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Registros recuperados: 17
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A new device to follow temporal variations of oxygen demand in deltaic sediments: the LSCE benthic station ArchiMer
Toussaint, Flora; Rabouille, Christophe; Cathalot, Cecile; Bombled, Bruno; Abchiche, Abdel; Aouji, Oualid; Buchholtz, Gilles; Clemencon, Aurelien; Geyskens, Nicolas; Repecaud, Michel; Pairaud, Ivane; Verney, Romaric; Tisnerat-laborde, Nadine.
A new benthic station equipped with oxygen microelectrodes and environmental sensors was developed by Laboratoire des Sciences du Climat et de L’Environnement (LSCE) and Division Technique of the Institut National des Sciences de L’Univers (DT-INSU) to perform in situ time series monitoring of sediment oxygen demand, linked to the mineralization of organic matter. The time series typically cover periods of 2-3 months, with a base frequency of 1 set of oxygen profiles per day. The profiling head assessed the lateral heterogeneity of the sediment oxygen demand at the beginning of the time series over a 0.8-m long rectangle to discriminate spatial and temporal variability. A continuous recalibration is performed using a moored oxygen optode anchored to the...
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00230/34126/32597.pdf
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Benthic alkalinity and dissolved inorganic carbon fluxes in the Rhône River prodelta generated by decoupled aerobic and anaerobic processes ArchiMer
Rassmann, Jens; Eitel, Eryn M.; Lansard, Bruno; Cathalot, Cecile; Brandily, Christophe; Taillefert, Martial; Rabouille, Christophe.
Estuarine regions are generally considered a major source of atmospheric CO2, as a result of the high organic carbon (OC) mineralization rates in their water column and sediments. Despite this, the intensity of anaerobic respiration processes in the sediments tempered by the reoxidation of reduced metabolites near the sediment–water interface controls the flux of benthic alkalinity. This alkalinity may partially buffer metabolic CO2 generated by benthic OC respiration in sediments. Thus, sediments with high anaerobic respiration rates could contribute less to local acidification than previously thought. In this study, a benthic chamber was deployed in the Rhône River prodelta and the adjacent continental shelf (Gulf of Lion, northwestern Mediterranean) in...
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Ano: 2020 URL: https://archimer.ifremer.fr/doc/00600/71163/69492.pdf
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Biogeochemical and contaminant cycling in sediments from a human-impacted coastal lagoon - Introduction and summary ArchiMer
Rabouille, Christophe; Amouroux, D; Anschutz, P; Jouanneau, J.-m.; Gilbert, F; Cossa, Daniel; Prevot, F.
A general decrease in the anthropogenic pressure on coastal ecosystems has been observed recently in developed countries. But coastal lagoon ecosystems are still undergoing major human impact (Lotze et al., 2006). A major environmental concern is the enhancement of contaminant dispersion and algal production due to eutrophication, associated with an increase in the duration of intermittent seasonal periods of anoxia. Due to past industrial activity, large concentrations of contaminants have been accumulated in sediments of natural water bodies. One of the issues raised by environmentalists is the fate of these contaminants with changing environmental conditions, such as restoration of water bodies to their "pristine" state (water framework directives), or...
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Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3037.pdf
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Carbon Dynamics Along the Seine River Network: Insight From a Coupled Estuarine/River Modeling Approach ArchiMer
Laruelle, Goulven G.; Marescaux, Audrey; Le Gendre, Romain; Garnier, Josette; Rabouille, Christophe; Thieu, Vincent.
The Seine river discharges over 700 Gg of carbon (C) every year into the sea mostly under the form of dissolved inorganic carbon (DIC) and emits 445 Gg under the form of carbon dioxide (CO2) to the atmosphere over its entire river network. The watershed, which drains 76,000 km2, is heavily populated with 18 106 inhabitants and is thus submitted to large anthropic pressure. The offline coupling of two Reactive Transport Models is used to understand the complex spatial and temporal dynamics of carbon, oxygen and nutrients and quantify the CO2 exchange at the air-water interface along the main axis of the river. The estuarine section of the Seine is simulated by the generic estuarine model C-GEM (for Carbon Generic Estuarine Model), while the upstream part of...
Tipo: Text Palavras-chave: Dissolved inorganic and organic carbon; Carbon dioxide; Reactive-transport model; Seine river and estuary; Biogeochemical budget.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00493/60421/63858.pdf
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Coupling and Decoupling of benthic elemental cycles (P, Si) along the salinity gradient of a subtidal temperate estuary : results from measurements and modeling. ArchiMer
Raimonet, Melanie; Ragueneau, Olivier; Andrieux-loyer, Francoise; Khalil, Karima; Kerouel, Roger; Philippon, Xavier; Soetaert,, Karline; Rabouille, Christophe; Memery, Laurent.
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00058/16909/14382.pdf
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Early diagenesis in the sediments of the Congo deep-sea fan dominated by massive terrigenous deposits: Part II – Iron–sulfur coupling ArchiMer
Taillefert, Martial; Beckler, Jordon S.; Cathalot, Cecile; Michalopoulos, Panagiotis; Corvaisier, Rudolph; Kiriazis, Nicole; Caprais, Jean-claude; Pastor, Lucie; Rabouille, Christophe.
Deep-sea fans are well known depot centers for organic carbon that should promote sulfate reduction. At the same time, the high rates of deposition of unconsolidated metal oxides from terrigenous origin may also promote metal-reducing microbial activity. To investigate the eventual coupling between the iron and sulfur cycles in these environments, shallow sediment cores (< 50 cm) across various channels and levees in the Congo River deep-sea fan (~5000 m) were profiled using a combination of geochemical methods. Interestingly, metal reduction dominated suboxic carbon remineralization processes in most of these sediments, while dissolved sulfide was absent. In some ‘hotspot’ patches, however, sulfate reduction produced large sulfide concentrations which...
Tipo: Text Palavras-chave: Sediment diagenesis; Iron reduction; Sulfate reduction; Deep-sea fans.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00389/50068/52254.pdf
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Evidence and age estimation of mass wasting at the distal lobe of the Congo deep-sea fan ArchiMer
Croguennec, Claire; Ruffine, Livio; Dennielou, Bernard; Baudin, Francois; Caprais, Jean-claude; Guyader, Vivien; Bayon, Germain; Brandily, Christophe; Le Bruchec, Julie; Bollinger, Claire; Germain, Yoan; Droz, Laurence; Babonneau, Nathalie; Rabouille, Christophe.
On continental margins, sulfate reduction occurs within the sedimentary column. It is coupled with the degradation of organic matter and the anaerobic oxidation of methane. These processes may be significantly disturbed by sedimentary events, leading to transient state profiles for the involved chemical species. Yet, little is known about the impact of turbidity currents and mass wasting on the migration of chemical species and the redox reactions in which they are involved. Due to its connection to the River, the Congo deep-sea fan continuously receives huge amount of organic matter-rich sediments primarily transported by turbidity currents, which impact on the development of the associated ecosystems (Rabouille et al., 2016). Thus, it is well suited to...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00363/47410/47403.pdf
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Fauna and habitat types driven by turbidity currents in the lobe complex of the Congo deep sea fan ArchiMer
Sen, Arunima; Dennielou, Bernard; Tourolle, Julie; Arnaubec, Aurelien; Rabouille, Christophe; Olu, Karine.
This study characterizes the habitats and megafaunal community of the Congo distal lobe complex driven by turbidity currents through the use of remotely operated vehicle (ROV) still imagery transects covering distances in the order of kilometers. In this sedimentary, abyssal area about 5000 m deep and 750 km offshore from western Africa, large quantities of deposited organic material supplied by the Congo River canyon and channel support aggregations of large sized foraminifers (Bathysiphon sp.) and vesicomyid clams (Christineconcha regab, Abyssogena southwardae) often associated with methane cold seeps, as well as opportunistic deep-sea scavengers. Additionally, bacterial mats, assumed to be formed by large sulfur-oxidizing filamentous bacteria (Beggiatoa...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00385/49614/50126.pdf
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MESURHO : a high frequency oceanographic buoy at the Rhone River mouth ArchiMer
Cadiou, Jean-francois; Repecaud, Michel; Arnaud, Mireille; Rabouille, Christophe; Raimbault, Patrick; Radakovitch, Olivier; Meule, Samuel; Gaufres, Pierre; Pairaud, Ivane.
As the current main source of continental fresh water discharge in the Mediterranean Sea, the Rhone River inputs are a key forcing for ecosystems of the Gulf of Lions in the western basin. In order to better characterize the exchanges at this key interface, an oceanographic buoy has been installed at the Rhone River mouth in June 2009 for high frequency multiparameter measurements with bottom, water column and air sensors. Data are sent in near real time towards an onshore data center.
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00070/18161/15718.pdf
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Morphology, structure, composition and build-up processes of the active channel-mouth lobe complex of the Congo deep-sea fan with inputs from remotely operated underwater vehicle (ROV) multibeam and video surveys ArchiMer
Dennielou, Bernard; Droz, Laurence; Babonneau, Nathalie; Jacq, Celine; Bonnel, Cedric; Picot, Marie; Le Saout, Morgane; Saout, Yohan; Bez, Martine; Savoye, Bruno; Olu, Karine; Rabouille, Christophe.
The detailed structure and composition of turbiditic channel-mouth lobes is still largely unknown because they commonly lie at abyssal water depths, are very thin and are therefore beyond the resolution of hull-mound acoustic tools. The morphology, structure and composition of the Congo turbiditic channel-mouth lobe complex (90×40 km; 2525 km2) were investigated with hull-mounted swath bathymetry, air gun seismics, 3.5 kHz sub-bottom profiler, sediment piston cores and also with high-resolution multibeam bathymetry and video acquired with a Remote Operating Vehicle (ROV). The lobe complex lies 760 km off the Congo River mouth in the Angola abyssal plain between 4740 and 5030 m deep. It is active and is fed by turbidity currents that deposit several...
Tipo: Text Palavras-chave: Congo deep-sea fan; Lobe; Lobe complex; Channel; Channel-Lobe Transition Zone; Angola basin; Slump; Slide; Debrite; Turbidite; ROV; Bathymetry; Seismic; Sediment core.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00378/48976/49383.pdf
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Organic carbon accumulation in modern sediments of the Angola basin influenced by the Congo deep sea fan ArchiMer
Baudin, Francois; Martinez, Philippe; Dennielou, Bernard; Charlier, Karine; Marsset, Tania; Droz, Laurence; Rabouille, Christophe.
Geochemical data (total organic carbon-TOC content, δ13Corg, C:N, Rock-Eval analyses) were obtained on 150 core tops from the Angola basin, with a special focus on the Congo deep sea fan. Combined with the previously published data, the resulting dataset (322 stations) shows a good spatial and bathymetric representativeness. TOC content and δ13Corg maps of the Angola basin were generated using this enhanced dataset. The main difference in our map with previously published ones is the high terrestrial organic matter content observed downslope along the active turbidite channel of the Congo deep sea fan till the distal lobe complex near 5,000 m of water-depth. Interpretation of downslope trends in TOC content and organic matter composition indicates that...
Tipo: Text Palavras-chave: Organic matter; Recent sediments; South Atlantic Ocean; Turbidites.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00369/47974/47999.pdf
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Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget ArchiMer
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
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Routing of terrestrial organic matter from the Congo River to the ultimate sink in the abyss: a mass balance approach (André Dumont medallist lecture 2017) ArchiMer
Baudin, François; Rabouille, Christophe; Dennielou, Bernard.
We address the role of the Congo River sediment dispersal in exporting and trapping organic carbon into deep offshore sediments. Of particular interest is the Congo submarine canyon, which constitutes a permanent link between the terrestrial sediment sources and the marine sink. The Congo River delivers an annual sediment load of ~40 Tg (including 2 Tg of C) that feed a mud-rich turbidite system. Previous estimates of carbon storage capacity in the Congo turbidite system suggest that the terminal lobe complex accounts for ~12% of the surface area of the active turbidite system and accumulates ~18% of the annual input of terrestrial particulate organic carbon exiting the Congo River. In this paper, we extend the approach to the whole active turbidite...
Tipo: Text Palavras-chave: Recent sediments; Congo turbidite system; Organic carbon; Burial efficiency; Source-to-sink.
Ano: 2020 URL: https://archimer.ifremer.fr/doc/00622/73394/72611.pdf
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Simulation of o-2, po4 and organic-carbon behavior during a benthic chamber experiment on the deep-sea floor ArchiMer
Rabouille, Christophe; Gaillard, Juliette.
Using a time-dependent model for organic matter mineralization by oxygen and the resulting phosphate production in deep-sea sediments, the progress of a benthic chamber experiment is simulated. Assuming a known steady state as starting condition, the vertical distribution of chemical species in the sediments, pore water and solids, and the concentrations in the benthic chamber are calculated. Compared to previous approaches, the computation scheme utilized here considers explicitly a coupled and non-linear kinetic formulation of organic carbon oxidation and oxygen reduction. The purpose of this modeling approach is to assess the validity of conventional interpretations of benthic chamber experimental data. The results of the calculations show that the...
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Ano: 1994 URL: http://archimer.ifremer.fr/doc/00099/21004/18630.pdf
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Spatial and temporal variability of sediment organic matter recycling in two temperate eutrophicated estuaries ArchiMer
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
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Temporal variability of live (stained) benthic foraminiferal faunas in a river-dominated shelf – Faunal response to rapid changes of the river influence (Rhône prodelta, NW Mediterranean) ArchiMer
Goineau, A.; Fontanier, C.; Jorissen, F.; Buscail, R.; Kerherve, P.; Cathalot, C.; Pruski, A. M.; Lantoine, F.; Bourgeois, S.; Metzger, E.; Legrand, E.; Rabouille, Christophe.
In the context of the French research project CHACCRA (Climate and Human-induced Alterations in Carbon Cycling at the River–seA connection), living (rose Bengal-stained) benthic foraminifera were investigated at two stations (24 and 67 m depth) in the Rhône prodelta (NW Mediterranean, Gulf of Lions). The aim of this study was to precise the response of benthic foraminiferal faunas to temporal changes of the Rhône River inputs (e.g. organic and terrigeneous material). Each site was sampled in April 2007, September 2007, May 2008 and December 2008, permitting to observe foraminiferal faunas of the 63–150 and >150 μm size fractions under a wide range of environmental conditions. Obvious variations in foraminiferal faunal composition were observed during...
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Ano: 2012 URL: https://archimer.ifremer.fr/doc/00140/25097/23323.pdf
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The fate of river organic carbon in coastal areas: A study in the Rhone River delta using multiple isotopic (delta C-13, Delta C-14) and organic tracers ArchiMer
Cathalot, Cecile; Rabouille, Christophe; Tisnerat-laborde, N.; Toussaint, Flora; Kerherve, P.; Buscail, R.; Loftis, K.; Sun, M. -y.; Tronczynski, Jacek; Azoury, S.; Lansard, Bruno; Treignier, Claire; Pastor, L.; Tesi, T..
A significant fraction of the global carbon flux to the ocean occurs in River-dominated Ocean Margins (RiOMar) although large uncertainties remain in the cycle of organic matter (OM) in these systems. In particular, the OM sources and residence time have not been well clarified. Surface (0-1 cm) and sub-surface (3-4 cm) sediments and water column particles (bottom and intermediate depth) from the Rhone River delta system were collected in June 2005 and in April 2007 for a multi-proxy study. Lignin phenols, black carbon (BC), proto-kerogen/BC mixture, polycyclic aromatic hydrocarbons (PAHs), carbon stable isotope (delta C-13(OC)), and radiocarbon measurements (delta C-14(OC)) were carried out to characterize the source of sedimentary organic material and to...
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Ano: 2013 URL: http://archimer.ifremer.fr/doc/00157/26784/25673.pdf
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