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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. Exp’Eau, a hybrid serious game to explore pathways towards better water quality in rural catchments

Author: Olivier Barreteau, Isabelle Charpentier, Hossam Elouati, Hugo Kelhetter, Daniil Kudriashov, Hélène Blanchoud, Mathieu Bonnefond, Sylvie Dousset, Véronique Gouy, Christophe Piscart, Marie-Noëlle Pons, Olivier Ragueneau, and Sébastien Salvador-Blanes
Abstract: Agriculture is considered today as having major impacts on water quality in river basins. Transition from this situation to a better integration of agricultural practices in their environment is sought by many stakeholders and policy makers, from water, land development and also agriculture sectors. This appears costly when incorporating their various constraints. With the on-going research project ExpEau, the LTSER-FR network aims at (1) raising awareness on the opportunities to handle agricultural sources of water pollution collectively, and (2) comparing them in various watersheds. To that end, we are developing a hybrid serious game featuring activities and relations between farmers, municipalities and river basin organization on a virtual river basin, generated from actual datasets for topography, soil properties, and climate. For comparison sake, the game features a framed number of entities and possibilities of action, and the process of transforming actual datasets is standardized. We consider representative small basins (ca. 100 km2) that we discretize into three sub-basins, each of them representing a municipality as the first level for collaboration. Each sub basin counts about 30 hexagons elementary tiles with a single land use for each.In practice, the game is made of a physical board and playing action cards, as well as a twin on-line version. Farmer players access to the information on their environment and choose cultural practices thanks to a smartphone. Municipality and river basin organisation roles use their time and budget to facilitate collaboration and support more virtuous practices as well as infrastructures to decrease pollution. A local server computes the impacts of these actions in terms of production, collective well-being and contamination, and updates the players’ data. During the game session, players can see the virtual watershed, the land use and the infrastructures on the physical board. According to their role, they receive situated information on production, on territorial well-being and water quality and quantity.Involving students or local stakeholders, each session is followed by a debriefing that could produce (1) a local understanding on the interactions between agriculture and water quality, and (2) socio-ecosystem data to feed a cross LTSER analysis of these interactions.
Published: 2022
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12. Sustainability

Author: Jon Marco Church, Andrew Tirrell, William R. Moomaw, and Olivier Ragueneau
Published: 2022
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13. Socio-political acceptability of floating offshore wind farms in France: challenges and perspectives for marine governance towards sustainability

Author: Rhoda Fofack-Garcia, Camille Mazé, Georges Safi, Morgane Lejart, Nathalie Chauvac, Maud Thermes, Olivier Ragueneau, François Le Loc'h, and Nathalie Niquil
Subjects: Management, Monitoring, Policy and Law, Aquatic Science, Oceanography
Published: 2023
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14. 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

15. 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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16. 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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17. 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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18. 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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19. 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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20. 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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21. 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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22. 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

23. 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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24. 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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25. 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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26. 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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27. 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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28. The impossible sustainability of the Bay of Brest? 40 years of ecosystem evolution, interdisciplinary knowledge construction and key questions at the science-policy-communities interface

Author: Olivier Ragueneau, Mélanie Raimonet, Camille Mazé, Jennifer Coston-Guarini, Anatole Danto, Laurent Chauvaud, Jacques Grall, Frédéric Jean, Yves-Marie Paulet, GERARD THOUZEAU, 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), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), 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)-Centre National de la Recherche Scientifique (CNRS), Centre de recherche bretonne et celtique (CRBC Brest), Institut Brestois des Sciences de l'Homme et de la Société (IBSHS), Université de Brest (UBO)-Université de Brest (UBO)-Centre de recherche bretonne et celtique (CRBC), Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), 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), Université de Brest (UBO), LabEx MER, CNRS, RZA, LTER-France - Zones Ateliers Network & Critical Zone Observatories, ANR-13-JCLI-0006,ARTISTICC,Recherche sur l'adaptation, une communauté transnationale et transdisciplinaire approche centrée sur la politique(2013), 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), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE)-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 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 de Brest (UBO)-Institut Brestois des Sciences de l'Homme et de la Société (IBSHS), 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), Université de Brest (UBO)-Centre de recherche bretonne et celtique (CRBC), Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)
Subjects: [SHS.SOCIO]Humanities and Social Sciences/Sociology, [SDE.MCG]Environmental Sciences/Global Changes, Interdisciplinarity, Savoirs, [SHS.ANTHRO-SE]Humanities and Social Sciences/Social Anthropology and ethnology, Social sciences of politics, Soutenabilité, [SDE.ES]Environmental Sciences/Environmental and Society, [SHS.SCIPO]Humanities and Social Sciences/Political science, Sciences sociales du politiques, [SHS.HISPHILSO]Humanities and Social Sciences/History, Philosophy and Sociology of Sciences, Knowledge, Sustainability, Power, [SHS.ENVIR]Humanities and Social Sciences/Environmental studies, Interdisciplinarité, Pouvoir, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: International audience; In this contribution, the evolution of the Bay of Brest ecosystem 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, N and Si biogeochemical cycles, the proliferation of an exotic benthic suspension feeder, the Great scallop fishing and biodiversity in maerl beds. This cascade leads to today’s situation where toxic phytoplankton blooms become recurrent in the Bay, preventing the fishery of the great scallop and leading the fishermen community to switchpray and alter the maerl habitat and the benthic biodiversity it hosts, despite the many scientific alerts and the protection of this habitat, 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 (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? Answering these questions requires an interdisciplinary approach, especially between natural sciences (NS) and human and social sciences (HSS). Here, we first show the importance of geographical proximity in the build-up of this interdisciplinary knowledge, first among biogeochemists and benthic biologists by the time the IUEM institute was built in the late 1990’s. We also confirm the importance of this proximity and the need for the establishment of boundary settings that allow for the crucially needed long-term interactions between the NS and HSS communities. Thecreation of the research group ApoliMer (for a political anthropology of the sea) in 2014 and the creation of a new axis on social-ecological systems (SES) within the LabexMer in 2015, are such examples of these boundary settings created recently. Combining natural sciences with political science, anthropology and the political sociology of science, we hope to improve the contribution of HSS to SES studies, creating the conditions to address these key questions at the science-policy interface. The ZABrI created in 2012 provides an ideal setting for inter- and trans-disciplinary studies through tight work with various stakeholders, hopefully improving the transformation towards sustainability.
Published: 2017

29. 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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30. 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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31. 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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32. 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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33. Mesopelagic zone ecology and biogeochemistry – a synthesis

Author: Bernard Quéguiner, Fereidoun Rassoulzadegan, Christian Tamburini, Carol V. Robinson, Javier Arístegui, Jean-François Ghiglione, Jing Zhang, Karen F. Wishner, Tsuneo Tanaka, Bruce H. Robison, Jessica R. Frost, Deborah K. Steinberg, Rolf Koppelmann, Olivier Ragueneau, Thomas R. Anderson, Santiago Hernández-León, Craig A. Carlson, George A. Jackson, Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN), Institut méditerranéen d'océanologie ( MIO ), Institut de Recherche pour le Développement ( IRD ) -Aix Marseille Université ( AMU ) -Université de Toulon ( UTLN ) -Centre National de la Recherche Scientifique ( CNRS ), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS)
Subjects: [ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere, microbial, SUB-ARCTIC PACIFIC, BIOGENIC SILICA DISSOLUTION, 0106 biological sciences, Biogeochemical cycle, NORTHWESTERN SARGASSO SEA, 010504 meteorology & atmospheric sciences, Mesopelagic zone, RIBOSOMAL-RNA GENES, twilight zone, Climate change, OXYGEN MINIMUM ZONE, Biology, Carbon sequestration, Oceanography, Oxygen minimum zone, 01 natural sciences, mesopelagic zone, CENTRAL EQUATORIAL PACIFIC, metazoan, 14. Life underwater, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Carbon dioxide in Earth's atmosphere, Ecology, 010604 marine biology & hydrobiology, marine ecology, Biogeochemistry, 15. Life on land, NW MEDITERRANEAN SEA, Food web, PARTICLE-SIZE DISTRIBUTIONS, 13. Climate action, ZOOPLANKTON VERTICAL MIGRATION, EASTERN TROPICAL PACIFIC
Abstract: International audience; The mesopelagic zone is the oceanic region through which carbon and other elements must pass in order to reach deeper waters or the sea floor. However, the food web interactions that occur in the mesopelagic zone are difficult to measure and so, despite their crucial importance to global elemental cycles, are not very well known. Recent developments in technology and new approaches have advanced the study of the variability in and controls upon the distribution and diversity of organisms in the mesopelagic zone, including the roles of respiration, recycling, and repackaging of particulate and dissolved organic material. However, there are remarkably few syntheses of the ecology and biogeochemistry of the microbes and metazoa that permanently reside or habitually visit this 'twilight zone'. Without this synthesis, it is difficult to assess the impact of ongoing changes in ocean hydrography and chemistry, due to increasing atmospheric carbon dioxide levels, on the biological carbon pump. This paper reviews what is known about the distribution of microbes and metazoa in the mesopelagic zone in relation to their activity and impact on global biogeochemical cycles. Thus, gaps in our knowledge are identified and suggestions made for priority research programmes that will improve our ability to predict the effects of climate change on carbon sequestration. (C) 2010 Elsevier Ltd. All rights reserved.
Published: 2010
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34. Diurnal heterogeneity in silicic acid fluxes in shallow coastal sites: Causes and implications

Author: Sorcha Ní Longphuirt, Aude Leynaert, Laurent Chauvaud, Olivier Ragueneau, Sophie Martin, Gérard Thouzeau, Frédéric Jean, 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), Marine Environment Laboratories, and International Atomic Energy Agency [Vienna] (IAEA)
Subjects: 0106 biological sciences, silicic acid, diurnal variations, microphytobenthos, 010504 meteorology & atmospheric sciences, Aquatic Science, Oceanography, 01 natural sciences, chemistry.chemical_compound, Benthos, Diurnal cycle, Phytoplankton, 14. Life underwater, Silicic acid, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, subtidal, migrations, 010604 marine biology & hydrobiology, Diurnal temperature variation, Bay of Brest, Pelagic zone, Plankton, chemistry, 13. Climate action, Benthic zone, Environmental science, France
Abstract: International audience; In shallow coastal areas the amplitude and range of benthic silicic acid fluxes can have a significant influence on benthic–pelagic coupling and the functioning of the pelagic system. To explore the oscillation in fluxes over the diurnal cycle and in particular the influence of microphytobenthos (MPB), an experiment was carried out in a shallow subtidal site in the Bay of Brest (France). Benthic chambers were employed over a 48 h period to measure the variability in silicic acid and oxygen fluxes; MPB migration was investigated using a diving Pulse Amplitude Modulated (PAM) fluorometer and uptake rhythms of silicic acid by natural MPB populations were measured using the 32Si isotope. It was discovered that silicic acid fluxes fluctuated greatly throughout the diurnal period resulting in an oscillation in the availability of this nutrient for phytoplankton communities. The uptake of silicic acid by the MPB was quantified for the first time and highlighted a 2-fold increase in the demand from night to afternoon periods. The combined silicic acid uptake and the concentration of cells at the sediment–water interface, forming a dense biofilm of MPB, were postulated to be the main processes reducing effluxes at midday. Our work highlighted the many processes which influence silicic acid effluxes in shallow coastal areas and the possible interaction between uptake and dissolution processes. The variations in benthic fluxes over the diurnal period were comparable to observations reported at the seasonal scale. Therefore, up-scaling hourly flux observations to daily and annual estimates should be undertaken with caution. Further we suggest that the main processes influencing flux oscillations over the diurnal period should be considered when planning sampling strategies and extrapolating to larger time scales.
Published: 2009
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35. Influence of seasonal phytodetritus deposition on biogenic silica dissolution in marine sediments—Potential effects on preservation

Author: Morgane Gallinari, Dirk Rickert, David J. DeMaster, Olivier Ragueneau, Hilairy E. Hartnett, Carrie J. Thomas, 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), Department of MEAS, North Carolina State University [Raleigh] (NC State), University of North Carolina System (UNC)-University of North Carolina System (UNC), Department of Geological Sciences, Arizona State University [Tempe] (ASU), Department of Chemistry and Biochemistry [Tempe], GEOMAR Froschungzentrum, Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), and BENGAL (MAS3-CT95-0018) and ORFOIS (EVK2-CT-2001-00100) NSF-FOODBANCS program INSU
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Dissolved silica, 010604 marine biology & hydrobiology, Phytodetritus, Sediment, Biogenic silica, Oceanography, 01 natural sciences, Diagenesis, Benthic zone, [SDE]Environmental Sciences, 14. Life underwater, Flow-through reactors, Deposition (chemistry), Bioturbation, Dissolution, Geology, 0105 earth and related environmental sciences
Abstract: International audience; The deposition of fresh phytoplankton detritus (phytodetritus) following phytoplankton blooms may influence biogenic silica (BSi) dissolution in marine sediments. We studied BSi dissolution properties before, during, and after periods of phytodetritus deposition during time-series field programs in the abyssal North Atlantic (the BENGAL project), and on the West Antarctic Peninsula Shelf (the FOODBANCS project). Dissolution experiments, performed by means of flow-through reactors, showed temporal variations in the dissolution properties of BSi in the sediment column after phytodetritus deposition. This non-steady-state character of benthic silica dynamics is an important aspect of pelagic-benthic coupling. The last FOODBANCS cruise occurred after a phytodetritus deposition event, and yielded high pore-water dissolved silica (DSi) concentrations and DSi effluxes in the upper centimetres of the sediment column, suggesting a rapid turnover of recently deposited siliceous material. Higher dissolution rates were measured in the phytodetritus-rich sediments relative to surface sediments collected during previous seasons on earlier FOODBANCS cruises. During the BENGAL project, high dissolution rates were measured at depth in the sediment column only after a summer phytodetritus deposition event. In the highly detrital sediment matrix of the abyssal North Atlantic Ocean, resolution of increased dissolution rates and experimental artefacts of the flow-through reactors can be difficult because of the low abundance of BSi. Depending on the sediment matrix, bioturbation can play a crucial role in transporting fresh BSi particles to depth, where DSi concentrations are close to experimentally determined BSi solubilities. The potential impacts of such processes on BSi preservation are discussed. We suggest that future models of BSi early diagenesis should include the rapid mixing of freshly deposited particles if we want to describe further the preservation of BSi in marine sediments.
Published: 2008
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36. Net and gross incorporation of nitrogen by marine copepods fed on 15N-labelled diatoms: Methodology and trophic studies

Author: Gerd Slawyk, Benoît Sautour, Olivier Ragueneau, Dorothée Vincent, Laurent Seuront, Morgane Gallinari, Stéphane L'Helguen, and Géraldine Sarthou
Subjects: biology, chemistry.chemical_element, Aquatic Science, biology.organism_classification, Nitrogen, chemistry.chemical_compound, Animal science, chemistry, Thalassiosira weissflogii, Algae, Phytoplankton, Botany, Ammonium, Nitrogen cycle, Ecology, Evolution, Behavior and Systematics, Copepod, Trophic level
Abstract: The stable isotope of nitrogen ( 15 N) and an appropriate three-compartment model were used in two 24-h lasting feeding experiments to trace the flow of N through the copepod Acartia discaudata and Calanus helgolandicus fed on 15 N-labelled Skeletonema costatum and Thalassiosira weissflogii, respectively. Details of the labelling technique and principles of the computation of N transport rates are given. At the end of a single 24-h feeding period only about one third of the total amount of N ingested by A. discaudata was incorporated into the copepod's body N; we refer to this rate as net incorporation. Most of the N ingested was lost as ammonium (48% of total N ingested), followed by losses in the form of eggs+fecal pellets (13%) and dissolved organic N (DON, 9%). The sum of net incorporation and the latter losses is defined as gross incorporation. Net incorporation by C. helgolandicus and N losses did not vary over time during a 24 h lasting time-series feeding experiment. On average, 79% of total N ingested was actually incorporated by the copepod whereas mean N losses as ammonium, eggs+fecal pellets represented only 12 and 9%, respectively. After a 24-h feeding period only 2% of N ingested was lost as DON. Inspection of individual DON pathways showed that both A. discaudata and C. helgolandicus highly contributed to total DON production via direct excretion (79 and 64%, respectively). The remaining DON appearing in the DON pool was derived from phytoplankton via direct release and/or indirect release (copepod ‘sloppy feeding’). © 2007 Elsevier B.V. All rights reserved.
Published: 2007
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37. Constraining biogenic silica dissolution in marine sediments: a comparison between diagenetic models and experimental dissolution rates

Author: Olivier Ragueneau, Karline Soetaert, Morgane Gallinari, David J. DeMaster, K. Khalil, Christophe Rabouille, 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 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), Netherlands Institute of Ecology (NIOO-KNAW), Department of MEAS, North Carolina State University [Raleigh] (NC State), University of North Carolina System (UNC)-University of North Carolina System (UNC), 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), 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), and Ecosystems Studies
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Equatorial Pacific, Mineralogy, Biogenic silica, Oceanography, 01 natural sciences, chemistry.chemical_compound, Flux (metallurgy), Biogenic silica dissolution, Sediment–water interface, Environmental Chemistry, 14. Life underwater, Southern Ocean, Dissolution, Early diagenesis, 0105 earth and related environmental sciences, Water Science and Technology, 010604 marine biology & hydrobiology, North Atlantic, Sediment, General Chemistry, Reprecipitation, Silicate, Diagenesis, chemistry, 13. Climate action, [SDE]Environmental Sciences, Seawater, Silica cycle, Geology
Abstract: International audience; The processes controlling preservation and recycling of particulate biogenic silica in sediments must be understood in order to calculate oceanic silica mass balances. The new contribution of this work is the coupled use of advanced models including reprecipitation and different phases of biogenic silica with different dissolution characteristics as well as new data sets concerning experimental dissolution rates of marine particles and sediment opal obtained in flow-through reactors. We have used three models representing early diagenesis of biogenic silica in sediments that calculate the vertical distributions of dissolved silicate and solid silica in sediments. Model 1 contains one type of biogenic silica and the dissolution rate is constant, whereas model 2 contains a variable dissolution rate constant with sediment depth (representing aging) and one type of biogenic silica. Model 3 incorporates aging by describing two types of biogenic silica that differ by their dissolution properties. An explicit term of reprecipitation is incorporated into the three models. The distributions of dissolved silicate and solid silica predicted by steady-state calculations are compared to 4 observed data sets, from the Southern Ocean, the Equatorial Pacific and the North Atlantic, covering a wide range of sediment compositions, from opal-rich to opal-poor sediments. After adjustment of the critical parameters (the apparent silica dissolution rate constants, the biogenic silica flux deposited at the sediment-water interface and the reprecipitation rate), the second and third models provide good agreements between predicted and measured dissolved Si and solid silica profiles for each data set, except for the second model in the Equatorial Pacific. However, a large discrepancy between the experimentally derived dissolution rate constants and those calculated by the models is observed at all sites at depth in the sediment, suggesting that either artifacts arise during dissolution experiments such as over-representation of rapidly dissolving silica or variation of dissolution properties during the experimental procedures or the model oversimplifies the processes associated to silica dissolution and alumino-silicate reprecipitation and their interaction.
Published: 2007
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38. 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

39. The importance of water column processes on the dissolution properties of biogenic silica in deep-sea sediments I. Solubility

Author: David J. DeMaster, Lydie Corrin, Paul Tréguer, Olivier Ragueneau, and Morgane Gallinari
Subjects: chemistry.chemical_compound, chemistry, Geochemistry and Petrology, Silicate minerals, Sediment trap, Mineralogy, Sediment, Silicic acid, Solubility, Biogenic silica, Dissolution, Geology, Diagenesis
Abstract: Flow-through experiments have been performed to study the thermodynamics of biogenic silica (opal) dissolution in deep-sea sediments. They were applied for the first time on sediment from the Southern Ocean Van Cappellen and Qiu 1997a , Van Cappellen and Qiu 1997b We have extended the use of these experiments to other deep-sea settings, thereby covering a wide range of in situ silicic acid asymptotic concentrations (Casympt; 200 to 900 μmol/L) and biogenic opal content (BSi; 0.5 to 80%). Performing these experiments under in situ bottom temperatures allows for the comparison between experimental apparent solubilities and Casympt concentrations. Low values of BSi apparent solubilities have been measured in the deepest sections of the multicores collected in the northeast Atlantic (229 μmol/L) and in the equatorial Pacific (505 μmol/L). They are only 10 to 20% higher than the in situ Casympt concentrations. This demonstrates a clear control of pore water silicic acid concentrations by the in situ apparent solubility of the BSi, i.e., the solubility of BSi within a complex sedimentary matrix that includes important quantities of silicate minerals. In regions where the percentage detrital/percentage biogenic ratio is low, the apparent solubility of the biogenic silica is close to that of in situ biogenic silica. In the opposite case, when the percentage detrital/percentage biogenic ratio is high, reprecipitation reactions induce strong interference on the dissolution properties of the opal, both in situ and in flow-through experiments. In such a sedimentary matrix, it is important to determine the appropriate opal solubility to be used in early diagenetic models, i.e., the solubility of the biogenic silica just before deposition on the seabed. This has been achieved by performing flow-through experiments on sediment trap material from the north Atlantic site. Comparison of apparent biogenic silica solubility measured by flow-through experiments and the silicic acid concentrations measured in the cups of the sediment traps suggested that the solubility of biogenic silica that reaches the sediment-water interface is not unique and varies spatially and temporally. In fact, it is the degree of coupling between surface waters and the sediment-water interface that will control the aging of biogenic silica in the water column and hence the dissolution properties of the biogenic silica deposited at the sediment-water interface. All these results call for a strong improvement of biogenic silica early diagenetic models that should include not only a reprecipitation term that takes into account interaction with silicate minerals but also the existence of several phases of biogenic silica and thus that should operate in a non-steady-state mode to account for seasonal variations in the quality of deposited biogenic silica.
Published: 2002
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40. Si/C decoupling in the world ocean: is the Southern Ocean different?

Author: Philippe Pondaven, Paul Tréguer, Nicolas Dittert, Lydie Corrin, and Olivier Ragueneau
Subjects: Physics, Oceanography, Physical geography, Humanities
Abstract: Le probleme du decouplage entre les cycles biogeochimiques du silicium et du carbone organique particulaire est ici traite a partir de donnees de flux provenant de 5 sites situes dans l'ocean austral (dans la zone du Front Polaire, au nord et au sud de celui-ci) et de 4 sites situes dans le reste de l'ocean mondial (series temporelles dans l'Atlantique et le Pacifique). Pour l'ensemble des sites etudies les flux annuels de silice produite dans la couche de surface sont les plus eleves dans l'ocean austral (environ 3 mol m -2 an -1 ) et les flux de carbone les plus eleves dans le Pacifique Equatorial (environ 25 mol m -2 an -1 ). Les rapports molaires Si:C dans la couche de surface varient de 0.04 en moyenne pour les sites du reste de l'ocean mondial, a comparer a 0.25 pour l'Ocean Austral ou le phytoplancton est domine par les diatomees. Dans l'Ocean Austral les rapports Si:C sont particulierement eleves, tant pour la colonne d'eau (rapports variant de 2.6 a 10.4 pour les flux profonds > 3000 m) que pour less sediments (rapports de 13 a 29 pour les flux d'accumulation sur le long terme). Les rapports les plus faibles sont calcules pour le site BATS (0, 55 et 0, 57, respectivement pour les flux profonds dans la colonne d'eau et dans les sediments). Cependant, quelque soit le site etudie le rapport Si:C dans la colonne d'eau s'accroit avec la profondeur: ainsi le rapport Si:C des flux de production en surface etant pris comme reference, les rapports Si:C s'accroissent d'un facteur 24-28 pour les flux profonds et d'un facteur 106-111 dans les sediments. Dans la colonne d'eau la variation du rapport Si:C en fonction de la profondeur z suit l'equation: (Si:C) z = a(Si:C) b 0 /z c , ou (Si:C) 0 est la valeur du rapport des flux dans les eaux de surface et a, b, and c sont des parametres ajustes en fonction des donnees de flux recueillis aux sites exterieurs a l'Ocean Austral. Cette equation permet de predire correctement les valeurs des rapports Si:C pour les 5 sties d'etude pour l'Ocean Austral, dans la limite des incertitudes des determinations des flux de matiere biogene. Ceci montre que le decouplage des flux de carbone et de silice dans l'Ocean Austral n'est finalement pas different de ce qui se passe dans le reste de l'ocean mondial, contrairement a ce que l'on pouvait penser. Cette etude est une etape importante pour l'utilisation ulterieure de la silice biogene comme traceur de la paleoproductivite oceanique.
Published: 2002
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41. 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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42. The benthic silica cycle in the Northeast Atlantic: annual mass balance, seasonality, and importance of non-steady-state processes for the early diagenesis of biogenic opal in deep-sea sediments

Author: Richard S. Lampitt, Olivier Ragueneau, A Hauvespre, Sibylle Grandel, Per O. J. Hall, A Tengberg, Rob Witbaard, Lydie Corrin, Dirk Rickert, Henrik Stahl, and Morgane Gallinari
Subjects: geography, geography.geographical_feature_category, Abyssal plain, Sediment, Geology, Aquatic Science, Biogenic silica, Diagenesis, Oceanography, Benthic zone, Sediment–water interface, Sediment trap, Porcupine Abyssal Plain
Abstract: Within the framework of the EU-funded BENGAL programme, the effects of seasonality on biogenic silica early diagenesis have been studied at the Porcupine Abyssal Plain (PAP), an abyssal locality located in the northeast Atlantic Ocean. Nine cruises were carried out between August 1996 and August 1998. Silicic acid (DSi) increased downward from 46.2 to 213 μM (mean of 27 profiles). Biogenic silica (BSi) decreased from ca. 2% near the sediment–water interface to
Published: 2001
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43. Material supply to the abyssal seafloor in the Northeast Atlantic

Author: Richard S. Lampitt, Ekaterina Popova, Olivier Ragueneau, George A. Wolff, Brian J. Bett, Konstadinos Kiriakoulakis, and Annick Vangriesheim
Subjects: Water column, Oceanography, Sediment trap, Phytodetritus, Flux, Geology, Porcupine Abyssal Plain, Photic zone, Aquatic Science, Seabed, Marine snow
Abstract: Downward particle flux was measured using sediment traps at various depths over the Porcupine Abyssal Plain (water depth ~4850 m) for prolonged periods from 1989 to 1999. A strong seasonal pattern of flux was evident reaching a maximum in mid-summer. The composition of the material changed with depth, reflecting the processes of remineralisation and dissolution as the material sank through the water column. However, there was surprisingly little seasonal variation in its composition to reflect changes in the biology of the euphotic zone. Currents at the site have a strong tidal component with speeds almost always less than 15 cm/sec. In the deeper part of the water column they tend to be northerly in direction, when averaged over periods of several months. A model of upper ocean biogeochemistry forced by meteorology was run for the decade in order to provide an estimate of flux at 3000 m depth. Agreement with measured organic carbon flux is good, both in terms of the timings of the annual peaks and in the integrated annual flux. Interannual variations in the integrated flux are of similar magnitude for both the model output and sediment trap measurements, but there is no significant relationship between these two sets of estimates. No long-term trend in flux is evident, either from the model, or from the measurements. During two spring/summer periods, the marine snow concentration in the water column was assessed by time-lapse photography and showed a strong peak at the start of the downward pulse of material at 3000 m. This emphasises the importance of large particles during periods of maximum flux and at the start of flux peaks. Time lapse photographs of the seabed show a seasonal cycle of coverage of phytodetrital material, in agreement with the model output both in terms of timing and magnitude of coverage prior to 1996. However, after a change in the structure of the benthic community in 1996 no phytodetritus was evident on the seabed. The model output shows only a single peak in flux each year, whereas the measured data usually indicated a double peak. It is concluded that the observed double peak may be a reflection of lowered sediment trap efficiency when flux is very high and is dominated by large marine snow particles. Resuspension into the trap 100 m above the seabed, when compared to the primary flux at 3000 m depth (1800 mab) was lower during periods of high primary flux probably because of a reduction in the height of resuspension when the material is fresh. At 2 mab, the picture is more complex with resuspension being enhanced during the periods of higher flux in 1997, which is consistent with this hypothesis. However there was rather little relationship to flux at 3000 m in 1998. At 3000 m depth, the Flux Stability Index (FSI), which provides a measure of the constancy of the seasonal cycle of flux, exhibited an inverse relationship with flux, such that the highest flux of organic carbon was recorded during the year with the greatest seasonal variation.
Published: 2001
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44. A review of the Si cycle in the modern ocean: recent progress and missing gaps in the application of biogenic opal as a paleoproductivity proxy

Author: Aude Leynaert, Véronique Martin-Jézéquel, Christoph Heinze, David M. Nelson, Roger Francois, Bernard Quéguiner, Paul Tréguer, Gerhard Fischer, Ernst Maier-Reimer, Mark A. Brzezinski, Robert F. Anderson, David J. DeMaster, Richard C. Dugdale, Olivier Ragueneau, and Jack Dymond
Subjects: Global and Planetary Change, Biogeochemical cycle, Water column, Oceanography, Benthic zone, Biological pump, Sediment, Biogenic silica, Geology, Diagenesis, Carbon cycle
Abstract: Due to the major role played by diatoms in the biological pump of CO2, and to the presence of silica-rich sediments in areas that play a major role in air–sea CO2 exchange (e.g. the Southern Ocean and the Equatorial Pacific), opal has a strong potential as a proxy for paleoproductivity reconstructions. However, because of spatial variations in the biogenic silica preservation, and in the degree of coupling between the marine Si and C biogeochemical cycles, paleoreconstructions are not straitghtforward. A better calibration of this proxy in the modern ocean is required, which needs a good understanding of the mechanisms that control the Si cycle, in close relation to the carbon cycle. This review of the Si cycle in the modern ocean starts with the mechanisms that control the uptake of silicic acid (Si(OH)4) by diatoms and the subsequent silicification processes, the regulatory mechanisms of which are uncoupled. This has strong implications for the direct measurement in the field of the kinetics of Si(OH)4 uptake and diatom growth. It also strongly influences the Si:C ratio within diatoms, clearly linked to environmental conditions. Diatoms tend to dominate new production at marine ergoclines. At depth, they also succeed to form mats, which sedimentation is at the origin of laminated sediments and marine sapropels. The concentration of Si(OH)4 with respect to other macronutrients exerts a major influence on diatom dominance and on the rain ratio between siliceous and calcareous material, which severely impacts surface waters pCO2. A compilation of biogenic fluxes collected at about 40 sites by means of sediment traps also shows a remarkable pattern of increasing BSi:Corg ratio along the path of the “conveyor belt”, accompanying the relative enrichment of waters in Si compared to N and P. This observation suggests an extension of the Si pump model described by Dugdale and Wilkerson (Dugdale, R.C., Wilkerson, F.P., 1998. Understanding the eastern equatorial Pacific as a continuous new production system regulating on silicate. Nature 391, 270–273.), giving to Si(OH)4 a major role in the control of the rain ratio, which is of major importance in the global carbon cycle. The fate of the BSi produced in surface waters is then described, in relation to Corg, in terms of both dissolution and preservation mechanisms. Difficulties in quantifying the dissolution of biogenic silica in the water column as well as the sinking rates and forms of BSi to the deep, provide evidence for a major gap in our understanding of the mechanisms controlling the competition between retention in and export from surface waters. The relative influences of environmental conditions, seasonality, food web structure or aggregation are however explored. Quantitatively, assuming steady state, the measurements of the opal rain rate by means of sediment traps matches reasonably well those obtained by adding the recycling and burial fluxes in the underlying abyssal sediments, for most of the sites where such a comparison is possible. The major exception is the Southern Ocean where sediment focusing precludes the closing of mass balances. Focusing in fact is also an important aspect of the downward revision of the importance of Southern Ocean sediments in the global biogenic silica accumulation. Qualitatively, little is known about the duration of the transfer through the deep and the quality of the material that reaches the seabed, which is suggested to represent a major gap in our understanding of the processes governing the early diagenesis of BSi in sediments. The sediment composition (special emphasis on Al availability), the sedimentation rate or bioturbation are shown to exert an important control on the competition between dissolution and preservation of BSi in sediments. It is suggested that a primary control on the kinetic and thermodynamic properties of BSi dissolution, both in coastal and abyssal sediments, is exerted by water column processes, either occuring in surface waters during the formation of the frustules, or linked to the transfer of the particles through the water column, which duration may influence the quality of the biogenic rain. This highlights the importance of studying the factors controlling the degree of coupling between pelagic and benthic processes in various regions of the world ocean, and its consequences, not only in terms of benthic biology but also for the constitution of the sediment archive. The last section, first calls for the end of the “NPZD” models, and for the introduction of processes linked to the Si cycle, into models describing the phytoplankton cycles in surface waters and the early diagenesis of BSi in sediments. It also calls for the creation of an integrated 1-D diagnostic model of the Si:C coupling, for a better understanding of the interactions between surface waters, deep waters and the upper sedimentary column. The importance of Si(OH)4 in the control of the rain ratio and the improved parametrization of the Si cycle in the 1-D diagnostic models should lead to a reasonable incorporation of the Si cycle into 3-D regional circulation models and OGCMs, with important implications for climate change studies and paleoreconstructions at regional and global scale.
Published: 2000
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45. 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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46. Changement global : impacts sur les écosystèmes et défis sociétaux

Author: Olivier Ragueneau, Frédérique Viard, Jean-Pierre Gattuso, Cyril Tissot, Jacques Grall, 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), DIVersité et COnnectivité dans le paysage marin côtier (DIVCO), 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), Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), 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)-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), UMS 3113, Institut de Recherche pour le Développement (IRD)-Université de Brest (UBO)-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), LITEAU Ra2Brest, Bruno David, Catherine Ozouf-Costaz, Marc Troussellier, 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 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), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), 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)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), 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: habitats benthiques, [SDV]Life Sciences [q-bio], pêche à la drague, OS, [SHS.GEO]Humanities and Social Sciences/Geography, interactions, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, simulation multi-agents, biodiversité
Abstract: Tout l'équilibre de notre planète repose sur les océans, qui recouvrent plus de 70 % de la surface de la Terre. Mais que sait-on vraiment de ce monde des profondeurs ? Si en quelques années les connaissances ont progressé, l'environnement marin et les interactions complexes qui régissent son fonctionnement restent mal connus. Sait-on, par exemple, que dans cet immense réservoir de biodiversité la grande majorité des espèces reste encore à identifier ? Que des organismes microscopiques y jouent des rôles essentiels, comme dans la formation des nuages ? Que les habitants des abysses y ont adopté des modes de vie surprenants leur permettant de tolérer des conditions toxiques, brûlantes ou pauvres en oxygène ?Évoquer les mondes marins, c'est aussi aborder la diversité des littoraux qui abritent une multiplicité d'écosystèmes. C'est enfin raconter l'histoire de l'humanité si intimement liée à celle des océans, humanité qui se doit d'apprendre à les préserver et à en faire un usage raisonné. La recherche, située au carrefour de nombreuses questions écologiques, environnementales et sociales, se fait plus que jamais l'écho de ces enjeux.Des spécialistes des mondes marins issus des laboratoires du CNRS, des universités et d'autres organismes de recherche français dressent un état des lieux des océans en présentant les travaux menés dans ce domaine et tracent les voies prospectives de recherche pour les années à venir. Un livre pour tous les amoureux de l'océan !Un ouvrage collectif sous la direction de Bruno David et Catherine Ozouf-Costaz et Marc TroussellierInstitut écologie et environnement (INEE) du CNRS.; National audience
Published: 2014

47. 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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48. 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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49. 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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50. Preservation efficiencies and accumulation rates for biogenic silica and organic C, N, and P in high-latitude sediments: The Ross Sea

Author: Charles A. Nittrouer, Olivier Ragueneau, and David J. DeMaster
Subjects: Atmospheric Science, Biogeochemical cycle, Soil Science, chemistry.chemical_element, Aquatic Science, Biogenic silica, Oceanography, chemistry.chemical_compound, Pore water pressure, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Earth-Surface Processes, Water Science and Technology, Total organic carbon, geography, geography.geographical_feature_category, Ecology, Continental shelf, Phosphorus, Paleontology, Sediment, Forestry, Silicate, Geophysics, chemistry, Space and Planetary Science, Environmental chemistry, Geology
Abstract: Rates of biogenic sediment accumulation (biogenic silica and organic C, N, and P) and pore water flux have been established for a variety of depositional environments in the Ross Sea. On the basis of 14C measurements in kasten cores, sediment accumulation rates ranged from 250 cm kyr−1 in the coastal basin of Granite Harbor to 1–2 cm kyr−1 in the shelf and slope environments of the northern and eastern Ross Sea. Burial of biogenic material was most rapid in the southwestern Ross Sea, where biogenic silica accumulation rates ranged from 2 to 31 g cm−2 kyr−1 and organic carbon accumulation rates ranged from 0.05 to 1.4 g cm−2 kyr−1. In the northern and eastern Ross Sea, biogenic silica and organic carbon accumulation rates typically equaled 0.02–0.03 g SiO2 cm−2 kyr−1 and 0.002–0.004 g C cm−2 kyr−1. Flux core measurements were used to estimate seabed regeneration rates for biogenic silica, organic carbon, and phosphorus. Pore water fluxes, in general, showed much less variability across the Ross Sea than did the biogenic accumulation rates. Pore water silicate fluxes in the study area ranged from 0.6 to 5.3 g SiO2 cm−2 kyr−1, whereas carbon fluxes ranged from 0.1 to 1.2 g C cm−2 kyr−1 and phosphate fluxes varied from −0.006 to 0.012 g P cm−2 kyr−1. Seabed preservation efficiencies were calculated for biogenic silica, organic carbon, and phosphorus by combining the solid-phase and pore water data. The seabed preservation efficiencies for biogenic silica (1–86%) were greater than for organic carbon (1–71%) at all nine stations examined. The preferential preservation of biogenic silica relative to organic carbon also was apparent in Ross Sea sediments because the biogenic silica/organic carbon ratio in the material buried in the seabed generally was 2 times greater than the ratio in sediment particles arriving at the sediment-water interface. Sediment accumulation rate correlated strongly with both the biogenic silica and the organic carbon preservation efficiency data. P preservation efficiencies remained relatively high (24–65%) even when the accumulation rates were low (1–2 cm kyr−1) because of the near-zero phosphate fluxes out of the seabed. Of the total P in the seabed (0.04–0.09 wt. %), approximately 25% existed in the form of organic P. The total amount of biogenic silica accumulating on the Ross Sea shelf is ∼2.3 × 1012 g SiO2 yr−1, which is approximately an order of magnitude less than the Ledford-Hoffman et al. [1986] estimate that was based on 210Pb chronologies. Biogenic silica accumulation rates in the southern, central, and western Ross Sea increased during the mid and late Holocene, reaching their maximum values during the past 500 to 1000 years.
Published: 1996
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