Collaborative Research: Manganese Cycling and Coupling Across Redox Boundaries within Stratified Basins of the Baltic Sea

微量元素锰（Mn）广泛分布于全球海洋中，在三种主要氧化态之间循环。处于较高氧化态的锰是高度反应性的，从而影响几乎所有其他元素循环的循环，包括氧和氮的循环。中间锰物种最近才被认为是锰池的丰富组成部分，现在提出了一个以前未被认识到的因素，可能会控制海洋的化学。波罗的海的锰浓度很高，初步调查表明存在操作上定义的“反应性”形式的锰，但该锰池的组成和后果尚不清楚。这项研究将探讨锰在波罗的海内的循环，这是与位于德国瓦尔内明德的莱布尼茨波罗的海研究所合作完成的。通过耦合现场测量和有针对性的船上孵化，这项研究将揭示控制锰循环的过程及其与氧，碘和氮循环的联系。该项目将教育一些本科生和研究生，并促进美国和德国研究小组之间的科学交流。此外，与这项研究相关的推广工作将继续现有的PI和南波士顿的波士顿绿色学院之间的合作，向高中学生介绍化学海洋学，特别是海洋地球化学。锰（Mn）是错综复杂地联系在一起，几乎所有的元素周期，但我们知道的过程中，它的氧化还原循环在自然系统中。在过去的十年中，一些关键的科学发现提供了更深入的了解锰氧化还原循环的过程和机制的多样性，并介绍了锰（III）配体络合物作为溶解的锰池的重要组成部分。波罗的海是一个最好的研究分层海洋系统和活性锰已牵连作为一个关键因素的形成和维持的亚氧区。因此，本研究的目标是探索循环和元素耦合的锰内分层盆地的波罗的海。PI预测，活性锰，锰（III）配体配合物和锰氧化物颗粒，是一个主要的控制分层海洋沃茨的氧化还原景观，特别是在氧化还原边界和内的亚氧化带。PI建议在当地永久分层的咸水池塘进行实地考察，以完善实验程序，然后与瓦尔内明德的莱布尼茨波罗的海研究所合作，对波罗的海的亚氧盆地进行两次巡航。现场测量将获得使用原位传感器和船舶/实验室为基础的仪器在几个波罗的海站点的组合，以确定锰物种的分布和锰氧化还原转换率跨越氧化还原跃层沿着与一套化学信息。此外，将进行船载培养的矩阵，以限制潜在的（a）生物过程负责观察到的锰配置文件。具体来说，在氧和锰梯度跨越氧化还原跃层，PI将询问锰循环和碘和氮物种之间的联系，这将最终有助于限制在波罗的海models.This奖项的这些元素的质量平衡目前的差距反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The trace element manganese (Mn) is distributed widely throughout the global ocean where it cycles among three dominant oxidation states. Manganese in the higher oxidation states is highly reactive and thereby influences the cycling of nearly all other elemental cycles, including those of oxygen and nitrogen. The intermediate Mn species has only recently become recognized as an abundant component of the Mn pool, presenting now a previously unrecognized factor that may control the chemistry of the ocean. The Baltic Sea contains high Mn concentrations and preliminary investigations have pointed to the presence of an operationally defined "reactive" form of Mn but the composition and consequence of this Mn pool are unknown. This research will explore the cycling of Mn within the Baltic Sea enabled by an established collaboration with the Leibniz Institute for Baltic Sea Research in Warnemunde, Germany. By coupling field measurements and targeted shipboard incubations, this study will shed light on the processes controlling the Mn cycle and its link to the oxygen, iodine, and nitrogen cycles. This project will educate several undergraduate and graduate students and promote scientific exchange between research groups within the United States and Germany. Further, outreach efforts associated with this research will continue an existing collaboration between the PIs and the Boston Green Academy in South Boston to introduce high school students to chemical oceanography, and in particular biogeochemistry.Manganese (Mn) is intricately linked to nearly all elemental cycles, and yet we know little about the processes governing its redox cycling within natural systems. Over the past decade a number of key scientific discoveries have provided greater insight into the diversity of processes and mechanisms involved in Mn redox cycling and introduced Mn(III) ligand complexes as important components of the dissolved Mn pool. The Baltic Sea is one of the most well studied stratified marine systems and reactive Mn has been implicated as a key factor in the formation and maintenance of suboxic zones. Thus, the goal of this research is to explore the cycling and elemental coupling of Mn within stratified basins of the Baltic Sea. The PIs predict that reactive Mn, as Mn(III) ligand complexes and Mn oxide particles, is a primary control on the redox landscape of stratified marine waters, particularly at redox boundaries and within the suboxic zone. The PIs propose fieldwork in a local permanently stratified brackish pond to refine experimental procedures followed by two cruises to suboxic basins in the Baltic Sea enabled by an established collaboration with the Leibniz Institute for Baltic Sea Research in Warnemunde. Field measurements will be obtained using a combination of in situ sensors and ship/lab-based instrumentation at several Baltic Sea sites to define the distribution of Mn species and the rates of Mn redox transformations spanning the redoxcline along with a suite of chemical information. Further, a matrix of shipboard incubations will be conducted to constrain the underlying (a)biotic processes responsible for the observed Mn profiles. Specifically, across oxygen and Mn gradients spanning the redoxcline, the PIs will interrogate the link between the Mn cycle and iodine and nitrogen species, which will ultimately help constrain current gaps in the mass balance of these elements in Baltic Sea models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.