Using experiments and stable isotopes to track the fate of fixed nitrogen in the marine environment

* * 0* 0* 1* 429* 2448* MIT/WHOI* 20* 5* 2872* 14.0* 正常 * 0* 假 * 假 ** 假 * * EN-US* JA* X-NONE* * * * * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *** * /* 样式定义 */*table.MsoNormalTable* {mso-style-name：“Table Normal”;* mso-tstyle-rowband-size：0;* mso-tstyle-colband-size：0;* mso-style-noshow：yes;* mso-style-priority：99;* mso-style-parent：“";* mso-padding-alt：0in 5.4pt 0in 5.4pt;* mso-para-margin-top：0in;* mso-para-margin-right：0in;* mso-para-margin-bottom：10.0pt;* mso-para-margin-left：0in;* mso-pagination：widow-orphan;* font-size：12.0pt;* 字体家族：Cambria;* mso-asphalt-font-family：Cambria;* mso-asphalt-theme-font：minor-latin;* mso-hansi-font-family：Cambria;* mso-hansi-theme-font：minor-latin;* mso-fareast-language：JA;}* 氮 * 是地球上所有生命的必需品。在海洋中，氮通常是限制性的营养物质，控制着初级生产，从而控制着从大气中吸收二氧化碳。虽然氮对生命很重要，但过量也可能有害。在沿海的沃茨中，氮作为一种污染物从农业和废水中排放出来，这反过来又导致藻类大量繁殖，当它们死亡时，微生物通过呼吸消耗水柱中的氧气，从而形成“死亡区”，在那里没有动物可以生存。人类创造了 * 这些“死亡地带”，使地球上的固定氮量增加了一倍（Gruber* 和Galloway，2008年）。环境中营养物质的增加也会刺激 * 微生物介导的N2 O产生。一氧化二氮是一种比二氧化碳强200倍的温室气体，因此限制这种来源对理解气候变化很重要。* 微生物是海洋中氮的整体控制者;有些微生物通过将氮气转化为生物质来自然地添加固定氮;其他微生物可以通过反硝化和厌氧氨氧化将其还原为气态形式。随着未来人类对环境的改变，了解这些微生物将如何应对和抵消富营养化的负面影响将是当务之急。在我的研究项目中，我有一个培养设施，将培养氮循环微生物，以回答关于微生物如何应对人为影响（如沿海营养负荷或气候变化）的过度问题。* 我在研究中使用的主要工具是稳定同位素。亚硝酸盐和硝酸盐的氮（N）和氧（O）同位素可以一起使用，以解开共同发生的海洋生物地球化学过程。使用任何稳定同位素标记的成功取决于对关键微生物过程的同位素系统学的深入理解。缺乏这一基本信息是目前 * 在 * 大多数海洋生物地球化学系统中成功使用天然丰度稳定同位素的主要障碍。我的研究项目的主要目标是确定天然丰度稳定同位素在回答复杂的地球化学和环境重要问题方面的作用，并为利用它们建立必要的框架。** 该计划的预期益处是：1）增加对微生物氮循环过程复杂性的理解 *，2）这些过程的稳定 * 同位素系统学，3）明确定义使用 * 氮和氧稳定同位素监测沿海 * 环境和水产养殖中氮的计划，以保护当地沃茨不受未来 * 气候和海洋污染的影响。

* * 0* 0* 1* 429* 2448* MIT/WHOI* 20* 5* 2872* 14.0* * * * *** * Normal* 0* * * * * false* false* false* * EN-US* JA* X-NONE* * * * * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *** **** /* Style Definitions */*table.MsoNormalTable* {mso-style-name:"Table Normal";* mso-tstyle-rowband-size:0;* mso-tstyle-colband-size:0;* mso-style-noshow:yes;* mso-style-priority:99;* mso-style-parent:"";* mso-padding-alt:0in 5.4pt 0in 5.4pt;* mso-para-margin-top:0in;* mso-para-margin-right:0in;* mso-para-margin-bottom:10.0pt;* mso-para-margin-left:0in;* mso-pagination:widow-orphan;* font-size:12.0pt;* font-family:Cambria;* mso-ascii-font-family:Cambria;* mso-ascii-theme-font:minor-latin;* mso-hansi-font-family:Cambria;* mso-hansi-theme-font:minor-latin;* mso-fareast-language:JA;}****Nitrogen*is essential for all life on this planet. In the ocean nitrogen is often the*limiting nutrient, controlling primary production and consequently carbon dioxide*uptake from the atmosphere. While nitrogen is important for life, it can also*be harmful in excess. In coastal waters nitrogen is added as a pollutant from*agriculture and wastewater run off, which in turn causes blooms of algae, which*when they die and are respired by microbes that consume oxygen from the water*column creating “dead zones,” where no animal can survive. Humans have created*these “dead zones” by doubling the amount of fixed nitrogen on the planet (Gruber*and Galloway, 2008). Increased nutrients in the environment can also stimulate*microbially mediated N2O production. N2O is a greenhouse*gas 200 times more potent than carbon dioxide, so constraining this source is*important for understanding climate change. ******Microbes are an integral controller of nitrogen in the ocean; some add fixed*nitrogen naturally by turning nitrogen gas into biomass; others can remove it*back to its gaseous form through denitrification and anammox. With future human*induced changes to the environment it will be imperative to understand how*these microbes will respond and counteract the negative impacts of*eutrophication. In my research program, I have a culture facility that will*grow nitrogen cycling microbes in order to answer over-arching questions on how*microbes can respond to anthropogenic influences such as coastal nutrient*loading or climate change. ******The main tools I use in my research are stable isotopes. The nitrogen (N) and*oxygen (O) isotopes of nitrite and nitrate can be used together to disentangle*co-occurring marine biogeochemical processes. The success of using any stable*isotope signature depends on an in depth understanding of isotope systematics*for key microbial processes. The lack of this basic information is currently*the major roadblock to successfully using natural abundance stable isotopes in*most marine biogeochemical systems. The major objectives of my research program*are to identify where natural abundance stable isotopes can be useful for*answering complex biogeochemical and environmentally important questions and to*develop the necessary framework for utilizing them. ******The anticipated benefits of this program will be 1) an increased understanding*of the complexity of microbial nitrogen cycling processes, 2) the stable*isotope systematics of these processes, and 3) a clearly defined plan for using*nitrogen and oxygen stable isotopes as a way to monitor nitrogen in the coastal*environment and aquaculture, in order to protect local waters from future*climate and anthropog