Molybdenum Biogeochemistry in the Open Ocean

在这项研究中，伍兹霍尔海洋研究所的研究人员将对公海中钼（Mo）的海洋化学进行仔细研究。目前认为，Mo在公海中表现为一种保守元素，因此在这种环境中具有相对无趣的化学性质。然而，Mo是一种重要的微量营养物质，是硝酸盐还原酶和最常见形式的氮酶所必需的，这两种酶分别是生物体利用硝酸盐和固定氮(N)所必需的。pi期望对悬浮颗粒物（SPM）和过滤海水中的Mo进行足够精确的分析，将揭示可能与Mo的生物利用有关的变化。该提案的具体目标是：(1)确定东太平洋中Mo的非保守分布是否源于Mo的生物利用；(2)确定SPM中Mo的富集是否源于Mo的生物利用与反硝化和/或固氮作用。为了评价Mo富集物作为海洋氮循环这些重要组成部分的示踪剂的潜力，实现这些目标是必要的。此外，由于Mo和Fe的生物利用是耦合的，本研究有助于更好地了解海洋中对铁（Fe）的生物需求。为实现上述目标，调查人员将：(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，这些样品代表了反硝化和锰氧化物氧化还原循环的不同制度；(2)完成一套实验室培养实验，旨在验证我们的假设，即细胞Mo浓度与含Mo酶活性水平相关；(3)收集和分析支持活性反硝化和固氮的区域的SPM，以确定与岩石碎屑、Mn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，研究人员希望能够对海水中溶解和/或颗粒Mo作为反硝化，固氮或铁利用示踪剂的分析潜力进行一级评估。此外，他们希望深入了解一种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.