Iron manganese co-limitation – a potential driver of Southern Ocean phytoplankton ecology

南大洋对全球碳循环具有不成比例的控制作用，从而在全球范围内影响气候。南大洋浮游植物是全球碳循环的主要驱动力，占全球年初级产量的20%。在SO中，二氧化碳的生物吸收主要受微量金属铁（Fe）和光的可用性的控制，两者都是光合作用所必需的。到目前为止，大多数研究都集中在解开铁和光如何影响so浮游植物的生长和生产力上，几乎没有人知道其他微量金属，如锰（Mn）是否也在so中起到限制或共同限制的营养作用。锰是浮游植物细胞中各种细胞过程所必需的，并被认为在SO的某些部分（如德雷克海峡）与铁（共）限制。目前，我们对SO浮游植物在Fe-Mn限制下的生长、光合作用、氧化胁迫以及Mn和Fe需求缺乏了解。本研究旨在进一步了解铁锰共限对SO浮游植物生理的潜在影响及其对当前和未来SO生态和生物地球化学的启示。为此，我们将模拟不同气候变化情景，研究不同光照条件下浮游植物对Fe和Mn有效度变化的响应。将采用多学科方法，将生物学和海洋化学结合起来，并将实验室和实地工作结合起来。在生态和生物地球化学上重要的浮游植物物种的实验室实验将提供对生理过程的机制理解，如光合作用和微量金属的需求。船上操纵实验对不同区域的天然SO浮游植物组合将进一步揭示Fe-Mn共限制的发生，并将有助于识别对痕量金属和光有效性变化特别敏感但也耐受的浮游植物物种。本研究将有助于对当前和未来海洋环境中主要浮游植物种类的空间分布进行生态生理学解释。提高对SO生态系统的功能和敏感性的认识，对于改进我们现有的预测工具（如建模）和增加我们对SO影响全球尺度气候过程的机制的理解至关重要。因此，本研究项目将对DFG schwerpunktprogram 1158 Antarktis-Forschung的关键研究课题2.2.4响应环境变化做出重大贡献。

The Southern Ocean (SO) exerts a disproportional control on the global carbon cycle, thus affecting climate at a global scale. Southern Ocean phytoplankton are major drivers of global carbon cycling accounting for 20% of the global annual primary production. In the SO, the biological uptake of carbon dioxide is mainly controlled by the availability of the trace metal iron (Fe) and light, both being essential for photosynthesis. Whereas most studies so far focused on disentangling how Fe and light influence SO phytoplankton growth and productivity, almost nothing is known whether other trace metals such as manganese (Mn) also act as limiting or co-limiting nutrient in the SO. Mn is required for various cellular processes in phytoplankton cells and has been suggested to be (co-)limiting with Fe in some parts of the SO such as the Drake Passage. Currently, we lack information on growth, photosynthesis, oxidative stress and Mn and Fe requirements under Fe-Mn limitation for SO phytoplankton species. This research project aims to improve our understanding about the potential effects of Fe-Mn co-limitation on SO phytoplankton physiology and their implications for the ecology and biogeochemistry in the present and future SO. To this end, the responses of SO phytoplankton will be studied in response to altered Fe and Mn availabilities under different light conditions, simulating different climate change scenarios. A multidisciplinary approach will be followed that integrates biology and marine chemistry and combines laboratory and field work. Laboratory experiments with ecologically and biogeochemically important phytoplankton species of the SO will provide a mechanistic understanding on physiological processes such as photosynthesis and trace metal requirements. Shipboard manipulation experiments with natural SO phytoplankton assemblages of different regions of the SO will further reveal the occurrence of Fe-Mn co-limitation and will help to identify phytoplankton species in the field, which are particularly sensitive, but also tolerant towards altered trace metal and light availabilities. All together this research project will help to assess an ecophysiological explanation for the spatial distribution of SO key phytoplankton species in the present and the future SO. Improved knowledge on the functioning and the sensitivity of the SO ecosystem is pivotal to improve our existing predictive tools (e.g. modelling) and increase our understanding on the mechanisms, by which the SO affects climatic processes at global scale. Therefore, this research project will significantly contribute to the key research topic 2.2.4 Response to Environmental Change within the DFG Schwerpunktprogramm 1158 Antarktis-Forschung.