Consulta: creatorFacets:"Ragueneau, Olivier"
Registros recuperados: 17
Data/hora: 04/06/2024 02:20:07

Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Raimonet, Melanie; Ragueneau, Olivier; Jacques, Vincent; Corvaisier, Rudolph; Moriceau, Brivaela; Khripounoff, Alexis; Pozzato, Lara; Rabouille, Christophe.
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....
Tipo: Text
Palavras-chave: Continental margin; Land-sea export; Silica cycle; Congo canyon; Deep-sea fan.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00251/36242/35797.pdf

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
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Ragueneau, Olivier; Raimonet, Melanie; Maze, Camille; Coston-guarini, Jennifer; Chauvaud, Laurent; Danto, Anatole; Grall, Jacques; Jean, Frederic; Paulet, Yves-marie; Thouzeau, Gerard.
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...
Tipo: Text
Palavras-chave: Sustainability; Land-ocean continuum; Bay of Brest; Interdisciplinarity; Science-policy-community interface.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00616/72792/72272.pdf

Observed and projected Sea Surface Temperature seasonal changes in the Western English Channel from satellite data and CMIP5 multi-model ensemble.
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: L'Heveder, Blandine; Speich, Sabrina; Ragueneau, Olivier; Gohin, Francis; Bryere, Philippe.
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...
Tipo: Text
Palavras-chave: SST; Climate change; Western English Channel; CMIP5; Regional study.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00350/46163/45861.pdf

Cartographic Atlas of Marine Environmental Law in West Africa. Methodology and use for spatial planning
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Le tixerant, Matthieu; Bonnin, Marie; Gourmelon, Françoise; Ragueneau, Olivier; Rouan, Mathias; Ly, Ibrahima; Ould zein, Ahmed; Ndiaye, Fatou; Diedhiou, Mohamed; Ndao, Souleye; Ndiaye, Mamadou Bassirou.
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...
Tipo: Text
Palavras-chave: Afrique de l’ouest; Mer; Littoral; Droit de la mer; Environnement; SIG; Cartographie; West Africa; Sea; Coastal zone; Law of the sea; Environment; GIS; Cartography.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00656/76813/81628.pdf

Element enrichment and provenance of the detrital component in Holocene sediments from the western Black Sea
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Dekov, Vesselin M.; Darakchieva, Valentina Y.; Billström, Kjell; Garbe-schönberg, C-dieter; Kamenov, George D.; Gallinari, Morgane; Dimitrov, Lyubo; Ragueneau, Olivier; Kooijman, Ellen.
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...
Tipo: Text
Palavras-chave: Anoxic; Black Sea; Element enrichment; Sr-Nd-Pb-isotopes; Holocene.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00590/70164/68171.pdf

Spatial and temporal variability of sediment organic matter recycling in two temperate eutrophicated estuaries
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Khalil, Karima; Raimonet, Melanie; Laverman, Anniet M.; Yan, Chen; Andrieux-loyer, Françoise; Viollier, Eric; Deflandre, Bruno; Ragueneau, Olivier; Rabouille, Christophe.
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...
Tipo: Text
Palavras-chave: Spatial and temporal variability; Estuarine sediment; Oxygen; Organic carbon and isotopic composition; Microelectrode; Organic matter recycling.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00164/27533/25691.pdf

Spatio-temporal variability in benthic silica cycling in two macrotidal estuaries: Causes and consequences for local to global studies
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Raimonet, Melanie; Ragueneau, Olivier; Andrieux Loyer, Francoise; Philippon, Xavier; Kerouel, Roger; Le Goff, Manon; Memery, Laurent.
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 porewater silicic acid (Si(OH)4) profiles e that integrate benthic transport and reaction processes e was investigated at different spatial (metre, longitudinal and crosssection, intra-estuary) and temporal (tidal, seasonal) scales in two macrotidal estuaries, very close geographically but essentially differing in their shape. Studying the spatial and temporal variability of Si(OH)4 concentrations in porewaters provided evidence for the importance of transport processes, e.g. bio-irrigation, tidal pumping,...
Tipo: Text
Palavras-chave: Heterogeneity; Season; Silicate; Sediment; Land-sea interface; Upscaling.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00124/23529/22370.pdf

Carbon and silica megasink in deep-sea sediments of the Congo terminal lobes
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Rabouille, C.; Dennielou, Bernard; Baudin, F.; Raimonet, M.; Droz, Laurence; Khripounoff, Alexis; Martinez, P.; Mejanelle, L.; Michalopoulos, P.; Pastor, Lucie; Pruski, A.; Ragueneau, Olivier; Reyss, J.-l.; Ruffine, Livio; Schnyder, J.; Stetten, E.; Taillefert, M.; Tourolle, Julie; Olu, Karine.
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...
Tipo: Text
Palavras-chave: Present; Paleoceanography; South Atlantic; Inorganic geochemistry; Organic geochemistry; Sedimentology-marine cores.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00511/62289/66720.pdf

Exploitation par la pêche de coquillages d’écloserie en rade de Brest : quels acteurs pour quelles perspectives ?
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Danto, Anatole; Boudry, Pierre; Ragueneau, Olivier; Maze, Camille.
Tipo: Text
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00375/48577/48899.pdf

Alkaline-extractable silicon from land to ocean: A challenge for biogenic silicon determination
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Barao, Lucia; Vandevenne, Floor; Clymans, Wim; Frings, Patrick; Ragueneau, Olivier; Meire, Patrick; Conley, Daniel J.; Struyf, Eric.
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...
Tipo: Text
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00276/38725/73177.pdf

Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Raimonet, Melanie; Andrieux, Francoise; Ragueneau, Olivier; Michaud, Emma; Kerouel, Roger; Philippon, Xavier; Nonent, Michel; Memery, Laurent.
Tipo: Text
Palavras-chave: Early diagenesis; Silicate; Phosphate; Authigenic phosphorus; Macrotidal; Estuary.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00130/24115/22493.pdf

Action-orientated research and framework: insights from the French long-term social-ecological research network
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Bretagnolle, Vincent; Benoit, Marc; Bonnefond, Mathieu; Breton, Vincent; Church, Jon M.; Gaba, Sabrina; Gilbert, Daniel; Gillet, François; Glatron, Sandrine; Guerbois, Chloé; Lamouroux, Nicolas; Lebouvier, Marc; Mazé, Camille; Mouchel, Jean-marie; Ouin, Annie; Pays, Olivier; Piscart, Christophe; Ragueneau, Olivier; Servain, Sylvie; Spiegelberger, Thomas; Fritz, Hervé.
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...
Tipo: Text
Palavras-chave: Adaptive governance; Ecosystem services; Landscape; LTER; Management; Practices; Research infrastructure; Social-ecological systems; Sustainability.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00588/70032/67950.pdf

ILTER - The International Long-Term Ecological Research Network as a Platform for Global Coastal and Ocean Observation
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Muelbert, Jose H.; Nidzieko, Nicholas J.; Acosta, Alicia T. R.; Beaulieu, Stace E.; Bernardino, Angelo F.; Boikova, Elmira; Bornman, Thomas G.; Cataletto, Bruno; Deneudt, Klaas; Eliason, Erika; Kraberg, Alexandra; Nakaoka, Masahiro; Pugnetti, Alessandra; Ragueneau, Olivier; Scharfe, Mirco; Soltwedel, Thomas; Sosik, Heidi M.; Stanisci, Angela; Stefanova, Kremena; Stephan, Pierre; Stier, Adrian; Wikner, Johan; Zingone, Adriana.
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...
Tipo: Text
Palavras-chave: Climate change; Marine ecosystems; Ecology; EOVs; SWOT; DEIMS.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00615/72756/72025.pdf

Modern palynological record in the Bay of Brest (NW France): Signal calibration for palaeo-reconstructions
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lambert, Clement; Vidal, Muriel; Penaud, Aurelie; Combourieu-nebout, Nathalie; Lebreton, Vincent; Ragueneau, Olivier; Gregoire, Gwendoline.
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...
Tipo: Text
Palavras-chave: Pollen; Dinocyst; Surface sediment; Estuarine dynamics; Vegetation cover.
Ano: 2017
URL: https://archimer.ifremer.fr/doc/00382/49371/49784.pdf

High alkaline phosphatase activity in phosphate replete waters: The case of two macrotidal estuaries
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Labry, Claire; Delmas, Daniel; Youenou, Agnes; Quere, Julien; Leynaert, Aude; Fraisse, Stephane; Raimonet, Melanie; Ragueneau, Olivier.
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...
Tipo: Text
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00337/44840/44428.pdf

Human-induced river runoff overlapping natural climate variability over the last 150 years: Palynological evidence (Bay of Brest, NW France)
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lambert, Clement; Penaud, Aurelie; Vidal, Muriel; Klouch, Khadidja; Gregoire, Gwendoline; Ehrhold, Axel; Eynaud, Frederique; Schmidt, Sabine; Ragueneau, Olivier; Siano, Raffaele.
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...
Tipo: Text
Palavras-chave: Pollen grains; Dinoflagellate cysts; Estuarine dynamics; River runoff; Climate variability.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00410/52110/52813.pdf

Coupling and Decoupling of benthic elemental cycles (P, Si) along the salinity gradient of a subtidal temperate estuary : results from measurements and modeling.
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Raimonet, Melanie; Ragueneau, Olivier; Andrieux-loyer, Francoise; Khalil, Karima; Kerouel, Roger; Philippon, Xavier; Soetaert,, Karline; Rabouille, Christophe; Memery, Laurent.
Tipo: Text
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00058/16909/14382.pdf