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

知识价值：海洋磷(P)循环的特点是溶解无机磷（DIP）和溶解有机磷（DOP）的吸收和分解之间的紧密耦合。DIP被纳入广泛的细胞化合物积分的能量存储，遗传物质和细胞结构。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，在环境中DOP可以解聚、水解、再同化、被吸收到下沉的颗粒上或在周围环境中积累。因此，海洋环境中P的形态和组成在很大程度上受微生物代谢活动的控制，并与碳(C)和氮(N)的循环密切相关，因为颗粒有机P （POP）和DOP以多种形式与C和N结合，包括酯类、磷脂和磷酸盐。因此，当P转化被视为海洋水柱中养分和能量流动的一部分时，考虑海洋P循环是最相关的。在生态系统尺度上，开放海洋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）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出口的规模和变异性的长期控制至关重要。然而，由于缺乏同时测量溶解有机碳（DOC）、溶解有机氮（DON）和DOP的方法，以及相对缺乏产生和分解过程的信息，阻碍了对这些池耦合动态的理解。最近对溶解有机物（DOM）动力学的研究表明，浮游植物种类组成、有机物生产的化学计量学和化学组成、有机物的差异不稳定性以及异养细菌对N和P的优先再矿化等因素的变化导致了与Redfield轨迹的巨大偏离。此外，越来越多的证据表明，通过DOP水解可以释放温室气体。在这项研究中，研究人员将表征生态上重要的光合植物产生的有机P-C-N的组成、不稳定性和再矿化化学计量学。他们将进行一系列现场和实验室生物分析，将从原绿球藻和含磷酸盐的Trichodesmium菌株中分离出的颗粒（POM）和DOM添加到天然微生物种群中，并在实验室和海上孵育。假设驱动的实验将解决以下目标：(1)确定在异养细菌自然种群中外源添加Trichodesmium和原绿球菌POM和DOM时发生的元素（P-C-N）化学计量学和生物分子变化（31p -核磁共振）；估算生态上重要的属产生的有机物质的不稳定和半不稳定部分，并测量选定温室气体（甲烷和乙烷）的潜在有氧生产。(2)在季节周期的不同阶段（夏/冬）启动NPSG的分解实验，以捕获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该项目的年轻科学家提供广泛的跨学科和实验室间培训，并为提高妇女在科学领域的地位提供机会。研究重点将纳入授课课程，包括传播海洋科学，科学发现将通过出版物、参加会议和研讨会以及维护研究博客进行分享。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人员合作，研究人员将开发一套科学工具来说明生物学在元素循环中的作用。该工具包将分发给所有伙伴机构。该研究的更广泛的社会效益是增加了对关键生物群在元素循环和基本海洋栖息地初级和出口生产调节中的作用的理解。

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.