Physical and chemical forcing of diazotrophy in the (sub)-tropical Atlantic Ocean

（亚）热带大西洋固氮营养的物理和化学强迫

基本信息

批准号：
NE/G018782/1
负责人：
Claire Mahaffey
金额：
$ 34.42万
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：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FG018782%2F1
关键词：
Physical chemical forcing diazotrophy sub

项目摘要

The oceans play a central role in the global carbon cycle, and have taken up ca. 30-40% of the anthropogenically produced CO2. It has long been known that ocean biota play a major role in sequestering CO2 on very long time scales (>1000 y). Recent evidence also suggests that the ocean biota play an important role on shorter time scales (10-100 y). The balance between phytoplankton photosynthesis and community respiration determines the ability of the oceans to take up CO2. Nitrogen (N) is generally considered to be the nutrient that limits phytoplankton photosynthesis. However, it is unclear what controls the amount of N in the ocean. Unlike most phytoplankton, which are N-limited, N2 fixing cyanobacteria (diazotrophs) have an unlimited supply of N in the form of N2 gas. N2-fixers play a significant role in ocean nutrient and biogeochemical cycles as they are a major source of N, providing N for up to 50% of primary productivity in nutrient poor oceanic regions. N2 fixation is a key process that modulates the ability of the oceans to sequester CO2 on time scales of 10 to 10,000 y. Limitation of N2 fixation results in lowered N availability for other primary producers reducing the potential of oceans to sequester carbon. Whilst the colony forming Trichodesmium is considered the most important oceanic diazotroph, recently a range of new diazotrophs have been discovered in the ocean. This brings us to the questions of 'what constrains the amount of N2 fixation in the ocean?', and 'what determines the species distribution of diazotrophs in the ocean?' Iron appears to be the key environmental factors constraining N2 fixation based on a recently observed direct link between Fe and N2 fixation in the Atlantic, with Fe determining surface ocean P cycling. The goal of this project is to investigate quantitatively the link between iron supply and N2 fixation in the Atlantic, and for this it is essential to understand the importance and strengths of various iron sources. The iron sources are considered to be atmospheric dust deposition and low oxygen shelf sediments in the NW African upwelling region. The strengths of these sources are expected to change in future with changes in dust deposition and expansion of the oxygen minimum zones in the oceans. Identification and quantification of the sources is hence key to undertake model estimates of N2 fixation under future climate scenarios. This proposal will relate the supply and biogeochemical cycling of Fe and P to N2 fixation and the community structure of diazotrophs in the (sub)-tropical Atlantic Ocean. We will undertake this research using a combination of ship-board observations and radiotracer uptake experiments, and modeling activities involving nutrients and Fe. We will quantify sources of these elements for the diazotroph community from the atmosphere and ocean circulation, and by use of chemical source tracers. We will link the supply of nutrients and Fe to the activity and species distribution of diazotrophs. Molecular techniques will be used to determine the different diazotrophs in the study region. We will undertake the work on a dedicated cruise in the (sub)-tropical Atlantic which involves east-west transect from the African shelf to characterise the trace element gradient in the oxygen minimum zone and thus the potential for lateral advection from the shelf. The cruise will also traverse the dust/redox plumes in the study region and characterize the horizontal trace element gradients along the edges of the dust/redox plumes. We will sample the common diazotroph Trichodesmium and study its uptake of Fe and P using radiotracers. We will use a circulation model to provide a large scale context for the programme, with sources and cycling of nutrients and Fe adapted according to the observational studies. This research will ultimately assist with oceanographic studies on nutrient cycling and modeling with a view on the future importance of the oceans as C sink.

海洋在全球碳循环中发挥着核心作用，并占据了约人为产生的二氧化碳的 30-40%。众所周知，海洋生物群在很长的时间尺度（>1000年）封存二氧化碳方面发挥着重要作用。最近的证据还表明，海洋生物群在较短的时间尺度（10-100 年）内发挥着重要作用。浮游植物光合作用和群落呼吸之间的平衡决定了海洋吸收二氧化碳的能力。氮（N）通常被认为是限制浮游植物光合作用的营养物质。然而，尚不清楚是什么控制着海洋中的氮含量。与大多数氮受限的浮游植物不同，固氮蓝藻（固氮生物）以氮气的形式无限供应氮。固氮剂在海洋养分和生物地球化学循环中发挥着重要作用，因为它们是氮的主要来源，为营养贫乏的海洋地区高达 50% 的初级生产力提供氮。 N2 固定是调节海洋在 10 至 10,000 年时间尺度上封存 CO2 能力的关键过程。氮固定的限制导致其他初级生产者的氮可用性降低，从而降低了海洋固碳的潜力。虽然形成毛藻的菌落被认为是最重要的海洋固氮生物，但最近在海洋中发现了一系列新的固氮生物。这给我们带来了“什么限制了海洋中氮气固定量？”以及“什么决定了海洋中固氮生物的物种分布？”的问题。根据最近观察到的大西洋中 Fe 和 N2 固定之间的直接联系，铁似乎是限制 N2 固定的关键环境因素，其中 Fe 决定了表层海洋 P 循环。该项目的目标是定量调查大西洋铁供应和固氮之间的联系，为此，了解各种铁源的重要性和优势至关重要。铁源被认为是西北非洲上升流区域的大气尘埃沉积和低氧陆架沉积物。随着灰尘沉积的变化和海洋中含氧量最低区的扩大，这些来源的强度预计会在未来发生变化。因此，来源的识别和量化是在未来气候情景下进行氮固定模型估计的关键。该提案将把 Fe 和 P 的供应和生物地球化学循环与 N2 固定以及（亚）热带大西洋固氮生物的群落结构联系起来。我们将结合船上观测和放射性示踪剂吸收实验以及涉及营养物和铁的建模活动来开展这项研究。我们将通过使用化学源示踪剂，从大气和海洋环流中量化固氮微生物群落的这些元素的来源。我们将把养分和铁的供应与固氮生物的活性和物种分布联系起来。分子技术将用于确定研究区域的不同固氮菌。我们将开展在（亚）热带大西洋的专门巡航工作，该巡航涉及非洲大陆架的东西向横断面，以表征最低含氧区的微量元素梯度，从而表征大陆架横向平流的潜力。巡航还将穿越研究区域的尘埃/氧化还原羽流，并表征沿尘埃/氧化还原羽流边缘的水平微量元素梯度。我们将对常见的固氮菌 Trichodesmium 进行取样，并使用放射性示踪剂研究其对 Fe 和 P 的吸收。我们将使用循环模型为该计划提供大范围的背景，并根据观察研究调整营养物和铁的来源和循环。这项研究最终将有助于营养物循环和建模的海洋学研究，以了解海洋作为碳汇的未来重要性。

项目成果

期刊论文数量（9）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Evidence for production and lateral transport of dissolved organic phosphorus in the eastern subtropical North Atlantic

北大西洋副热带东部溶解有机磷的产生和横向输送的证据

DOI：
http://dx.10.1002/2013gb004801
发表时间：
2014
期刊：
Global Biogeochemical Cycles
影响因子：
5.2
作者：
Reynolds S
通讯作者：
Reynolds S

The supply of excess phosphate across the Gulf Stream and the maintenance of subtropical nitrogen fixation MAINTENANCE OF SUBTROPICAL N 2 FIXATION

穿过墨西哥湾流的过量磷酸盐供应和亚热带固氮作用的维持亚热带固氮作用的维持

DOI：
http://dx.10.1029/2010gb003955
发表时间：
2011
期刊：
Global Biogeochemical Cycles
影响因子：
5.2
作者：
Palter J
通讯作者：
Palter J

Temporal variability of nitrogen fixation and particulate nitrogen export at Station ALOHA

ALOHA 站固氮和颗粒氮输出的时间变化

DOI：
10.1002/lno.10386
发表时间：
2016-02-01
期刊：
Limnology and Oceanography
影响因子：
4.5
作者：
D. Böttjer;J. Dore;D. Karl;Ricardo M Letelier;C. Mahaffey;Samuel T. Wilson;J. Zehr;M. Church
通讯作者：
M. Church

Wind-driven changes in Southern Ocean residual circulation, ocean carbon reservoirs and atmospheric CO2

风驱动的南大洋残余环流、海洋碳库和大气二氧化碳的变化