化。从这项研究的测量将被集成到一个耦合牡蛎生物能量沉积物地球化学模型比较系统水平的牡蛎礁作为牡蛎密度和水质的函数N循环率。模拟结果将用于评估牡蛎恢复与N循环相关的相对权衡。他们希望提供以下最终产品：1）估计牡蛎礁的年度N2O通量作为河口温室气体的额外来源，2）更好地了解影响潮汐河口N2O和N2通量的环境和微生物因素，3）牡蛎恢复对水质改善和生态系统功能影响的变革性知识，4）直接指导牡蛎恢复项目，其目标包括水质改善，以及5）用于研究和恢复规划的建模工具。更广泛的影响将通过各种教育组成部分和外联活动体现出来。四名主要研究员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额外的教育影响将在课堂上完成，并通过个人本科研究项目。跨学科机构小组将根据这项研究提供为期一学期的本科生实地经验。该项目将为高中生提供研究经验，让他们参与牡蛎孵化实验并监测N2O的产生。生态模型将被转化为一个用户友好的在线工具，供其他科学家、恢复管理人员和教育工作者使用，并开发相关的宣传材料。来自该项目的数据将被用作“同位素生物地球化学和反应与传输”课程的问题集。将通过为妇女和代表性不足的群体提供海洋科学研究生奖学金，在研究生一级实现对科学领域代表性不足的群体的承诺。