Seasonal Primary Productivity and Nitrogen Cycling in Photosynthetic Mats, Lake Fryxell, McMurdo Dry Valleys

第一部分：非技术总结：该项目的重点是了解生长在南极洲弗里克塞尔湖底的微生物生命的年度变化。由于其极纬度，光合作用只能在夏季发生。在夏季，光合细菌为群落提供能量和氧气。然而，目前尚不清楚这些微生物在黑暗的冬季是如何表现的，因为当时不可能进行观察。该项目将在这些社区的部分地区安装环境监测器和遮光罩。遮阳棚将把冬季的条件延长到春季，使研究人员能够描述微生物群落的冬季行为。研究人员将测量由于微生物活动而导致的水化学变化，当遮阳物被移除，席子第一次接收到光。研究结果有望为生物体如何与环境相互作用和改变环境提供见解。该项目包括对研究生和早期职业科学家进行实地考察的培训，包括科学的冰潜技术。此外，项目团队成员将开发一个基于网络的“茁壮成长指南”，其中将汇编从基本装备使用到先进环保技术的现场提示。这将是一个宝贵的资源，小组领导，从本科助教到南极考察领导，领导精心策划和量身定制的实地考察。第二部分：技术总结：研究小组将利用差异基因表达和地球化学梯度测量底栖垫的季节性代谢和生物地球化学变化。他们将确定微生物群落的季节性表型差异和春季氧气产生引起的生态系统效应。为了做到这一点，研究人员将在湖的三个深度的垫子上安装环境传感器和不透明的阴影。第二年春天，将对遮荫和未遮荫的垫子进行取样。然后去除阴影，并使用微电极测量孔隙水O2， H2S， pH和氧化还原的变化。在地球化学变化的指导下，草席也将取样进行转录组基因表达分析。将对孔隙水取样进行营养分析。实地研究将辅以实验室实验，以完善实地技术、基因表达数据分析，并将结果整合到弗里克塞尔湖生产力和氮循环的季节性模型中。结果将为NSF的几个关键优先事项提供见解，包括底栖垫的生物，非生物和环境成分如何相互作用以影响南极湖泊。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。

Part I: Non-technical summary:This project focuses on understanding annual changes in microbial life that grows on the bottom of Lake Fryxell, Antarctica. Because of its polar latitude, photosynthesis can only occur during the summer months. During summer, photosynthetic bacteria supply communities with energy and oxygen. However, it is unknown how the microbes behave in the dark winter, when observations are not possible. This project will install environmental monitors and light-blocking shades over parts of these communities. The shades will extend winter conditions into the spring to allow researchers to characterize the winter behavior of the microbial communities. Researchers will measure changes in the water chemistry due to microbial activities when the shades are removed and the mats first receive light. Results are expected to provide insights into how organisms interact with and change their environments. The project includes training of graduate students and early career scientists in fieldwork, including scientific ice diving techniques. In addition, the members of the project team will develop a web-based “Guide to Thrive”, which will compile field tips ranging from basic gear use to advanced environmental protection techniques. This will be a valuable resource for group leaders ranging from undergraduate teaching assistants to Antarctic expedition leaders to lead well-planned and tailored field expeditions. Part II: Technical summary:The research team will measure seasonal metabolic and biogeochemical changes in benthic mats using differential gene expression and geochemical gradients. They will identify seasonal phenotypic differences in microbial communities and ecosystem effects induced by spring oxygen production. To do so, researchers will install environmental sensors and opaque shades over mats at three depths in the lake. The following spring, shaded and unshaded mats will be sampled. The shades will then be removed, and changes in pore water O2, H2S, pH, and redox will be measured using microelectrodes. Mats will also be sampled for transcriptomic gene expression analyses at intervals guided by geochemical changes. Pore water will be sampled for nutrient analyses. Field research will be supplemented with laboratory experiments to refine field techniques, gene expression data analysis, and integration of results into a seasonal model of productivity and nitrogen cycling in Lake Fryxell. Results will provide insights into several key priorities for NSF, including how biotic, abiotic and environmental components of the benthic mats interact to affect Antarctic lakes.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.