Collaborative Research: Biogeochemistry of Cyanobacterial Mats and Hyporheic Zone Microbes in McMurdo Dry Valley glacial meltwater streams

麦克默多干谷的冰川溪流中有大量的蓝藻垫，它们可能是山谷中固定碳和氮的来源。该研究将考察短暂的冰川溪流中的微生物垫与垫下和垫附近的潜流土壤（湿润土壤带）的微生物群之间的相互作用。研究认为，草席是潜流带土壤群落有机碳和固定氮的重要来源，并释放溶解有机碳（DOC）和氮（DON），为整个干谷生态系统提供服务。实地工作将包括观测和实验两部分。将直接比较垫层和自然复水和干燥垫层区域下的微生物种群，以及亚当斯和迈尔斯山谷冰川融化流中的垫层区域。将研究土壤微生物群的生理和系统发育指标。观察将包括估算土壤细菌对土壤碳和氮的固定速率、土壤呼吸和对赖氨酸和胸苷的摄取（分别作为蛋白质和DNA合成的测量）、细菌密度和它们的分子生态学。实验操作将包括土壤的实验再润湿和微生物群落响应的时间过程的观察。该研究将整合现代分子遗传学方法（ARISA-DNA指纹和超深16S rDNA微生物系统发育分析）和地球化学，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。该项目更广泛的影响包括为研究生和博士后提供研究和教育机会。pi将包括大学生作为勤工俭学学生和REU项目，并将参与教育和推广项目。

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.