Cycling of Vitamin B12 in the Ocean

035199尽管有超过65种浮游植物对维生素B12具有营养缺乏性，这意味着它们的生长需要外源供应，但对海洋初级生产力的有机调节还不是很清楚。虽然在过去10年中，一项主要的研究工作旨在了解微量金属和其他无机微量营养素对浮游植物生产的重要性，但人们忽视了有机生长因素，如维生素B12的作用。对海洋环境中维生素B12的循环缺乏明确认识，也妨碍了对世界海洋某些区域观察到的甲烷产生、有机螯合剂的形成(可能控制钴等一些生物活性痕量金属的生物可利用性)以及浮游植物组合变化(从需要维生素的物种到不需要维生素的物种)的了解。不幸的是，缺乏一种快速可靠的技术来量化维生素B12，阻碍了海洋环境中维生素B12研究的进展。在这项研究中，纽约州立大学石溪分校的研究人员开发了一种直接测定海水中维生素B12的新方法，该方法采用固相萃取预浓缩，反相高效液相色谱梯度洗脱定量，紫外-可见吸收检测。通过使用这项新技术，研究人员将在不同的生物地球化学省份研究维生素B12的海洋循环。需要这些信息来评估这种维生素在海洋环境中的重要性，以及验证以前使用生物测定技术进行的研究。选定实地考察地点是为了提供有关维生素B12在各种海洋环境(南大洋、马尾藻海、加利福尼亚州中部和下加利福尼亚州的上升区、Cariaco盆地和沿海环境)中循环的最大量信息。这些B12的测量将使用一套分析来确定被采样水中的主要浮游植物类群，以及DOC、POC、PON、叶绿素a、无机营养物质和细菌生物量的分析。在不同的海洋环境中确定B12循环，不仅可以更好地理解影响“生物泵”的过程，而且还可以更好地了解世界海洋中的甲烷。因此，这种新的维生素B12方法的应用有可能在进一步了解如何增强海洋的碳固定能力方面发挥至关重要的作用。

ABSTRACTOCE-035199 The organic regulation of primary production in the ocean is not well understood, despite the fact that more than 65 species of phytoplankton are known to be auxotrophic for vitamin B12, meaning they require exogenous supplies for growth. While a major research effort has been directed in the last 10 years to understand the importance of trace metals and other inorganic micronutrients on phytoplankton production, the role of organic growth factors such vitamin B12 has been overlooked. The lack of clear understanding of the cycling of vitamin B12 in the marine environment has also hindered the understanding of methane production, the formation of organic chelators (which may control the bioavailability of some bioactive trace metals such as cobalt), and phytoplankton assemblage shifts (from vitamin-requiring to non-vitamin-requiring species) observed in some regions of the world ocean. Unfortunately, the lack of availability for a quantifying B12 in a quick and reliable technique has hindered the progress of vitamin B12 studies in the marine environment. In this study, researchers at SUNY at Stony Brook have developed a new method for the direct determination of vitamin B12 in seawater by pre-concentration using solid phase extraction, quantification using reversed phase HPLC with gradient elution, and detection by UV-visible absorption. By using this new technique the researchers will study the marine cycling of vitamin B12 in various biogeochemical provinces. This information is needed to evaluate the importance of this vitamin in the marine environment, as well as to validate previous studies carried out using the bioassay technique. The field study sites have been selected to give the maximum amount of information about the cycling of vitamin B12 in a broad range of marine environments (Southern Ocean, Sargasso Sea, upwelling regions of central and Baja California, the Cariaco Basin and a coastal environment). These B12 measurements will be interpreted using a suite of analyses to determine the dominant phytoplankton groups in the water being sampled, as well as analyses of DOC, POC, PON, chlorophyll a, inorganic nutrients and bacterial biomass. The determination of B12 cycling in contrasting oceanographic regimes will not only provide a better understanding of the processes influencing the "biological pump" but also of methane in the world ocean. Therefore, the application of this new vitamin B12 method has the potential to play a vital role in furthering our understanding of how the carbon sequestration capacity of the ocean could be enhanced.