Consulta: creatorFacets:"Khripounoff, Alexis"
Registros recuperados: 39
Data/hora: 01/06/2024 07:53:20

Rapid transport and high accumulation of amorphous silica in the Congo deep-sea fan: A preliminary budget
Provedor de dados: 5
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

HOT 96 News
Provedor de dados: 5
Autores: 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

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
Provedor de dados: 5
Autores: 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

Spatial heterogeneity of macrofaunal communities in and near a giant pockmark area in the deep Gulf of Guinea
Provedor de dados: 5
Autores: Menot, Lenaick; Galeron, Joelle; Olu, Karine; Caprais, Jean-claude; Crassous, Philippe; Khripounoff, Alexis; Sibuet, Myriam.
The structure and familial-level composition of macrofaunal communities were examined within and at distance from the giant pockmark Regab in the Southern Gulf of Guinea, at 3200 m depth. The two main questions addressed in this study were (i) does habitat partitioning by large symbiont-bearing taxa. influence macrofaunal assemblages and their environment? and (ii) to what extent does the chemosynthesis-based ecosystem influence the structure and the composition of nearby macrobenthic communities? Along two radials, at sites from 250 to 1000 m away from the active centre of the cold seep, the abundance and composition of the macrofauna were typical of a deep-sea community at that depth. Except for a few cores sampled in or near dead vesicomyid fields at...
Tipo: Text
Palavras-chave: Cold seep; Diversity; Gulf of Guinea; Habitat heterogeneity; Macrofauna; Open slope; Siboglinid tubeworms; Vesicomyid clams.
Ano: 2010
URL: https://archimer.ifremer.fr/doc/00002/11282/8099.pdf

Ecophysiological differences between vesicomyid species and metabolic capabilities of their symbionts influence distribution patterns of the deep‐sea clams
Provedor de dados: 5
Autores: Cruaud, Perrine; Decker, Carole; Olu, Karine; Arnaud-haond, Sophie; Papot, Claire; Le Baut, Jocelyn; Vigneron, Adrien; Khripounoff, Alexis; Gayet, Nicolas; Cathalot, Cecile; Caprais, Jean-claude; Pignet, Patricia; Godfroy, Anne; Cambon Bonavita, Marie-anne.
This study provides an analysis of vesicomyid bivalve–symbiont community distribution across cold seep and hydrothermal vent areas in the Guaymas Basin (Gulf of California, Mexico). Using a combination of morphological and molecular approaches including fluorescent in situ hybridization (FISH), and electronic microscopy observations, vesicomyid clam species and their associated symbionts were characterized and results were analyzed in light of geochemical conditions and other on‐site observations. A greater diversity of vesicomyids was found at cold seep areas, where three different species were present (Phreagena soyoae [syn. kilmeri], Archivesica gigas, and Calyptogena pacifica). In contrast, A. gigas was the only species sampled across the hydrothermal...
Tipo: Text
Palavras-chave: Deep-sea ecosystems; Guaymas Basin; Marine ecology; Pliocardinae bivalve; Sulfur storage; Vesicomyid movements.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00493/60426/64028.pdf

Impact of open sea deep convection on sediment remobilization in the western Mediterranean
Provedor de dados: 5
Autores: 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

Remises en suspension sédimentaires observées en Méditerranée par 2 000 m de profondeur à l'aide de pièces à particules
Provedor de dados: 5
Autores: Crassous, Philippe; Khripounoff, Alexis; Larosa, Jacques; Miquel, Juan-carlos.
Four sediment traps of two different types and two current meters were deployed fixed to two identical moorings, at a depth of 2 000 m, off the coast at Nice, for 70 days between April and June 1987. The particulate flux measured with sediment traps decreased from 1 000 to 95 mg/m2/day during this experiment. The carbonate carbon concentration of the particles also decreased during this period; organic carbon concentrations varied inversely with the flux, increasing from 1.8 to 3.7 % of the particle dry weight. It is concluded that these changes reveal the presence of a deep-sea storm with a significant resuspension of sediment to a height greater than 200 m (distance of the traps from the bottom). By the end of the experiment, identical sediment traps had...
Tipo: Text
Ano: 1991
URL: http://archimer.ifremer.fr/doc/00101/21244/18859.pdf

The Congolobe project, a multidisciplinary study of Congo deep-sea fan lobe complex: Overview of methods, strategies, observations and sampling
Provedor de dados: 5
Autores: Rabouille, C.; Olu, Karine; Baudin, F.; Khripounoff, Alexis; Dennielou, Bernard; Arnaud-haond, Sophie; Babonneau, Nathalie; Bayle, Christophe; Beckler, J.; Bessette, Sandrine; Bombled, B.; Bourgeois, S.; Brandily, Christophe; Caprais, Jean-claude; Cathalot, Cecile; Charlier, K.; Corvaisier, R.; Croguennec, Chantal; Cruaud, Perrine; Decker, Carole; Droz, L.; Gayet, Nicolas; Godfroy, Anne; Hourdez, S.; Le Bruchec, J.; Saout, Johan; Le Saout, Marie-helene; Lesongeur, Francoise; Martinez, P.; Mejanelle, L.; Michalopoulos, P.; Mouchel, Olivier; Noel, Philippe; Pastor, Lucie; Picot, M.; Pignet, Patricia; Pozzato, L.; Pruski, A. M.; Rabiller, Manuella; Raimonet, M.; Ragueneau, O.; Reyss, J. L.; Rodier, Philippe; Ruesch, Blandine; Ruffine, Livio; Savignac, F.; Senyarich, C.; Schnyder, J.; Sen, Arunima; Stetten, E.; Sun, Ming Yi; Taillefert, M.; Teixeira, S.; Tisnerat-laborde, N.; Toffin, Laurent; Tourolle, Julie; Toussaint, F.; Vetion, G.; Jouanneau, J. M.; Bez, M.
The presently active region of the Congo deep-sea fan (around 330 000 km2), called the terminal lobes or lobe complex, covers an area of 2500 km2 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...
Tipo: Text
Palavras-chave: Chemosynthetic habitats; Congo deep-sea fan; Fine sediment; Sedimentation rate; Seafloor morphology; Turbidite; Vesicomyidae.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00335/44580/44298.pdf

Multiscale spatio-temporal variability of sedimentary deposits in the Var turbidite system (North-Western Mediterranean Sea)
Provedor de dados: 5
Autores: Mas, Virginie; Mulder, T.; Dennielou, Bernard; Schmidt, S.; Khripounoff, Alexis; Savoye, Bruno.
The Var turbidite system is a small sandy system located in the Ligurian Basin (Mediterranean Sea). It is active during present sea-level highstand and shows four types of sediment transfer processes: (1) low-density turbidity surges generated by small-scale failures (2) low-magnitude, high-frequency (yearly) hyperpycnal turbid plumes, (3) high-magnitude, less-frequent, hyperpycnal currents and (4) high-magnitude flows generated by large slope failures. These processes have different imprints on the morphology of the system. Inversely, the topography plays a role on the behaviour of these flows. The depositional and erosional architecture of the system has been investigated in detail on the basis of SAR imagery and a set of cores using an interface corer...
Tipo: Text
Palavras-chave: Var; France; Gravity processes; Mediterranean; Turbidity current; Hyperpycnal; Flood.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/00013/12458/11862.pdf

Les apports organiques et leur transformation en milieu abyssal à l'interface eau-sédiment dans l'Océan Atlantique tropical
Provedor de dados: 5
Autores: 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

Anomalies of oxygen measurements performed with Aanderaa optodes
Provedor de dados: 5
Autores: 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 &gt; 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...
Tipo: Text
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00045/15584/14489.pdf

Peuplements benthiques et caractéristiques trophiques du milieu dans la plaine abyssale de Demerara
Provedor de dados: 5
Autores: Sibuet, Myriam; Monniot, C; Desbruyeres, Daniel; Dinet, A; Khripounoff, Alexis; Rowe, G; Segonzac, Michel.
Tipo: Text
Ano: 1984
URL: http://archimer.ifremer.fr/doc/00131/24217/22210.pdf

Different types of sediment gravity flows detected in the Var submarine canyon (northwestern Mediterranean Sea)
Provedor de dados: 5
Autores: 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 (&gt;100 m high) and relatively low velocity (40 cm s(-1)). The second event,...
Tipo: Text
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00113/22394/20343.pdf

Turbidity events observed in situ along the Congo submarine channel
Provedor de dados: 5
Autores: Vangriesheim, Annick; Khripounoff, Alexis; Crassous, Philippe.
As part of the multidisciplinary programme BIOZAIRE devoted to studying deep-sea benthic ecosystems in the Gulf of Guinea, particulate input and its relationship with near-bottom hydrodynamics were monitored using long-term moorings from 2000 to early 2005. Particular attention was given to material input through the Congo (ex-Zaïre) submarine channel that extends 760 km from the Congo River mouth to the abyssal plain (&gt;5100 m) near 6°S. Due to its direct connection to the Congo River, the Congo canyon and channel system are characterised by particularly active recent sediment transport. During this first in situ long-term monitoring along the channel, an energetic turbidity event was observed in January 2004 at three locations along the channel from...
Tipo: Text
Palavras-chave: Suspended sediment transport; Turbidity current; Deep current; Congo canyon; Zaïre; Gulf of Guinea.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6738.pdf

Export of deep-sea hydrothermal particles, indigenous thermophilic microorganisms and larvae to the surrounding Ocean
Provedor de dados: 5
Autores: 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

Dynamics of benthic copepods and other meiofauna in the benthic boundary layer of the deep NW Mediterranean Sea
Provedor de dados: 5
Autores: 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

Cold-seep assemblages on a giant pockmark off West Africa: spatial patterns and environmental control
Provedor de dados: 5
Autores: 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

Organic matter budget in the Southeast Atlantic continental margin close to the Congo Canyon: In situ measurements of sediment oxygen consumption
Provedor de dados: 5
Autores: Rabouille, C.; Caprais, Jean-claude; Lansard, B.; Crassous, Philippe; Dedieu, K.; Reyss, J. L.; Khripounoff, Alexis.
A study of organic carbon mineralization from the Congo continental shelf to the abyssal plain through the Congo submarine channel and Angola Margin was undertaken using in situ measurements of sediment oxygen demand as a tracer of benthic carbon recycling. Two measurement techniques were coupled on a single autonomous platform: in situ benthic chambers and microelectrodes, which provided total and diffusive oxygen uptake as well as oxygen microdistributions in porewaters. In addition, sediment trap fluxes, sediment composition (Org-C, Tot-N, CaCO3, porosity) and radionuclide profiles provided measurements of, respectively input fluxes and burial rate of organic and inorganic compounds. The in situ results show that the oxygen consumption on this margin...
Tipo: Text
Palavras-chave: Sediment carbon budget; Organic carbon burial; Congo Submarine Canyon; Organic carbon recycling in sediments; In situ oxygen demand.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-7316.pdf

Natural and anthropogenic trace metals in sediments of the Ligurian Sea (Northwestern Mediterranean)
Provedor de dados: 5
Autores: Heimbuerger, Lars-eric; Cossa, Daniel; Thibodeau, Benoit; Khripounoff, Alexis; Mas, Virginie; Chiffoleau, Jean-francois; Schmidt, Sabine; Migon, Christophe.
The magnitude and the chronology of anthropogenic impregnation by Hg and other trace metals of environmental concern (V, Cr, Ni, Cu, Zn, Ag, Cd and Pb, including its stable isotopes) in the sediments are determined at the DYFAMED station, a site in the Ligurian Sea (Northwestern Mediterranean) chosen for its supposed open-sea characteristics. The DYFAMED site (VD) is located on the right levee of the Var Canyon turbidite system, at the end of the Middle Valley. In order to trace the influence of the gravity current coming from the canyon on trace metal distribution in the sediment, we studied an additional sediment core (VA) from a terrace of the Var Canyon, and material collected in sediment traps at the both sites at 20 m above sea bottom. The patterns...
Tipo: Text
Palavras-chave: Marine sediments; Sediment traps; Mercury; Trace metals; Lead isotopes; Geochronology.
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00073/18435/16125.pdf

Deep cold-water coral ecosystems in the Brittany submarine canyons (Northeast Atlantic): Hydrodynamics, particle supply, respiration, and carbon cycling
Provedor de dados: 5
Autores: 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...
Tipo: Text
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00173/28380/26695.pdf

Variability in gas and solute fluxes through deep-sea chemosynthetic ecosystems inhabited by vesicomyid bivalves in the gulf of Guinea
Provedor de dados: 5
Autores: Khripounoff, Alexis; Caprais, Jean-claude; Decker, Carole; Essirard, Mikael; Le Bruchec, Julie; Noel, Philippe; Olu, Karine.
We have studied two species of vesicomyid bivalves inhabiting different areas of sulfide-rich sediments in association with methane seepage at two pockmarks located at about 650 m and 3150 m depth, respectively, along the Gabon-Congo margin, and organic-rich sediments in the deepest zone (4950 m depth) of the Congo deep-sea fan. Benthic chambers Calmar were deployed on three study sites to assess gas and solute exchanges at the water-sediment interface. We recorded in situ measurements of oxygen, total carbon dioxide, ammonium, methane, and sulfide in two clam beds at each site. At all sites, irrespective of which the vesicomyid species are present, oxygen consumption was high and variable (28–433 mmol m−2 d−1) as was total carbon dioxide emission (36–1857...
Tipo: Text
Palavras-chave: Benthic chamber; Cold-seep ecosystem; Reduced sediment; Gas fluxes; Vesicomyid bivalves; Gulf of Guinea.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00226/33746/32160.pdf

Particle flux in the Rainbow hydrothermal vent field (Mid-Atlantic Ridge): Dynamics, mineral and biological composition
Provedor de dados: 5
Autores: Khripounoff, Alexis; Vangriesheim, Annick; Crassous, Philippe; Segonzac, Michel; Colaco, Ana; Desbruyeres, Daniel; Barthelemy, Roxane.
In order to provide information about the export and the distribution of hydrothermal particulate material to the surrounding deep ocean, four moorings were deployed in the vicinity of the hydrothermal Rainbow vent field (Mid-Atlantic Ridge, 36 degrees 14'N, 2250 m depth). The first mooring was a sediment trap with a current meter deployed at 2 m from a chimney of the Rainbow vent field and 1.5 m above the bottom (a.b.) for 16 days. It represented the reference for the initial composition of particles produced by the vent. The total mean mass particle flux (6.9 g m(-2) d(-1)) was distinctly higher than the flux measured at the shallower hydrothermal vents on the MAR segment. This particulate flux showed a high temporal variation at the scale of a few days...
Tipo: Text
Palavras-chave: Zooplankton; Biochemistry; Geochemistry; Particle flux; Hydrothermal vent.
Ano: 2001
URL: https://archimer.ifremer.fr/doc/2001/publication-801.pdf

Rare earth elements and neodymium isotopes in sedimentary organic matter
Provedor de dados: 5
Autores: Freslon, Nicolas; Bayon, Germain; Toucanne, Samuel; Bermell, Sylvain; Bollinger, Claire; Chéron, Sandrine; Etoubleau, Joel; Germain, Yoan; Khripounoff, Alexis; Ponzevera, Emmanuel; Rouget, Marie Laure.
We report rare earth element (REE) and neodymium (Nd) isotope data for the organic fraction of sediments collected from various depositional environments, i.e. rivers (n=25), estuaries (n=18), open-ocean settings (n=15), and cold seeps (n=12). Sedimentary Organic Matter (SOM) was extracted using a mixed hydrogen peroxide/nitric acid solution (20%-H2O2 – 0.02M-HNO3), after removal of carbonate and oxy-hydroxide phases with dilute hydrochloric acid (0.25M-HCl). A series of experimental tests indicate that extraction of sedimentary organic compounds using H202 may be complicated occasionally by partial dissolution of sulphide minerals and residual carbonates. However, this contamination is expected to be minor for REE because measured concentrations in H2O2...
Tipo: Text
Palavras-chave: Organic matter; Rare earth elements; REE; Neodymium isotopes; ΕNd; Sediment; Boundary Exchange; Paleoceanography.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00191/30250/28682.pdf

Carbon and silica megasink in deep-sea sediments of the Congo terminal lobes
Provedor de dados: 5
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

Cold-seep-like macrofaunal communities in organic- and sulfide-rich sediments of the Congo deep-sea fan
Provedor de dados: 5
Autores: 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

La nutrition d'echinodermes abyssaux I. Alimentation des holothuries
Provedor de dados: 5
Autores: 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...
Tipo: Text
Ano: 1980
URL: http://archimer.ifremer.fr/doc/1980/publication-5309.pdf

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)
Provedor de dados: 5
Autores: 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

Evaluation of a lifetime-based optode to measure oxygen in aquatic systems
Provedor de dados: 5
Autores: 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

Variation horizontale du flux particulaire à micro- et méso-échelle dans la plaine abyssale de Californie (4 100 m de profondeur)
Provedor de dados: 5
Autores: Crassous, Philippe; Khripounoff, Alexis.
Nine sediment traps were assembled in triplicate on a frame and deployed at 100 m above the bottom in the California abyssal plain (4 100 m depth) for ten days. The distances between traps were from 30 cm to 11 km. The main flux measured during this period was 167 mg m(-2) day(-1) with a minimum of 43 mg m(-2) d(-1) and a maximum of 283 mg m(-2) d(-1). This high variation of the particulate flux at the kilometric scale was also observed at a metric scale: for example, the particulate flux measured with one of triplicate traps was equal to 82.3 +/- 46.5 mg m(-2) d(-1) (more than 50 % of variation) between traps distant of less than 1 m. To explain this heterogeneity of the flux measurement, some hypotheses are developed in this study: sampling artefact,...
Tipo: Text
Palavras-chave: SEDIMENT TRAPS; DEEP SEA; HORIZONTAL FLUX VARIATION.
Ano: 1994
URL: http://archimer.ifremer.fr/doc/00098/20885/18499.pdf

Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions
Provedor de dados: 5
Autores: 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...
Tipo: Text
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00125/23654/21571.pdf

Colonization patterns along the equatorial West African margin: Implications for functioning and diversity maintenance of bathyal and abyssal communities
Provedor de dados: 5
Autores: 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

Mixotrophy in the deep sea: a dual endosymbiotic hydrothermal mytilid assimilates dissolved and particulate organic matter
Provedor de dados: 5
Autores: Riou, Virginie; Colaco, Ana; Bouillon, Steven; Khripounoff, Alexis; Dando, Paul; Mangion, Perrine; Chevalier, Emilie; Korntheuer, Michael; Santos, Raphael; Dehairs, Frank.
Bathymodiolus azoricus mussels thrive 840 to 2300 m deep at hydrothermal vents of the Azores Triple Junction on the Mid-Atlantic Ridge. Although previous studies have suggested a mixotrophic regime for this species, no analysis has yet yielded direct evidence for the assimilation of particulate material. In the present study, tracer experiments in aquaria with C-13- and N-15-labelled amino acids and marine cyanobacteria demonstrate for the first time the incorporation of dissolved and particulate organic matter in soft tissues of vent mussel. The observation of phytoplanktonic tests in wild mussel stomachs highlights the occurrence of in situ ingestion of sea-surface-derived material. Particulate organic carbon fluxes in sediment traps moored away from...
Tipo: Text
Palavras-chave: Bathymodiolus azoricus; Particulate and dissolved material; Nitrogen and carbon assimilation; Deep sea; Hydrothermal vent; Mussel.
Ano: 2010
URL: https://archimer.ifremer.fr/doc/00005/11589/8230.pdf

Respiration of bivalves from three different deep-sea areas: cold seeps, hydrothermal vents and organic carbon-rich sediments
Provedor de dados: 5
Autores: Khripounoff, Alexis; Caprais, Jean-claude; Decker, Carole; Le Bruchec, J.; Noel, Philippe; Husson, Berengere.
We studied bivalves (vesicomyids and mytilids) inhabiting four different areas of high sulfide and methane production: 1) in the Gulf of Guinea, two pockmarks (650 m and 3150 m depth) and one site rich in organic sediments in the deepest zone (4950 m average depth), 2) at the Azores Triple Junction on the Mid-Atlantic Ridge, one hydrothermal site (Lucky Strike vent field, 1700 m depth). Two types of Calmar benthic chambers were deployed, either directly set into the sediment (standard Calmar chamber) or fitted with a tank to isolate organisms from the sediment (modified Calmar chamber), to assess gas and solute exchanges in relation to bivalve bed metabolism. Fluxes of oxygen, total carbon dioxide, ammonium and methane were measured. At the site with...
Tipo: Text
Palavras-chave: Deep-sea; Benthic chamber; Vesicomyid and Mytilid bivalves; Respiration rate; Cold seep; Hydrothermal vent.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00341/45204/44614.pdf

Aliphatic hydrocarbons and triterpenes of the Congo deep sea fan
Provedor de dados: 5
Autores: 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

High frequency of sediment gravity flow events in the Var submarine canyon (Mediterranean Sea)
Provedor de dados: 5
Autores: 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

Intercalibration of benthic flux chambers II. Hydrodynamic characterization and flux comparisons of 14 different designs
Provedor de dados: 5
Autores: 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

Direct observation of intense turbidity current activity in the Zaire submarine valley at 4000 m water depth
Provedor de dados: 5
Autores: 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

Spatial and temporal patterns of benthic macrofaunal communities on the deep continental margin in the Gulf of Guinea
Provedor de dados: 5
Autores: Galeron, Joelle; Menot, Lenaick; Renaud, Nolwenn; Crassous, Philippe; Khripounoff, Alexis; Treignier, C.; Sibuet, M.
Density, taxonomic composition at higher taxon level and vertical distribution of benthic macrofaunal communities and sediment characteristics (pore water, nitrogen, organic carbon, sulfur, C/N ratio, n-alcohol biomarkers) were examined at three deep sites on the Congo-Gabon continental margin. This study was part of the multidisciplinary BIOZAIRE project that aimed at studying the deep benthic ecosystems in the Gulf of Guinea. Sampling of macrofaunal communities and of sediment was conducted during three cruises (January 2001, December 2001 and December 2003) at two downslope sites (4000 m depth), one located near the Congo submarine channel (15 km in the south) and the other one far from the channel (150km in the South). The third area located 8 km north...
Tipo: Text
Palavras-chave: Deep sea; Distribution; Community structure; Macrofauna; Congo canyon; Congo Angola margin; Equatorial west Africa margin; Atlantic.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-7315.pdf

Temporal variation of currents, particulate flux and organism supply at two deep-sea hydrothermal fields of the Azores Triple Junction
Provedor de dados: 5
Autores: Khripounoff, Alexis; Vangriesheim, Annick; Crassous, Philippe; Segonzac, Michel; Lafon, V; Waren, A.
In order to provide information on the production and the distribution of hydrothermal particulate and biological material produced by deep-sea hydrothermal vents, three moorings with sediment traps and currentmeters were deployed for one year in the Azores Triple Junction region. Two moorings were positioned close to two hydrothermal vent fields at the Mid-Atlantic Ridge (Rainbow, 36 degrees 14'N, 33 degrees 54'W, 2250 in depth and Lucky Strike 37 degrees 17'N, 32 degrees 17'W, 1600 in depth). A third was moored out of the influence of the Rainbow vents representing the reference of the pelagic flux in this area. At the Rainbow field, particulate flux (range 341-634 g m(-2)d(-1)) showed a high temporal variation controlled essentially by the current...
Tipo: Text
Palavras-chave: Bivalve reproduction; Bivalve larvae; Particle composition; Particle flux; Currents; Deep sea hydrothermal vents.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4059.pdf