Control of Denitrification in a Permanently Ice Covered Antarctic Lake: Potential for Regulation By Bioactive Metals

abstractopp97 - 25345 - p。反硝化作用是生态系统中固定氮的主要损失项，其速率和调节可能直接影响短期和长期的初级生产和碳循环。这项拟议的研究通过利用一个自然实验系统来调查生物活性金属在调节反硝化中的作用，该实验系统发生在南极洲东部泰勒山谷的一个永久冰雪覆盖的湖泊中。邦尼湖两个裂片的化学分布表明反硝化作用发生在一个裂片而不是另一个裂片。大多数明显的生物和化学变量通常影响反硝化，并可能解释两个叶之间的差异，已被先前的研究排除。反硝化细菌存在于湖泊的两个裂片中，从湖泊中分离出来的细菌显示出与它们在这种环境中的持久性一致的最佳温度和盐度。该研究将结合培养实验和实地考察来检验这一悖论，包括：(1)确定反硝化菌株生长和反硝化所需的金属耐受性和要求的实验，(2)测量表面断面和深度剖面中的金属浓度和金属形态，以及(3)确定反硝化细菌如何应对金属可用性变化的实验。这种方法可以检查邦尼湖微生物活动和金属分布之间的关系，并对其他水生系统的元素循环有影响。此外，这些见解将有助于评估古反硝化指标在过去气候重建中的拟议用途，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。

AbstractOPP97-25345P.I. Mark L. WellsDenitrification 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.