Collaborative Research: Biogeochemistry of Cyanobactrial Mats and Hyporheic Zone Microbes in McMurdo Dry Valley Glacial Meltwater Streams

麦克默多干河谷的冰川溪流有广泛的蓝藻垫子，这可能是山谷固定碳和氮的来源。这项研究将研究短暂冰川溪流中的微生物垫子与这些垫子下面和邻近的浅层土壤(湿润土层)的微生物群之间的相互作用。据推测，草席是低渗带土壤群落有机碳和固定氮的重要来源，并释放出服务于整个干谷生态系统的溶解有机碳(DOC)和氮(DON)。实地工作将包括观测和实验两个部分。将直接比较垫子和天然补水和干燥垫子下的微生物种群，以及迈尔斯河谷亚当斯和迈尔斯冰川融流中的垫子区域。将检查土壤微生物区系的生理和系统发育指数。观察将包括估计土壤细菌的固定碳和氮的速率、土壤呼吸和亮氨酸和胸腺嘧啶核苷的吸收(分别作为蛋白质和DNA合成的衡量标准)、细菌密度及其分子生态。实验操作将包括土壤的实验重新润湿和对微生物群落反应时间过程的观察。这项研究将把现代分子遗传学方法(ARSA-DNA指纹和超深16S rDNA微生物系统发育分析)与地球化学相结合，研究在这些极端环境中茁壮成长的微生物群落的多样性、生态学和功能。该项目的更广泛影响包括为研究生和博士后助理提供研究和教育机会。P.I.将让本科生作为勤工俭学的学生参加REU项目，并将参与教育和外展项目。

The glacial streams of the McMurdo Dry Valleys have extensive cyanobacterial mats that are a probable source of fixed C and N to the Valleys. The research will examine the interplay between the microbial mats in the ephemeral glacial streams and the microbiota of the hyporheic soils (wetted soil zone) underlying and adjacent to those mats. It is hypothesized that the mats are important sources of organic carbon and fixed nitrogen for the soil communities of the hyporheic zone, and release dissolved organic carbon (DOC) and nitrogen (DON) that serves the entire Dry Valley ecosystem. Field efforts will entail both observational and experimental components. Direct comparisons will be made between the mats and microbial populations underlying naturally rehydrated and desiccated mat areas, and between mat areas in the melt streams of the Adams and Miers Glaciers in Miers Valley. Both physiological and phylogenetic indices of the soil microbiota will be examined. Observations will include estimates of rates of mat carbon and nitrogen fixation, soil respiration and leucine and thymidine uptake (as measures of protein & DNA synthesis, respectively) by soil bacteria, bacterial densities and their molecular ecology. Experimental manipulations will include experimental re-wetting of soils and observations of the time course of response of the microbial community. The research will integrate modern molecular genetic approaches (ARISA-DNA fingerprinting and ultra deep 16S rDNA microbial phylogenetic analysis) with geochemistry to study the diversity, ecology, and function of microbial communities that thrive in these extreme environments. The broader impacts of the project include research and educational opportunities for graduate students and a postdoctoral associate. The P.I.s will involve undergraduates as work-study students and in REU programs, and will participate in educational and outreach programs.