Transforming our understanding of DIC Photoproduction in Oceanic Waters

光生产描述了利用太阳光的能量将一种产物的分子结构改变为另一种产物的化学反应。这一过程在沿海海洋溶解有机碳（DOC）向溶解无机碳（DIC）转变过程中发挥了重要作用；然而，关于这一过程在公海中发生的程度的资料很少。获取开阔海域DIC产量数据的主要障碍是无法在海水DIC大背景下测量小DIC产量。目前最常用的高精度测量DIC产品的方法有不可接受的检测限来解决这一差异。佐治亚大学的研究人员开发了mode（中度DI13C同位素富集），这是一种高精度测定公海中低水平DIC的新方法。作为该项目的一部分，他们计划改进他们的mode方法，并在开阔海域（即南大西洋湾、北大西洋和北太平洋亚热带环流）测量DIC光产生。这项工作的结果将提供对开放海洋中DIC光产生的改进估计，这反过来将改进现有的碳循环模型。这个项目的广泛影响尤其令人兴奋。支持者计划在乔治亚大学海洋推广公共水族馆举办一个展览，向公众介绍海洋颜色和海洋碳循环。此外，他们还计划参加斯基德威海洋学研究所。海洋科学日？向公众开放，与公众分享他们的科学成果，并将成果纳入课堂课程。其中一名研究人员是第一次从事研究，他计划将本科生和研究生的教育和培训纳入该项目。最后，来自代表性不足群体的本科生实习生将参与该项目，为他们提供研究经验，并帮助他们留在科学学科和职业生涯中。溶解有机碳（DOC）光产生溶解无机碳（DIC）已被证明是海洋碳循环中一个不可忽视的过程；然而，目前尚不清楚这一过程对公海整体碳循环的程度和重要性（蓝水化学）。造成这种不确定性的主要问题是缺乏具有可接受检测限的可用方法。开放海域DIC的高背景（2mM）使得在检测限高的情况下难以测量DIC的光产生部分。此外，目前最好的方法需要预先剥离背景DIC样本，这可能会由于过度操作样本而引入不必要的误差。该项目将开发一种名为MoDIE（中度DI13C同位素富集）的新方法，以精确测量开放海洋中的DIC光生产。MoDIE的工作原理是用13C富集样品，并使用液相色谱-同位素比质谱法（LC-IRMS）监测辐照下DI13C的稀释度。通过消除样品前处理的需要和引入一种高度精确的测量技术，研究人员将能够将他们的技术与已发表的光化学DIC检测方法进行比较，并对全球海洋中海洋DIC光产生提出更准确的估计。这将大大改善海洋碳循环模型。

Photoproduction describes chemical reactions which use the energy of sunlight to change the molecular structure of one product to another. This process has been shown to play an important role in the coastal ocean changing dissolved organic carbon (DOC) to dissolved inorganic carbon (DIC); however, minimal information is available on the extent to which this process takes place in the open ocean. The main obstacle to obtaining DIC production data for open ocean waters is the inability to measure the small DIC production rates against the large background of seawater DIC. Currently the most common method for high precision measurement of DIC production has unacceptable detection limits to resolve this difference. Researchers from the University of Georgia have developed MoDIE (Moderate DI13C Isotope Enrichment), a novel means of determining low levels of DIC produced in the open ocean with high precision. As part of this project, they plan to refine their MoDIE method and obtain measurements of DIC photoproduction in open ocean waters (i.e, South Atlantic Bight, North Atlantic Ocean and North Pacific Ocean subtropical gyres). Results from this work will provide improved estimates of DIC photoproduction in the open ocean which in turn will improve existing models of carbon cycling. The broader impacts of this project are particularly exciting. The proponents plan to create an exhibit at the University of Georgia Marine Extension public aquarium to teach the general public about ocean color and marine carbon cycling. In addition, they plan to participate in the Skidaway Institute for Oceanography ?Marine Science Day? open house to share their science with the public and incorporate results into their class curricula. One of the researchers is a first-time investigator who plans to incorporate education and training of undergraduate and graduate students in the project. Finally, undergraduate interns from underrepresented groups will be involved in the project to give them research experience and help with retention in a science discipline and career.Photoproduction of dissolved inorganic carbon (DIC) from dissolved organic carbon (DOC) has been shown to be a non-negligible process in the marine carbon cycle; however, it is still unclear the extent and importance of this process to the overall carbon cycle in the open ocean (blue water chemistry). The major issue causing this uncertainty is the lack of available methods with acceptable detection limits. The high background of DIC in the open ocean (2mM) makes it difficult to measure the photoproduced portion of DIC when the detection limits are high. Additionally, the current best method requires pre-stripping samples of background DIC, which could introduce unnecessary errors by over manipulating samples. This project will develop a new method called MoDIE (Moderate DI13C Isotope Enrichment) to get accurate measurements of DIC photoproduction in the open ocean. MoDIE works by enriching a sample in 13C and monitoring the dilution of DI13C under irradiation using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). By removing the need for pre-sample treatment and introducing a highly precise measurement technique, the researchers will be able to compare their techniques with published methods of photochemical DIC detection and put forth more accurate estimate of marine DIC photoproduction in the global ocean. This will greatly improve marine carbon cycle models.