Production and Fate of Oxylipins in Waters of the Western Antarctic Penninsula: Linkages Between UV Radiation, Lipid Peroxidation, and Carbon Cycling

南极洲上空平流层臭氧的消耗导致到达海洋表面的太阳紫外线辐射（UVR）水平异常高。这一现象预计将持续半个世纪，尽管禁止破坏臭氧层的污染物。近海面的浮游植物受到不同程度的紫外线辐射，并含有大量的脂类（脂肪）。由于浮游植物处于食物链的底部，它们的脂质进入南极海洋生态系统的食物网。浮游植物脂类的分子结构在紫外线照射下容易发生改变。当这种情况发生时，它们的脂质可以从健康分子转化为潜在的有害分子（氧脂素），已知会破坏生殖和发育过程。该项目将使用最先进的分子方法来回答以下问题：紫外线辐射在多大程度上损害了浮游植物中的脂质分子，以及这些分子如何影响南极洲附近海洋的食物链。脂质过氧化通常被认为是浮游植物暴露于uvr产生的活性氧（ROS）的增加的结果，但文献实际上对海洋中过氧化脂质及其副产物（即氧化脂质）保持沉默。在南极半岛西部（WAP）水域，春季硅藻华对海洋初级生产的总体贡献显著。硅藻中的氧脂类具有很高的生物活性；它们对浮游动物、细菌和其他浮游植物的影响一直是人们密切研究的主题。然而，几乎所有这些工作都集中在通过酶促途径产生氧化脂素，而不是通过涉及UVR和/或ROS的途径。此外，关于氧化脂素作用的严格实验工作几乎完全局限于纯培养物和人工群落。因此，这些分子破坏碳循环的真正潜力是非常有限的，在WAP的水域是完全未知的。利用基于高质量分辨率质谱法的新型高灵敏度、最先进的分析技术，首席研究员和他的研究小组已经开始在天然WAP浮游生物群落中发现精致的氧化脂质多样性。这些技术将应用于了解UVR， ROS，氧化脂素和碳循环之间的联系。该项目将在一个实地站进行的对照实验中回答紫外线辐射如何通过活性氧影响WAP地表水中硅藻生产氧化脂素的问题。有了这个问题的答案，该项目还将在研究巡航期间寻求回答这种现象如何影响碳的流动，特别是系统中有机碳的出口。WAP中富含氧脂素的浮游生物群落所经历的uvr诱导的应激水平是独一无二的，这使得南极洲成为回答这些基本问题的唯一地点。主要活动将包括人工膜和硅藻培养的实验室实验，以及在WAP水域进行浮游植物、浮游动物和细菌的实地实验。

The depletion of stratospheric ozone over Antarctica leads to abnormally high levels of ultraviolet radiation (UVR) from the sun reaching the surface of the ocean. This phenomenon is predicted to continue for the next half century, despite bans on ozone-destroying pollutants. Phytoplankton in the near surface ocean are subjected to variable amounts of UVR and contain a lot of lipids (fats). Because phytoplankton are at the base of the food chain their lipids makes their way into the Antarctic marine ecosystem's food web. The molecular structures of phytoplankton lipids are easily altered by UVR. When this happens, their lipids can be transformed from healthy molecules into potentially harmful molecules(oxylipins) known to be disruptive to reproductive and developmental processes. This project will use state-of-the-art molecular methods to answer questions about extent to which UVR damages lipid molecules in phytoplankton, and how these resultant molecules might effect the food chain in the ocean near Antarctica. Lipid peroxidation is often invoked as consequence of increased exposure of phytoplankton to UVR-produced reactive oxygen species (ROS), but the literature is practically silent on peroxidized lipids and their byproducts (i.e. oxylipins) in the ocean. In waters of the West Antarctic Peninsula (WAP), spring-time blooms of diatoms contribute significantly to overall marine primary production. Oxylipins from diatoms can be highly bioactive; their impact on zooplankton grazers, bacteria, and other phytoplankton has been the subject of intense study. However, almost all of this work has focused on the production of oxylipins via enzymatic pathways, not by pathways involving UVR and/or ROS. Furthermore, rigorous experimental work on the effects of oxylipins has been confined almost exclusively to pure cultures and artificial communities. Thus, the true potential of these molecules to disrupt carbon cycling is very poorly-constrained, and is entirely unknown in the waters of the WAP. Armed with new highly-sensitive, state-of-the-art analytical techniques based on high-mass-resolution mass spectrometry, the principal investigator and his research group have begun to uncover an exquisite diversity of oxylipins in natural WAP planktonic communities. These techniques will be applied to understand the connections between UVR, ROS, oxylipins, and carbon cycling. The project will answer the question of how UVR, via ROS, affects oxylipin production by diatoms in WAP surface waters in controlled experiments conducted at a field station. With the answer to this question in hand, the project will also seek to answer how this phenomenon impacts the flow of carbon, particularly the export of organic carbon from the system, during a research cruise. The level of UVR-induced stresses experienced by oxylipin-rich planktonic communities in the WAP is unique, making Antarctica the only location for answering these fundamental questions. Major activities will include laboratory experiments with artificial membranes and diatom cultures, as well field experiments with phytoplankton, zooplankton, and bacteria in WAP waters.