Molybdenum Biogeochemistry in the Open Ocean

摘要：在这项研究中，伍兹霍尔海洋研究所的研究人员将对开阔海洋中钼的海洋化学进行仔细研究。 目前认为Mo在公海中表现为保守元素，因此在这种环境中具有相对不感兴趣的化学性质。 然而，已经确定钼是硝酸还原酶和最常见形式的固氮酶所需的重要微量营养素，固氮酶是生物体分别利用硝酸盐和固定氮（N）所需的酶。 PI预计，悬浮颗粒物（SPM）和过滤海水中钼的足够精确的分析将揭示可能与钼的生物利用有关的变化。该提案的具体目标是：（1）确定钼在东太平洋的非保守分布是否是生物利用钼的结果;（2）确定悬浮颗粒物中钼的富集是否是生物利用钼与反硝化和/或固氮有关的结果。 实现这些目标是必要的，以评估钼富集作为海洋氮循环的这些重要组成部分的示踪剂的潜力。 此外，这项工作可能有助于更好地了解海洋中铁（Fe）的生物需求，因为生物利用钼和铁是耦合的。 为实现上述目标，研究者将：（1）确定来自东太平洋几个地点的过滤和未过滤海水样品中Mo的垂直分布，这些地点代表反硝化和氧化锰氧化还原循环的对比机制，（2）完成一套实验室培养实验，旨在验证我们的假设，即细胞钼浓度与钼水平的协变，（3）收集和分析来自支持活性反硝化和固氮的区域的SPM，以建立与成岩碎屑、锰氧化物和生物源物质相关的Mo的相对比例。 在完成拟议的工作后，调查人员希望能够对海水中溶解和/或颗粒Mo作为反硝化，固氮或Fe利用示踪剂的分析潜力进行一级评估。 此外，他们希望深入了解非限制性微量营养素的生物利用模式。

ABSTRACTOCE-0096453In this study, researchers at the Woods Hole Oceanographic Institution will conduct a careful study of the marine chemistry of molybdenum (Mo) in the open ocean. Mo is currently believed to behave as a conservative element in the open ocean and therefore to have a relatively uninteresting chemistry in this environment. However, it is well established that Mo is an important micro-nutrient that is required in nitrate reductase and in the most common form of nitrogenase, enzymes which are required for organisms to utilize nitrate and to fix nitrogen (N), respectively. The PIs expect that sufficiently precise analyses of Mo in suspended particulate matter (SPM), and in filtered seawater will reveal variations that are potentially related to biological utilization of Mo. The specific objectives of this proposal are: (1) to establish whether or not non-conservative distributions of Mo in the eastern Pacific result from biological utilization of Mo; and (2) to determine whether or not enrichments of Mo in SPM result from biological utilization of Mo in association with denitrification and/or N-fixation. Accomplishing these objectives is necessary in order to evaluate the potential of Mo enrichments as tracers of these important components of the marine nitrogen cycle. In addition, this work could contribute to a better understanding the biological demand for iron (Fe) in the ocean because biological utilization of Mo and Fe are coupled. To accomplish the objectives stated above the investigators will: (1) determine the vertical distribution of Mo in filtered and unfiltered seawater samples from several sites in the eastern Pacific that represent contrasting regimes of denitrification and Mn oxide redox cycling, (2) complete a suite laboratory culture experiments designed to test our hypothesis that cellular Mo concentration covary with levels of Mo-containing enzyme activity and (3) collect and analyze SPM from regions that support active denitrification and N-fixation in order to establish the relative proportions of Mo associated with lithogenic debris, Mn oxides and biogenic material. Upon completing the proposed work the investigators expect to be able to make a first order assessment of the potential of analyses of dissolved and/or particulate Mo in seawater as tracers of denitrification, N-fixation or Fe-utilization. In addition, they hope to gain insight into the patterns of biological utilization of a non-limiting micronutrient.