Vitamin and trace metal dynamics in the Southern Ocean: The Biological input vs removal processes of B-vitamins, iron, zinc and cobalt measured using a novel mass balance approach

世界海洋的广大地区，包括南大洋（SO）由高营养低叶绿素（HNLC）区组成。微量元素，如微量金属（TM）和维生素，限制初级生产，塑造浮游生物群落组成，而不是硝酸盐等宏量营养素。虽然在过去的三十年中，人们对TM浓度、新的TM输入以及浮游生物/颗粒在较小程度上去除TM的过程进行了广泛的研究，但令人惊讶的是，人们对原地速率过程（如再循环/放牧）在补充生物可利用TM库中的作用知之甚少。此外，尽管维生素对SO浮游植物群落的重要性最近得到了强调，但迄今为止，还没有关于SO的维生素浓度或利用/去除率的数据。此外，从未对任何海洋系统的维生素产量进行过评估。与去除过程相比，TMs/维生素回收/生产的速度如何？放牧对生物可利用TMs的贡献有多重要？由于TM化学和/或生物反应的变化，气候变化、二氧化碳分压升高以及由此导致的海洋碱性降低是否有利于再循环？为了回答这些问题，我们将探索一种新的质量平衡方法来测量不同SO浮游生物群落中三种生态TMs铁（Fe）、锌（Zn）和钴（Co）的原位再循环速率以及维生素的生产/再循环速率。此外，实地和实验室实验将检验在这些速率下，更高营养水平的放牧对微浮游生物和纳米浮游生物群落的相对重要性，并研究海洋酸化如何影响这些循环过程。这些数据将填补TM/维生素研究的巨大空白，并为目前和未来气候条件下关于维生素、铁和其他生态相关TM循环的全球海洋模型提供重要数据。

Vast regions of the worlds ocean, including the Southern Ocean (SO) consist of high nutrient low chlorophyll (HNLC) areas. Rather than macronutrients such as nitrate, micronutrients such as trace metals (TM) and vitamins limit primary production and shape plankton community composition. While concentrations of TMs, new TM inputs and to a lesser extend TM removal processes by the plankton/particles have been extensively studied in the last three decades surprisingly little is known about the role of in situ rate processes such as recycling/grazing in replenishing the bioavailable TM pools. In addition while the importance of vitamins for SO phytoplankton communities has recently been highlighted, to date, no vitamin concentration or utilization/removal rates data exist for the SO. Also, vitamin production rates have never been assessed for any marine system. How do rates of TMs/vitamins recycling/production compare to removal processes and how important is grazing in contributing to bioavailable TMs? Will climate change, higher pCO2 and the resulting less alkaline ocean favor recycling due to changes in TM chemistry and/or biological responses? To answer these questions a novel mass balance approach to measure in situ recycling rates of the three ecological TMs iron (Fe), zinc (Zn) and cobalt (Co) as well as production/recycling rates of vitamins in different SO plankton communities will be explored. In addition, field and laboratory experiments will examine the relative importance of grazing on the pico- and nanoplankton community by higher trophic levels on these rates and investigate how ocean acidification may affect these recycling processes. Together this data will fill in a large gap in TM/vitamin research and provide vital data for global ocean models on the cycling of vitamins, iron and other ecologically relevant TMs under present and future climatic conditions.