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

* * 0 * 0 * 1 * 429 * 2448 *麻省理工学院/ WHOI * 20 * 5 * 2872 * 14.0 * * * * *** * 正常* 0 * * * * * 假*假*假* * en - us *是* X-NONE * * * * * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *** **** /* 样式定义* / *表。MsoNormalTable* {mso-style-name:"Table Normal"；* mso-tstyle-rowband-size: 0;* mso-tstyle-colband-size: 0;* mso-style-noshow:是的;* mso-style-priority: 99;* mso-style-parent:“”;* font - family：宋体；* mso-para-margin-top: 0;* mso-para-margin-right: 0;* mso-para-margin-bottom: 10.0分;* mso-para-margin-left: 0;* mso-pagination: widow-orphan;*字体大小:12.0分;*字体类型:威尔士;* mso-ascii-font-family:威尔士;* mso-ascii-theme-font: minor-latin;* mso-hansi-font-family:威尔士;* mso-hansi-theme-font: minor-latin;* mso-fareast-language:是;****氮*是这个星球上所有生命所必需的。在海洋中，氮通常是限制性营养物质，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。在沿海水域，氮作为一种来自农业和废水排放的污染物被添加，这反过来又导致藻类大量繁殖，当藻类死亡时，被微生物呼吸，这些微生物消耗了水柱中的氧气，形成了“死区”，在那里没有动物可以生存。人类制造了这些“死亡地带”，使地球上的固定氮量增加了一倍（Gruber和Galloway， 2008）。环境中营养物质的增加也可以刺激微生物介导的N2O生成。一氧化二氮是一种比二氧化碳强200倍的温室气体，所以限制一氧化二氮的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；有些通过将氮气转化为生物质自然添加固定氮；另一些可以通过反硝化和厌氧氨氧化将其还原为气态。随着未来人类引起的环境变化，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势在必行的。在我的研究项目中，我有一个培养设备，可以培养氮循环微生物，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）的首要问题。******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)同位素可以一起用来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特征的成功取决于对关键微生物过程的同位素系统学的深入了解。缺乏这些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自然丰度稳定同位素的主要障碍。我的研究计划的主要目标是确定自然丰度稳定同位素可以用于回答复杂的生物地球化学和环境重要问题的地方，并开发利用它们的必要框架。******该计划的预期好处将是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，以及3)明确定义的计划，使用氮和氧稳定同位素作为监测沿海环境和水产养殖中的氮的一种方式，以保护当地水域免受未来气候和人类活动的影响

* * 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