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1. Benthic contribution to seasonal silica budgets in two macrotidal estuaries in North-Western France

Author: Mélanie Raimonet, Olivier Ragueneau, Karline Soetaert, Karima Khalil, Aude Leynaert, Emma Michaud, Brivaela Moriceau, Christophe Rabouille, and Laurent Memery
Subjects: silica cycle, estuary, diagenetic modeling, bioturbation, benthic-pelagic coupling, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract: The paper aims to build seasonal silica budgets in two macrotidal estuaries, the Elorn and Aulne estuaries of the Bay of Brest (North-Western France), based on modeling and measurements, in order to increase our understanding of the silica (Si) cycle at land-sea interfaces. A diagenetic model was developed to quantify benthic Si fluxes, e.g. aSiO2 deposition fluxes that are difficult to assess through direct measurements. Sediment cores were also seasonally sampled at six stations to provide data essential to parametrize and validate the model. Vertical profiles of porosity, burrowing depth, biodiffusive coefficients, concentrations of amorphous silica (aSiO2) and silicic acid (Si(OH)4 and the proportion of reactive aSiO2 were measured. The results show that sites sampled along the Elorn and Aulne estuaries constitute significant net Si deposition areas (1-4.5 mmol Si m-2 d-1), particularly in the upstream during winter and in midstream and downstream during summer. Year round, reprecipitation is negligible (< 3%) while burial accounts for the retention of ~ 30-80% of deposited aSiO2. In winter, burial dominates the benthic Si budget. As surface-integrated benthic Si fluxes are low compared to riverine aSiO2 fluxes, the Si export to coastal waters is high (93%) during winter. In contrast, in summer, burial accounts for 38% of river Si fluxes, and Si(OH)4 flux from the sediment is high as a result of enhanced benthic recycling and bioirrigation. Internal estuarine processes, e.g., benthic and pelagic primary production, dissolution and benthic Si fluxes, surpass river fluxes in magnitude during summer. Overall, we conclude that the Elorn and Aulne macrotidal estuaries are efficient filters of Si, retaining about 4-38% of river Si fluxes, and even 6-67% when accounting for retention in intertidal marshes, but with massive exports occurring during winter floods.
Published: 2023
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2. La solidarité écologique de la science à l’(in)action publique

Author: Camille Mazé and Olivier Ragueneau
Subjects: ecological solidarity, power asymmetries (power gap), socio-ecosystems, governance and environmental management, scientific paradigms, ontology of human/environmental relations, Environmental sciences, GE1-350
Abstract: This article is intended to discuss the conditions of possibility and impossibility of making the legal (and therefore normative) concept of ecological solidarity an a priori effective instrument for reinforcing the entry of public policies into contemporary environmental governance regimes and management modes, with a view to the transformation towards sustainability. To do this, it proposes to decipher in an epistemological and theoretical way the dichotomies socially constructed by modern European societies, such as nature/culture, science/decision or human/non-human, and which still structure today the forms of governability of nature, of our environments and of the natural resources we depend on. We argue that, in the context of global change, the regimes of governance of human/environment relations must be reinvented, adapted to complexity, change and uncertainty, defragmented and de-sectorized in order to better integrate interdependencies as the very substrate of sustainability. The concept of governance of socio-ecosystems, fundamentally based on the recognition of the principle of ecological solidarity with its strong transformative power as highlighted by science (in particular ecology), has, in our opinion, the capacity to make this principle operational for public policies. But to do so, it is necessary to proceed to an anthropological introspection, and to a combined analysis between social sciences and natural sciences, for the only one able to bring to light the conditions of possibility and impossibility of the transfer of this concept from legal science and ecology itself, to environmental public action. The challenge of this article is to make explicit what emerges from this critical analysis: beyond incentives, normative injunctions and scattered initiatives, the institutionalization of the transformation towards sustainability continues to be hampered by three types of asymmetries (gaps), closely intertwined: knowledge, implementation and power.
Published: 2022
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3. Element enrichment and provenance of the detrital component in Holocene sediments from the western Black Sea

Author: Vesselin M. Dekov, Valentina Y. Darakchieva, Kjell Billström, C. Dieter Garbe-Schönberg, George D. Kamenov, Morgane Gallinari, Lyubomir Dimitrov, Olivier Ragueneau, and Ellen Kooijman
Subjects: Oceanography, GC1-1581
Abstract: Summary: Concentrations of a large set of major and trace elements, and Sr, Nd and Pb isotope ratios were measured in Holocene sediments cored in the western deep Black Sea in order to unravel: (1) the controls of element enrichment, and (2) sources of the detrital component. The transition of the basin from oxic to euxinic resulted in enrichment or depletion in a number of elements in the deep-sea sediments. Authigenic Fe enrichment appears to depend on the amount of Fe mobilized from the sediment through the benthic redox shuttle mechanism and free H2S in the water column (degree of “euxinization”). Manganese enrichment is controlled by diagenetic reactions within the sediment: the dissolution of Mn minerals, Mn2+ diffusion upward and reprecipitation. Barium enrichment is also controlled by diagenetic reactions, sulfate reduction and methanogenesis, that take place above and below the sulfate-methane transition, respectively. The major part of V, Co, Ni, Cu, Zn, Cr, Mo, Cd and Sb is inferred to have co-precipitated with Fe in the euxinic deep waters and to have been incorporated into authigenic Fe-sulfides. Basin reservoir effect additionally influences the Mo enrichment. The U enrichment is interpreted to have a different origin in the two organic-rich stratigraphic units (II and I). It is inferred to be: (i) at the expense of the U inventory of the deepwater pool and a result of inorganic reduction of U at euxinic conditions in the lower Unit II; and (ii) at the expense of the U inventory of the surface water pool and a result of biogenic uptake and transfer to the sediment by the plankton in the upper Unit I. The high field strength elements are closely linked to the detrital component and their depletion in the organic-rich sediments reflects a dilution of the detrital component by the biogenic one. The enrichments of REE, Sn and Th are likely controlled by adsorption on clay minerals. Sr-Nd-Pb isotope compositions of the alumino-silicate component of the studied sediments are relatively uniform. They are most likely controlled by riverine suspended matter supplied mainly in the NW Black Sea (Danube Delta) and transported southward by marine currents, and to a lesser degree by suspended matter from the small rivers draining SE Bulgaria and NW Turkey. Wind-blown dust from the Sahara Desert appears to have a minor contribution to the alumino-silicate component of the sediments. The slight shift in the Pb isotopes in Unit I upper layers is possibly caused by the addition of anthropogenic Pb. Keywords: Anoxic, Black Sea, Element enrichment, Sr-Nd-Pb-isotopes, Holocene
Published: 2020
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4. Atlas cartographiques du droit de l’environnement marin en Afrique de l’Ouest. Méthodologie et usage pour la planification spatiale

Author: Matthieu Le Tixerant, Marie Bonnin, Françoise Gourmelon, Olivier Ragueneau, Mathias Rouan, Ibrahima Ly, Ahmed Ould Zein, Fatou Ndiaye, Mohamed Diedhiou, Souleye Ndao, and Mamadou Bassirou Ndiaye
Subjects: GIS, cartography, environment, coastal zone, law of the sea, sea, Geography (General), G1-922
Abstract: In the marine environment, positive law generates multiple zones and regulatory limits that overlap in space, justifying a cartographic representation as a relevant approach to promote understanding (synthetic vision), analysis (highlighting legal anomalies, inconsistencies and redundancies), dissemination and communication to different audiences (awareness-raising). The article presents a methodology leading to the mapping of marine and coastal environmental law in West Africa, using a geographic information base to produce static or interactive cartographic representations via a Geographic Data Infrastructure (GDI). It shows the contribution of this type of mapping to a transversal approach in a multi-activity, multi-sectoral and multi-scale context. A series of interviews with Senegalese stakeholders, mainly State services, is carried out in order to assess the practices, expectations and limitations of this atlas of marine environmental law. Even if its use currently remains limited, the interest of the atlas is underlined by stakeholders who are facing growing challenges (preservation of resources and biodiversity, development of new activities, conflicts of use...) and who need to initiate a marine spatial planning process. Recommendations can now be put forward to promote the use of environmental law atlases to help implement an implementation of an operational strategy for integrated management of the sea and coast.
Published: 2020
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5. Corrigendum: ILTER – The International Long-Term Ecological Research Network as a Platform for Global Coastal and Ocean Observation

Author: José H. Muelbert, Nicholas J. Nidzieko, Alicia T. R. Acosta, Stace E. Beaulieu, Angelo F. Bernardino, Elmira Boikova, Thomas G. Bornman, Bruno Cataletto, Klaas Deneudt, Erika Eliason, Alexandra Kraberg, Masahiro Nakaoka, Alessandra Pugnetti, Olivier Ragueneau, Mirco Scharfe, Thomas Soltwedel, Heidi M. Sosik, Angela Stanisci, Kremena Stefanova, Pierre Stéphan, Adrian Stier, Johan Wikner, and Adriana Zingone
Subjects: climate change, marine ecosystems, ecology, EOVs, SWOT, DEIMS, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Published: 2020
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6. ILTER – The International Long-Term Ecological Research Network as a Platform for Global Coastal and Ocean Observation

Author: José H. Muelbert, Nicholas J. Nidzieko, Alicia T. R. Acosta, Stace E. Beaulieu, Angelo F. Bernardino, Elmira Boikova, Thomas G. Bornman, Bruno Cataletto, Klaas Deneudt, Erika Eliason, Alexandra Kraberg, Masahiro Nakaoka, Alessandra Pugnetti, Olivier Ragueneau, Mirco Scharfe, Thomas Soltwedel, Heidi M. Sosik, Angela Stanisci, Kremena Stefanova, Pierre Stéphan, Adrian Stier, Johan Wikner, and Adriana Zingone
Subjects: climate change, marine ecosystems, ecology, EOVs, SWOT, DEIMS, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract: Understanding the threats to global biodiversity and ecosystem services posed by human impacts on coastal and marine environments requires the establishment and maintenance of ecological observatories that integrate the biological, physical, geological, and biogeochemical aspects of ecosystems. This is crucial to provide scientists and stakeholders with the support and knowledge necessary to quantify environmental change and its impact on the sustainable use of the seas and coasts. In this paper, we explore the potential for the coastal and marine components of the International Long-Term Ecological Research Network (ILTER) to fill this need for integrated global observation, and highlight how ecological observations are necessary to address the challenges posed by climate change and evolving human needs and stressors within the coastal zone. The ILTER is a global network encompassing 44 countries and 700 research sites in a variety of ecosystems across the planet, more than 100 of which are located in coastal and marine environments (ILTER-CMS). While most of the ILTER-CMS were established after the year 2000, in some cases they date back to the early 1900s. At ILTER sites, a broad variety of abiotic and biotic variables are measured, which may feed into other global initiatives. The ILTER community has produced tools to harmonize and compare measurements and methods, allowing for data integration workflows and analyses between and within individual ILTER sites. After a brief historical overview of ILTER, with emphasis on the marine component, we analyze the potential contribution of the ILTER-CMS to global coastal and ocean observation, adopting the “Strength, Weakness, Opportunity and Threats (SWOT)” approach. We also identify ways in which the in situ parameters collected at ILTER sites currently fit within the Essential Ocean Variables framework (as proposed by the Framework for Ocean Observation recommendations) and provide insights on the use of new technology in long-term studies. Final recommendations point at the need to further develop observational activities at LTER sites and improve coordination among them and with external related initiatives in order to maximize their exploitation and address present and future challenges in ocean observations.
Published: 2019
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7. The Impossible Sustainability of the Bay of Brest? Fifty Years of Ecosystem Changes, Interdisciplinary Knowledge Construction and Key Questions at the Science-Policy-Community Interface

Author: Olivier Ragueneau, Mélanie Raimonet, Camille Mazé, Jennifer Coston-Guarini, Laurent Chauvaud, Anatole Danto, Jacques Grall, Frédéric Jean, Yves-Marie Paulet, and Gérard Thouzeau
Subjects: sustainability, land-ocean continuum, Bay of Brest, interdisciplinarity, science-policy-community interface, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract: In this contribution, the study of the Bay of Brest ecosystem changes over the past 50 years is used to explore the construction of interdisciplinary knowledge and raise key questions that now need to be tackled at the science-policy-communities interface. The Bay of Brest is subject to a combination of several aspects of global change, including excessive nutrient inputs from watersheds and the proliferation of invasive species. These perturbations strongly interact, affecting positively or negatively the ecosystem functioning, with important impacts on human activities. We first relate a cascade of events over these five decades, linking farming activities, nitrogen, and silicon biogeochemical cycles, hydrodynamics of the Bay, the proliferation of an exotic benthic suspension feeder, the development of the Great scallop fisheries and the high biodiversity in maerl beds. The cascade leads to today's situation where toxic phytoplankton blooms become recurrent in the Bay, preventing the fishery of the great scallop and forcing the fishermen community to switch pray and alter the maerl habitat and the benthic biodiversity it hosts, despite the many scientific alerts and the protection of this habitat. In the second section, we relate the construction of the interdisciplinary knowledge without which scientists would never have been able to describe these changes in the Bay. Interdisciplinarity construction is described, first among natural sciences (NS) and then, between natural sciences and human and social sciences (HSS). We finally ask key questions at the science-policy interface regarding this unsustainable trend of the Bay: How is this possible, despite decades of joint work between scientists and fishermen? Is adaptive co-management a sufficient condition for a sustainable management of an ecosystem? How do the different groups (i.e., farmers, fishermen, scientists, environmentalists), with their diverse interests, take charge of this situation? What is the role of power in this difficult transformation to sustainability? Combining natural sciences with political science, anthropology, and the political sociology of science, we hope to improve the contribution of HSS to integrated studies of social-ecological systems, creating the conditions to address these key questions at the science-policy interface to facilitate the transformation of the Bay of Brest ecosystem toward sustainability.
Published: 2018
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8. Action-orientated research and framework: insights from the French long-term social-ecological research network

Author: Vincent Bretagnolle, Marc Benoit, Mathieu Bonnefond, Vincent Breton, Jon M. Church, Sabrina Gaba, Daniel Gilbert, François Gillet, Sandrine Glatron, Chloé Guerbois, Nicolas Lamouroux, Marc Lebouvier, Camille Mazé, Jean-Marie Mouchel, Annie Ouin, Olivier Pays, Christophe Piscart, Olivier Ragueneau, Sylvie Servain, Thomas Spiegelberger, and Hervé Fritz
Subjects: adaptive governance, ecosystem services, landscape, lter, management, practices, research infrastructure, social-ecological systems, sustainability, Biology (General), QH301-705.5, Ecology, QH540-549.5
Abstract: Many social-ecological system(SES)-based approaches have been proposed to address environmental problems. Most social-ecological frameworks developed to date, however, lack clear operational linkages between humans and nature to efficiently guide SESs toward resilience. A conceptual framework designed to be operational is therefore necessary, as well as a network of research platforms with which to apply it. We defined explicit coupling processes that can be used as leverages to pilot an SES toward sustainability. We proposed to formalize an SES as a dynamic entity composed of two coupling interfaces, i.e., adaptive management and ecosystem services, both set within a landscape context to provide an actionable framework. These interfaces describe the way various actors, including scholars, benefit from and manage complex and changing interactions between the biophysical and social templates. Understanding the key processes underlying the interaction dynamics, especially those leveraging adaptive management processes, would help identify adaptive pathways for practices and collective actions, provide a crucial knowledge base for policy makers, and foster operationality as a requisite of an SES research agenda. Using several examples, we explained why long-term social-ecological research platforms provide an ideal operational network of research infrastructures to conduct place-based action-orientated research targeting the sustainability of SESs.
Published: 2019
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9. Chapitre 16. L’interdisciplinarité en questions

Author: Olivier Ragueneau
Published: 2023
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10. Le Réseau des Zones Ateliers (RZA) : un terrain expérimental et réflexif pour la co-construction des savoirs et la transformation des territoires

Author: Olivier Ragueneau, Mathieu Bonnefond, Isabelle Charpentier, Herve Fritz, Vanessa Lea, Christophe Piscart, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géomatique et foncier (GeF), Conservatoire National des Arts et Métiers [CNAM] (CNAM), HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), Laboratoire des sciences de l'ingénieur, de l'informatique et de l'imagerie (ICube), École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Université de Strasbourg (UNISTRA)-Institut National des Sciences Appliquées - Strasbourg (INSA Strasbourg), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Institut National de Recherche en Informatique et en Automatique (Inria)-Les Hôpitaux Universitaires de Strasbourg (HUS)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Reconciling Ecological and Human Adaptations for Biosphere Sustainability (REHABS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Nelson Mandela University [Port Elizabeth], Travaux et recherches archéologiques sur les cultures, les espaces et les sociétés (TRACES), École des hautes études en sciences sociales (EHESS)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Ministère de la Culture et de la Communication (MCC)-Centre National de la Recherche Scientifique (CNRS), Ecosystèmes, biodiversité, évolution [Rennes] (ECOBIO), Université de Rennes (UR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), and univOAK, Archive ouverte
Subjects: [SHS.ENVIR] Humanities and Social Sciences/Environmental studies, [SHS.ENVIR]Humanities and Social Sciences/Environmental studies
Published: 2022

11. Cartographic Atlas of Marine Environmental Law in West Africa. Methodology and use for spatial planning

Author: Marie Bonnin, Mohamed Diedhiou, Matthieu Le Tixerant, Mamadou Bassirou Ndiaye, I. Ly, Fatou Ndiaye, Souleye Ndao, Françoise Gourmelon, Mathias Rouan, Olivier Ragueneau, and Ahmed Ould Zein
Subjects: droit de la mer, law of the sea, cartografía, 010504 meteorology & atmospheric sciences, sea, 0211 other engineering and technologies, 02 engineering and technology, litoral, 01 natural sciences, mar, medio ambiente, mer, cartography, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Geography (General), derecho marítimo, SIG, GIS, environnement, littoral, 13. Climate action, cartographie, coastal zone, G1-922, environment, Social Sciences (miscellaneous)
Abstract: En mer, le droit positif génère de multiples zones et limites réglementaires qui se superposent dans l’espace, justifiant une représentation cartographique comme approche pertinente pour en favoriser l’appréhension (vision synthétique), l’analyse (mise en évidence d’anomalies, d’incohérences et de redondances juridiques), la diffusion et la communication auprès de différents publics (sensibilisation). L’article présente une méthodologie conduisant à la représentation cartographique du droit de l’environnement marin et côtier en Afrique de l’Ouest, exploitant une base d’information géographique permettant de produire des représentations cartographiques de manière statique ou interactive via une Infrastructure de Données Géographiques (IDG). Il montre l’apport de ce type de cartographies pour contribuer à une approche transversale dans un contexte multi-activités, multi-sectoriels et multi-échelles. Une série d’entretiens avec des acteurs sénégalais, dont principalement des services de l’État, est réalisée de manière à évaluer les pratiques, les attentes et les limites de cet atlas du droit de l’environnement marin. Même si son usage reste actuellement limité, l’intérêt de l’atlas est souligné par les acteurs qui font face à des enjeux croissants (préservation des ressources et de la biodiversité, développement de nouvelles activités, conflits d’usages…) et qui se doivent d’initier un processus de planification de l’espace marin. Des recommandations peuvent désormais être proposées afin de favoriser l’usage des atlas du droit de l’environnement pour aider à la mise en œuvre d’une stratégie opérationnelle de gestion intégrée de la mer et du littoral. In the marine environment, positive law generates multiple zones and regulatory limits that overlap in space, justifying a cartographic representation as a relevant approach to promote understanding (synthetic vision), analysis (highlighting legal anomalies, inconsistencies and redundancies), dissemination and communication to different audiences (awareness-raising). The article presents a methodology leading to the mapping of marine and coastal environmental law in West Africa, using a geographic information base to produce static or interactive cartographic representations via a Geographic Data Infrastructure (GDI). It shows the contribution of this type of mapping to a transversal approach in a multi-activity, multi-sectoral and multi-scale context. A series of interviews with Senegalese stakeholders, mainly State services, is carried out in order to assess the practices, expectations and limitations of this atlas of marine environmental law. Even if its use currently remains limited, the interest of the atlas is underlined by stakeholders who are facing growing challenges (preservation of resources and biodiversity, development of new activities, conflicts of use...) and who need to initiate a marine spatial planning process. Recommendations can now be put forward to promote the use of environmental law atlases to help implement an implementation of an operational strategy for integrated management of the sea and coast. En el mar, el derecho positivo genera múltiples zonas y límites reglamentarios que se superponen en el espacio, justificando una representación cartográfica como un enfoque pertinente para promover su comprensión (visión sintética), análisis (destacando anomalías, inconsistencias y redundancias jurídicas), difusión y comunicación a diferentes públicos (sensibilización). Este artículo presenta una metodología orientada a la representación cartográfica del derecho del medio marino y costero en África Occidental, a partir de una base de información geográfica que permite producir representaciones cartográficas de forma estática o interactiva por medio de una Infraestructura de Datos Geográficos (IDG). Se expresa el aporte de este tipo de cartografías para un enfoque transversal en un contexto de variadas actividades, acciones sectoriales y distintas escalas. Se realizaron una serie de entrevistas a actores senegaleses, principalmente vinculados a servicios del Estado, evaluando las prácticas, expectativas y límites de este atlas de derecho ambiental marino. Si bien actualmente su uso es limitado, se destaca el interés del atlas por parte de actores, los cuales enfrentan desafíos cada vez mayores (preservación de recursos y biodiversidad, desarrollo de nuevas actividades, conflictos de uso, etc.) y que implican iniciar procesos de planificación espacial marina, contexto que posibilita promover el uso del atlas de derecho ambiental, con la finalidad de contribuir a implementar una estrategia operativa en la gestión integrada del mar y la costa.
Published: 2020

12. Human-induced river runoff overlapping natural climate variability over the last 150 years: Palynological evidence (Bay of Brest, NW France)

Author: Sabine Schmidt, Clément Lambert, Khadidja Klouch, Muriel Vidal, Gwendoline Gregoire, Raffaele Siano, Axel Ehrhold, Olivier Ragueneau, Frédérique Eynaud, Aurélie Penaud, Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Ecologie Pélagique (PELAGOS), Dynamiques des Écosystèmes Côtiers (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Unité Dyneco, Laboratoire Pelagos, Dynamiques de l'Environnement Côtier (DYNECO), Laboratoire Géodynamique et enregistrement Sédimentaire - Geosciences Marines (GM-LGS), and Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)
Subjects: 010506 paleontology, 010504 meteorology & atmospheric sciences, Oceanography, 01 natural sciences, Estuarine dynamics, Phytoplankton, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology, Dinocyst, River runoff, 14. Life underwater, Climate variability, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Palynology, Global and Planetary Change, geography, geography.geographical_feature_category, Dinoflagellate cysts, Acl, Pollen grains, Estuary, 15. Life on land, 13. Climate action, Salt marsh, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology, Eutrophication, Bay, Surface water, Geology
Abstract: International audience; For the first time a very high resolution palynological study (mean resolution of 1 to 5 years) was carried out over the last 150 years in a French estuarine environment (Bay of Brest; NW France), allowing direct comparison between the evolution of landscapes, surface water, and human practices on Bay of Brest watersheds, through continental (especially pollen grains) and marine (phytoplanktonic microalgae: cysts of dinoflagellates or dinocysts) microfossils. Thanks to the small size of the watersheds and the close proximity of the depositional environment to the mainland, the Bay of Brest represents an ideal case study for palynological investigations. Palynological data were then compared to published palaeo-genetic analyses conducted on the same core and to various available instrumental data, allowing us to better characterize past environmental variability since the second half of the 19th century in Western Brittany. We provide evidence of some clues of recent eutrophication and/or pollution that affected phytoplankton communities and which appears linked with increased runoff (higher precipitations, higher percentages of riparian forest pollen, decline of salt marsh-type indicators, and higher values of the XRF Ti/Ca signal), mainly explained by the evolution of agricultural practices since 1945 superimposed on the warming climate trend. We assume that the significant relay observed between dinocyst taxa: Lingulodinium machaerophorum and Spiniferites bentorii around 1965 then followed by Spiniferites membranaceus after 1985, attests to a strong and recent eutrophication of Bay of Brest surface waters induced by high river runoff combined with abnormally elevated air temperatures, especially obvious in the data from 1990. The structure of the dinocyst community has thus been deeply altered, accompanied by an unprecedented increase of Alexandrium minutum toxic form at the same period, as confirmed by the genetic quantification. Despite this recent major anthropogenic forcing, the fossil pollen sequence also records natural climate variability. We highlight, for the first time, a possible connection between climate (AMO modes) and fossil pollen records (especially tree pollination rates) in coastal sediments using tree percentage fluctuations as an indirect proxy for past sea surface and atmospheric temperatures.
Published: 2018
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13. Element enrichment and provenance of the detrital component in Holocene sediments from the western Black Sea

Author: Valentina Y. Darakchieva, C.-Dieter Garbe-Schönberg, Kjell Billström, Lyubomir Dimitrov, Olivier Ragueneau, Vesselin M. Dekov, Morgane Gallinari, George D. Kamenov, Ellen Kooijman, Tokyo University of Marine Science and Technology (TUMSAT), Unité de recherche Géosciences Marines (Ifremer) (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institute of Mineralogy and Crystallography - IMC (Sofia, Bulgaria), Bulgarian Academy of Sciences (BAS), Swedish Museum of Natural History (NRM), Christian-Albrechts-Universität zu Kiel (CAU), University of Florida [Gainesville] (UF), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institute of Oceanology of Bulgarian Academy of Sciences (IO-BAS), Géosciences Marines (GM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Atmospheric Science, Provenance, 010504 meteorology & atmospheric sciences, Geochemistry, Ocean Engineering, Aquatic Science, Oceanography, 01 natural sciences, Sr-Nd-Pb-isotopes, lcsh:Oceanography, Water column, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, 14. Life underwater, lcsh:GC1-1581, Anoxic, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Isotope analysis, Holocene, 010604 marine biology & hydrobiology, Sediment, Authigenic, 6. Clean water, Diagenesis, Element enrichment, Black Sea, 13. Climate action, Enrichment factor, Clay minerals, Geology
Abstract: Place: Sopot Publisher: Polish Acad Sciences Inst Oceanology WOS:000528728600003; International audience; Concentrations of a large set of major and trace elements, and Sr, Nd and Pb isotope ratios were measured in Holocene sediments cored in the western deep Black Sea in order to unravel: (1) the controls of element enrichment, and (2) sources of the detrital component. The transition of the basin from oxic to euxinic resulted in enrichment or depletion in a number of elements in the deep-sea sediments. Authigenic Fe enrichment appears to depend on the amount of Fe mobilized from the sediment through the benthic redox shuttle mechanism and free H2S in the water column (degree of “euxinization”). Manganese enrichment is controlled by diagenetic reactions within the sediment: the dissolution of Mn minerals, Mn2+ diffusion upward and reprecipitation. Barium enrichment is also controlled by diagenetic reactions, sulfate reduction and methanogenesis, that take place above and below the sulfate-methane transition, respectively. The major part of V, Co, Ni, Cu, Zn, Cr, Mo, Cd and Sb is inferred to have co-precipitated with Fe in the euxinic deep waters and to have been incorporated into authigenic Fe-sulfides. Basin reservoir effect additionally influences the Mo enrichment. The U enrichment is interpreted to have a different origin in the two organic-rich stratigraphic units (II and I). It is inferred to be: (i) at the expense of the U inventory of the deepwater pool and a result of inorganic reduction of U at euxinic conditions in the lower Unit II; and (ii) at the expense of the U inventory of the surface water pool and a result of biogenic uptake and transfer to the sediment by the plankton in the upper Unit I. The high field strength elements are closely linked to the detrital component and their depletion in the organic-rich sediments reflects a dilution of the detrital component by the biogenic one. The enrichments of REE, Sn and Th are likely controlled by adsorption on clay minerals. Sr-Nd-Pb isotope compositions of the alumino-silicate component of the studied sediments are relatively uniform. They are most likely controlled by riverine suspended matter supplied mainly in the NW Black Sea (Danube Delta) and transported southward by marine currents, and to a lesser degree by suspended matter from the small rivers draining SE Bulgaria and NW Turkey. Wind-blown dust from the Sahara Desert appears to have a minor contribution to the alumino-silicate component of the sediments. The slight shift in the Pb isotopes in Unit I upper layers is possibly caused by the addition of anthropogenic Pb.
Published: 2020
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14. Carbon and silica megasink in deep-sea sediments of the Congo terminal lobes

Author: Martial Taillefert, Karine Olu, Mélanie Raimonet, Lucie Pastor, Jean-Louis Reyss, Olivier Ragueneau, Philippe Martinez, Laurence Méjanelle, Laurence Droz, P. Michalopoulos, Elsa Stetten, François Baudin, Christophe Rabouille, Bernard Dennielou, Audrey M. Pruski, Johann Schnyder, Julie Tourolle, Alexis Khripounoff, Livio Ruffine, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut des Sciences de la Terre de Paris (iSTeP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géosciences Océan (LGO), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Environnement Profond (LEP), Etudes des Ecosystèmes Profonds (EEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Ecogéochimie des environnements benthiques (LECOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Hellenic Centre for Marine Research (HCMR), Paléoenvironnemements Paléoclimats, Bassins (ISTEP-PPB), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], ANR-11-BS56-0030,CONGOLOBE,Transfert de carbone organique et fonctionnement des écosystèmes dans les lobes terminaux de l'éventail sous-marin du Congo(2011), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Unité de recherche Géosciences Marines (Ifremer) (GM), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), IFREMER- Département Etude des Ecosystèmes Profonds (DEEP/LEP), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Conception, Optimisation et Modélisation des Systèmes (LCOMS), Université de Lorraine (UL), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: 010506 paleontology, Archeology, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Geochemistry, Sedimentology-marine cores, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Submarine canyon, 01 natural sciences, Deep sea, South Atlantic, Paleoceanography, Organic geochemistry, 14. Life underwater, Glacial period, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Total organic carbon, Present, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, geography, geography.geographical_feature_category, ACL, Geology, Last Glacial Maximum, 13. Climate action, Inorganic geochemistry, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: International audience; Carbon and silicon cycles at the Earth surface are linked to long-term variations of atmospheric CO2 and oceanic primary production. In these cycles, the river-sea interface is considered a biogeochemical hotspot, and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments. In contrast, periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep-sea via submarine canyons and accumulation in deep-sea fans. Here, we calculate present-day mass balances for organic carbon (OC) and amorphous silica (aSi) in the terminal lobe complex of the Congo River deep-sea fan as an analogue for glacial periods. We show that this lobe complex constitutes a megasink with the current accumulation of 18 and 35% of the OC and aSi river input, respectively. This increases the estimates of organic carbon burial by 19% in the South Atlantic Ocean in a zone representing less than 0.01% of the basin. These megasinks might have played a role in carbon trapping in oceanic sediments during glacial times.
Published: 2019
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15. Observed and projected sea surface temperature seasonal changes in the Western English Channel from satellite data and CMIP5 multi-model ensemble

Author: Francis Gohin, Blandine L'Hévéder, Sabrina Speich, Olivier Ragueneau, and Philippe Bryere
Subjects: 0106 biological sciences, Marine biology, Atmospheric Science, 010504 meteorology & atmospheric sciences, Phenology, 010604 marine biology & hydrobiology, Climate change, Plankton, Seasonality, medicine.disease, 01 natural sciences, Sea surface temperature, Oceanography, 13. Climate action, Climatology, Phytoplankton, medicine, Environmental science, Climate model, 14. Life underwater, 0105 earth and related environmental sciences
Abstract: Seasonal Sea Surface Temperature (SST) changes in the Western English Channel have been estimated for the previous decades from high-resolution satellite data. Coastal seas, well separated from offshore waters by intense frontal structures, show colder SST by 1 to 2°C in summer. A significant warming trend is observed in the autumn season. This positive trend is stronger offshore, with an annual mean SST increase of 0.32°C/decade, but weaker in coastal waters (0.23°C/decade), where strong vertical mixing induced by tides and winds acts to reduce surface warming. The performance of an ensemble of CMIP5 climate model in simulating recent seasonal changes of SST in the region is estimated. The median of CMIP5 models reproduces very well the observed SST mean seasonal cycle in offshore waters but is less proficient in the coastal sector due to the coarse resolution of the models and the absence of tidal forcing and related processes. In the Iroise Sea, a region of intense biological activity located off the western tip of Brittany, the trend of the annual mean SST is relatively well simulated, albeit somewhat underestimated (0.20°/decade) and evenly distributed throughout the year. Here, the increase in annual mean SST in CMIP5 future scenarios simulations ranges from 0.5°C (RCP2.6) to 2.5°C (RCP8.5) by year 2100, with a seasonal modulation leading to a more intense warming in summer than in winter. This increase in SST may strongly affect marine biology, particularly phytoplankton phenology, macro-algae biomass and benthic fauna, including exploited shellfish, in the Western English Channel.
Published: 2016
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16. High alkaline phosphatase activity in phosphate replete waters: The case of two macrotidal estuaries

Author: Agnes Youenou, Julien Quere, Stéphane Fraisse, Mélanie Raimonet, Claire Labry, Daniel Delmas, Olivier Ragueneau, and Aude Leynaert
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, education, Aquatic Science, Biology, Oceanography, 01 natural sciences, Mineralization (biology), chemistry.chemical_compound, mental disorders, 14. Life underwater, 0105 earth and related environmental sciences, geography, Biomass (ecology), geography.geographical_feature_category, 010604 marine biology & hydrobiology, Estuary, Particulates, Phosphate, biology.organism_classification, 6. Clean water, Salinity, chemistry, 13. Climate action, Environmental chemistry, Alkaline phosphatase, psychological phenomena and processes, Bacteria
Abstract: The occurrence of alkaline phosphatase activity (APA) that hydrolyses organic phosphorus into phosphate (PO4) is commonly related to PO4 deficiency of oceanic, coastal and fresh waters. APA is almost never investigated in PO4-rich estuaries, since very low activities are expected to occur. As a consequence, microbial mineralization of organic phosphorus into PO4 has often been ignored in estuaries. In this study, we examined the importance of potential APA and the associated microbial dynamics in two estuaries, the Aulne and the Elorn (Northwestern France), presenting two different levels of PO4 concentrations. Unexpected high potential APA was observed in both estuaries. Values ranged from 50 to 506 nmol L−1 h−1, which range is usually found in very phosphorus-limited environments. High potential APA values were observed in the oligohaline zone (salinity 5–15) in spring and summer, corresponding to a PO4 peak and a maximum bacterial production of particle-attached bacteria. In all cases, high potential APA was associated with high suspended particulate matter and total particulate phosphorus. The low contribution of the 0.2–1 μm fraction to total APA, the strong correlation between particulate APA and bacterial biomass, and the close relationship between the production of particle-attached bacteria and APA, suggested that high potential APA is mainly due to particle-attached bacteria. These results suggest that the microbial mineralization of organic phosphorus may contribute to an estuarine PO4 production in spring and summer besides physicochemical processes.
Published: 2016
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17. Action-orientated research and framework: insights from the French long-term social-ecological research network

Author: Nicolas Lamouroux, Camille Mazé-Lambrechts, Chloé Guerbois, Sabrina Gaba, Olivier Ragueneau, Vincent Breton, Sylvie Servain, Jon Marco Church, François Gillet, Annie Ouin, Mathieu Bonnefond, Daniel Gilbert, Thomas Spiegelberger, Vincent Bretagnolle, Marc Lebouvier, Marc Benoit, Hervé Fritz, Christophe Piscart, Jean-Marie Mouchel, Olivier Pays, Sandrine Glatron, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Agro-Systèmes Territoires Ressources Mirecourt (ASTER Mirecourt), Institut National de la Recherche Agronomique (INRA), Laboratoire Géomatique et foncier (GeF), Conservatoire National des Arts et Métiers [CNAM] (CNAM), HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM)-HESAM Université - Communauté d'universités et d'établissements Hautes écoles Sorbonne Arts et métiers université (HESAM), Laboratoire de Physique de Clermont (LPC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), HABITER - EA 2076 (HABITER), Université de Reims Champagne-Ardenne (URCA)-Maison des Sciences Humaines de Champagne-Ardenne (MSH-URCA), Université de Reims Champagne-Ardenne (URCA)-Université de Reims Champagne-Ardenne (URCA), Laboratoire Chrono-environnement (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Laboratoire Image, Ville, Environnement [Strasbourg] (LIVE), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Nelson Mandela University [Port Elizabeth], RiverLy (UR Riverly), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Ecosystèmes, biodiversité, évolution [Rennes] (ECOBIO), Université de Rennes (UR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Dynamiques Forestières dans l'Espace Rural (DYNAFOR), Institut National de la Recherche Agronomique (INRA)-École nationale supérieure agronomique de Toulouse (ENSAT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT), École nationale supérieure agronomique de Toulouse (ENSAT), Littoral, Environnement, Télédétection, Géomatique (LETG-Angers), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Cités, Territoires, Environnement et Sociétés (CITERES), Université de Tours (UT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des EcoSystèmes et des Sociétés en Montagne (UR LESSEM), Laboratoire de Biométrie et Biologie Evolutive - UMR 5558 (LBBE), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de Recherche en Informatique et en Automatique (Inria)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Université de Strasbourg (UNISTRA), Nelson Mandela Metropolitan University [Port Elizabeth, South Africa], Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-École nationale supérieure agronomique de Toulouse [ENSAT]-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, École nationale supérieure agronomique de Toulouse [ENSAT], Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Tours, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Centre National de la Recherche Scientifique (CNRS)-Université de Tours (UT), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Clermont Auvergne (UCA)-Centre National de la Recherche Scientifique (CNRS), Université de Reims Champagne-Ardenne (URCA), Laboratoire Chrono-environnement - UFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs), École pratique des hautes études (EPHE)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Ecole Nationale Supérieure Agronomique de Toulouse-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Littoral, Environnement, Télédétection, Géomatique - Laboratoire d’Etudes Environnementales des Systèmes Anthropisés (LETG-ANGERS), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-Université de Nantes (UN)-École pratique des hautes études (EPHE)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Tours-Centre National de la Recherche Scientifique (CNRS), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-École pratique des hautes études (EPHE)-Université de Nantes (UN)-Université d'Angers (UA)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 2 (UR2), Normandie Université (NU)-Normandie Université (NU), and Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Process management, QH301-705.5, Computer science, practices, adaptive governance, Context (language use), LTER, 01 natural sciences, Ecosystem services, 03 medical and health sciences, 0302 clinical medicine, 11. Sustainability, research infrastructure, Biology (General), Set (psychology), Resilience (network), QH540-549.5, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Ecology, business.industry, ACL, landscape, sustainability, ecosystem service, lter, management, practice, social-ecological system, 010601 ecology, Adaptive management, social-ecological systems, Knowledge base, Conceptual framework, Sustainability, [SDE]Environmental Sciences, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, business, ecosystem services, 030217 neurology & neurosurgery
Abstract: [Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples; International audience; Many social-ecological system(SES)-based approaches have been proposed to address environmental problems. Most social-ecological frameworks developed to date, however, lack clear operational linkages between humans and nature to efficiently guide SESs toward resilience. A conceptual framework designed to be operational is therefore necessary, as well as a network of research platforms with which to apply it. We defined explicit coupling processes that can be used as leverages to pilot an SES toward sustainability. We proposed to formalize an SES as a dynamic entity composed of two coupling interfaces, i.e., adaptive management and ecosystem services, both set within a landscape context to provide an actionable framework. These interfaces describe the way various actors, including scholars, benefit from and manage complex and changing interactions between the biophysical and social templates. Understanding the key processes underlying the interaction dynamics, especially those leveraging adaptive management processes, would help identify adaptive pathways for practices and collective actions, provide a crucial knowledge base for policy makers, and foster operationality as a requisite of an SES research agenda. Using several examples, we explained why long-term social-ecological research platforms provide an ideal operational network of research infrastructures to conduct place-based action-orientated research targeting the sustainability of SESs.
Published: 2019
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18. Dealing with impact. An interdisciplinary, multi-site ethnography of Environmental Impact Assessment in the coastal zone

Author: Olivier Ragueneau, Camille Mazé, Jennifer Coston-Guarini, Adrien Lambrechts, Anatole Danto, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Centre de Recherches sur l'Action Politique en Europe (ARENES), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut d'Études Politiques [IEP] - Rennes-École des Hautes Études en Santé Publique [EHESP] (EHESP)-Centre National de la Recherche Scientifique (CNRS), Biotope [Mèze], MITI CNRS, Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Institut d'Études Politiques [IEP] - Rennes-École des Hautes Études en Santé Publique [EHESP] (EHESP)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Boundary object, knowledge, ApoliMer, 010504 meteorology & atmospheric sciences, interest, Saint-Pierre and Miquelon, Public policy, Context (language use), LTSER, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, 12. Responsible consumption, lcsh:Social Sciences, Appropriation, 11. Sustainability, Environmental impact assessment, 14. Life underwater, Decision-making, Architecture, savoir, lcsh:Science, zone côtière, ACLN, 0105 earth and related environmental sciences, General Environmental Science, processus de décision, decision-making process, Saint-Pierre et Miquelon, business.industry, Environmental resource management, General Social Sciences, [SHS.ANTHRO-SE]Humanities and Social Sciences/Social Anthropology and ethnology, intérêts, [SDE.ES]Environmental Sciences/Environmental and Society, [SHS.SCIPO]Humanities and Social Sciences/Political science, 010601 ecology, lcsh:H, Geography, 13. Climate action, Sustainable management, impact, General Earth and Planetary Sciences, coastal zone, lcsh:Q, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, General Agricultural and Biological Sciences, business
Abstract: International audience; The SPA (“Savoir, Pouvoir, Avoir”) project (CNRS, 2017-2019) presented in this article focuses on the ways French society deals with the issue of environmental impact – from the vast question of impact in the context of global change and the issue of the measurement of impact in science, to the specific case of the public policy instrument known as “environmental impact assessment”. Impact is considered as a boundary object at the intersection of several fields of inquiry which captures both the architecture and the dynamics of relationships between “savoir” (scientific and lay knowledge), “pouvoir” (power and decision) and “avoir” (economy/appropriation), that aggregate different interests around the sustainable management of coastal socio-ecological systems. Three sites were selected along a north-south gradient of Long-Term Ecological Research sites: the Bay of Brest and the Iroise Sea, the National Nature Reserve of the French islands in the Southern Ocean and the overseas collectivity of Saint Pierre and Miquelon. The approach of the SPA project is to link concretely social sciences, natural sciences and engineering sciences on these study sites, in an interdisciplinary, multi-site and multi-scale methodology that makes it possible to reveal the conditions for the possible – or impossible – implementation of sustainable management of coastal socio-ecological systems.; Le projet SPA (Savoir, Pouvoir, Avoir) (CNRS, 2017-2019) présenté dans cet article se concentre sur la manière dont la société française aborde la question de lʼimpact environnemental – de son évaluation et sa mesure à son traitement. Le processus réglementaire de lʼ « étude dʼimpact environnemental » qui consiste en lʼanalyse préalable des impacts potentiels prévisibles dʼune activité donnée sur lʼenvironnement est donc placé ici au cœur de nos préoccupations dans ce projet qui considère lʼimpact comme un objet frontière, à lʼintersection de plusieurs champs, permettant de saisir lʼarchitecture et la dynamique des relations entre savoir (savoir scientifique et profane), pouvoir (pouvoir et décision) et avoir (économie/appropriation). Pour ce faire, nous proposons de saisir les différents intérêts qui sʼagrègent autour de la gestion durable des socio-écosystèmes côtiers. Trois sites ont été choisis selon un gradient nord-sud dans des sites de recherche écologique à long terme : la rade de Brest et la mer dʼIroise, la réserve naturelle nationale des îles françaises de lʼocéan Austral et la collectivité dʼoutre-mer de Saint-Pierre-et-Miquelon. Lʼapproche du projet SPA consiste à lier concrètement les sciences sociales, les sciences naturelles et les sciences de lʼingénieur sur ces sites dʼétude, dans une approche interdisciplinaire multi-sites et multi-échelles qui permet de mettre au jour les conditions de possibilité (ou dʼimpossibilité) de mise en œuvre dʼune gestion soutenable des socio-écosystèmes côtiers.
Published: 2018
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19. Impact of nutrient starvation on the biochemical composition of the marine diatom Thalassiosira weissflogii: from the whole cell to the frustule fraction

Author: Madeleine Goutx, Brivaëla Moriceau, Pascal Claquin, C. Soler, Olivier Ragueneau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de MicrobiologiE de Géochimie et d'Ecologie Marines (LMGEM), and Université de la Méditerranée - Aix-Marseille 2-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, chemistry.chemical_classification, 0303 health sciences, biology, Frustule, 010604 marine biology & hydrobiology, fungi, Biogenic silica, biology.organism_classification, Phosphate, 01 natural sciences, 03 medical and health sciences, chemistry.chemical_compound, Diatom, Nutrient, Nitrate, chemistry, Thalassiosira weissflogii, Biochemistry, [SDU]Sciences of the Universe [physics], 13. Climate action, Organic matter, 030304 developmental biology
Abstract: Interactions between carbon and silica in the diatom frustule play an important role in carbon export through their impact on diatom remineralization (carbon degradation and biogenic silica dissolution). To ameliorate model prediction of the fate of Si and organic matter during sedimentation, there is a need to first understand the origin and nature of Si-OC interactions, their impact on diatom remineralization and their variability with environmental conditions. In this study we focus on the impact of nutrient starvations on the formation and nature of these interactions in an ubiquitous diatom, Thalassiosira weissflogii. Fluorescence reveals the strong impact of all starvations on diatom metabolism while Fourier transformed infrared (FTIR) spectroscopy clearly showed that starvations altered the composition of the different diatom fractions. The relative compositions of whole cells were almost not impacted by starvations except Si(OH)4 starvation that slightly increased proteins relative contribution while decreasing carbohydrate. Starvation impacts became obvious looking at the composition of the different part of the diatom. The relative biochemical composition of the organic coating, protecting the frustule from the environment, was strongly affected by starvation. Under nitrate starvation, carbohydrate contribution increased while protein contribution decreased. Inversely, phosphate starvation increased the proportion of proteins and decreased carbohydrates contribution. Starvations also modified the different frustule phases. bSiO2 contribution decreased in the less reactive phase under silicate and phosphate starvation whereas nitrate starvation rather increased carbohydrate and protein pools. Phosphate starvation also led to an important shift of dominance among protein groups between amide I and amide II which compounds are suspected to play a key role in the frustule synthesis and architecture. Nutrient starvations affected the relative biochemical composition of diatom frustule fractions and organic coating which could imply a strong impact on frustule structure and architecture but also on frustule mechanical and chemical resistance.
Published: 2018

20. Sur le terrain de l’océanographie politique : carnets de terrain, ethnographie multi-sites et modes de gouvernement de la Mer au croisement des sciences sociales et des sciences de la nature

Author: Olivier Ragueneau, Camille Mazé, Anatole Danto, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches sur l'Action Politique en Europe (ARENES), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut d'Études Politiques [IEP] - Rennes-École des Hautes Études en Santé Publique [EHESP] (EHESP)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), ANR-13-JCLI-0006,ARTISTICC,Recherche sur l'adaptation, une communauté transnationale et transdisciplinaire approche centrée sur la politique(2013), ANR-10-LABX-0019/10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), and Université de Rennes (UR)-Institut d'Études Politiques [IEP] - Rennes-École des Hautes Études en Santé Publique [EHESP] (EHESP)-Centre National de la Recherche Scientifique (CNRS)
Subjects: interdisciplinarité, 010504 meteorology & atmospheric sciences, Russie, océanographie politique, 010501 environmental sciences, 01 natural sciences, Political anthropology, Russia, [SHS.HISPHILSO]Humanities and Social Sciences/History, Philosophy and Sociology of Sciences, interdisciplinarity, Île de Kihnu, Ethnography, Iakutia, anthropologie politique, gouvernement de la mer, Tiksi, ComputingMilieux_MISCELLANEOUS, Bay of Qingdao, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SHS.SOCIO]Humanities and Social Sciences/Sociology, Saint Pierre and Miquelon, Saint-Pierre et Miquelon, Bay of Brest, General Social Sciences, Riga Gulf, Iakoutie, Baie de Qingdao, Thematic network, Golfe de Riga, Sibérie, government of the sea, Rade de Brest, Estonia, China, Saint-Pierre and Miquelon, [SDE.MCG]Environmental Sciences/Global Changes, Finno-ougrien, Post-soviétisme, Library and Information Sciences, Estonie, Political science, political anthropology, 14. Life underwater, Chine, 0105 earth and related environmental sciences, Kihnu island, ETUDES-NORDIQUES, [SHS.ANTHRO-SE]Humanities and Social Sciences/Social Anthropology and ethnology, Delta de la Léna, [SDE.ES]Environmental Sciences/Environmental and Society, [SHS.SCIPO]Humanities and Social Sciences/Political science, Siberia, ethnographie multi-site, [SHS.ENVIR]Humanities and Social Sciences/Environmental studies, Finno-ugric, multi-sited ethnography, Post-sovietism, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Humanities, oceanography policy, Lena delta
Abstract: This article presents a part of the Field notebooks' of the members of the International Multidisciplinary Thematic Network (RTPi) of CNRS ApoliMer (political anthropology of the sea), which focuses on the form of government of the sea, at the crossroads of the social sciences policy and natural sciences. Throughout the text, some of the ethnographic materials from the team's fieldwork surveys are used to describe how ApoliMer tracks governance on marine and coastal lands in an interdisciplinary manner. This article is also an opportunity to expose the genesis and evolution of the RTPi, through the various seasons' of research that has marked its existence since its birth in 2013-2014., Cet article présente une partie des « carnets de terrain » des membres du groupe ApoliMer (Anthropologie politique de la Mer / Approche éco-politiste de la mer). Ce réseau thématique pluridisciplinaire international (RTPi) du CNRS s’intéresse aux modes de gouvernement de la mer, en combinant sciences sociales du politique, sciences de la nature et sciences de l’ingénieur. Tout au long du texte, une partie des matériaux ethnographiques issus des enquêtes de terrain de l’équipe basée au Laboratoire des sciences de l’environnement marin (LEMAR) à Brest, est mobilisée pour décrire la manière dont les chercheurs décryptent les formes de gouvernement des terrains maritimes et littoraux, dans une étroite interdisciplinarité. Cet article est l’occasion d’exposer la genèse et l’évolution du RTPi, au travers de différentes “saisons” de recherches ayant marqué son existence, depuis sa naissance en 2013–2014.
Published: 2018
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21. Trends and seasonality of river nutrients in agricultural catchments: 18 years of weekly citizen science in France

Author: Florentina Moatar, Ophélie Fovet, Olivier Ragueneau, Virginie Antoine, Olivier Gauthier, Benjamin W. Abbott, Ecosystèmes, biodiversité, évolution [Rennes] (ECOBIO), Université de Rennes (UR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR), Université de Rennes (UR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 2 (UR2)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centre National de la Recherche Scientifique (CNRS), Brigham Young University (BYU), GéoHydrosystèmes COntinentaux (GéHCO EA6293), Université de Tours (UT), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Sol Agro et hydrosystème Spatialisation (SAS), Institut National de la Recherche Agronomique (INRA)-AGROCAMPUS OUEST, European Institute for Marine Studies (IUEM), CNRS, Conseil General du Finistere, European Project: 607150,EC:FP7:PEOPLE,FP7-PEOPLE-2013-ITN,INTERFACES(2013), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Centre National de la Recherche Scientifique (CNRS), Université de Tours, Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), AGROCAMPUS OUEST-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), AGROCAMPUS OUEST, and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de la Recherche Agronomique (INRA)
Subjects: Environmental Engineering, 010504 meteorology & atmospheric sciences, Nitrogen, Agricultural pollution, Land management, Time series analysis, 010501 environmental sciences, Citizen science, 01 natural sciences, Freshwater ecosystem, Nutrient, medicine, Environmental Chemistry, Waste Management and Disposal, 0105 earth and related environmental sciences, Land use, ACL, Phosphorus, Silica, 15. Life on land, Seasonality, Eutrophication, medicine.disease, Pollution, 6. Clean water, 13. Climate action, Environmental science, Water quality, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Water resource management
Abstract: International audience; Agriculture and urbanization have disturbed three-quarters of global ice-free land surface, delivering huge amounts of nitrogen and phosphorus to freshwater ecosystems. These excess nutrients degrade habitat and threaten human food and water security at a global scale. Because most catchments are either currently subjected to, or recovering from anthropogenic nutrient loading, understanding the short- and long-term responses of river nutrients to changes in land use is essential for effective management. We analyzed a never-published, 18-year time series of anthropogenic (NO3 − and PO4 3 −) and naturally derived (dissolved silica) riverine nutrients in 13 catchments recovering from agricultural pollution in western France. In a citizen science initiative, high-school students sampled catchments weekly, which ranged from 26 to 1489 km2. Nutrient concentrations decreased substantially over the period of record (19 to 50% for NO3 − and 14 to 80% for PO4 3 −), attributable to regional, national, and international investment and regulation, which started immediately prior to monitoring. For the majority of catchments, water quality during the summer low-flow period improved faster than during winter high-flow conditions, and annual minimum concentrations improved relatively faster than annual maximum concentrations. These patterns suggest that water-quality improvements were primarily due to elimination of discrete nutrient sources with seasonally-constant discharge (e.g. human and livestock wastewater), agreeing with available land-use and municipal records. Surprisingly, long-term nutrient decreases were not accompanied by changes in nutrient seasonality in most catchments, attributable to persistent, diffuse nutrient stocks. Despite decreases, nutrient concentrations in almost all catchments remained well above eutrophication thresholds, and because additional improvements will depend on decreasing diffuse nutrient sources, future gains may be much slower than initial rate of recovery. These findings demonstrate the value of citizen science initiatives in quantifying long-term and seasonal consequences of changes in land management, which are necessary to identify sustainable limits and predict recovery timeframes.
Published: 2018
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22. Effect of trace metal-limited growth on the postmortem dissolution of the marine diatomPseudo-nitzschia delicatissima

Author: Julia Boutorh, Brivaëla Moriceau, Olivier Ragueneau, Morgane Gallinari, and Eva Bucciarelli
Subjects: 0106 biological sciences, Atmospheric Science, Global and Planetary Change, 010504 meteorology & atmospheric sciences, biology, 010604 marine biology & hydrobiology, Mineralogy, chemistry.chemical_element, Biogenic silica, biology.organism_classification, 01 natural sciences, Copper, Silicate, chemistry.chemical_compound, chemistry, Environmental chemistry, Environmental Chemistry, Photic zone, Trace metal, Seawater, Pseudo-nitzschia, Dissolution, Geology, 0105 earth and related environmental sciences, General Environmental Science
Abstract: We investigated the effects of iron (Fe) and copper (Cu) limitations on biogenic silica (bSiO(2)) dissolution kinetics of the marine diatom Pseudo-nitzschia delicatissima during a 3 week batch dissolution experiment. The dissolution of this species was faster during the first week than thereafter. Modeling results from four dissolution models and scanning electron microcopy images suggested the successive dissolution of two phases of bSiO(2), with two different dissolution constants. Micronutrient limitation during growth affected the respective proportion of the two phases and their dissolution constants. After 3 weeks of dissolution, frustules from micronutrient-limited diatoms were better preserved than those of replete cells. Our results also confirm that micronutrient-limited cells may export more Si relative to N than replete cells and may increase the silicate pump: This may not only be due to a higher degree of silicification of the live cells but also to a decoupling between the recycling of Si and N during dissolution. We suggest that a mechanistic understanding of the evolution of the dissolution constant during dissolution is needed. This would improve the parameterization of dissolution in ecosystem models, and ultimately their predictions on the amount of bSiO(2) that dissolves in the photic zone, and the amount of bSiO(2) that is exported to the seafloor.
Published: 2016
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23. Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget

Author: Olivier Ragueneau, Christophe Rabouille, Mélanie Raimonet, Lara Pozzato, Vincent Jacques, Alexis Khripounoff, Brivaëla Moriceau, Rudolph Corvaisier, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Laboratoire Environnement Profond (LEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Océan et Interfaces (OCEANIS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Etudes des Ecosystèmes Profonds (EEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
Subjects: Geochemistry, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Aquatic Science, Oceanography, Congo canyon, Continental margin, 14. Life underwater, Ecology, Evolution, Behavior and Systematics, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Canyon, geography, geography.geographical_feature_category, Deep-sea fan, Continental shelf, ACL, Bioirrigation, Biological pump, Sediment, Carbon sink, Sedimentation, [SDE]Environmental Sciences, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Land-sea export, Silica cycle, Geology
Abstract: Mechanisms controlling the transfer and retention of silicon (Si) along continental margins are poorly understood, but play a major role in the functioning of coastal ecosystems and the oceanic biological pump of carbon. Deep-sea fans are well recognized as carbon sink spots, but we lack knowledge about the importance of the fans in the global Si cycle. Here, we provide a first estimate of the role played by the Congo deep-sea fan, one of the biggest in the world, in the Si cycle. Sediment cores sampled in the deep-sea fan were analyzed to build a Si mass balance. An exceptionally high accumulation rate of amorphous silica aSiO 2 (2.29 ± 0.58 mol Si m − 2 y − 1 ) was found, due to a high sedimentation rate and the presence of aluminum in the sediments. Although favored by bioirrigation, recycling fluxes remained low (0.3 mol Si m − 2 y − 1 ) and reconstructed input fluxes could only be explained by lateral inputs coming from the canyon. Preliminary calculations show that the rapid transport of aSiO 2 through the canyon and the excellent preservation efficiency in the sediments imply that 50% of aSiO 2 river inputs from the Congo River accumulate annually in the deep-sea fan. Si:C ratios in deep-sea fan sediments were very low (0.2) and only three times as high as those measured in the river itself, which suggests that material from the river and the continental shelf was delivered directly through the canyon, with very little time for Si and C cycle decoupling to take place.
Published: 2015
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24. Comparative biogeochemistry–ecosystem–human interactions on dynamic continental margins

Author: Wajih Naqvi, Olivier Ragueneau, Michele Giani, Sumei Liu, Zouhair Lachkar, Curtis Deutsch, Kay-Christian Emeis, Karen F. Wishner, Denise L. Breitburg, Enrique Montes, James E. Cloern, Karin E. Limburg, Lisa A. Levin, Kon-Kee Liu, Anne Goffart, Christophe Rabouille, Eileen E. Hofmann, Dennis P. Swaney, Paul Wassman, Santosh Kumar Sarkar, Scripps Institution of Oceanography (SIO - UC San Diego), University of California [San Diego] (UC San Diego), University of California (UC)-University of California (UC), National Central University [Taiwan] (NCU), Institut für Küstenforschung / Institute of Coastal Research, Helmholtz-Zentrum Geesthacht (GKSS), Smithsonian Environmental Research Center, Smithsonian Institution, US Geological Survey [Menlo Park], United States Geological Survey [Reston] (USGS), School of Oceanography [Seattle], University of Washington [Seattle], Istituto Nazionale di Geofisica e di Oceanografia Sperimentale (OGS), Université de Liège, Station de Recherche Océanographiques et sous-marines (STARESO ), Stareso, Pointe Revellata, BP 33, 20260 Calvi, France, Center for Coastal Physical Oceanography (CCPO), Old Dominion University [Norfolk] (ODU), Institute of Biogeochemistry and Pollutant Dynamics [ETH Zürich] (IBP), Department of Environmental Systems Science [ETH Zürich] (D-USYS), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich), SUNY College of Environmental Science and Forestry (SUNY-ESF), State University of New York (SUNY), Ocean University of China (OUC), College of Marine Science [St Petersburg, FL], University of South Florida [Tampa] (USF), CSIR National Institute of Oceanography [India] (NIO), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), University of Calcutta, Cornell University [New York], University of Tromsø (UiT), University of Rhode Island (URI), European Project: 287600,EC:FP7:ENV,FP7-OCEAN-2011,PERSEUS(2012), Scripps Institution of Oceanography (SIO), University of California-University of California, Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: Biogeochemical cycle, Time series, [SDE.MCG]Environmental Sciences/Global Changes, Biodiversity, Climate change, Aquatic Science, Oceanography, Anthropogenic factors, Ecosystem services, Arctic, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Continental margin, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Ecosystem, North Pacific, 14. Life underwater, skin and connective tissue diseases, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Ecology, Evolution, Behavior and Systematics, Ecology, ACL, Climate oscillation, Continental margins, North Atlantic, Coastal biogeochemistry, Biogeochemistry, Eutrophication, 15. Life on land, Europe, 13. Climate action, Environmental science, sense organs
Abstract: International audience; The oceans' continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO2-induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins, (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO2-induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services. These include primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.
Published: 2015
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25. Vulnerability of inter-tropical littoral areas

Author: Anatole Danto, Emilie Mariat-Roy, Julien Weisbein, Olivier Ragueneau, Tarik Dahou, Mélanie Raimonet, Camille Mazé, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Institut de Recherche pour le Développement (IRD), Patrimoines locaux, Environnement et Globalisation (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU), Centre de Recherches sur l'Action Politique en Europe (ARENES), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut d'Études Politiques [IEP] - Rennes-École des Hautes Études en Santé Publique [EHESP] (EHESP)-Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences Sociales du Politique (LaSSP), Institut d'Études Politiques [IEP] - Toulouse, CNRS, IRD, Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Centre d'études africaines (CEAf), École des hautes études en sciences sociales (EHESS)-Centre National de la Recherche Scientifique (CNRS), GGH-Terres, École des hautes études en sciences sociales (EHESS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut d'Études Politiques [IEP] - Rennes-École des Hautes Études en Santé Publique [EHESP] (EHESP)-Centre National de la Recherche Scientifique (CNRS), École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Manighetti, I (ed.), De Witt, R. (ed.), Duvail, Stéphanie (ed.), and Seyler, Patrick (ed.)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Systemic management, 01 natural sciences, Political anthropology, [SHS]Humanities and Social Sciences, Politics, Political science, Gouvernance de la mer, Gestion systémique, Governance of the sea, 14. Life underwater, Integrated coastal zone management, 0105 earth and related environmental sciences, Sustainable development, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, Government, Corporate governance, ACL, Environmental ethics, Science politique, Anthropologie, 010601 ecology, Action (philosophy), Anthropology, Power, [SDE]Environmental Sciences, Natural sciences, General Earth and Planetary Sciences, Pouvoir, Political sciences, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Coastal management, Sciences de la nature
Abstract: International audience; This article presents an innovative collaborative approach, which aims to reinforce and institutionalize the field of the political anthropology of the sea combined with the natural sciences. It begins by relating the evolution in coastal areas, from integrated coastal zone management to the notion of adaptive co-management. It then sets out what contribution the social sciences of politics may bring to our understanding of the government/governance of the sea in terms of sustainable development, starting with political science and then highlighting the importance of a deep anthropological and socio-historical approach. Finally, it gives us a glimpse of the benefits of combining the human and social sciences with the natural sciences to produce a critical analysis of the categories of thought and action associated with the systemic management of the environment, especially the coastal areas.
Published: 2017
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26. Modern palynological record in the Bay of Brest (NW France): Signal calibration for palaeo-reconstructions

Author: Gwendoline Gregoire, Aurélie Penaud, Clément Lambert, Olivier Ragueneau, Muriel Vidal, Vincent Lebreton, Nathalie Combourieu-Nebout, Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), Histoire naturelle de l'Homme préhistorique (HNHP), Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Unité de recherche Géosciences Marines (Ifremer) (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géosciences Océan (LGO), Université de Brest (UBO)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Université de Perpignan Via Domitia (UPVD), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Géosciences Marines (GM), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Brest (UBO)-Université de Bretagne Sud (UBS)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
Subjects: 010506 paleontology, Taphonomy, 010504 meteorology & atmospheric sciences, [SHS.ARCHEO]Humanities and Social Sciences/Archaeology and Prehistory, Fluvial, medicine.disease_cause, Pollen core, 01 natural sciences, Estuarine dynamics, Paleontology, Pollen, medicine, Dinocyst, 14. Life underwater, Ecology, Evolution, Behavior and Systematics, Holocene, 0105 earth and related environmental sciences, Palynology, ACL, Vegetation cover, 15. Life on land, 13. Climate action, Surface sediment, Physical geography, Bay, Geology
Abstract: International audience; Modern palynological investigations (pollen and non-pollen palynomorphs) have been carried out for the first time in the entire Bay of Brest (BB; NW France), a semi-enclosed oceanic basin flooded during the Holocene that today is exposed to both marine (North Atlantic surface waters) and fluvial (Aulne and Elorn rivers) influences. Palynological analyses were conducted on 41 surface sediments collected in several mudded bays where low-energy conditions prevail, allowing for fine particle decantation, and also on 12 moss samples considered to be pollen rain collectors taken on the periphery of the BB. Furthermore, the BB allows a direct comparison between landscapes and fossilized pollen assemblages in sediments thanks to relatively small watersheds and well-studied vegetation cover on land. Our data display a well-known distortion between pollen taxa percentages calculated from palynological slides and current vegetation cover on land, with a particular overestimation of arboreal taxa as well as an underestimation of herbaceous ones, especially of cereal crops that represent a major component of the regional continental vegetation. Various factors may be involved, including pollen transport issues, taphonomic processes, and different pollination rates according to trees/herbaceous taxa. Under close examination, we find that while all surface sediments show the same major species, palynological maps established in the BB regarding some specific pollen taxa exhibit differences and upstream-downstream gradients. Also, the comparison between the pollen content in BB surface sediments and in mosses supports the hydrodynamic influence acting on the pollen distribution in sediments. More specifically, we suggest that some arboreal taxa reflect a watershed effect, especially Alnus, which seems to be highly correlated to river influences and could therefore be considered as a potential proxy for fluvial Holocene palaeo-discharges within the BB.
Published: 2017
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27. The Congolobe project, a multidisciplinary study of Congo deep-sea fan lobe complex: Overview of methods, strategies, observations and sampling

Author: Nicolas Gayet, Karine Charlier, Mélanie Raimonet, Olivier Ragueneau, Philippe Noel, J. Le Saout, Christophe Rabouille, Florence Savignac, Laurent Toffin, Gilles Vétion, Ming-Yi Sun, Lucie Pastor, Perrine Cruaud, S. Bourgeois, Anne Godfroy, Françoise Lesongeur, F. Toussaint, Julie Tourolle, François Baudin, Olivier Mouchel, Elsa Stetten, Philippe Rodier, Audrey M. Pruski, Martine Bez, Cecile Cathalot, Martial Taillefert, Sophie Arnaud-Haond, Lara Pozzato, Rudolph Corvaisier, Laurence Méjanelle, N. Tisnerat-Laborde, Claire Croguennec, Christophe Brandily, Philippe Martinez, Jean-Claude Caprais, Arunima Sen, Bernard Dennielou, Bruno Bombled, Sandrine Bessette, C. Senyarich, Alexis Khripounoff, Karine Olu, Laurence Droz, M. Lesaout, Marie Picot, Stéphane Hourdez, Jordon S. Beckler, J. Le Bruchec, Johann Schnyder, Patricia Pignet, Nathalie Babonneau, Livio Ruffine, M. Rabiller, J.L. Reyss, P. Michalopoulos, J.-M. Jouanneau, C. Bayle, Carole Decker, Sara Teixeira, B. Ruesch, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Océan et Interfaces (OCEANIS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire Environnement Profond (LEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Evolution et Modélisation des Bassins Sédimentaires (EMBS), Institut des Sciences de la Terre de Paris (iSTeP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS), Unité de recherche Géosciences Marines (Ifremer) (GM), Laboratoire de microbiologie des environnements extrêmophiles (LM2E), Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Domaines Océaniques (LDO), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Observatoire des Sciences de l'Univers-Institut d'écologie et environnement-Centre National de la Recherche Scientifique (CNRS), School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], Laboratoire d'Ecogéochimie des environnements benthiques (LECOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Adaptation et Biologie des Invertébrés en Conditions Extrêmes (ABICE), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Hellenic Centre for Marine Research (HCMR), Department of Marine Sciences [Athens], University of Georgia [USA], Centre of Marine Sciences [Faro] (CCMAR), University of Algarve [Portugal], Géochrononologie Traceurs Archéométrie (GEOTRAC), TOTAL-Scientific and Technical Center Jean Féger (CSTJF), TOTAL FINA ELF, ANR-11-BS56-0030,CONGOLOBE,Transfert de carbone organique et fonctionnement des écosystèmes dans les lobes terminaux de l'éventail sous-marin du Congo(2011), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Etudes des Ecosystèmes Profonds (EEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Géosciences Marines (GM), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Adaptation et diversité en milieu marin (ADMM), Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre scientifique et Technique Jean Feger (CSTJF), and Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Turbidity current, Continental-Margin, 010504 meteorology & atmospheric sciences, Fine sediment, Sedimentation rate, Transport, Submarine canyon, Vesicomyidae, 010502 geochemistry & geophysics, Oceanography, Turbidite, 01 natural sciences, Deep sea, Particulate Materials, Guaymas Basin, 14. Life underwater, Congo deep-sea fan, Chemosynthetic habitats, Turbidity-Current, 0105 earth and related environmental sciences, Canyon, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, ACL, Organic-Carbon Accumulation, Particle Fluxes, Estuary, Seafloor morphology, 15. Life on land, M Water Depth, 13. Climate action, Mud Volcano, [SDE]Environmental Sciences, Chemosynthetic Ecosystems, Submarine pipeline, Sedimentary rock, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Geology
Abstract: The presently active region of the Congo deep-sea fan (around 330,000 km(2)), called the terminal lobes or lobe complex, covers an area of 2500 km(2) at 4700-5100 m water depth and 750-800 km offshore. It is a unique sedimentary area in the world ocean fed by a submarine canyon and a channel-levee system which presently deliver large amounts of organic carbon originating from the Congo River by turbidity currents. This particularity is due to the deep incision of the shelf by the Congo canyon, up to 30 km into the estuary, which funnels the Congo River sediments into the deep-sea. The connection between the river and the canyon is unique for major world rivers. In 2011, two cruises (WACS leg 2 and Congolobe) were conducted to simultaneously investigate the geology, organic and inorganic geochemistry, and micro- and macro-biology of the terminal lobes of the Congo deep-sea fan. Using this multidisciplinary approach, the morpho-sedimentary features of the lobes were characterized along with the origin and reactivity of organic matter, the recycling and burial of biogenic compounds, the diversity and function of bacterial and archaeal communities within the sediment, and the biodiversity and functioning of the faunal assemblages on the seafloor. Six different sites were selected for this study: Four distributed along the active channel from the lobe complex entrance to the outer rim of the sediment deposition zone, and two positioned cross-axis and at increasing distance from the active channel, thus providing a gradient in turbidite particle delivery and sediment age. This paper aims to provide the general context of this multidisciplinary study. It describes the general features of the site and the overall sampling strategy and provides the initial habitat observations to guide the other in-depth investigations presented in this special issue. Detailed bathymetry of each sampling site using 0.1-1 m resolution multibeam obtained with a remotely operated vehicle (ROV) shows progressive widening and smoothing of the channel-levees with increasing depth and reveals a complex morphology with channel bifurcations, erosional features and massive deposits. Dense ecosystems surveyed in the study area gather high density clusters of two large-sized species of symbiotic Vesicomyidae bivalves and microbial mats. These assemblages, which are rarely observed in sedimentary zones, resemble those based on chemosynthesis at cold-seep sites, such as the active pockmarks encountered along the Congo margin, and share with these sites the dominant vesicomyid species Christineconcha regab. Sedimentation rates estimated in the lobe complex range between 0.5 and 10 cm yr(-1), which is 2-3 orders of magnitude higher than values generally encountered at abyssal depths. The bathymetry, faunal assemblages and sedimentation rates make the Congo lobe complex a highly peculiar deep-sea habitat driven by high inputs of terrigenous material delivered by the Congo channel-levee system. (c) 2016 Elsevier Ltd. All rights reserved. ZAIANGO ANR Congolobe (ANR Blanc SIMI5-6) [11 BS56 030] IFREMER CEA through LSCE U.S. National Science Foundation [OCE-0831156] info:eu-repo/semantics/acceptedVersion
Published: 2017
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28. MICROBIAL EFFECTS ON EARLY DIAGENETIC SI CYCLING IN DEEP-SEA AND DELTAIC SEDIMENTS

Author: Martial Taillefert, Rudolph Corvaisier, Christophe Rabouille, Rebecca A. Pickering, Jeffrey W. Krause, P. Michalopoulos, Eleni Rouselaki, and Olivier Ragueneau
Subjects: Geochemistry, Cycling, Deep sea, Geology, Diagenesis
Published: 2017
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29. Alkaline-extractable silicon from land to ocean : a challenge for biogenic silicon determination

Author: Lúcia Barão, Patrick J. Frings, Daniel J. Conley, Eric Struyf, Patrick Meire, Olivier Ragueneau, Wim Clymans, and Floor Vandevenne
Subjects: Biogeochemical cycle, Mineralogy, Ocean Engineering, Geokemi, 15. Life on land, Biogenic silica, Particulates, Silicate, chemistry.chemical_compound, Geochemistry, chemistry, 13. Climate action, Environmental chemistry, Silicate minerals, Soil water, Soil horizon, Dissolution, Biology, Geology
Abstract: The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contributions of nonbiogenic sources of Si dissolving during alkaline extractions, not corrected by standard silicate mineral dissolution correction protocols, can be substantial. The ratio between dissolved Si and aluminum (Al) monitored continuously during the alkaline extraction can be used to infer the origin of the Si fractions present. In this study, we applied both a continuous analysis method (0.5 M NaOH) and a traditional 0.1 M Na2CO3 extraction to a wide array of samples: (1) terrestrial vegetation, (2) soils from forest, cropland and pasture, (3) lake sediments, (4) suspended particulate matter and sediments from rivers, (5) sediments from estuaries and salt marshes and (6) ocean sediments. Our results indicate that the 0.1 M Na2CO3 extraction protocol can overestimate the BSi content, by simultaneously dissolving Si fractions of nonbiogenic origin that may represent up to 100% of the Si traditionally considered as biogenic, hampering interpretation especially in some deeper soil horizons, rivers and coastal oceanic sediments. Moreover, although the term amorphous Si was coined to reflect a growing awareness of nonbiogenic phases we show it is actually inappropriate in samples where silicate minerals may account for a large part of the extracted Si even after linear mineral correction.
Published: 2015

30. Biogenic silica dissolution in diatom aggregates: Insights from reactive transport modelling

Author: Goulven Gildas Laruelle, Olivier Ragueneau, Uta Passow, Philippe Van Cappellen, Brivaëla Moriceau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Faculty of Geosciences [Utrecht], Utrecht University [Utrecht], Université libre de Bruxelles (ULB), Marine Science Institute [Santa Barbara] (MSI), University of California [Santa Barbara] (UC Santa Barbara), University of California (UC)-University of California (UC), Department of Earth and Environmental Sciences [Waterloo], University of Waterloo [Waterloo], We acknowledge funding to B.M. from theEU, partly through the ORFOIS (EVK2-CT2001-00100) project and partly through the Si-WEBS (HPRN-CT-2002-00218) Research Training network of the Marie Curie programme, and funding to U.P. from the National ScienceFoundation (NSF). This research was also partly funded byKing Abdullah University of Science and Technology(KAUST) Center-in-Development Award to Utrecht University (project No. KUK-C1-017-12), European Project, Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of California [Santa Barbara] (UCSB), and University of California-University of California
Subjects: diatom aggregate, Mineralogy, Aquatic Science, Biogenic silica, chemistry.chemical_compound, Adsorption, Silicic acid, 14. Life underwater, Diffusion (business), Dissolution, Ecology, Evolution, Behavior and Systematics, dSi diffusion, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Si cycle, Ecology, biology, Chemistry, ACL, silicic acid accumulation, Transparent exopolymer particles, Particulates, biology.organism_classification, biogenic silica dissolution, TEP, Diatom, Viability, Chemical engineering, dSi adsorption, dSi accumulation, Seawater, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: International audience; Diatom aggregates contribute significantly to the vertical sinking flux of particulate matter in the ocean. These fragile structures form a specific microhabitat for the aggregated cells but their internal chemical and physical characteristics remain largely unknown. Studies on the impact of aggregation on Si cycle led to what appears to be inconsistency. Despite a lower biogenic silica (bSiO2) dissolution rate and a diffusion of the silicic acid (dSi) similar in aggregate and in seawater, dSi surprisingly accumulate in aggregates. A reaction-diffusion model helps to clarify this incoherence by reconstructing dSi accumulation measured during batch experiments with aggregated and non-aggregated Skeletonema marinoi and Chaetoceros decipiens. The model calculates the effective bSiO2 dissolution rate as opposed to the experimental apparent bSiO2 dissolution rate, which results on the effective bSiO2 dissolution and transport of dSi out of the aggregate. In the model, dSi transport out of the aggregate is modulated considering alternatively retention -decrease of dSi diffusion constant- and adsorption -reversible chemical bounds between dSi and the aggregate matrix- processes. Modelled bSiO2 dissolution is modulated by the impact of dSi concentration inside aggregate and diatom viability, as enhanced persistence of metabolically active diatom has been observed in aggregates. Adsorption better explains dSi accumulation within and outside aggregates, raising the possible importance of dSi travelling within aggregates to the deep sea (potentially 20% of the total silica flux). Moreover, the model states that bSiO2 dissolution is effectively decreased in aggregates mainly due to higher diatom viability but also to other parameters discussed here; Les agrégats de diatomées contribuent de façon significative au flux vertical de matière dans l'océan. Ces fragiles structures forment un microhabitat particulier dont les caractéristiques physico-chimiques internes sont pourtant encore peu connues. Les études menées jusqu'à présent sur l'impact de l'agrégation sur le cycle du silicium conduisent à des conclusions à première vue incohérentes: malgré une vitesse de dissolution de la silice biogénique (bSiO2) plus faible dans les agrégats de diatomées, et une vitesse de diffusion de la silice dissoute (dSi) similaire à celle de l'eau de mer, la dSi s'accumule dans l'eau intersticielle des agrégats pour atteindre des valeurs jusqu'à 200 fois supérieures à celle de l'eau de mer environnante. En utilisant un modèle de reaction-diffusion qui reproduit l'accumulation de la dSi mesurée expérimentalement à l'intérieur et à l'extérieur d'agrégats monospécifiques de diatomée Skeletonema marinoii et Chaetoceros decipiens, le modèle calcule la vitesse effective de dissolution de la bSiO2 dans un agrégat. Par comparaison, la vitesse de dissolution accessible experimentalement et appelée dans cette étude "vitesse de dissolution apparente" résulte de la vitesse de dissolution effective et du transport de dSi hors de l'agrégat. Dans le modèle, le transport de dSi est modulé en considérant alternativement deux processus: la rétention qui implique un ralentissement de la diffusion de la dSi et de la constante diffusion, et l'adsorption qui est un processus reversible impliquant des liaisons faibles entre la dSi et la matrice de l'agrégat. la dissolution de la bSiO2 est modélisée en considérant l'impact de la concentration en dSi à l'intérieur de l'agrégat et la viabilité des diatomées. Les résultats montrent que des processus d'adsorption permettent de mieux reconstruire la dissolution de la bSiO2 dans un agrégats. Cette conclusion souligne l'importance du transport vertical de silice dissoute par les agrégats jusqu'aux couches profondes océaniques (potentiellement 20% du flux total de sédimentation du silicium). Deplus, le modèle tend à confirmer la diminution de la vitesse effective de dissolution de la bSiO2 dans les agrégats et non plus seulement de la vitesse de dissolution apparente. Ce ralentissement serait principalement le resultat d'une viabilité maintenue plus longtemps dans les agrégats que dans lorsque les cellules sont libres, mais aussi d'autres processus non-identifiés mais discutés dans cette étude.
Published: 2014
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31. Long-term variation of the Bay of Brest ecosystem:benthic-pelagic coupling revisited

Author: Laurent Chauvaud, Gérard Thouzeau, Frédéric Jean, and Olivier Ragueneau
Subjects: Biomass (ecology), Ecology, biology, fungi, Pelagic zone, Aquatic Science, Spring bloom, Biogenic silica, biology.organism_classification, Oceanography, Diatom, Benthic zone, Phytoplankton, Bay, Ecology, Evolution, Behavior and Systematics
Abstract: Observations over the last 20 yr of the development of pelagic and benthic communities of a western European coastal ecosystem (Bay of Brest) provide complementary hypotheses to the 'silicic acid pump' hypothesis. An increase in nitrogen inputs, independent of silicic acid levels, has lowered the Si:N molar ratios during the last 20 yr in river discharges. Since 1981, maximum concen- trations of chlorophyll a during the first spring bloom of the annual cycle have decreased, in contrast to the subsequent spring and summer blooms. Concomitantly, extensive spreading of an exotic gas- tropod Crepidula fornicata has modified the trophic structure of benthic communities by increasing suspension-feeder biomass. The following hypotheses on ecosystem functioning are made: (1) the decrease of chlorophyll biomass during the first spring bloom results from silicic acid limitation and increased suspension feeder activity, (2) benthic filtration and biodeposition activities enhance bio- genic silica retention at the sediment-water interface, and (3) recycling of trapped biogenic silica maintains diatom populations by providing silicic acid in summer and reduces primary production seasonality. These hypotheses suggest that benthic organisms control the export rate of biogenic silica towards the open-water ocean and thus the specific composition of secondary phytoplankton blooms in the Bay.
Published: 2000
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32. Spatial and Temporal Variability of Sediment Organic Matter Recycling in Two Temperate Eutrophicated Estuaries

Author: Anniet M. Laverman, Olivier Ragueneau, Bruno Deflandre, Françoise Andrieux-Loyer, Eric Viollier, Christophe Rabouille, Mélanie Raimonet, Chen Yan, Karima Khalil, Ecole Supérieure de Technologie d'Essaouira, Université Cadi Ayyad [Marrakech] (UCA), Structure et fonctionnement des systèmes hydriques continentaux (SISYPHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Dynamiques des Écosystèmes Côtiers (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Dynamiques de l'Environnement Côtier (DYNECO), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)
Subjects: 0106 biological sciences, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, 01 natural sciences, Organic carbon and isotopic composition, Bottom water, Water column, Geochemistry and Petrology, Organic matter, 14. Life underwater, Estuarine sediment, 0105 earth and related environmental sciences, chemistry.chemical_classification, Total organic carbon, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, Sediment, Estuary, Mineralization (soil science), 15. Life on land, Oxygen, Geophysics, Organic matter recycling, chemistry, 13. Climate action, Environmental chemistry, Microelectrode, [SDE]Environmental Sciences, Environmental science, Spatial and temporal variability
Abstract: International audience; This paper deals with the spatial and seasonal recycling of organic matter in sediments of two temperate small estuaries (Elorn and Aulne, France). The spatio-temporal distribution of oxygen, nutrient and metal concentrations as well as the organic carbon and nitrogen contents in surficial sediments were determined and diffusive oxygen fluxes were calculated. In order to assess the source of organic carbon (OC) in the two estuaries, the isotopic composition of carbon (δ 13C) was also measured. The temporal variation of organic matter recycling was studied during four seasons in order to understand the driving forces of sediment mineralization and storage in these temperate estuaries. Low spatial variability of vertical profiles of oxygen, nutrient, and metal concentrations and diffusive oxygen fluxes were monitored at the station scale (within meters of the exact location) and cross-section scale. We observed diffusive oxygen fluxes around 15 mmol m−2 day−1 in the Elorn estuary and 10 mmol m−2 day−1 in the Aulne estuary. The outer (marine) stations of the two estuaries displayed similar diffusive O2 fluxes. Suboxic and anoxic mineralization was large in the sediments from the two estuaries as shown by the rapid removal of very high bottom water concentrations of NO x − (>200 μM) and the large NH4 + increase at depth at all stations. OC contents and C/N ratios were high in upstream sediments (11-15 % d.w. and 4-6, respectively) and decreased downstream to values around 2 % d.w. and C/N ≤ 10. δ 13C values show that the organic matter has different origins in the two watersheds as exemplified by lower δ 13C values in the Aulne watershed. A high increase of δ 13C and C/N values was visible in the two estuaries from upstream to downstream indicating a progressive mixing of terrestrial with marine organic matter. The Elorn estuary is influenced by human activities in its watershed (urban area, animal farming) which suggest the input of labile organic matter, whereas the Aulne estuary displays larger river primary production which can be either mineralized in the water column or transferred to the lower estuary, thus leaving a lower mineralization in Aulne than Elorn estuary. This study highlights that (1) meter scale heterogeneity of benthic biogeochemical properties can be low in small and linear macrotidal estuaries, (2) two estuaries that are geographically close can show different pattern of organic matter origin and recycling related to human activities on watersheds, (3) small estuaries can have an important role in recycling and retention of organic matter.
Published: 2013
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33. Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles

Author: Olivier Ragueneau, Roger Kerouel, Françoise Andrieux-Loyer, Xavier Philippon, Michel Nonent, Laurent Memery, Mélanie Raimonet, Emma Michaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Structure et fonctionnement des systèmes hydriques continentaux (SISYPHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Dynamiques des Écosystèmes Côtiers (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Groupe d'Etude de la Thrombose de Bretagne Occidentale (GETBO), Université de Brest (UBO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut Brestois Santé Agro Matière (IBSAM), Université de Brest (UBO)-Université de Brest (UBO), Département de radiologie [Brest] (DR - Brest), Centre Hospitalier Régional Universitaire de Brest (CHRU Brest), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Dynamiques de l'Environnement Côtier (DYNECO), and Université de Brest (UBO)-Institut Brestois Santé Agro Matière (IBSAM)
Subjects: 0106 biological sciences, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Phosphate, 01 natural sciences, Macrotidal, estuary, Environmental Chemistry, Organic matter, 14. Life underwater, Early diagenesis, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, phosphate, chemistry.chemical_classification, geography, geography.geographical_feature_category, Brackish water, silicate, 010604 marine biology & hydrobiology, Estuary, Sediment, Biogeochemistry, Silicate, Authigenic, 15. Life on land, 6. Clean water, macrotidal, Oceanography, chemistry, 13. Climate action, Benthic zone, Authigenic phosphorus, authigenic phosphorus, [SDE]Environmental Sciences, early diagenesis, Geology
Abstract: This study aims to investigate the role of spatial and temporal physical, biological and biogeochemical gradients on sediment biogeochemistry along a macrotidal and Si-rich estuary. Scanning and biogeochemical analyses were performed in the inner, mid and outer Aulne Estuary (France) at four seasons. The inner estuary shows high diagenetic activity linked to fluid mud dynamics and river loads. The highest authigenic phosphorus (Aut-P) concentrations ever found in the literature are observed in the inner estuary (18 μmol g−1 PS sediment). This is explained by a combination of favorable factors, i.e. the high organic matter and nutrient loads, the reductive conditions, the freshwater properties (low pH, OH−, sulfate and Mg2+ concentrations), the increase of particle residence time by the upward convergence of particles due to residual currents, and allochthonous riverine Aut-P. We suggest that the high Si(OH)4 concentrations (>400 μM) may even increase Aut-P precipitation through the increase of Fe–P formation in these low salinity conditions. In the mid estuary, erosion–deposition dynamics dominate in point bars and lead to the succession of poor and rich organic and authigenic phosphorus layers, recording thus the seasonality of matter loads and its seasonal translocation from the inner estuary. In the outer estuary, deposition rates are high and constant and biogeochemical properties are characteristic of marine environments. The precipitation of Aut-P from free phosphate (PO4 3−) is lower than in the inner estuary and might be limited by higher Mg2+ concentrations in saline waters. This study highlights that small macrotidal estuaries, and especially their freshwater sediments, may constitute an important phosphorus sink through the precipitation of Aut-P. This precipitation could even be enhanced in fresh or brackish environments, thus increasing long term phosphorus storage and altering benthic fluxes of PO4 3− to the pelagic ecosystem.
Published: 2013
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34. Spatio-temporal variability in benthic silica cycling in two macrotidal estuaries: causes and consequences for local to global studies

Author: Laurent Memery, Françoise Andrieux-Loyer, Mélanie Raimonet, Manon Le Goff, Xavier Philippon, Olivier Ragueneau, Roger Kerouel, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Structure et fonctionnement des systèmes hydriques continentaux (SISYPHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Dynamiques de l'Environnement Côtier (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Mines Paris - PSL (École nationale supérieure des mines de Paris), and Dynamiques des Écosystèmes Côtiers (DYNECO)
Subjects: 0106 biological sciences, Delta, upscaling, 010504 meteorology & atmospheric sciences, Fjord, Aquatic Science, Oceanography, 01 natural sciences, land-sea interface, Pore water pressure, Ecosystem, 14. Life underwater, Temporal scales, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, silicate, 010604 marine biology & hydrobiology, Sediment, Estuary, 15. Life on land, sediment, 13. Climate action, Benthic zone, [SDE]Environmental Sciences, Environmental science, heterogeneity, season
Abstract: International audience; The high heterogeneity of silica cycling in coastal margins and the lack of silica data (compared to nitrogen and phosphorus) prevent the estimation of global silica retention in estuaries. In this study, the spatial and temporal variability of pore water silicic acid (Si(OH)4) profiles - that integrate benthic transport and reaction processes - was investigated at different spatial (meter, longitudinal and cross-section, intra-estuary) and temporal (tidal, seasonal) scales in two macrotidal estuaries, very close geographically but differing essentially in their shape. Studying the spatial and temporal variability of Si(OH)4 concentrations in pore waters provided evidence for the importance of transport processes, e.g. bio-irrigation, tidal pumping, resuspension and any combination of these processes, in affecting Si(OH)4 concentrations and fluxes and hence, temporary or permanent retention along the land-ocean continuum. We confirm that aSiO2 transported by rivers and estuaries clearly deserves to be better characterized as it provides an important source of reactive aSiO2 to sediments. This study brings crucial information which allows to (1) deconvoluate spatial and temporal scales, although both are most often in complete interaction, (2) design the most appropriate sampling schemes to be representative of any given system and to extrapolate at the scale of the whole estuary, (3) quantify uncertainty associated to the estimations of Si(OH)4 stocks and fluxes in this type of ecosystem, essential for budget calculations. We showed that two adjacent small macrotidal estuaries, may exhibit different behaviors regarding Si retention. Temporary retention has been observed in the meanders of the Aulne Estuary and not along the more linear Elorn Estuary, demonstrating the importance of the morphology and hydrodynamism component of the estuarine filter. This effort needs to be pursued in other systems and climatic zones, but our study suggests that the typology should not only account for the different types of land-ocean continuum (fjord, delta, mangrove...), but also incorporate the physical or biological attributes of the estuarine filter.
Published: 2013
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35. Controls on the Recycling and Preservation of Biogenic Silica from Biomineralization to Burial

Author: Socratis Loucaides, Brivaëla Moriceau, Olivier Ragueneau, Philippe Van Cappellen, Vincent Roubeix, National Oceanography Centre [Southampton] (NOC), University of Southampton, School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], Réseaux épuration et qualité des eaux (UR REBX), Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Biomineralization, Materials science, 010504 meteorology & atmospheric sciences, Mineralogy, Weathering, Biogenic silica, 01 natural sciences, Diagenesis, Water column, Silicate minerals, 14. Life underwater, Dissolution, 0105 earth and related environmental sciences, Total organic carbon, biology, 010604 marine biology & hydrobiology, fungi, biology.organism_classification, 6. Clean water, Electronic, Optical and Magnetic Materials, Diatom, Silicon cycle, 13. Climate action, Environmental chemistry, [SDE]Environmental Sciences
Abstract: [Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA; International audience; The recycling of biogenic silica (bSiO2) produced by diatoms is a vital process sustaining a significant fraction of primary production in the oceans. The efficiency with which bSiO2 dissolves controls the availability of nutrient silicon in the water column, and modulates the export of organic carbon to the deep sea. Environmental conditions during biomineralization (temperature, nutrient availability, light, etc.) affect the silicification and weathering resistance of diatom frustules, while ecosystem processes, including grazing and aggregation, are determining factors for the recycling of bSiO2 in the water column. Bacterial colonization of dead diatoms leads to the decomposition of the protective organic layers allowing for the dissolution of bSiO2 to begin. The dissolution rate of diatom frustules is a function of the physicochemical properties of both the silica (e.g., specific surface area, degree of hydration and condensation, impurities) and the aqueous medium (e.g., temperature, pH, pressure, electrolyte composition). In sediments, the dissolution of bSiO2 is controlled by the presence of lithogenic minerals, aging processes and the build up of dSi in the pore waters. In particular, interactions between lithogenic silicate minerals and bSiO2 may initiate rapid diagenetic alterations that favor the preservation of bSiO2.
Published: 2012
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36. In situ biogenic silica variations in the invasive salt marsh plant, Spartina alterniflora : A possible link with environmental stress

Author: Olivier Ragueneau, Nathalie Poupart, Jérémy Querné, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Écophysiologie et de Biotechnologie des Halophytes et des Algues Marines (LEBHAM), Université de Brest (UBO), Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), and Université de Nantes (UN)-Université de Nantes (UN)
Subjects: 0106 biological sciences, Duration of immersion, Marsh, Soil Science, Wetland, Plant Science, Biogenic silica, Spartina alterniflora, 01 natural sciences, Abiotic factors, Wave activity, Abiotic component, geography, geography.geographical_feature_category, biology, Ecology, 010604 marine biology & hydrobiology, Estuarine salinity, Estuary, 15. Life on land, biology.organism_classification, Salinity, Salt marsh, Environmental chemistry, [SDE]Environmental Sciences, Environmental science, 010606 plant biology & botany
Abstract: International audience; Aims Higher plants are an understudied component of the global silicon cycle; they absorb silicic acid (dSi) which is stored as biogenic silica (bSiO2). Si is believed to alleviate physical, chemical, and biological stresses such as storms, high salinity, heavy metal toxicity, grazing, and disease. We investigated a Si-accumulating invasive species growing in the tidal marshes of the Bay of Brest (France), viz., Spartina alterniflora. Our objectives were to determine (1) where and when bSiO2 accumulates in the plant during its life cycle, (2) whether this accumulation varies with abiotic factors: wave action, estuarine salinity, and duration of immersion, and (3) if the accumulation was limited by dSi availability in marsh porewater. Methods A 2 years field survey permitted to sample plants which were analyzed for there bSiO2 concentrations. Sediment cores were sampled seasonally and the dSi concentrations in the porewater were measured from 0 to 10 cm. Results bSiO2 accumulated more in mature leaves than in other organs. There was a strong linear relationship between bSiO2 concentration and plant length. bSiO2 concentrations did not increase, but rather decreased as a function of exposure to the three abiotic factors tested. dSi availability was not significantly different for each of the tested sites and dSi profiles did not exhibit huge losses in the root zone. Conclusions Our evidence suggests that dSi availability did not seem to be a limiting factor. bSiO2 did not increase with increasing abiotic stresses but was strongly correlated with growth. Hence, S. alterniflora is likely to have other adaptive strategies for dealing with environmental stressors but it did not exclude the possible role of Si in alleviating these stresses. If this is the case, there remain intriguing questions about Si uptake, its availability, and its role in silicification and growth.
Published: 2012
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37. Anthropogenic perturbations of the silicon cycle at the global scale: Key role of the land-ocean transition

Author: Caroline P. Slomp, Hans H. Dürr, Olivier Ragueneau, S. Ni Longphuirt, Jean-Dominique Meunier, Loredana Saccone, Brivaëla Moriceau, Pierre Regnier, C. Spiteri, P. Michalopoulos, Daniel J. Conley, Agata Sferratore, Socratis Loucaides, Michel Meybeck, D. Ciuffa, Vincent Roubeix, Goulven Gildas Laruelle, Liana Papush, Josette Garnier, P. Van Cappellen, B. Brodherr, Massimo Presti, Q. Le Thi Phuong, and Christiane Lancelot
Subjects: 0106 biological sciences, Atmospheric Science, Global and Planetary Change, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Global temperature, 010604 marine biology & hydrobiology, Biogeochemistry, Biogenic silica, 01 natural sciences, Deep sea, Silicate, chemistry.chemical_compound, Oceanography, chemistry, 13. Climate action, Environmental Chemistry, Ecosystem, Terrestrial ecosystem, 14. Life underwater, Geology, 0105 earth and related environmental sciences, General Environmental Science
Abstract: Silicon (Si), in the form of dissolved silicate (DSi), is a key nutrient in marine and continental ecosystems. DSi is taken up by organisms to produce structural elements (e.g., shells and phytoliths) composed of amorphous biogenic silica (bSiO(2)). A global mass balance model of the biologically active part of the modern Si cycle is derived on the basis of a systematic review of existing data regarding terrestrial and oceanic production fluxes, reservoir sizes, and residence times for DSi and bSiO(2). The model demonstrates the high sensitivity of biogeochemical Si cycling in the coastal zone to anthropogenic pressures, such as river damming and global temperature rise. As a result, further significant changes in the production and recycling of bSiO(2) in the coastal zone are to be expected over the course of this century.
Published: 2009
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38. A benthic Si mass balance on the Congo margin: Origin of the 4000 m DSi anomaly and implications for the transfer of Si from land to ocean

Author: François Baurand, Alexis Khripounoff, Morgane Gallinari, Aurore Regaudie-de-Gioux, Olivier Ragueneau, Annick Vangriesheim, Brivaëla Moriceau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut Mediterrani d'Estudis Avancats (IMEDEA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de las Islas Baleares (UIB), Laboratoire Environnement Profond (LEP), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Si-WEBS RTN (HPRN-CT-2002-00218), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Etudes des Ecosystèmes Profonds (EEP), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Mineralogy, Biogenic silica, Oceanography, 01 natural sciences, chemistry.chemical_compound, Flux (metallurgy), Organic matter, 14. Life underwater, Silicic acid, 0105 earth and related environmental sciences, chemistry.chemical_classification, geography, geography.geographical_feature_category, Continental shelf, 010604 marine biology & hydrobiology, Pelagic zone, Continental margin, Sedimentation, Preservation, chemistry, Congo, 13. Climate action, Benthic zone, [SDE]Environmental Sciences, Geology, Dissolution
Abstract: 11 pages, 6 figures, 3 tables.-- Article in press., To elucidate the origin of the silicic acid (DSi) anomaly observed along the 4000 isobath on the Congo margin, we have established a benthic Si mass balance and performed direct measurements of biogenic silica (bSiO2) dissolution in the deep waters and in the sediments. Results strongly suggest that the anomaly originates from the sediments; the intensity of DSi recycling is consistent with the degradation of organic matter, as observed from Si:O2 ratios in the benthic fluxes compared to that ratio observed in the anomalies. Strong imbalances, observed in both the Si and C mass balances, suggest that the biogenic matter that degrades and dissolves in these sediments near 4000 m does not come from pelagic sedimentation. It is probably not coming also from the deep channel, because observations were similar in the deep channel vicinity (site D) and further south, far from its influence (site C). The composition of the sediments, with an Si:C ratio close to that observed on continental shelves, suggests that this matter is coming from downslope transport. A first estimate of the magnitude of this flux at global scale, close to 12 T mol Si yr−1, suggests that it may be an important path for transferring Si from land to ocean., This study has been partly funded through the Si-WEBS RTN (HPRN-CT-2002-00218) and the European Commission is greatly acknowledged.
Published: 2009
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39. Recycling and uptake of Si(OH)4 when protozoan grazers feed on diatoms

Author: Philippe Pondaven, Rudolph Corvaisier, Sandra Jansen, Sabine Schultes, Olivier Ragueneau, Christophe Lambert, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université européenne de Bretagne - European University of Brittany (UEB), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Marie Curie Intra-European Fellowship no. 010882 (ZOOPALIS), CNRS post-doc fellowship (project VICOFLUX), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Frustule, Thalassiosira pseudonana, Silicic Acid, Heterotroph, 01 natural sciences, Microbiology, Zooplankton, 03 medical and health sciences, Oxyrrhis marina, Botany, Animals, 14. Life underwater, 030304 developmental biology, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Ciliate, Diatoms, 0303 health sciences, biology, [SDV.BA]Life Sciences [q-bio]/Animal biology, 010604 marine biology & hydrobiology, fungi, Dinoflagellate, biology.organism_classification, Top-down effects, Diatom, Alveolata, Microzooplankton, Silica recycling, Water Microbiology, Microbial loop
Abstract: International audience; Herbivory of microzooplankton is an emerging key factor of diatom mortality in the ocean. As part of the microbial loop, protozoan grazers also feed on bacteria that accelerate the degradation of diatom detritus. The potentially pivotal effect of microzooplankton grazing on Si(OH)4 recycling was investigated with cultures of single-celled diatoms, Thalassiosira pseudonana and Chaetoceros gracilis, and heterotrophic protozoans, the dinoflagellate Oxyrrhis marina and the ciliate Strombidium sp. Both grazers ingested diatoms and the bacteria in the non-axenic cultures. C. gracilis, whose frustule is “armed” with setae, was less suitable as a prey than T. pseudonana. Ingestion rates of T. pseudonana were comparable for O. marina and Strombidium, but the dinoflagellate produced two orders of magnitude more detrital bSiO2 than the ciliate, due to the higher abundance reached by O. marina. Total net release of Si(OH)4 was lower in the grazing treatments compared to the control possibly due to the reduced bacterial growth by microzooplankton bacterivory, and to the transient protection of detrital bSiO2 in discarded feeding vacuoles. Over the first 24h, microzooplankton grazing even led to enhanced uptake of Si(OH)4 by diatoms, confirming the potential of grazing to influence the silicification of diatom frustules. Subsequently however, the Si dynamics in bottles with grazers turned rapidly from net uptake to net Si(OH)4 release. Protozoan grazers hence tie Si(OH)4 recycling into the microbial loop by producing detrital bSiO2.
Published: 2009
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40. Benthic pelagic coupling and the seasonal silica cycle in the Bay of Brest (France): new insights from a coupled physical-biological model

Author: Laruelle, G., Regnier, P., Olivier Ragueneau, Kempa, M., Brivaëla Moriceau, Ni Longphuirt, S., Aude Leynaert, GERARD THOUZEAU, Laurent Chauvaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: [SDE.MCG] Environmental Sciences/Global Changes, [SDE.MCG]Environmental Sciences/Global Changes, ComputingMilieux_MISCELLANEOUS
Abstract: International audience
Published: 2009

41. No limit? : the multiphasic uptake of silicic acid by benthic diatoms

Author: Pascal Claquin, Sorcha Ní Longphuirt, Olivier Ragueneau, Aude Leynaert, Laurent Chauvaud, Leynaert, Aude, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Physiologie et Ecophysiologie des Mollusques Marins (PE2M), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS), Research Training Network, funded by the European Union (HPRN-CT-2002-00218), Laboratoire des Sciences de l'Environnement Marin (LEMAR) ( LEMAR ), Institut de Recherche pour le Développement ( IRD ) -Institut Français de Recherche pour l'Exploitation de la Mer ( IFREMER ) -Université de Brest ( UBO ) -Institut Universitaire Européen de la Mer ( IUEM ), Institut de Recherche pour le Développement ( IRD ) -Université de Brest ( UBO ) -Centre National de la Recherche Scientifique ( CNRS ) -Institut de Recherche pour le Développement ( IRD ) -Université de Brest ( UBO ) -Centre National de la Recherche Scientifique ( CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Physiologie et Ecophysiologie des Mollusques Marins ( PE2M ), Université de Caen Normandie ( UNICAEN ), Normandie Université ( NU ) -Normandie Université ( NU ) -Institut Français de Recherche pour l'Exploitation de la Mer ( IFREMER ) -Centre National de la Recherche Scientifique ( CNRS ), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Kinetics, Aquatic Science, Oceanography, [SDU.STU.OC] Sciences of the Universe [physics]/Earth Sciences/Oceanography, 01 natural sciences, 03 medical and health sciences, chemistry.chemical_compound, Nutrient, Algae, TRACER, Botany, 14. Life underwater, Silicic acid, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 030304 developmental biology, 0303 health sciences, [ SDU.STU.OC ] Sciences of the Universe [physics]/Earth Sciences/Oceanography, biology, 010604 marine biology & hydrobiology, fungi, Pelagic zone, biology.organism_classification, chemistry, Benthic zone, Environmental chemistry, Saturation (chemistry)
Abstract: International audience; Silicic acid uptake kinetics for a field population of benthic diatoms were examined using a radioisotope tracer over a concentration range of 0-300 μmol L-1. The microphytobenthos half saturation constant (54 μmol L-1) and specific uptake rates (0.096 h-1) for silicic acid were well above those usually found in the pelagic environment. Silicic acid kinetics were hyperbolic only at low concentrations (< 60 μmol L-1). At higher concentrations, a second mechanism that did not suggest saturation was activated. Many benthic diatoms are motile and migrate vertically in the upper few centimeters of sediment where there are strong gradients of nutrient concentrations. The multiphasic uptake may allow them to take maximum advantage of the high silicic acid concentrations found at depth.
Published: 2009

42. Benthic-pelagic coupling and the seasonal silica cycle in the Bay of Brest (France): new insights from a coupled physical-biological model

Author: Olivier Ragueneau, Goulven Gildas Laruelle, M. Kempa, Gérard Thouzeau, Brivaëla Moriceau, Pierre Regnier, Ni S.N. Longphuirt, Aude Leynaert, Laurent Chauvaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Mass distribution, 0106 biological sciences, 010504 meteorology & atmospheric sciences, Dissolved silica, Numerical models, Population, Aquatic Science, Biology, Coastal zone, 01 natural sciences, Algal bloom, 14. Life underwater, education, Crepidula fornicata, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, education.field_of_study, geography, geography.geographical_feature_category, Ecology, Harmful algal bloom, 010604 marine biology & hydrobiology, Silica, Pelagic zone, Estuary, ANE, France, Brittany, Brest Bay, Benthic-pelagic coupling, Plankton, Estuarine environment, Oceanography, 13. Climate action, Benthic zone, Nutrient cycles, [SDE]Environmental Sciences, Algal blooms, Heterogeneity, Crepidula fornicata (Linnaeus, 1758), Bay
Abstract: International audience; A fully transient, 2-dimensional physical and biological model has been developed to quantify the seasonal cycle of silica in the estuaries-coastal zone continuum of the Bay of Brest (France). The numerical model includes an explicit representation of the benthic-pelagic coupling, which is stimulated by the increasing density of an invasive megabenthic filter feeder, the slipper limpet Crepidula fornicata. The selected spatial resolution allows resolution of the heterogeneous density distribution of these organisms in the bay. Results show that the benthic nutrient dynamics are highly variable and strongly depend on the local conditions. This heterogeneity is not reflected in the pelagic phytoplankton Population dynamics because transport and mixing homogenize the distribution of nutrients and biomass. A seasonally resolved silica budget over the entire bay and estuaries emphasizes the important contribution of the benthic recycling fluxes to the supply of dissolved silica (dSi) during the productive period (similar to 50%, from 1 April to 1 September). In a prognostic scenario which forecasts the impact of removing the invasive benthic filter feeders, the dSi efflux is reduced by 63% and a pronounced harmful algal bloom of dinoflagellates develops in late summer.
Published: 2009
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43. Si–C interactions during degradation of the diatom Skeletonema marinoi

Author: Marie Duflos, Robert Armstrong, Brivaëla Moriceau, Olivier Ragueneau, Catherine Guigue, Cindy Lee, Christian Tamburini, Madeleine Goutx, Bruno Charrière, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de MicrobiologiE de Géochimie et d'Ecologie Marines (LMGEM), Centre National de la Recherche Scientifique (CNRS)-Université de la Méditerranée - Aix-Marseille 2, Marine Sciences Research Center (MSRC), Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY), OIF Marie Curie, Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université de la Méditerranée - Aix-Marseille 2-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Frustule, Membrane lipids, Inorganic chemistry, Oceanography, 01 natural sciences, Organic compound, Degradation, Reaction rate constant, Biogenic silica, Organic matter, Dissolution, 0105 earth and related environmental sciences, chemistry.chemical_classification, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, biology, 010604 marine biology & hydrobiology, Diatom, biology.organism_classification, Lipids, chemistry, Degradation (geology), Amino acids
Abstract: While a relationship between ballast and carbon in sedimenting particles has been well-documented, the mechanistic basis of this interaction is still under debate. One hypothesis is that mineral ballast protects sinking organic matter from degradation. To test this idea, we undertook a laboratory experiment using the diatom Skeletonema marinoi to study in parallel the dissolution of one of the most common mineral ballasts, biogenic silica (bSiO2), and the associated degradation of organic matter. Three different models were applied to our results to help elucidate the mechanisms driving bSiO2 dissolution and organic compound degradation. Results of this modeling exercise suggest that the diatom frustule is made up of two bSiO2 phases that dissolve simultaneously, but at different rates. In our experiments, the first phase was more soluble ( k bSiO 2 = 0.27 d - 1 ) and made up 31% of the total bSiO2. In this phase, bSiO2 was mainly associated with membrane lipids and the amino acids glutamic acid, tyrosine, and leucine. The second phase was more refractory ( k bSiO 2 = 0.016 d - 1 ), and contained more neutral lipid alcohols and glycine. Until it dissolved, the first bSiO2 phase effectively protected much of the organic matter from degradation: particulate organic carbon (POC) degradation rate constants increased from 0.025 to 0.082 d−1 after the total dissolution of this phase, and particulate organic nitrogen (PON) degradation rate constants increased from 0.030 to 0.094 d−1. Similar to POC and PON, the total hydrolyzable amino acids (THAA) degradation rate constant increased from 0.054 to 0.139 d−1 after dissolution of the first bSiO2 phase. The higher THAA degradation rate constant is attributed to a pool of amino acids that was produced during silicification and enclosed between the two silica phases. This pool of amino acids might come from the incorporation of silica deposition vesicles into the diatom wall and might not be directly associated with bSiO2. In contrast, most lipid degradation was not prevented by association with the more soluble bSiO2 phase, as the average lipid degradation rate constant decreased from 0.048 to 0.010 d−1 after 17 d of degradation. This suggests that most lipids were associated with rather than protected by silica, except pigments that appeared resistant to degradation, independently from silica dissolution. When the only organic compounds remaining were associated with the second bSiO2 phase, degradation rate constants decreased greatly; concentrations changed only slightly after day 25.
Published: 2008
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44. Importance of particle formation to reconstructed water column biogenic silica fluxes

Author: Brivaëla Moriceau, Olivier Ragueneau, Karline Soetaert, and Morgane Gallinari
Subjects: 0106 biological sciences, Atmospheric Science, Global and Planetary Change, 010504 meteorology & atmospheric sciences, Frustule, biology, 010604 marine biology & hydrobiology, Pellets, Mineralogy, Biogenic silica, biology.organism_classification, 01 natural sciences, Oceanography, Water column, Diatom, Environmental Chemistry, Particle, 14. Life underwater, Surface layer, Dissolution, 0105 earth and related environmental sciences, General Environmental Science
Abstract: The particles sinking out of the ocean's surface layer are made up of a mixture of living and dead algal cells, fecal pellets, and aggregates, while the parameters used to describe the behavior of biogenic silica (bSiO2) in today's models are experimentally determined on freely suspended diatoms (FC). In a simple advection-reaction model we combine sinking rates of FC, zooplankton fecal pellets, and aggregates with recent measurements of bSiO2 dissolution to reconstruct theoretical downward profiles of bSiO2 fluxes at eight sites in the world ocean. Statistical analyses showed that sinking and dissolution parameters for two pools of bSiO2 are required to model particle fluxes accurately. The two-pool model results confirm the importance of seasonality for particle formation and its connection to the percentage of the bSiO2 production that reaches the seafloor. The depth of bSiO2 recycling appears to be influenced more by particle formation than by dissolution rates of bSiO2 or the ballast effect of the dense diatom frustules.
Published: 2007
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45. Evidence for reduced biogenic silica dissolution rates in diatom aggregates

Author: Olivier Ragueneau, Brivaëla Moriceau, Uta Passow, Michael Garvey, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Biogeoscience (AWI), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Frustule, Exopolymer, Mineralogy, Aquatic Science, Biogenic silica, 01 natural sciences, Water column, Biogenic silica dissolution, Dissolution, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Marine snow, Diatom aggregate, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Ecology, biology, Chemistry, 010604 marine biology & hydrobiology, fungi, biology.organism_classification, Aggregate pore water, Diatom, Thalassiosira weissflogii, Viability, Environmental chemistry, Silica recycling
Abstract: International audience; Because aggregated diatoms sink rapidly through the water column, leaving little time for dissolution, aggregation influences the balance between recycling of biogenic silica (bSiO2) and its sedimentation and preservation at the seafloor. Additionally, aggregation may directly impact dissolution rates of opal. Laboratory experiments were conducted to investigate the influence of aggregation on bSiO2 dissolution rates using 3 different batch cultures of the diatoms Chaetoceros decipiens, Skeletonema costatum, and Thalassiosira weissflogii. Specific dissolution rates of bSiO2 of aggregated and freely suspended diatoms were compared. Additionally, the influences of the dissolved silicon (dSi) concentration in the pore water of aggregates, the viability of diatoms, and the concentrations of transparent exopolymer particles (TEP) and of bacteria on bSiO2 dissolution rates were determined. Initial specific dissolution rates of diatom frustules were significantly lower for aggregated diatoms (2.9% d–1) than for freely suspended diatoms (6.6% d–1). Lower specific dissolution rates in aggregates were attributed to elevated dSi concentrations in aggregate pore water (maximum 230 vs. 20 µmol l–1) and to the fact that aggregated diatoms remained viable for longer than freely suspended diatoms. Specific bSiO2 dissolution was significantly correlated to viability of cells independent of treatment. Bacterial concentrations in both treatments appeared high enough, so that after cell death the coating protecting the silica frustule was degraded without measurable delay. The TEP content of aggregates appeared to affect dissolution rates, possibly by retaining solutes within aggregates.
Published: 2007
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46. Si and C interactions in the world ocean: Importance of ecological processes and implications for the role of diatoms in the biological pump

Author: Olivier Ragueneau, Brivaëla Moriceau, Sabine Schultes, Kay D. Bidle, and Pascal Claquin
Subjects: 0106 biological sciences, Atmospheric Science, Global and Planetary Change, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Ecology, Mesopelagic zone, 010604 marine biology & hydrobiology, Biogeochemistry, Biological pump, Biology, biology.organism_classification, 01 natural sciences, Deep sea, Food web, Oceanography, Diatom, 13. Climate action, Sediment trap, Environmental Chemistry, 14. Life underwater, 0105 earth and related environmental sciences, General Environmental Science
Abstract: [1] Diatoms play a major role in carbon export from surface waters, but their role in the transport of carbon to the deep sea has been questioned by global analyses of sediment trap fluxes which suggest that organic carbon fluxes and transfer efficiencies through the mesopelagic are tightly correlated with CaCO 3 (Klaas and Archer, 2002; Francois et al., 2002). Here we explore the role of diatoms in the biological pump through a study of Si and C interactions from the molecular to the global scale. Recent findings on molecular interactions between Si and C are reviewed. The roles of bacteria, grazers and aggregation are explored and combined, to account for the extent of Si and C decoupling between surface waters and 1000 m, observed to be very homogeneous in different biogeochemical provinces of the ocean. It is suggested that the mesopelagic food web plays a crucial role in this homogeneity: Sites of high export are also sites where diatom C is being either remineralized or channeled toward the long-lived carbon pool most efficiently in the mesopelagic zone. The amount of carbon participating in the biological pump but not collected in sediment traps remains to be explored. It is also demonstrated that statistical analyses performed at global scales hide spatial variability in carrying coefficients, indicating a clear need to understand the mechanisms that control spatial and temporal variations in the relative importance of ballast minerals and other export mechanisms such as particle dynamics.
Published: 2006
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47. Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

Author: Olivier Aumont, Christoph Heinze, Laurent Bopp, N. Emprin, Olivier Ragueneau, Marion Gehlen, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), University of Bergen (UiB), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Mixed layer, lcsh:Life, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Atmospheric sciences, 01 natural sciences, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Flux (metallurgy), [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, lcsh:QH540-549.5, 14. Life underwater, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Earth-Surface Processes, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010604 marine biology & hydrobiology, lcsh:QE1-996.5, Sediment, Biological pump, lcsh:Geology, lcsh:QH501-531, Oceanography, Benthic zone, 13. Climate action, Environmental science, Particle, lcsh:Ecology, Particle size
Abstract: This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1) the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2) an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3) a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. The integrated representation of material fluxes from the productive surface ocean down to the sediment-water interface allows taking advantage of surface ocean observations, sediment trap data and exchange fluxes at the sediment-water interface. The capability of the model to reproduce yearly averaged particulate organic carbon fluxes and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Model results obtained with the standard version and with the one including a particle size spectrum and prognostic sinking speed are not significantly different. Both model versions overestimate particulate organic carbon between 1000 and 2000 m, while deep fluxes are of the correct order of magnitude. Predicted benthic oxygen fluxes correspond with respect to their large scale distribution and magnitude to data based estimates. Modeled particulate organic C fluxes across the mesopelagos are most sensitive to the intensity of zooplankton flux feeding. An increase of the intensity of flux feeding in the standard version results in lower mid- and deep-water particulate organic carbon fluxes, shifting model results to an underestimation of particulate organic carbon fluxes in the deep. The corresponding benthic oxygen fluxes are too low. The model version including the mineral ballast parameterization yields an improved fit between modeled and observed particulate organic carbon fluxes below 2000 m and down to the sediment-water interface. Our results suggest that aggregate formation alone might not be sufficient to drive an intense biological pump. The later is most likely driven by the combined effect of aggregate formation and mineral ballasting.
Published: 2006
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48. Biodeposition by an invasive suspension feeder impacts the biogeochemical cycle of Si in a coastal ecosystem (Bay of Brest, France)

Author: Olivier Ragueneau, Frédéric Jean, Gérard Thouzeau, F. Le Loc’h, Brivaëla Moriceau, Laurent Chauvaud, Aude Leynaert, Anne Donval, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Ecology, 010604 marine biology & hydrobiology, [SDE.MCG]Environmental Sciences/Global Changes, Plankton, Biogenic silica, 01 natural sciences, Geochemical cycle, [SDE.MCG] Environmental Sciences/Global Changes, Oceanography, 13. Climate action, Benthic zone, Sediment–water interface, Phytoplankton, Environmental Chemistry, Environmental science, 14. Life underwater, Bay, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology
Abstract: Biodeposition is a process that strongly affects physical, chemical and biological properties near the sediment–water interface, and mollusks have been shown to influence the cycling of many biogenic elements. In the Bay of Brest ecosystem, the invasive benthic suspension feeder Crepidula fornicata has been proliferating for 50 years, and its influence on phytoplankton dynamics at a seasonal scale, via its role on a coastal silicate pump, has been suggested by Chauvaud et al. (2000) [Chauvaud L., Jean F., Ragueneau O. and Thouzeau G. 2000. Mar. Ecol. Prog. Ser. 200: 35–48] and tested by Ragueneau et al. (2002a) [Ragueneau O., Chauvaud L., Leynaert A., Thouzeau G., Paulet Y.-M., Bonnet S., Lorrain A., Grall J., Corvaisier R., Le Hir M., Jean F. and Clavier J. (2002a). Limnol. Oceanogr. 47(6): 1849–1854]. In the present manuscript, we explore further, at an annual scale, the role of biodeposition in the Si cycle of the Bay of Brest. We show that annual biodeposition Si can represent up to 84% of river silicic acid inputs. We also show that preservation of biogenic silica in C. fornicata mats is very good (27%), leading to an annual retention of Si of 23% of river inputs. We suggest that this high retention is essentially controlled by the biodeposition mechanism, which is directly under the control of the proliferation of the exotic suspension feeder. We conclude that this mechanism might be very important in controlling the Si retention along the land–ocean continuum and should be tested in the many areas of the coastal ocean submitted to the proliferation of such exotic species that modify sedimentation of biogenic matter.
Published: 2005

49. Effect of iron deficiency on diatom cell size and silicic acid uptake kinetics

Author: Richard C. Dugdale, Aude Leynaert, Philippe Pondaven, Pascal Claquin, Olivier Ragueneau, Eva Bucciarelli, Véronique Martin-Jézéquel, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Physiologie et Ecophysiologie des Mollusques Marins (PE2M), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS), Romberg Tiburon Center, San Francisco State University (SFSU), ORFOIS (European Community project EVK2-CT-2001-00100) and by CNRS, Grigorov, Ivo, Laboratoire des Sciences de l'Environnement Marin (LEMAR) ( LEMAR ), Centre National de la Recherche Scientifique ( CNRS ) -Université de Brest ( UBO ) -Institut Français de Recherche pour l'Exploitation de la Mer ( IFREMER ) -Institut Universitaire Européen de la Mer ( IUEM ), Centre National de la Recherche Scientifique ( CNRS ) -Institut de Recherche pour le Développement ( IRD ) -Université de Brest ( UBO ) -Centre National de la Recherche Scientifique ( CNRS ) -Institut de Recherche pour le Développement ( IRD ) -Université de Brest ( UBO ) -Institut de Recherche pour le Développement ( IRD ), Physiologie et Ecophysiologie des Mollusques Marins ( PE2M ), Université de Caen Normandie ( UNICAEN ), Normandie Université ( NU ) -Normandie Université ( NU ) -Institut Français de Recherche pour l'Exploitation de la Mer ( IFREMER ) -Centre National de la Recherche Scientifique ( CNRS ), and San Francisco State University ( SFSU )
Subjects: 0106 biological sciences, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Aquatic Science, Oceanography, [SDU.STU.OC] Sciences of the Universe [physics]/Earth Sciences/Oceanography, 01 natural sciences, chemistry.chemical_compound, Nutrient, Nitrate, Botany, 14. Life underwater, Silicic acid, Iron deficiency (plant disorder), [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, [ SDU.STU.OC ] Sciences of the Universe [physics]/Earth Sciences/Oceanography, biology, 010604 marine biology & hydrobiology, Plankton, biology.organism_classification, Phosphate, Diatom, chemistry, 13. Climate action, Environmental chemistry
Abstract: We studied the silicic acid uptake kinetics of the pennate diatom Cylindrotheca fusiformis grown under a wide range of iron concentrations (from Fe-limiting to Fe-sufficient conditions) to assess the effect of iron availability on diatom cell size, silicon content, and silicic acid uptake kinetic parameters. As the iron stress increased, the growth rate slowed, cell size decreased, and silicification increased. A series of Si kinetic uptake experiments (from Si-limiting to Si-sufficient conditions) performed at different iron concentrations demonstrated the extent of the colimitation domain, where the specific Si uptake rate (VSi) varied as a function of both silicic acid and Fe availability. A decrease in maximal specific uptake rate of silicic acid (VSi-max) under iron limitation was observed along with a decrease in half-saturation constant for silicic acid uptake ( KSi). Because VSi-max and KSi vary in the same direction, the specific affinity for silicic acid does not change under iron stress. The variation in cell size is an acclimation to low nutrient concentrations. Our study shows that Si uptake kinetics parameters, especially VSi-max, are strongly related to cell size, which is itself constrained by the degree of iron limitation. Thus, the surface to volume ratio should be related to silicic acid flows in size-based biogeochemical models of planktonic ecosystems. Another way to describe the observed variations of Si uptake over the full range of Si and Fe concentrations tested in the present study would be to implicitly take into account the variations in cell size through a scaling of the maximal specific uptake rate (Vmax) by the iron-limitation term in a multiplicative manner. Diatoms account for about 40% of the primary production in highly productive coastal and nutrient-replete oceanic waters (Nelson et al. 1995) and play a major role in the export of organic carbon (Buesseler 1998). Hence, they are important in aquatic ecosystems and in the global carbon cycle. Studying the factors controlling the contribution of diatoms to total production is therefore essential for our understanding of the mechanisms controlling the efficiency of the biological pump of carbon in various regions of the oceans. In particular, their role in high-nutrient low-chlorophyll (HNLC) regions is unclear. These areas have elevated nitrate and phosphate concentrations throughout the year in surface waters, but chlorophyll levels remain ‘‘lower than expected’’ (Minas et al. 1986). Several hypotheses have been proposed to explain the paradox of these areas: high grazing pressure (Landry et al. 1997), unfavorable light-mixing regime (Nelson and Smith 1991), and limitation by nutrients other than nitrate or phosphate, in particular by the micronutrient iron
Published: 2004

50. Sensitivity of the marine biospheric Si cycle for biogeochemical parameter variations

Author: Christoph Heinze, Nicolas Dittert, Ernst Maier-Reimer, Olivier Ragueneau, and A. Hupe
Subjects: Atmospheric Science, Global and Planetary Change, Biogeochemical cycle, Mineralogy, Sediment, Ocean general circulation model, Geochemical cycle, Water column, Settling, Sediment–water interface, Environmental Chemistry, Deposition (chemistry), Geology, General Environmental Science
Abstract: [1] A systematic quantitative assessment of the marine silicon cycle is presented, based on a prognostic coupled water column-sediment global biogeochemical ocean general circulation model (HAMOCC). The resulting tracer distributions are compared with a comprehensive marine Si database of measurements. The model parameters which govern the Si cycle within the model world are optimized through a linear response model. The functional relationships between the Si cycle parameters and the Si tracer distributions are derived from a series of sensitivity experiments addressing opal export production, particle flux through the water column, porewater chemistry, and external biogeochemical forcing. The most important parameters for a further quantitative improvement of the simulation are depth-dependent opal dissolution kinetics, a productivity-dependent opal settling velocity, a general change in maximum Si uptake velocity Vmaxopal, and the clay as well as the Si input from continental weathering. The modeled Si budget shows a larger global export production, larger opal deposition rates onto the sediment surface and higher diffusive transports of porewater silicic acid into the open water column as estimated by Treguer et al. [1995].
Published: 2003
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