The impact of Mid-Ocean Ridges on the Ocean's Iron cycle

大洋中脊对海洋铁循环的影响

• 批准号: NE/N009525/1
• 负责人: Alessandro Tagliabue
• 金额: $ 30.14万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN009525%2F1
• 关键词: impact; Mid; Ocean; Ridges; Iron

Photosynthesis by marine phytoplankton provides energy to higher trophic levels (such as fish and marine mammals), as well as contributing to the partitioning of carbon dioxide between the atmosphere and the ocean. Iron is essential for phytoplankton growth as it is required for a number of important enzymes that participate in both photosynthesis and respiration. In contrast with terrestrial systems, iron is present at very low concentrations (less than 1 iron atom to every billion water molecules) in the open ocean. Thus phytoplankton photosynthesis is limited by iron over large parts of the ocean. This iron deficiency has important ramifications for the earth system since phytoplankton photosynthesis is an important means by which the ocean regulates global climate. Mid-ocean ridges are an important source of iron with estimates suggesting that ridge-derived iron makes up 25-75% of global ocean iron stocks. These mid-ocean ridges are the deep-sea mountain ranges that form a single global mid-ocean ridge system throughout the world's ocean, making it the longest mountain range in the world. At these ridges, new magma mixes with seawater and is exhaled as a high temperature fluid. While this ridge fluid has been noted to be a large source of iron to the deep-sea, the far field influence of this iron depends on its retention in dissolved forms by ocean chemistry. Our recent work shows that iron from mid-ocean ridges appears to have a much longer lifetime than previously thought and be exported up to 4000km away from the ridge. Despite the emerging role for ridge-derived iron, we do not understand its impact on deep ocean iron stocks, as well as how iron is mixed into surface waters to drive biological activity. We have highlighted that understanding the fate of ridge-derived iron and its ultimate influence on the ocean requires more information on the quantity and chemical form of iron supplied by ridges (e.g. dissolved or particles) and how these change with distance from source. To do this we need to appraise the role of small organic molecules called ligands and so-called iron nanoparticles, which have been invoked to control the lifetime of ridge-derived iron. Accounting for the specificity of iron within hydrothermal systems is key to constraining its wider impact. In addition, recent work by our colleagues has shown that interactions between the deep ocean tide and the ridge itself can elevate rates of physical mixing. If increased vertical mixing typifies mid-ocean ridges it implies that these regions may also exhibit efficient transfer of iron to surface waters. Given the ubiquity of mid-ocean ridges, the synergistic combination of these phenomena may be key to the large-scale supply of iron to surface waters.Sampling and measurement of iron at very low concentrations in seawater is challenging and the applicants are among the few research groups in the world who are able to do this reliably. Our group is at the forefront of representing the role of iron is global ocean models, which are crucial tools for assessing larger scale impacts on biological productivity. This project will participate in a NERC funded research cruise where scientists with expertise in measuring mixing and other macronutrients will be studying the nutrient and carbon pump over mid-ocean ridges. This proposal will therefore benefit from these measurements and will add value to this cruise by determining the associated role for iron.Overall, this project will provide state of the art observational and modelling constraints on two important aspects of the ocean iron cycle: 1) How does the ocean ridge impact physical mixing of iron to the surface and 2) what chemical processes control the large scale influence of the iron directly supplied by mid-ocean ridges. Ultimately we will be able to address the broader question of how the amount and chemical form of iron from mid-ocean ridges can influence phytoplankton growth in the open ocean.

海洋浮游植物的光合作用为更高营养水平的生物（如鱼类和海洋哺乳动物）提供能量，也有助于大气和海洋之间的二氧化碳分配。铁对浮游植物的生长是必不可少的，因为它是参与光合作用和呼吸作用的许多重要酶所必需的。与陆地系统相比，在开阔的海洋中，铁的浓度非常低（每10亿个水分子中不到1个铁原子）。因此，浮游植物的光合作用受到海洋大部分地区铁元素的限制。由于浮游植物光合作用是海洋调节全球气候的重要手段，因此这种铁缺乏对地球系统具有重要影响。海洋中脊是铁的重要来源，据估计，海洋中脊产生的铁占全球海洋铁储量的25-75%。这些洋中脊是深海山脉，在整个世界海洋中形成了一个单一的全球洋中脊系统，使其成为世界上最长的山脉。在这些隆起处，新的岩浆与海水混合，并以高温流体的形式呼出。虽然这种脊状流体被认为是深海铁的主要来源，但这种铁的远场影响取决于它在海洋化学作用下以溶解形式保留下来。我们最近的工作表明，来自大洋中脊的铁似乎比以前认为的寿命要长得多，并且可以出口到距离海脊4000公里远的地方。尽管脊源铁的作用正在显现，但我们不了解它对深海铁储量的影响，以及铁如何混合到地表水中以驱动生物活动。我们强调指出，要了解脊源铁的命运及其对海洋的最终影响，就需要更多关于脊源提供的铁的数量和化学形式（如溶解铁或颗粒铁）以及这些铁如何随着距离源的远近而变化的信息。要做到这一点，我们需要评估被称为配体的小有机分子和所谓的铁纳米颗粒的作用，它们被用来控制脊源铁的寿命。在热液系统中考虑铁的特异性是限制其更广泛影响的关键。此外，我们的同事最近的工作表明，深海潮汐和山脊本身之间的相互作用可以提高物理混合的速度。如果增加的垂直混合是洋中脊的典型特征，则意味着这些地区也可能表现出铁向地表水的有效转移。鉴于大洋中脊无处不在，这些现象的协同组合可能是向地表水大规模供应铁的关键。对海水中极低浓度的铁进行采样和测量是一项挑战，申请人是世界上为数不多的能够可靠地做到这一点的研究小组之一。我们的团队在全球海洋模型中代表了铁的作用，这是评估对生物生产力的更大规模影响的关键工具。该项目将参与NERC资助的研究巡航，届时具有测量混合和其他常量营养素专业知识的科学家将研究大洋中脊的营养和碳泵。因此，该提案将受益于这些测量，并将通过确定铁的相关作用为这次巡航增加价值。总体而言，该项目将提供海洋铁循环两个重要方面的最新观测和建模约束：1)洋脊如何影响铁与表面的物理混合；2)什么化学过程控制着洋中脊直接提供的铁的大规模影响。最终，我们将能够解决一个更广泛的问题，即来自大洋中脊的铁的数量和化学形式如何影响开阔海洋中的浮游植物生长。

项目成果

The unaccounted dissolved iron (II) sink: Insights from dFe(II) concentrations in the deep Atlantic Ocean.

未解释的溶解铁 (II) 沉降：来自大西洋深海 dFe(II) 浓度的见解。

• DOI: 10.1016/j.scitotenv.2022.161179
• 发表时间: 2023
• 期刊: The Science of the total environment
• 作者: González-Santana D

Variability in iron (II) oxidation kinetics across diverse hydrothermal sites on the northern Mid Atlantic Ridge

• DOI: 10.1016/j.gca.2021.01.013
• 发表时间: 2021-02-04
• 期刊: GEOCHIMICA ET COSMOCHIMICA ACTA
• 影响因子: 5
• 作者: Gonzalez-Santana, David;Gonzalez-Davila, Melchor;Santana-Casiano, J. Magdalena
• 通讯作者: Santana-Casiano, J. Magdalena

Constraining the Contribution of Hydrothermal Iron to Southern Ocean Export Production Using Deep Ocean Iron Observations

利用深海铁观测限制热液铁对南大洋出口生产的贡献

• DOI: 10.3389/fmars.2022.754517
• 发表时间: 2022
• 期刊: Frontiers in Marine Science
• 影响因子: 3.7
• 作者: Tagliabue A

Mechanisms Driving the Dispersal of Hydrothermal Iron From the Northern Mid Atlantic Ridge

驱动北大西洋中脊热液铁扩散的机制

• DOI: 10.1029/2022gl100615
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Tagliabue, Alessandro;Lough, Alastair J. M.;Vic, Clément;Roussenov, Vassil;Gula, Jonathan;Lohan, Maeve C.;Resing, Joseph A.;Williams, Richard G.
• 通讯作者: Williams, Richard G.

Tracing differences in iron supply to the Mid-Atlantic Ridge valley between hydrothermal vent sites: implications for the addition of iron to the deep ocean

追踪热液喷口地点之间大西洋中脊山谷的铁供应差异：对深海添加铁的影响

• DOI: 10.5194/bg-20-405-2023
• 发表时间: 2023
• 期刊: Biogeosciences
• 影响因子: 4.9
• 作者: Lough A