Collaborative Research: Development of a New Instrument for Underway High-Resolution Estimates of Aquatic Gross Primary Production

光合作用可以说是我们气候系统中最关键的生物过程。它也是生态系统营养和新陈代谢状态的中心。因此，对光合作用的精确估计对于我们理解生物地球化学和全球气候至关重要。由于技术的限制，光合作用的空间变异性很难解决；需要开发高分辨率的仪器来缩小这一差距。为了描述海洋光合作用的地理分布，本研究将开发一种通过对溶解氧(O2)同位素进行光谱监测来进行水生光合作用船用测量的仪器。这台名为GOPTICAS(三同位素腔衰荡激光吸收光谱)的仪器将能够通过波长扫描的腔衰荡吸收光谱(CRDS)监测溶解的氧三同位素信号，从而高分辨率地观测光合作用的氧气释放或初级生产力(GPP)。新仪器将把溶解的氧气提取到干燥的气流中，然后在燃料电池中将其转化为水(H2O)，其下游的产出水(H2O)的同位素特征将通过CRDS进行监测。GOPTICAS将1)提供高分辨率、接近实时和精确的GPP比率地图，以指导抽样战略；2)允许简单的实地部署；以及3)可供对海洋和淡水生态系统GPP感兴趣的其他研究小组复制。直接在现场进行测量也将限制与样品处理和长期保存相关的人工制品。该仪器将在Pamlico Sound的R/V Searwater号和墨西哥湾流的短途邮轮上以及东北大陆架LTER邮轮上进行测试。GOPTICAS将改进海洋光合作用生物地理学的特征，这是一种具有深刻生物地球化学意义的微生物过程。一旦开发和验证，GOPTICAS将有助于限制全球碳收支，并最终提高我们对光合作用和气候之间的反馈和耦合的机械理解，并在此过程中为海洋生物地球化学模型提供信息并提出挑战。最后，这项研究将作为一个平台，1)通过在工程和环境科学方面创造基于研究的体验式学习机会，扩大不同人群高中和本科生对STEM的参与；2)教我们的实验室成员如何向公众传播气候科学；3)让学生和公众共同参与关于气候变化的讨论，气候变化是21世纪我们社会面临的最紧迫的问题之一。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Photosynthesis is arguably the most critical biological process of our climate system. It is also central to the trophic and metabolic states of ecosystems. Refining estimates of photosynthesis is therefore critical to our understanding of biogeochemistry and the global climate. Spatial variability of photosynthesis is difficult to resolve due to limitations in technology; the development of high-resolution instrumentation is needed to close this gap. To characterize the geographical distribution of marine photosynthesis, this research will develop an instrument for underway shipboard measurements of aquatic photosynthesis by spectral monitoring of dissolved oxygen (O2) isotopes. Named GOPTICAS (Gross Oxygen Production by Triple Isotope Cavity ringdown laser Absorption Spectroscopy), this instrument will allow for high-resolution observations of photosynthetic O2 evolution, or gross primary production (GPP) by monitoring the dissolved O2 triple isotope signature by wavelength-scanned cavity ring-down absorption spectroscopy (CRDS). The new instrument will extract dissolved O2 into a dried gas stream, then convert it to water (H2O) in a fuel cell downstream of which the isotopic signature of the produced water (H2O) will be monitored with a CRDS. GOPTICAS will 1) provide high-resolution, near real-time and precise mapping of GPP rates to guide sampling strategies, 2) allow for simple field deployment, and finally 3) can be duplicated by other research groups interested in GPP in marine and freshwater ecosystems. Measurements directly in the field will also limit artifacts associated with sample handling and long-term preservation. The instrument will be tested on short cruises aboard the R/V Shearwater in Pamlico Sound and in the Gulf Stream, and on Northeast Shelf LTER cruises. GOPTICAS will improve the characterization of the biogeography of marine photosynthesis, a microbial process with profound biogeochemical implications. Once developed and validated, GOPTICAS will help constrain the global carbon budget and ultimately improve our mechanistic understanding of the feedbacks and coupling between photosynthesis and climate and, in the process, inform and challenge models of ocean biogeochemistry. Finally, this study will be used as a platform to 1) broaden participation in STEM among a diverse population of High School and Undergraduate students through creation of research-based, experiential learning opportunities in engineering and environmental science, 2) teach our lab members how to communicate climate science to the public, and 3) collectively engage students and the public in a discourse about climate change, one of the most pressing issues facing our society in the 21st century.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.