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Biotic Regulation of Global Biogeochemical Cycles : a Theoretical Perspective Anne-Sophie Auguères

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Biotic Regulation of Global Biogeochemical Cycles : a Theoretical Perspective Anne-Sophie Auguères Biotic regulation of global biogeochemical cycles : a theoretical perspective Anne-Sophie Auguères To cite this version: Anne-Sophie Auguères. Biotic regulation of global biogeochemical cycles : a theoretical perspective. Biodiversity. Université Paul Sabatier - Toulouse III, 2015. English. NNT : 2015TOU30290. tel- 01412291 HAL Id: tel-01412291 https://tel.archives-ouvertes.fr/tel-01412291 Submitted on 8 Dec 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. THÈSETHÈSE En vue de l’obtention du DOCTORAT DE L’UNIVERSITÉ DE TOULOUSE Délivré par : l’Université Toulouse 3 Paul Sabatier (UT3 Paul Sabatier) Présentée et soutenue le 23/10/2015 par : Anne-Sophie AUGUÈRES Régulation biotique des cycles biogéochimiques globaux: Une approche théorique JURY Jérôme CHAVE Directeur de Recherche Président du Jury Donald L. DEANGELIS Research Professor Rapporteur Gilles BILLEN Directeur de Recherche Membre du Jury Michel LOREAU Directeur de Recherche Directeur de Thèse École doctorale et spécialité : SEVAB : Écologie, biodiversité et évolution Unité de Recherche : Station d’Écologie Expérimentale du CNRS (USR 2936) Directeur de Thèse : Michel LOREAU Rapporteurs : Donald L. DEANGELIS et Timothy M. LENTON Summary List of Figures 8 List of Tables 9 Préface 11 Remerciements ..................................... 11 Avant-propos ...................................... 15 Résumé général 17 General introduction 23 Impact of global change on biogeochemical cycles . 23 Direct effects of increasing nutrient supply on global biogeochemical cycles . 24 Indirect effects of increasing nutrient supply on global biogeochemical cycles 25 Impact of organisms on biogeochemical cycles at local scales . 28 Biotic alteration of the local environment . ...... 28 Feedbacks between autotroph growth and nutrient availability . 29 Adaptable stoichiometry of autotrophs and its impact on local nutrient pools 32 Impact of herbivores and detritivores on nutrient cycles . 34 Impact of organisms on biogeochemical cycles at global scales . 35 Biotic regulation at global scales: the Gaia hypothesis . 35 Regulation of atmospheric oxygen cycle . 38 Redfield ratios in the ocean . 39 3 Resource access limitation . 44 Objectives, methods and main questions . 46 Generalobjective ................................. 46 Theoretical modelling and application to the global ocean . 47 Mainquestions .................................. 48 References........................................ 49 1 Can organisms regulate global biogeochemical cycles? 51 Résumé ......................................... 52 Abstract......................................... 54 Introduction....................................... 55 Methods......................................... 58 Results.......................................... 61 Discussion........................................ 64 Acknowledgements ................................... 69 References........................................ 69 Figures and Tables . 70 Supplementary Tables . 77 Connecting statements 80 2 Biotic regulation of non-limiting nutrient pools and coupling of nutrient cycles 81 Résumé ......................................... 83 Abstract......................................... 85 Introduction....................................... 86 Modeldescription................................... 88 Results.......................................... 90 Discussion........................................ 93 Acknowledgements ................................... 96 4 References........................................ 96 Figures and Tables . 97 Appendix 2.A: Regulation coefficients and interaction between cycles . 100 Connecting statements 103 3 Regulation of Redfield ratios in the deep ocean 104 Résumé ......................................... 105 Abstract......................................... 107 Introduction....................................... 108 Methods......................................... 111 Results.......................................... 115 Discussion........................................ 119 Acknowledgements ................................... 123 References........................................ 123 Figures and Tables . 124 Supplementary Tables . 130 Appendix 3.A: Comparison of models with fixed and variable stoichiometry . 131 Connecting statements 136 4 Ultimate colimitation of oceanic primary production 137 Résumé ......................................... 138 Abstract......................................... 140 Introduction....................................... 141 Methods......................................... 143 Results.......................................... 146 Discussion........................................ 148 Acknowledgements ................................... 150 References........................................ 150 5 Figures and Tables . 151 Supplementary Figures and Tables . 156 Appendix 4.A: Phytoplankton growth rate from synthesizing unit model . 158 Appendix 4.B: Model with variable stoichiometry . 161 Discussion and perspectives 165 Synthesisofresults ................................. 165 Implications on global scale regulation . 169 Effects of global change on regulation of biogeochemical cycles . 170 Effects of variable stoichiometry on regulation of biogeochemical cycles . 171 Effects of herbivores on regulation of biogeochemical cycles . 172 Generalconclusion ................................... 176 References 178 6 List of Figures A1: Impact of anthropogenic activities on the global nitrogencycle ........ 25 B1: Time series of changes in large-scale ocean climate properties . .. 27 C1: Comparison between two concepts of limitation for two essential resources . 30 D1: Daisy occupancy and planetary temperature in the Daisyworld model . 37 E1: Global relationship between nitrate and phosphate concentrations in seawater 40 1.1 Generic model of nutrient dynamics with resource access limitation . 70 1.2 Regulation processes in the generic model . 71 1.3 Regulation of iron concentrations in the ocean . 72 1.4 Regulation of silicic acid concentrations in the ocean . 73 1.5 Regulation of phosphorus concentrations in the ocean . 74 2.1 Nutrient stocks and flows in the stoichiometric model . 97 2.2 Regulation processes in the stoichiometric model . 98 3.1 Model of coupled N and P oceanic cycles . 124 3.2 Sensitivity of the deep-water N:P ratio . 125 3.3 Regulation of N and P concentrations and the N:P ratio in the ocean . 126 3.4 Regulation processes in the ocean model with N-fixers and non-fixers . 127 3.5 Sensitivity of regulation of deep-water N:P ratio . 128 4.1 Model of N, P and Fe oceanic cycles . 151 4.2 Impact of nutrient supplies on primary production (Liebig) . 152 4.3 Impact of nutrient supplies on primary production (MLH Synthesizing Units) 153 7 S4.1: Impact of nutrient supplies on production (MLH Monod) . 156 F1: Impact of herbivory on regulation of inaccessible nutrient concentration . 175 8 List of Tables 1.1 Parametersofthegenericmodel. .... 75 1.2 Impact of parameters on biotic regulation of the inaccessible nutrient pool . 76 S1.1: Parameter values for numerical simulations of the oceanic iron cycle . 77 S1.2 Parameter values for numerical simulations of the oceanic silicon cycle . 78 S1.3 Parameter values for numerical simulations of the oceanic phosphorus cycle . 79 2.1 Parameters of the stoichiometric model . 99 3.1 Parameters of the model of N and P oceanic cycles . 129 S3.1: Sensitivity of the value and regulation of the deep-water N:P ratio . 130 4.1 Parameters of the model of N, P and Fe oceanic cycles . 154 4.2 Sensitivity of primary production with respect to nutrient supplies . 155 S4.1: Sensitivity of primary production in the model with variable stoichiometry . 157 9 Préface Remerciements Pour commencer, je voudrais dire un très grand merci à Michel Loreau, mon directeur de thèse. Merci tout d’abord pour ton encadrement, l’autonomie que tu m’as laissée dans le choix du sujet, merci pour toutes les discussions et bien sûr les (très nombreuses) relectures de papiers. Merci de m’avoir appris à prendre du recul sur mes équations. Merci d’avoir été présent et de m’avoir encouragée et remotivée durant ces trois années, bien que j’aie vraiment un problème avec la notion de planning et de deadline. Merci de m’avoir secouée quand c’était nécessaire, mais toujours avec le sourire et la manière ! Je voudrais tout particulièrement remercier les membres de mon comité de thèse, Claire de Mazancourt, Sergio Vallina et Jérôme Chave, qui m’ont guidée lors de la réunion du comité de thèse. Claire, merci particulièrement pour tes conseils avisés sur les différentes parties de ma thèse ainsi que pour la relecture des papiers. Merci à toutes les personnes avec qui j’ai partagé à un moment le bureau : Tomas Revilla, Jarad Mellard, Shaopeng Wang, Romain Bertrand, Audrey. Un grand merci tout particulier à Anne-Sophie Lafuite, copine de “qu’est-ce qu’on crève de chaud dans ce bureau !”, pour les pauses thé du matin (et de l’après-midi) et toutes les conversations sérieuses ou pas qui vont avec, et pour l’écoute aussi. Merci pour
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