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的海洋化学进行仔细的研究。钼目前被认为在开阔的海洋中表现为一种保守的元素，因此在这种环境中有一种相对乏味的化学作用。然而，众所周知，钼是硝酸还原酶和最常见的固氮酶所需的一种重要的微量营养物质，这两种酶分别是生物体利用硝酸盐和固定氮所需的酶。PIS预计，对悬浮颗粒物(SPM)和过滤后的海水中钼的足够精确的分析将揭示与钼的生物利用潜在相关的变化。这项建议的具体目标是：(1)确定东太平洋中钼的非保守分布是否源于钼的生物利用；以及(2)确定钼在SPM中的富集性是否源于与反硝化和/或固氮有关的钼的生物利用。实现这些目标是必要的，以便评估钼富集作为海洋氮循环这些重要组成部分的示踪剂的潜力。此外，这项工作有助于更好地了解海洋对铁(Fe)的生物需求，因为钼和铁的生物利用是耦合的。为了实现上述目标，研究人员将：(1)确定东太平洋几个地点过滤和未过滤海水样品中钼的垂直分布，这些样品代表了反硝化和氧化锰氧化还原循环的不同模式；(2)完成一套实验室培养实验，旨在验证我们的假设，即细胞中的钼浓度与含钼酶活性水平有关；(3)收集并分析支持活跃反硝化和固氮作用地区的SPM，以确定与成岩碎屑、锰氧化物和生物物质相关的钼的相对比例。在完成拟议的工作后，调查人员预计将能够对海水中溶解和/或微粒钼作为反硝化、固氮或铁利用示踪剂的潜力进行第一级评估。此外，他们还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.