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A benthic Si mass balance on the Congo margin: Origin of the 4000 m DSi anomaly and implications for the transfer of Si from land to ocean ArchiMer
Ragueneau, O.; Regaudie-de-gioux, A.; Moriceau, B.; Gallinari, M.; Vangriesheim, Annick; Baurand, F.; Khripounoff, Alexis.
To elucidate the origin of the silicic acid (DSi) anomaly observed along the 4000 isobath on the Congo margin, we have established a benthic Si mass balance and performed direct measurements of biogenic silica (bSiO(2)) dissolution in the deep waters and in the sediments. Results strongly suggest that the anomaly originates from the sediments; the intensity of DSi recycling is consistent with the degradation of organic matter, as observed from Si:O-2 ratios in the benthic fluxes compared to that ratio observed in the anomalies. Strong imbalances, observed in both the Si and C mass balances, suggest that the biogenic matter that degrades and dissolves in these sediments near 4000 m does not come from pelagic sedimentation. It is probably not coming also...
Tipo: Text Palavras-chave: Congo; Continental margin; Preservation; Dissolution; Biogenic silica.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-7410.pdf
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Aliphatic hydrocarbons and triterpenes of the Congo deep sea fan ArchiMer
Mejanelle, Laurence; Riviere, Beatrice; Pinturier, Laurence; Khripounoff, Alexis; Baudin, Francois; Dachs, Jordi.
Hydrocarbons were analyzed in sediments from the Congo River deep-sea fan, from the Congo River, and in sinking particles collected by sediment traps 40 m above the sediment. Studied sites encompassed three lobes of decreasing age of formation along the canyon: sites A, F and C and a another lobe system, disconnected from the active channel since 4 ka, Site E. Terrestrial long-chain odd n-alkanes were dominant in all sediments of the lobe system. Unsaturated terpenoids sourced by higher plants, such as gammacerene, lupene, ursene and oleanene, were also detected. At site C, characterized by high accumulation rates (10–20 cm yr−1), the organic matter spends less time in the oxic layer than at other sites and high phytadiene concentrations (10 to 17 μg...
Tipo: Text Palavras-chave: Congo fan; Hydrocarbons; NAH; Hopanes; Hopenes; Sediments; Turbidite system.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00388/49902/50472.pdf
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Anomalies of oxygen measurements performed with Aanderaa optodes ArchiMer
Lo Bue, N.; Vangriesheim, Annick; Khripounoff, Alexis; Soltwedel, T..
Four sets of measurements performed between 2005 and 2010 in the deep central Atlantic, the deep north-western Mediterranean Sea, and in the Arctic Ocean revealed strange anomalies in the performance of the Aanderaa optode 3830 sensors mounted on RCMI I current meters in low current regimes (current speeds > 10 cm s(-1)). All oxygen datasets collected during these deployments showed significant drops of oxygen (50-100 mu mol) affecting the data stability of the optode sensors in low hydrodynamic conditions. High correlations between all acquired parameters (temperature, turbidity, speed and direction of currents) verified that no unusual event occurred in the mooring areas during the periods of acquisition, although natural events responsible for such...
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00045/15584/14489.pdf
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Cold-seep assemblages on a giant pockmark off West Africa: spatial patterns and environmental control ArchiMer
Olu, Karine; Caprais, Jean-claude; Fifis, Alexis; Fabri, Marie-claire; Galeron, Joelle; Budzinsky, H; Le Menach, K; Khripounoff, Alexis; Ondreas, Helene; Sibuet, Myriam.
A giant pockmark colonised by dense cold-seep assemblages near 3160 m depth along the Congo-Angola margin has been surveyed by the ROV Victor 6000. The quantitative distribution of chemosynthetic communities was mapped along the dive tracks from a video study using GIS and image mosaicking. Several types of faunal assemblages, either dominated by bivalves of the families Mytilidae (Bathmodiolus sp.) Vesicom idae (Calyptogena sp., 'Vesicomya' aff. chuni), or by Siboglinidae polychaetes (Escarpia southwardae) were mapped over the 800-m diameter pockmark area and sampled for fauna, water and sediment. The isotopic analyses (delta C-13) of tissues from symbiont-bearing species were within the range typical of nutrition via symbiosis using methane for mussels...
Tipo: Text Palavras-chave: Symbiont bearing species; Spatial distribution; Methane; Megafauna; Cold seeps.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-2681.pdf
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Cold-seep-like macrofaunal communities in organic- and sulfide-rich sediments of the Congo deep-sea fan ArchiMer
Olu, Karine; Decker, Carole; Pastor, Lucie; Caprais, Jean-claude; Khripounoff, Alexis; Morineaux, Marie; Ain Baziz, M.; Menot, Lenaick; Rabouille, C..
Methane-rich fluids arising from organic matter diagenesis in deep sediment layers sustain chemosynthesis-based ecosystems along continental margins. This type of cold seep develops on pockmarks along the Congo margin, where fluids migrate from deep-buried paleo-channels of the Congo River, acting as reservoirs. Similar ecosystems based on shallow methane production occur in the terminal lobes of the present-day Congo deep-sea fan, which is supplied by huge quantities of primarily terrestrial material carried by turbiditic currents along the 800 km channel, and deposited at depths of up to nearly 5000 m. In this paper, we explore the effect of this carbon enrichment of deep-sea sediments on benthic macrofauna, along the prograding lobes fed by the current...
Tipo: Text Palavras-chave: Chemosynthesis-based ecosystems; Cold seeps; Organic rich sediments; Macrofaunal communities.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00384/49561/50053.pdf
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Colonization patterns along the equatorial West African margin: Implications for functioning and diversity maintenance of bathyal and abyssal communities ArchiMer
Menot, Lenaick; Crassous, Philippe; Desbruyeres, Daniel; Galeron, Joelle; Khripounoff, Alexis; Sibuet, M..
In the framework of the deep-sea environmental programme BIOZAIRE (Ifremer-Total), colonization trays were deployed for 283-433 days at three sites along the equatorial West African margin: ZA at 1300-m depth, ZC at 4000-m depth far from the Congo canyon and ZD at 4000-m depth close to the Congo canyon. The experiments aimed at determining the influence of depth and local environmental settings on macrofaunal colonization patterns and organic carbon degradation rates. The trays were filled with glass beads and this artificial substrate was enriched with ground particulate organic matter in a gradient of 0%, 0.34%, 1.02% and 3.43% organic carbon. The highest rates of organic carbon degradation ranged, according to the duration of the experiments, from 1.59...
Tipo: Text Palavras-chave: Diversity; Organic enrichment; Macrofauna; Deep sea; Colonization; Biozaire.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-7323.pdf
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Deep cold-water coral ecosystems in the Brittany submarine canyons (Northeast Atlantic): Hydrodynamics, particle supply, respiration, and carbon cycling ArchiMer
Khripounoff, Alexis; Caprais, Jean-claude; Le Bruchec, Julie; Rodier, Philippe; Noel, Philippe; Cathalot, Cecile.
The submarine canyons of the Brittany continental slope (Bay of Biscay–Northeast Atlantic) were studied to describe the conditions in which cold-water corals occur in these areas and their consequences for coral metabolism. Near-bottom current, oxygen, temperature, and particle flux, simultaneously measured for 2 yr at 850 m depth, revealed by spectral analysis the presence of several frequencies with a dominant semidiurnal tidal cycle and a current direction determined exclusively by the canyon topography. Sediment trap data also showed a seasonal input of material with a large peak of particles and carbon fluxes at the end of winter. Daily particle and carbon fluxes at 20 m above the bottom were 2.49 g m−2 d−1 and 20 mg C m−2 d−1, respectively. At the...
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00173/28380/26695.pdf
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Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea) ArchiMer
Khripounoff, Alexis; Crassous, Philippe; Lo Bue, N.; Dennielou, Bernard; Silva Jacinto, Ricardo.
Current velocities and vertical sediment fluxes in the Var submarine canyon were assessed at three stations respectively at 800 m, 1200 m and 1800 m depth, using moorings deployed for 4 months during winter 2008-2009. During this period, we observed three major sediment gravity flows, all characterized by sudden increases in current velocity that lasted 2-5 h and by downward particle fluxes. Each gravity flow, described using a high frequency current meter and two Acoustic Doppler Current Profiler (75 and 300 kHz ADCP) showed distinctive features. The first event, triggered during a flood of the Var River, was determined to be a hyperpycnal current with a large vertical extent (>100 m high) and relatively low velocity (40 cm s(-1)). The second event,...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00113/22394/20343.pdf
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Direct observation of intense turbidity current activity in the Zaire submarine valley at 4000 m water depth ArchiMer
Khripounoff, Alexis; Vangriesheim, Annick; Babonneau, Nathalie; Crassous, Philippe; Dennielou, Bernard; Savoye, Bruno.
A large turbidity current was detected in the Zaire submarine valley at 4000 m water depth. Current meters, turbidimeter and sediment trap deployed on a mooring located in the channel axis, although they were damaged, recorded the signature of a very high energy event. An average velocity of more than 121 cm s-1 was measured 150 m above the channel floor. Coarse sand and plant debris were collected at 40 m height. The turbidity current clearly overflowed the edges of the valley as demonstrated by the large quantity of turbiditic material (464 mg organic carbon m-2 d-1) found in the sediment trap moored 13 km south from the channel axis.
Tipo: Text Palavras-chave: West equatorial Africa; Particle composition; Particle flux; Zaire channel; Turbidity current.
Ano: 2003 URL: http://archimer.ifremer.fr/doc/2003/publication-1419.pdf
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Dynamics of benthic copepods and other meiofauna in the benthic boundary layer of the deep NW Mediterranean Sea ArchiMer
Guidi-guilvard, L. D.; Thistle, D.; Khripounoff, Alexis; Gasparini, S..
A continuous high-resolution time-series survey of the hyperbenthic community and local environmental conditions was conducted in the benthic boundary layer (BBL) of the DYFAMED-BENTHOS station (43 degrees 24.61'N, 7 degrees 51.67'E at 2347 in depth in the NW Mediterranean) between January 1996 and April 1998 using bottom-moored sediment traps and a current meter. Sediment traps were set 4 m above the bottom. Hyperbenthos was collected as 'swimmers', i.e. those organisms that are alive when they enter the traps but are not part of the particle flux. Identification of these organisms showed that similar to 90%, were meiobenthic, Copepods dominated and comprised on average 75%, of total swimmers. They were followed by nauplii (12%), annelids (7.8%),...
Tipo: Text Palavras-chave: Biodiversity; Population growth; Emergence; Resuspension; Benthic storms; Hyperbenthos; Swimmers; Deep sea.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-7416.pdf
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Evaluation of a lifetime-based optode to measure oxygen in aquatic systems ArchiMer
Tengberg, A; Hovdenes, J; Andersson, H; Brocandel, O; Diaz, R; Hebert, D; Arnerich, T; Huber, C; Kortzinger, A; Khripounoff, Alexis; Rey, F; Ronning, C; Schimanski, J; Sommer, S; Stangelmayer, A.
In this article, we evaluate the performance of a commercially available lifetime-based optode and compare it with data obtained by other methods. We performed a set of 10 different tests, including targeted laboratory evaluations and field studies, covering a wide range of situations from shallow coastal waters and wastewater treatment plants to abyssal depths. Our principal conclusion is that, owing to high accuracy (+/- 2 mu M), long-term stability (more than 20 months), lack of pressure hysteresis, and limited cross-sensitivity, this method is overall more suitable for oxygen monitoring than other methods.
Tipo: Text Palavras-chave: Lifetime based optode; Measure; Oxygen; Aquatic systems.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-1413.pdf
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Export of deep-sea hydrothermal particles, indigenous thermophilic microorganisms and larvae to the surrounding Ocean ArchiMer
Lesongeur, Francoise; Briand, Patrick; Godfroy, Anne; Crassous, Philippe; Byrne, Nathalie; Khripounoff, Alexis.
To assess the production and the export of particulate and biological material in deep-sea hydrothermal vents, four moorings with sediment traps and current meters were deployed for 24 days in the Azores Triple Junction (ATJ) region. They were deployed along an axis starting at the base of a hydrothermal vent chimney and ending 1000 m away. The particles sampled at the base of the chimney were characterized by high concentrations in total sulfur (16%) and iron (4%). The particle composition changed drastically with distance from the vent: the sulfur concentration decreased with an increase in clay components. Thermophilic microorganisms were successfully enriched from all the particle samples. Cultured strains were closely related to hydrothermal species,...
Tipo: Text Palavras-chave: Deep-sea hydrothermal vents; Particle flux; Hydrothermal microorganisms; Larvae; Regional index: North Atlantic; Mid-Atlantic Ridge; Azores Triple Junction.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00230/34111/33046.pdf
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High frequency of sediment gravity flow events in the Var submarine canyon (Mediterranean Sea) ArchiMer
Khripounoff, Alexis; Vangriesheim, Annick; Crassous, Philippe; Etoubleau, Joel.
This study aimed to analyze the role river floods play in triggering gravity flows and to investigate the role of submarine canyon systems as a conduit for terrigenous material to the deep sea. Two years of measurements in the Var canyon at depths ranging from 1200 m to 2350 m indicate that six floods of the Var River triggered hyperpycnal flows, an important mechanism for transporting particulate matter to the deep-sea floor. These sediment gravity flows were characterized by a sudden increase of current velocity that lasted 8 to 22 h and by downward particle fluxes that reached up to 600 g m(-2)d(-1) of particles and 3.1 g m(-2)d(-1) in terms of organic carbon. These large inputs of sediment and organic carbon may have a significant impact on deep-sea...
Tipo: Text Palavras-chave: West Mediterranean Sea; Particle flux; Var canyon; Hyperpycnal flow; Turbidity current.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6640.pdf
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HOT 96 News ArchiMer
Gaill, Francoise; Felbeck, Horst; Desbruyeres, Daniel; Lallier, Francois; Toulmond, A.; Alayse, Anne-marie; Briand, Patrick; Brulport, Jean-pierre; Caprais, Jean-claude; Chevaldonne, P.; Coail, Jean-yves; Cosson, R.; Crassous, Philippe; Delachambre, J.; Durif, C.; Echardour, L.; Herve, G.; Hourdez, Stephane; Jollivet, D.; Kerdoncuff, Jacques; Khripounoff, Alexis; Lechaire, J.p.; Pruski, Audrey; Ravaux, Juliette; Sarradin, Pierre-marie; Shillito, Bruce; Toullec, J.y.; Arndt, C.; Fisher, C.; Lutz, Richard; Childress, J..
Tipo: Text
Ano: 1996 URL: http://archimer.ifremer.fr/doc/00179/29003/27431.pdf
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Impact of open sea deep convection on sediment remobilization in the western Mediterranean ArchiMer
Martin, Jacobo; Miquel, Juan-carlos; Khripounoff, Alexis.
The northwestern Mediterranean is known to be a privileged area of deep water formation via dense shelf water cascading and offshore convection. The impact of the former in the sedimentary dynamics of the deep basin has been highlighted in recent years, while open sea convection has been solely studied from a hydrological perspective. Particle fluxes and hydrodynamics were monitored at the DYFAMED site (Ligurian Sea, western Mediterranean) at 200, 1000 m and near the seafloor (2350 m depth) during winter 2005-2006. From February to April 2006, and in coincidence with an unusual episode of deep water formation, a notable intensification of currents was observed in the entire water column and near-bottom particle flux increased up to two orders of magnitude....
Tipo: Text Palavras-chave: Water formation.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00011/12235/9016.pdf
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Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions ArchiMer
Stabholz, M.; Durrieu De Madron, X.; Canals, M.; Khripounoff, Alexis; Taupier-letage, Isabelle; Testor, Pierre; Heussner, S.; Kerherve, P.; Delsaut, N.; Houpert, Loic; Lastras, G.; Dennielou, Bernard.
The deep outer margin of the Gulf of Lions and the adjacent basin, in the western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e., temperature and salinity), currents, and particle fluxes were monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350-m depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW-SE transect, while the fifth one was located on a sediment wave...
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Ano: 2013 URL: http://archimer.ifremer.fr/doc/00125/23654/21571.pdf
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Influence of seep emission on the non-symbiont-bearing fauna and vagrant species at an active giant pockmark in the Gulf of Guinea (Congo-Angola margin) ArchiMer
Olu, Karine; Caprais, Jean-claude; Galeron, Joelle; Causse, R.; Von Cosel, R.; Budzinski, H.; Le Menach, K.; Le Roux, C.; Levache, D.; Khripounoff, Alexis; Sibuet, Myriam.
Detailed surveying with an ROV found that a dense and diverse cold-seep community colonises a giant pockmark located at 3200 m depth, 8 km north from the deep Congo channel. Several types of assemblages, either dominated by Mytilidae and Vesicomyidae bivalves or Siboglinidae polychaetes, are distributed on the 800-m diameter active area. The site is characterised by a most active central zone in a depression with abundant carbonate concretions and high methane fluxes where high-density clusters of mussels and siboglinids dominate. In contrast, the peripheral zones display large fields of dead and live vesicomyids on soft sediment, with a lower mean density and lower methane concentration in seawater. The associated megafauna includes Alvinocarididae...
Tipo: Text Palavras-chave: Congo Angola margin; Atlantic Equatorial African margin; Vagrant species; Isotopic signature; Megafauna; Cold seep.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-7478.pdf
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Intercalibration of benthic flux chambers II. Hydrodynamic characterization and flux comparisons of 14 different designs ArchiMer
Tengberg, Anders; Hall, P; Andersson, U; Linden, B; Styrenius, O; Boland, G; De Bovee, F; Carlsson, B; Ceradini, S; Devol, A; Duineveld, G; Friemann, J; Glud, R; Khripounoff, Alexis; Leather, J; Linke, P; Lund Hansen, L; Rowe, G; Santschi, P; De Wilde, P; Witte, U.
We have compared 14 different sediment incubation chambers, most of them were used on bottom landers. Measurements of mixing time, pressure gradients at the bottom and Diffusive Boundary Layer thickness (DBL) were used to describe the hydrodynamic properties of the chambers and sediment-water solute fluxes of silicate (34 replicates) and oxygen (23 replicates) during three subsequently repeated incubation experiments on a homogenized, macrofauna-free sediment. The silicate fluxes ranged from 0.24 to 1.01 mmol m(-2) day(-1) and the oxygen fluxes from 9.3 to 22.6 mmol m(-2) day(-1). There was no statistically significant correlation between measured fluxes and the chamber design or between measured fluxes and hydrodynamic settings suggesting that type of...
Tipo: Text Palavras-chave: Comparative flux incubations; Hydrodynamic properties; Calibration; Benthic chambers.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-750.pdf
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La nutrition d'echinodermes abyssaux I. Alimentation des holothuries ArchiMer
Khripounoff, Alexis; Sibuet, Myriam.
In deep waters, deposit-feeding holothurians represent a high percentage of the total abyssal biomass and play an important ecological role in sediment modification. The feeding of these organisms, which inhabit a nutritively poor environment, has been studied by means of analyses of intestinal contents. Four abundant species : Psychropotes longicauda Theel, Paroriza pallens (Koehler), Benthogone rosea Koehler and Molpadia blakei (Theel), collected between 2000 and 4500 m in the Bay of Biscay during three cruises organized by CNEXO-COB, were chosen for this study. The morphological characteristics of the ingested alimentary particles are described and the results of analyses of the organic matter in the guts reported. The species studied do not exhibit a...
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Ano: 1980 URL: http://archimer.ifremer.fr/doc/1980/publication-5309.pdf
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Les apports organiques et leur transformation en milieu abyssal à l'interface eau-sédiment dans l'Océan Atlantique tropical ArchiMer
Khripounoff, Alexis; Rowe, Gilbert T.
Five particle traps were deployed at depths of 4 400 to 4 900 rn at two stations on the Demerara abyssal plain and one station on the Cape Verde abyssal plain (tropical Atlantic). At the same time, an intensive sampling of superficial sediments was carried out using a 0,25 m2 box corer. The total particle flux varied from 372 to 87,7 mg dry weightfm2/day. The average concentration of organic carbon was 40 mg/g of material collected. ln the surface sediment this was only 4 mg/g. A direct relationship existed between the intensity of the flux of organic matter and the richness of the organic matter of the deposited sediment. According to our calculations, more than 90% of the organic matter arriving at the bottom is consumed by the abyssal benthos and only...
Tipo: Text Palavras-chave: Milieu abyssal; Flux particulaire; Bilan d'énergie; Biochimie des particules et des sédiments; Atlantique tropical; Deep-sea; Particles flux; Tropical atlantic; Energy budget; Biochemitry of particles and sediments.
Ano: 1985 URL: http://archimer.ifremer.fr/doc/00112/22318/19991.pdf
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