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

• 批准号: NE/G016267/1
• 负责人: Maeve Lohan
• 金额: $ 7.72万
• 依托单位: Plymouth University
• 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%2FG016267%2F1
• 关键词: Physical; chemical; forcing; diazotrophy; sub

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扮演着中心角色，约占人类活动产生的二氧化碳的30%-40%。人们很早就知道，海洋生物群在很长时间尺度(&gt；1000y)的二氧化碳封存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)上发挥着重要作用。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，目前还不清楚是什么控制了海洋中的氮含量。与大多数浮游植物不同的是，固定氮气的蓝藻(重氮菌)以氮气的形式无限供应氮气。氮固定剂在海洋营养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，为营养贫乏海洋地区高达50%的初级生产力提供氮。氮气固定是调节海洋在10到10000年的时间尺度上固定二氧化碳的能力的关键过程。限制氮气固定会导致其他初级生产者的N有效性降低，从而降低海洋固定碳的潜力。虽然形成毛霉菌的菌落被认为是最重要的海洋重氮菌，但最近在海洋中发现了一系列新的重氮菌。这给我们带来了这样的问题：“是什么限制了海洋中固定氮气的数量？”以及“是什么决定了海洋中重氮菌的物种分布？”铁似乎是限制氮固定的关键环境因素，根据最近在大西洋观察到的铁和氮固定之间的直接联系，铁决定了表层海洋P的循环。该项目的目标是定量调查大西洋铁供应和氮气固定之间的联系，为此，了解各种铁源的重要性和强度是至关重要的。铁的来源被认为是大气尘埃沉积和非洲西北部上升流区的低氧陆架沉积物。随着尘埃沉积的变化和海洋中最低含氧区的扩大，这些来源的强度预计将在未来发生变化。因此，确定和量化污染源是在未来气候情景下对氮气固定进行模型估计的关键。这一建议将把铁和磷的供应和生物地球化学循环与氮的固定和(亚热带)大西洋重氮菌的群落结构联系起来。我们将结合船上观察和放射性示踪剂摄取实验，以及涉及营养和铁的模拟活动来进行这项研究。我们将通过使用化学来源示踪剂，从大气和海洋循环中量化重氮菌群落的这些元素的来源。我们将把营养物质和铁的供应与重氮菌的活性和物种分布联系起来。将使用分子技术来确定研究区域内不同的重氮菌。我们将在(亚)热带大西洋进行一次专门的巡航工作，其中涉及非洲大陆架的东西横断面，以表征氧气最小区域中的微量元素梯度，从而确定从大陆架横向平流的可能性。巡航还将穿越研究区域的尘埃/氧化还原羽状物，并表征沿尘埃/氧化还原羽状物边缘的水平微量元素梯度。我们将对常见的重氮菌Trichodesum进行采样，并利用放射性示踪剂研究其对铁和磷的吸收。我们将使用一个环流模型来为该方案提供一个大范围的背景，根据观测研究调整营养物质和铁的来源和循环。这项研究最终将有助于海洋学对营养循环的研究和建模，以期了解海洋作为碳汇的未来重要性。

项目成果

Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES.

• DOI: 10.1098/rsta.2016.0076
• 发表时间: 2016-11-28
• 期刊: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
• 作者: Charette MA;Lam PJ;Lohan MC;Kwon EY;Hatje V;Jeandel C;Shiller AM;Cutter GA;Thomas A;Boyd PW;Homoky WB;Milne A;Thomas H;Andersson PS;Porcelli D;Tanaka T;Geibert W;Dehairs F;Garcia-Orellana J
• 通讯作者: Garcia-Orellana J

The GEOTRACES Intermediate Data Product 2017

• DOI: 10.1016/j.chemgeo.2018.05.040
• 发表时间: 2018-08
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: R. Schlitzer;R. Anderson;Elena Masferrer Dodas;M. Lohan;W. Geibert;A. Tagliabue;A. Bowie;C. Jeandel;M. T. Maldonado;W. Landing;Donna Cockwell;Cyril Abadie;W. Abouchami;E. Achterberg;A. Agather;Ana Aguliar-Islas;H. V. Aken;M. B. Andersen;C. Archer;M. Auro;H. Baar;O. Baars;A. Baker;K. Bakker;C. Basak;M. Baskaran;N. Bates;D. Bauch;P. Beek;M. Behrens;Erin E. Black;K. Bluhm;L. Bopp;H. Bouman;K. Bowman;J. Bown;P. Boyd;M. Boyé;E. Boyle;Pierre Branellec;Luke Bridgestock;G. Brissebrat;T. Browning;K. Bruland;H. Brumsack;M. Brzezinski;C. Buck;K. Buck;K. Buesseler;Abby Bull;E. Butler;P. Cai;P. Mor;D. Cardinal;C. Carlson;Gonzalo Carrasco;N. Casacuberta;K. Casciotti;M. Castrillejo;E. Chamizo;R. Chance;M. Charette;J. Chaves;Hai-Lan Cheng;F. Chever;M. Christl;T. Church;I. Closset;A. Colman;T. Conway;D. Cossa;P. Croot;J. Cullen;G. Cutter;C. Daniels;F. Dehairs;Feifei Deng;Huong Thi Dieu;B. Duggan;G. Dulaquais;C. Dumousseaud;Yolanda Echegoyen-Sanz;R. Edwards;M. Ellwood;E. Fahrbach;J. Fitzsimmons;A. Flegal;M. Fleisher;T. Flierdt;M. Frank;J. Friedrich;F. Fripiat;H. Fröllje;S. Galer;T. Gamo;R. Ganeshram;J. García-Orellana;E. Garcia-Solsona;M. Gault‐Ringold;E. George;L. Gerringa;M. Gilbert;J. Godoy;S. Goldstein;S. R. Gonzalez;K. Grissom;C. R. Hammerschmidt;A. E. Hartman;C. Hassler;E. Hathorne;M. Hatta;N. Hawco;C. T. Hayes;L. Heimbürger;Joshua Helgoe;M. Heller;G. Henderson;P. Henderson;S. Heuven;Peng Ho;T. Horner;Y. Hsieh;Kuo‐Fang Huang;M. Humphreys;K. Isshiki;Jeremy E. Jacquot;D. J. Janssen;W. Jenkins;S. John;E. Jones;Janice L. Jones;D. Kadko;Rick Kayser;T. Kenna;R. Khondoker;Taejin Kim;L. Kipp;J. Klar;M. Klunder;S. Kretschmer;Y. Kumamoto;P. Laan;M. Labatut;F. Lacan;P. Lam;M. Lambelet;C. Lamborg;F. L. Moigne;E. L. Roy;O. Lechtenfeld;Jong‐Mi Lee;P. Lherminier;S. Little;M. López-Lora;Yanbin Lu;P. Masqué;Edward Mawji;C. McClain;C. Measures;S. Mehic;J. M. Barraqueta;P. Merwe;R. Middag;S. Mieruch;A. Milne;Tomoharu Minami;J. Moffett;G. Moncoiffe;W. Moore;P. Morris;P. Morton;Y. Nakaguchi;N. Nakayama;J. Niedermiller;J. Nishioka;Akira Nishiuchi;A. Noble;H. Obata;S. Ober;D. Ohnemus;J. Ooijen;J. O'Sullivan;S. Owens;K. Pahnke;M. Paul;F. Pavia;L. Pena;B. Peters;F. Planchon;H. Planquette;C. Pradoux;Viena Puigcorbé;P. Quay;F. Quéroué;A. Radic;S. Rauschenberg;M. Rehkämper;R. Rember;T. Remenyi;J. Resing;J. Rickli;S. Rigaud;M. Rijkenberg;S. Rintoul;L. Robinson;M. Roca-Martí;V. Rodellas;Tobias Roeske;J. Rolison;M. Rosenberg;S. Roshan;M. Loeff;E. Ryabenko;M. Saito;L. Salt;V. Sanial;G. Sarthou;Christina Schallenberg;U. Schauer;H. Scher;C. Schlosser;B. Schnetger;Peter Scott;P. Sedwick;I. Semiletov;R. Shelley;R. Sherrell;A. Shiller;D. Sigman;Sunil Kumar Singh;H. Slagter;Emma Slater;W. Smethie;H. Snaith;Y. Sohrin;B. Sohst;J. Sonke;S. Speich;R. Steinfeldt;G. Stewart;T. Stichel;C. Stirling;J. Stutsman;G. Swarr;J. Swift;Alexander L. Thomas;K. Thorne;Claire P. Till;Ralph Till;A. Townsend;Emily Townsend;R. Tuerena;B. Twining;D. Vance;Sue Velazquez;C. Venchiarutti;M. Villa-Alfageme;Sebastián M. Vivancos;A. Voelker;B. Wake;M. Warner;R. Watson;E. V. Weerlee;M. A. Weigand;Y. Weinstein;D. Weiss;A. Wisotzki;E. Woodward;Jingfeng Wu;Yingzhe Wu;K. Wuttig;N. Wyatt;Yang Xiang;R. Xie;Z. Xue;Hisayuki Yoshikawa;Jing Zhang;Pu Zhang;Ye Zhao;Linjie Zheng;Xin-Yuan Zheng;M. Zieringer;L. Zimmer;P. Ziveri;P. Zunino;C. Zurbrick

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

• DOI: 10.1016/j.gca.2018.01.018
• 发表时间: 2018-03-15
• 期刊: GEOCHIMICA ET COSMOCHIMICA ACTA
• 影响因子: 5
• 作者: Bridgestock, Luke;Rehkaemper, Mark;Achterberg, Eric P.
• 通讯作者: Achterberg, Eric P.

The GEOTRACES Intermediate Data Product 2014

• DOI: 10.1016/j.marchem.2015.04.005
• 发表时间: 2015-12-20
• 期刊: MARINE CHEMISTRY
• 影响因子: 3
• 作者: Mawji, Edward;Schlitzer, Reiner;Zimmer, Louise A.
• 通讯作者: Zimmer, Louise A.

Return of naturally sourced Pb to Atlantic surface waters.

• DOI: 10.1038/ncomms12921
• 发表时间: 2016-09-28
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Bridgestock, Luke;van de Flierdt, Tina;Rehkamper, Mark;Paul, Maxence;Middag, Rob;Milne, Angela;Lohan, Maeve C.;Baker, Alex R.;Chance, Rosie;Khondoker, Roulin;Strekopytov, Stanislav;Humphreys-Williams, Emma;Achterberg, Eric P.;Rijkenberg, Micha J. A.;Gerringa, Loes J. A.;de Baar, Hein J. W.
• 通讯作者: de Baar, Hein J. W.