Control of Denitrification in a Premanently Ice Covered Antarctic Lake: Potential for a Regulation by Bioactive Metals

摘要OPP 98 - 17617 P.I. 贝丝B。沃德反硝化作用是生态系统中固定氮的主要损失形式，其速率和调控直接影响着生态系统的初级生产力和碳循环。 拟议的研究调查生物活性金属在调节反硝化作用中的作用，通过利用发生在南极洲东部泰勒谷永久冰封的湖泊中的自然实验系统。 邦尼湖的两个叶的化学分布意味着反硝化作用发生在一个叶，而不是其他。 大多数明显的生物和化学变量，通常影响反硝化作用，并可能解释两个叶之间的差异，已被排除在以前的研究。 反硝化细菌存在于两个叶的湖泊和分离物来自湖泊显示的温度和盐度的最佳与他们在这种环境中的持久性。 拟议的研究代表了文化实验和实地工作的结合，以研究这一悖论，包括：（1）通过实验确定金属耐受性以及微生物分离物生长和反硝化的要求，（2）测量表面剖面和深度剖面中的金属浓度和金属形态，（3）确定微生物如何对金属有效性的改变作出反应的实验。 这种方法可以检查微生物的活动和金属分布在邦尼湖之间的关系，并在其他水生系统中的元素循环的影响。 此外，这些见解将有助于评估过去气候重建的古反硝化指标的拟议使用，以及全球海洋反硝化/固氮比对大气二氧化碳水平的潜在意义。

AbstractOPP98-17617P.I. Bess B. Ward Denitrification is the main loss term for fixed nitrogen from ecosystems, and thus its rate and regulation may directly affect primary production and carbon cycling over short and long time scales. The proposed research investigates the role of bioactive metals in regulating denitrification by exploiting a natural experimental system that occurs in a permanently ice-covered lake in the Taylor Valley of East Antarctica. Chemical distributions in the two lobes of Lake Bonney imply that denitrification occurs in one lobe but not the other. Most of the obvious biological and chemical variables that usually influence denitrification, and might account for the difference between the two lobes, have been ruled out by previous study. Denitrifiying bacteria are present in both lobes of the lake and isolates derived from the lake show temperature and salinity optima consistent with their persistence in this environment. The proposed research represents a combination of culture experiments and field work to examine this paradox, and include: (1) Experiments to determine the metal tolerances and requirements for growth and denitrification by the denitrifying isolates, (2) Measurement of metal concentrations and metal speciation in surface transects and depth profiles, and (3) Experiments to determine how denitrifying bacteria respond to alterations in metal availability. This approach allows examination of the relationship between microbial activity and metal distributions in Lake Bonney and has implications for elemental cycling in other aquatic systems. Moreover, the insights will be useful for evaluating the proposed used of paleo-denitrification indicators for past climate reconstructions, as well as the potential significance of the global marine denitrification/nitrogen fixation ratio on atmospheric carbon dioxide levels.