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/G015732/1
负责人：
Eric Achterberg
金额：
$ 57.03万
依托单位：
University of Southampton
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%2FG015732%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起着核心作用，并且已经占据了CA。 30-40％的人为产生的二氧化碳。长期以来，众所周知，海洋生物群在很长的时间尺度上（> 1000 y）中起主要作用。最近的证据还表明，海洋生物群在较短的时间尺度（10-100 y）中起着重要作用。浮游植物光合作用与社区呼吸之间的平衡决定了海洋占用二氧化碳的能力。氮（N）通常被认为是限制浮游植物光合作用的营养。但是，目前尚不清楚是什么控制着海洋中N的数量。与大多数植物浮游植物不同，N2固定蓝细菌（重18zotrophs）具有N2气体形式的无限n供应。 N2固定器在海洋养分和生物地球化学周期中起着重要作用，因为它们是N的主要来源，在养分贫困的海洋地区提供了多达50％的初级生产率的N。 N2固定是一个关键过程，可调节海洋以10至10,000 y的时间尺度隔离CO2的能力。 N2固定的局限性导致其他主要生产者降低了N的可用性，从而降低了海洋隔离碳的潜力。虽然形成毛trichodesmium的菌落被认为是最重要的海洋重氮植物，但最近在海洋中发现了一系列新的重18zotrophs。这使我们提出了“什么限制了海洋中N2固定数量？”以及“什么决定了海洋中的物种分布？”铁似乎是基于最近观察到的大西洋中Fe和N2固定之间的直接联系的关键环境因素，其中Fe确定了表面海洋P循环。该项目的目的是定量研究大西洋的铁供应与N2固定之间的联系，为此，必须了解各种铁源的重要性和优势。铁源被认为是西北非洲上升流地区的大气尘埃沉积和低氧货架沉积物。随着灰尘沉积和海洋中氧气最小区域的膨胀变化，这些来源的优势预计将在未来变化。因此，来源的识别和量化是在未来气候场景下进行N2固定模型估计的关键。该提案将将Fe和P的供应和生物地球化学与N2固定以及（子） - 热带大西洋中的重18zotrophs的社区结构有关。我们将使用船板观测和放射性示例摄取实验以及涉及营养和FE的建模活动的结合进行这项研究。我们将通过大气和海洋循环以及使用化学源示踪剂来量化重18zotroph社区的这些元素的来源。我们将将营养素和FE的供应与重18zozotrophs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中不同的重18zotrophs。我们将在（亚） - 热带大西洋的专用巡航上进行这项工作，该巡航涉及从非洲架子的东西方面的样带，以表征氧最小区域中的痕量元素梯度，从而从架子上进行横向对流的潜力。巡航还将穿越研究区域中的灰尘/氧化还原羽，并表征沿灰尘/氧化还原羽流的边缘的水平痕量梯度。我们将采样常见的重18zogotroph trichodesmium，并使用放射性示例研究其对Fe和P的摄取。我们将使用循环模型为该程序提供大规模的环境，并根据观察性研究的来源和循环量和Fe循环。这项研究最终将有助于对养分循环和建模的海洋学研究，以了解海洋作为C下沉的未来重要性。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Particulate phases are key in controlling dissolved iron concentrations in the (sub)tropical North Atlantic

颗粒相是控制北大西洋（亚）热带溶解铁浓度的关键

DOI：
10.1002/2016gl072314
发表时间：
2017
期刊：
Geophysical Research Letters
影响因子：
5.2
作者：
Milne A
通讯作者：
Milne A

Environmental controls on the biogeography of diazotrophy and Trichodesmium in the Atlantic Ocean

DOI：
10.1002/2015gb005090
发表时间：
2015-06
期刊：
Global Biogeochemical Cycles
影响因子：
5.2
作者：
Joseph T. Snow;Christian Schlosser;E. Malcolm S. Woodward;Matthew M. Mills;E. Achterberg;C. Mahaffey;T. Bibby;C. M. Moore
通讯作者：
Joseph T. Snow;Christian Schlosser;E. Malcolm S. Woodward;Matthew M. Mills;E. Achterberg;C. Mahaffey;T. Bibby;C. M. Moore

Where is mineral ballast important for surface export of particulate organic carbon in the ocean?

DOI：
10.1002/2014gl061678
发表时间：
2014-12-16
期刊：
GEOPHYSICAL RESEARCH LETTERS
影响因子：
5.2
作者：
Le Moigne, Frederic A. C.;Pabortsava, Katsiaryna;Marcinko, Charlotte L. J.;Martin, Patrick;Sanders, Richard J.
通讯作者：
Sanders, Richard J.

The distribution of lead concentrations and isotope compositions in the eastern Tropical Atlantic Ocean