Collaborative Research: Dynamics of dissolved organic phosphorus production, composition and bioavailability along a natural marine phosphate gradient

浮游植物，也被称为初级生产者，是海洋食物网底部的微小漂浮植物。 作为光合生物，浮游植物直接吸收溶解无机碳（DIC），利用太阳能合成其组织。 除了碳（C），这些初级生产者还需要必需的营养素，如磷（P）和氮（N）。 虽然溶解无机磷（DIP）是P的优选形式，因为它是一种足够小的分子，浮游植物可以直接吸收它，但在阳光照射的海洋表面沃茨中，DIP的浓度可以降低到极限水平。 在这种情况下，较大的溶解有机磷（DOP）分子可以通过酶水解反应，将DOP转化为DIP。 越来越多的证据表明，DOP可以在支持海洋初级生产方面发挥关键作用，但人们对DOP池的性质知之甚少。 在获得关于DOP的化学结构和组成的信息方面存在许多分析障碍，并且在不了解其组成的情况下，没有基础来评估DOP对初级生产者的潜在生物利用度。拟议的工作将采用一种独特的方法组合，以获得新的洞察DOP的组成和生物利用度。 现场和实验室（培养）营养添加孵化实验将针对DOP变化的驱动因素，这些信息对于解决海洋初级生产模型至关重要。这项工作的结果将是变革性的了解DOP的组成，DOP在空间和时间的变化，和微生物控制的性质的海洋DOP池。 该提案将支持一名博士后学者，两名本科生和两名本科生。本科生的招聘将侧重于吸引美洲原住民和太平洋岛民，通过SACNAS（社会促进奇卡诺人/西班牙裔和美洲原住民在科学）和相关场地。研究结果将发表在同行评审的期刊上，并在国家和国际会议上发表。 我们还建议对中学进行推广，包括将艺术海洋学家计划，一个通过将海洋科学素养与艺术相结合的概念，针对中学年龄科学和艺术标准的互动探究计划，带到纽约和夏威夷的当地中学。拟议的工作将提供关于DOP分子特征如何转化为海洋微生物的P生物利用度的基础信息，以及在不同溶解无机氮：溶解无机磷（DIN：DIP）下生长的微生物如何影响DOP的组成和生物利用度。 一个新开发的顺序超滤（SUF）方法将适用于收集的样品沿着自然P-梯度在北大西洋西部。SUF方法定量分离和浓缩DOP到4个分子量大小的类，这可以进行生物利用度测定使用磷酸水解酶，和液相色谱-质谱法，以提供详细的组成信息。 使用这些组合的方法，我们将探测在原位DOP，在船上孵育过程中不同DIN：DIP，DOP的组成和生物利用度的DOP产生的生物分离的关键站沿着天然磷酸盐梯度的演变。 原位模式的对比，在控制培养实验中使用现场分离株将实现通过识别细胞的有机磷生物合成途径的转变，并跟踪这种转变如何影响DOP组合物。 结合的方法将提供无与伦比的深入了解DOP的组成和生物利用度，解决这一重大的知识差距。 这项工作的结果将是变革性的了解DOP的组成，DOP在空间和时间的变化，和微生物控制的性质的海洋DOP池。 这些信息是建立生态系统模型的先决条件，这些模型可以捕捉到磷地球化学对初级生产和水生系统中碳循环的影响。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Phytoplankton, also known as primary producers, are microscopic floating plants at the base of the marine food web. As photosynthetic organisms, phytoplankton directly take up dissolved inorganic carbon (DIC) to synthesize their tissues using energy from the sun. In addition to carbon (C), essential nutrients such as phosphorus (P) and nitrogen (N) are required by these primary producers. While dissolved inorganic phosphorus (DIP) is the preferred form of P because it is a small enough molecule that phytoplankton can directly absorb it, in the sunlit surface waters of the ocean the concentration of DIP can be drawn down to limiting levels. In this situation, the larger dissolved organic phosphorus (DOP) molecules can become available through enzyme hydrolysis reactions, which convert DOP to DIP. There was mounting evidence that DOP can play a crucial role in supporting primary production in the ocean, yet very little is known about the nature of the DOP pool. There are many analytical impediments to gaining information about the chemical structure and composition of DOP, and without knowledge of its composition there is no basis for evaluating the potential bioavailability of DOP to primary producers. The proposed work will employ a unique combination of methods to gain novel insight into the composition and bioavailability of DOP. Field and laboratory (culture) nutrient addition incubation experiments will target the drivers of DOP variability, information crucial to resolving models of primary production in the ocean. Results of this work will be transformative for understanding DOP composition, DOP variability in space and time, and microbial control on the nature of the marine DOP pool. This proposal will support a postdoctoral scholar, two undergraduate students and two undergraduate students. Recruitment of undergraduate students will focus on entraining Native Americans and Pacific Islanders, through SACNAS (Society for Advancement of Chicanos/Hispanics and Native Americans in Science) and related venues. Results will be published in peer-reviewed journals and presented at national and international meetings. We also propose to conduct outreach to middle schools, including bringing The Artistic Oceanographer Program, an interactive inquiry-based program targeting middle school age science and art standards by integrating concepts in ocean science literacy with art, to local middle schools in New York and Hawaii.The proposed work will provide foundational information on the way DOP molecular characteristics translate into P-bioavailability to marine microorganisms, and in turn how microorganisms growing under different dissolved inorganic nitrogen: dissolved inorganic phosphorus (DIN:DIP) impact the composition and bioavailability of DOP. A newly developed sequential ultrafiltration (SUF) method will be applied to samples collected along a natural P-gradient in the western North Atlantic. The SUF method quantitatively segregates and concentrates DOP into 4 molecular weight size classes, which can be subjected to bioavailability assays using phosphohydrolytic enzymes, and to liquid chromotography-mass spectrometry to provide detailed compositional information. Using these combined methods we will probe in situ DOP, the evolution of in situ DOP during shipboard incubations under different DIN:DIP, and the composition and bioavailability of DOP produced by organisms isolated from key stations along the natural phosphate gradient. Contrast of in situ patterns to those developed in controlled culture experiments using field isolates will be achieved by identifying cellular shifts in organic phosphorus biosynthesis pathways, and tracing how such shifts impact DOP composition. The combined methodological approach will provide unparalleled insight into DOP composition and bioavailability, addressing this major knowledge gap. Results of this work will be transformative for understanding DOP composition, DOP variability in space and time, and microbial control on the nature of the marine DOP pool. Such information is a prerequisite to building ecosystem models that capture the influence of P biogeochemistry on primary production and carbon cycling in aquatic systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.