Collaborative Research - Taxon-Specific Variability of Organiz Matter Production and Remineralization Potential

智力优势：海洋磷(P)循环的特点是溶解的无机磷(DIP)和溶解的有机磷(DOP)的吸收和分解紧密耦合。DIP被整合到广泛的细胞化合物中，对能量储存、遗传物质和细胞结构不可或缺。细胞死亡和自溶、渗出、病毒裂解和放牧都会导致DOP释放到环境中，在那里它可以解聚、水解、再同化、被吸收到下沉颗粒上或在周围环境中积累。在这种情况下，海洋环境中磷的形态和组成在很大程度上受微生物的代谢活动控制，并与碳(C)和氮(N)作为颗粒有机磷(POP)的循环密切相关，DOP以多种形式与C和N结合，包括酯、磷脂和磷酸盐。因此，当磷的转化被视为海洋水柱中营养和能量流动的一部分时，对海洋磷循环的考虑是最相关的。在生态系统尺度上，开阔海域的生产力和呼吸平衡受到潜在限制性营养物质如C、N和P的可用性的调节。因此，了解C、N和P循环的耦合对于确定初级生产和颗粒输出的大小和变异性的长期控制至关重要。然而，缺乏对溶解有机碳(DOC)、溶解有机氮(DON)和溶解有机氮(DOP)的同步测量，以及相对缺乏关于生产和分解过程的信息，阻碍了理解这些池的耦合动态的进展。最近对溶解有机物(DOM)动力学的研究表明，由于浮游植物种类组成、有机质生产的化学计量和化学组成、有机物的差异性以及异养细菌对N和P的优先再矿化，DOM的动态变化与Redfield轨迹有很大偏离。此外，越来越多的证据表明，通过DOP水解酶可能会释放温室气体。在这项研究中，研究人员将表征具有生态意义的光合作用属产生的有机P-C-N的组成、稳定性和再矿化化学计量学。他们将进行一系列现场和基于实验室的生物检测，将从原氯球菌和含有磷酸盐的木霉菌株中分离出的颗粒物(POM)和DOM添加到自然微生物种群中，并在实验室和海洋中培养。假设驱动的实验将解决以下目标：(1)确定元素(P-C-N)化学计量和生物分子变化(31P-核磁共振)响应于外源添加到异养菌自然种群中的毛霉菌和原氯球菌POM和DOM，估计具有生态意义的属产生的不稳定和半不稳定的有机物比例，并测量选定温室气体(甲烷和乙烷)的潜在需氧生产。(2)在季节循环的相反阶段(夏季/冬季)启动NPSG的分解实验，以捕捉具有不同初始代谢状态和群落结构的不同微生物组合。更广泛的影响：研究目标的实施将有助于通过数据共享和批判性话语建立协作网络。更广泛的教育影响包括为项目中的青年科学家提供广泛的跨学科和跨实验室培训，以及提高妇女在科学领域地位的机会。研究重点将纳入所教授的课程，包括传播海洋科学和科学发现，将通过出版物、参加会议和讲习班以及维护研究博客来分享。研究人员将与美国国家科学基金会资助的微生物研究和教育中心的教育工作人员合作，开发一套科学工具包，以说明生物学在元素周期中的作用。该工具包将分发给所有伙伴机构。这项研究的更广泛的社会效益是加深了对关键生物群在元素循环中的作用的了解，以及对基本海洋生境中初级和出口生产的调节。

INTELLECTUAL MERIT: The marine phosphorus (P) cycle is characterized by tight coupling between the uptake and decomposition of dissolved inorganic P (DIP) and dissolved organic P (DOP). DIP is incorporated into a broad range of cellular compounds integral for energy storage, genetic material and cell structure. Cell death and autolysis, exudation, viral lysis and grazing all lead to the release of DOP into the environment where it can be depolymerized, hydrolyzed, reassimilated, removed by absorption onto sinking particles or accumulate in the surrounding environment. In this manner, the form and composition of P in the marine environment is largely controlled by the metabolic activity of microorganisms and is intimately linked to the cycling of carbon (C) and nitrogen (N) as particulate organic P (POP) and DOP is bound to C and N in multiple forms, including esters, phospholipids and phosphonates. Thus, a consideration of marine P cycling is most relevant when P transformations are viewed as part of the nutrient and energy flow in the oceanic water column. At the ecosystem scale, the balance of productivity and respiration in the open ocean is regulated by the availability of potentially limiting nutrients such as C, N and P. Therefore, understanding the coupling of C, N, and P cycles is central to the determination of the long-term controls of the magnitude and variability of primary production and particle export. Nonetheless, a paucity of simultaneous measures of dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and DOP and a relative lack of information on production and decomposition processes have hindered progress in understanding the coupled dynamics of these pools. Recent studies of dissolved organic matter (DOM) dynamics show large departures from Redfield trajectories driven by alterations in phytoplankton species composition, the stoichiometry and chemical composition of organic matter production, differential lability of organic compounds and preferential remineralization of N and P by heterotrophic bacteria. Furthermore, there is mounting evidence of the potential liberation of greenhouse gases occurring via DOP hydrolysis.In this research, the investigators will characterize the composition, lability and remineralization stoichiometry of organic P-C-N produced by ecologically significant photosynthetic genera. They will conduct a series of in situ and laboratory-based bio-assays where particulate (POM) and DOM isolated from Prochlorococcus and phosphonate-containing strains of Trichodesmium are added to natural microbial populations and incubated in the laboratory and at sea. Hypothesis driven experiments will address the following objectives:(1) Determine the elemental (P-C-N) stoichiometry and biomolecular alterations (31P-nuclear magnetic resonance) occurring in response to exogenous additions of Trichodesmium and Prochlorococcus POM and DOM to natural populations of heterotrophic bacteria, estimate the labile and semi-labile fraction of organic material generated by ecologically significant genera and measure potential aerobic production of select greenhouse gases (methane and ethane). (2) Initiate decomposition experiments in the NPSG at opposing phases of the seasonal cycle (summer/winter) in order to capture varying microbial assemblages having different initial metabolic status and community structure. BROADER IMPACTS: Implementation of the research objectives will serve to build collaborative networks through data sharing and critical discourse. Broader educational impacts include the provision of extensive interdisciplinary and inter-laboratory training for the young scientists included in the project and opportunities for the advancement of women in science. Research highlights will be incorporated into courses taught, including Communicating Ocean Science and scientific findings will be shared via publications, participation in conferences and workshops and maintenance of a research blog. Partnering with education staff at the NSF-funded Center for Microbial Research and Education, the investigators will develop a science kit to illustrate the role of biology in elemental cycles. The kit will be made available for distribution to all partner institutions. The broader societal benefits of the research are an increased understanding of the role of key biota in elemental cycling and the regulation of primary and export production in a fundamental oceanic habitat.