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的无机碳（DIC），利用太阳的能量合成自己的组织。除了碳(C)，这些初级生产者还需要必需的营养物质，如磷(P)和氮(N)。溶解的无机磷（DIP）是磷的首选形式，因为它是一个足够小的分子，浮游植物可以直接吸收它，在阳光照射的海洋表面水域，DIP的浓度可以降低到限制水平。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获得，将DOP转化为DIP。越来越多的证据表明，DOP在支持海洋初级生产方面发挥着至关重要的作用，但人们对DOP池的性质知之甚少。在获取多环芳烃的化学结构和组成信息方面存在许多分析障碍，如果不了解其组成，就无法评估多环芳烃对初级生产者的潜在生物利用度。所提出的工作将采用独特的方法组合来获得对DOP的组成和生物利用度的新见解。现场和实验室（培养）营养物添加培养实验将针对DOP变异的驱动因素，这是解决海洋初级生产模型的关键信息。这项工作的结果将对理解DOP组成、DOP在空间和时间上的变化以及微生物对海洋DOP池性质的控制具有革命性意义。本项目资助博士后1人，本科生2人，本科生2人。通过奇卡诺人/西班牙裔美国人和土著美国人科学促进协会（SACNAS）和相关场所，本科学生的招聘将侧重于吸引美洲原住民和太平洋岛民。研究结果将发表在同行评议的期刊上，并在国内和国际会议上发表。我们还建议向中学推广，包括将“艺术海洋学家计划”（The Artistic Oceanographer Program）引入纽约和夏威夷当地的中学，这是一个基于互动式探究的计划，通过将海洋科学素养与艺术的概念结合起来，针对中学年龄的科学和艺术标准。本研究将为DOP分子特征转化为海洋微生物p生物利用度的途径提供基础信息，以及微生物在不同溶解无机氮和溶解无机磷（DIN:DIP）条件下生长如何影响DOP的组成和生物利用度。一种新开发的顺序超滤（SUF）方法将应用于北大西洋西部沿自然p梯度采集的样品。SUF方法将DOP定量分离并浓缩为4个分子量大小的类别，可以使用磷酸水解酶进行生物利用度测定，并通过液相色谱-质谱法提供详细的成分信息。通过这些综合方法，我们将探索原位DOP，不同DIN:DIP下船上孵育期间原位DOP的演变，以及沿天然磷酸盐梯度从关键站点分离的生物产生的DOP的组成和生物利用度。通过识别有机磷生物合成途径中的细胞变化，并追踪这种变化如何影响DOP组成，将原位模式与使用田间分离物进行的对照培养实验进行对比。综合方法学方法将提供对DOP组成和生物利用度的无与伦比的见解，解决这一主要知识空白。这项工作的结果将对理解DOP组成、DOP在空间和时间上的变化以及微生物对海洋DOP池性质的控制具有革命性意义。这些信息是建立生态系统模型的先决条件，这些模型可以捕获磷生物地球化学对水生系统初级生产和碳循环的影响。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

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.