Water Column Transformations of Nitrogen in a Perennially Ice-Covered Antarctic Lake

永久冰雪覆盖的邦尼湖是南极的一个湖泊，有两个不同的裂片，呈现出一种特殊的情况，在那里湍流和上层营养水平几乎不存在。这种不寻常的环境产生了一个微生物介导的过程主导生物地球化学反应的系统。目前关于邦尼湖氮动态的信息表明，浮游植物是缺氮的，东叶的化斜区氧化亚氮浓度是自然界中有记录以来最高的，东叶不存在大量反硝化作用，而西叶的氮值是水生系统中测量到的最高的。假设1)氨氮和氧化氮都是上层滋养带的重要再生营养物质；2)氧化亚氮是硝化作用的产物；3)大量反硝化作用是氧化亚氮在西叶的汇，调节其积累。这些假设将通过测量氨、亚硝酸盐和硝酸盐的微生物再生和利用、氧化亚氮的生产以及硝化和反硝化细菌的分布来解决。这项研究将是第一个在缺乏“自上而下”调节的系统中检查氮动力学的研究之一，并将提供有关微生物氧化亚氮生产的重要线索。该项目由美国国家科学基金会和美国国家航空航天局联合资助。

Permanently ice-covered Lake Bonney, an Antarctic lake with two distinct lobes, presents a special situation where turbulence and upper trophic levels are virtually non-existent. This unusual environment yields a system where microbially-mediated processes dominate biogeochemical reactions. Current information on nitrogen dynamics in Lake Bonney indicates that phytoplankton are nitrogen-deficient, that nitrous oxide concentration in the chemocline of the east lobe is the highest recorded in nature, that bulk denitrification does not exist in the east lobe and that nitrogen values in the west lobe are the highest ever measured in an aquatic system. It is hypothesized that 1) both ammonia and oxidized nitrogen are significant regenerated nutrients in the upper trophogenic zone, 2) nitrous oxide is a product of nitrification and 3) bulk denitrification acts as a sink for nitrous oxide in the west lobe, regulating its accumulation. These hypotheses will be addressed by measuring microbial regeneration and utilization of ammonia, nitrite and nitrate, nitrous oxide production, and the distribution of nitrifying and denitrifying bacteria. This study will be one of the first to examine nitrogen dynamics in a system lacking "top- down" regulation and will provide important clues regarding microbial nitrous oxide production. This project is jointly supported by the National Science Foundation and the National Aeronautics and Space Administration.