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南极洲弗里克塞尔湖底部微生物生命的年度变化。由于其极地纬度，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，目前尚不清楚微生物在黑暗的冬季如何表现，因为当时无法进行观察。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。这些阴影将把冬季条件延长到春季，使研究人员能够描述微生物群落的冬季行为。研究人员将测量当阴影被移除并且垫子第一次接受光线时由于微生物活动引起的水化学变化。预计结果将提供深入了解生物体如何与环境相互作用并改变环境。该项目包括对研究生和早期职业科学家进行实地工作培训，包括科学的冰上潜水技术。此外，项目小组成员将编制一份网上“茁壮成长指南”，其中将汇编从基本渔具使用到先进环保技术的实地提示。这将是一个宝贵的资源，从本科教学助理到南极考察队领导人领导精心策划和量身定制的实地考察。 第二部分：技术摘要：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生产引起的生态系统效应。为此，研究人员将在湖中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，将对阴影和未阴影的垫子进行采样。然后将去除阴影，并使用微电极测量孔隙水O2，H2S，pH值和氧化还原的变化。还将根据地球化学变化的指导间隔对垫进行转录组基因表达分析。将对孔隙水进行取样，用于营养分析。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的生产力和氮循环的季节性模型中。研究结果将为NSF的几个关键优先事项提供深入的见解，包括底栖垫的生物，非生物和环境成分如何相互作用影响南极湖泊。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.