Consulta: subjectFacets:"Gulf of Guinea"
Registros recuperados: 20
Data/hora: 16/06/2024 09:17:42

The vesicomyid bivalve habitat at cold seeps supports heterogeneous and dynamic macrofaunal assemblages
Provedor de dados: 5
Autores: Guillon, Erwan; Menot, Lenaick; Decker, Carole; Krylova, Elena; Olu, Karine.
The high biodiversity found at cold seeps, despite elevated concentrations of methane and hydrogen sulfide, is attributed to multiple sources of habitat heterogeneity. In addition to geological and geochemical processes, biogenic habitats formed by large symbiont-bearing taxa, such as bivalves and siboglinid tubeworms, or by microbial mats drive the biodiversity of small-sized fauna. However, because these habitat-forming species also depend on geochemical gradients, the respective influence of abiotic and biotic factors in structuring associated macrofaunal communities is often unresolved. The giant pockmark Regab located at 3200 m depth on the Congo margin is characterized by different fluid-flow regimes, providing a mosaic of the most common biogenic...
Tipo: Text
Palavras-chave: Cold-seep; Macrofauna; Diversity; Dynamics; Vesicomyid clams; Gulf of Guinea.
Ano: 2017
URL: http://archimer.ifremer.fr/doc/00361/47210/47165.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

Spatial and Seasonal Variability of Mixed Layer Depth in the Tropical Atlantic at 10 °W using 40 Years of Observation Data
Provedor de dados: 5
Autores: Kouame Kanga, Désiré; Kouassi Aka, Marcel; Trokourey, Albert; Toualy, Elisée; N’guessan, Benjamin K.; Brehmer, Patrice; Ostrowski, Marek.
The spatial and seasonal variability of the mixed layer depth (MLD) was studied using hydrological data from several databases collected over the period October 1973 to March 2017 at 10 °W between latitudes 2 °N and 10 °S in the Gulf of Guinea. The density threshold method with 0.03 kg m-3 criterion was used to calculate the MLD. In the equatorial band, the seasonal average MLD is 20 m whatever the season. At 6 °S and 10 °S, the MLD is relatively higher during the cold season. The MLD varies between 21 and 37 m at 6 °S, and the seasonal averages MLD are 21 and 40 m respectively during the hot and cold seasons. At 10 °S, during the hot season, the MLD varies between 28 and 52 m and the seasonal average is 39.5 m. During the cold season, the MLD varies...
Tipo: Text
Palavras-chave: Atlantic Ocean; Gulf of Guinea; Mixed Layer; Spatial Variability; Seasonal Variability.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00684/79619/82344.pdf

Seasonal and inter-annual ONSET Sea Surface Temperature variability along the northern coast of the Gulf of Guinea
Provedor de dados: 5
Autores: Sohou, Z.; Koné, V.; Da-allada, Y.c.; Djakouré, S.; Bourlès, Bernard; Racape, Virginie; Degbe, G.; Adje, C.
The aim of this study is to characterize the coastal upwelling variability at seasonal and inter-annual time scales in the northern Gulf of Guinea (NGoG) using Sea Surface Temperature (SST) collected with autonomous “ONSET” thermometers. Results show that the ONSET SST data are suitable for numerical model evaluation, and provide relevant information in addition to satellite and reanalysis data at seasonal cycle. The minor and major coastal upwellings are present in all the products. The inter-annual SST variability is more pronounced in the western part of the region (Côte d’Ivoire and Ghana) than in the eastern part (Benin and Nigeria). The pattern differences between the west and the east of the region highlight a large spatial variability of the SST in...
Tipo: Text
Palavras-chave: Sea Surface Temperature; ONSET data; Gulf of Guinea; Coastal upwelling; Seasonal variability; Inter-annual variability.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00607/71885/70583.pdf

On the Nutrient distribution and phytoplankton biomass in the Gulf of Guinea equatorial band as inferred from In-situ measurements
Provedor de dados: 5
Autores: Nubi, O A; Bourles, Bernard; Edokpayi, C A; Hounkonnou, M N.
Oceanographic in situ data collected in the Gulf of Guinea during six cruises carried out between 2005 and 2007 were analysed to study the influence of equatorial upwelling on the productivity of the region. At 10°W, observations during boreal summer and autumn cruises captured seasonal upwelling influences. In response to the shoaling pycnocline in June 2005, higher concentrations of nitrate and chlorophyll fluorescence were recorded at the ocean surface in June than in September. Our findings challenge the paradigm that westward advection from the nutrient-rich African coast is responsible for equatorial enrichment in the Gulf of Guinea. Vertical sections of the parameters under study in the summer of 2005 showed no westward advection from 3°E to 10°W...
Tipo: Text
Palavras-chave: Advection; Equatorial undercurrent; Equatorial upwelling; Gulf of Guinea; Nutrients; Phytoplankton biomass.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00621/73324/72489.pdf

Modélisation haute-résolution des courants dans le Golfe de Guinée : Etude des oscillations bimensuelles.
Provedor de dados: 5
Autores: Guiavarch, Catherine.
Currentmeter measurements on the continental slope of the Gulf of Guinea (near 7°40 S) point out a biweekly oscillation of the currents, bottom intensified and oriented along the bathymetry. Those energetic oscillations dominate the signal. A three-dimensional high-resolution primitive equation model  (NEMO/OPA) of the Gulf of Guinea has been developed to study the oscillations and their forcing mechanism.  The data does not support the tide as a forcing mechanism and the wind-forced regional model reproduces biweekly oscillations, which fit the data quite well. Experiments with different forcings have been run to explore the origin of the biweekly variability. Those experiments highlight the equatorial origin of the oscillations forced by equatorial...
Tipo: Text
Palavras-chave: Deep current; Biweekly oscillations; Equatorial waves; Coastal trapped waves; Gulf of Guinea; Numerical modelling; Courant profond; Oscillations bimensuelles; Ondes équatoriales; Ondes piégées à la côte; Golfe de Guinée; Modélisation numérique.
Ano: 2007
URL: http://archimer.ifremer.fr/doc/2007/these-3647.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

Diversity of symbioses between chemosynthetic bacteria and metazoans at the Guiness cold seep site (Gulf of Guinea, West Africa)
Provedor de dados: 5
Autores: Duperron, Sebastien; Rodrigues, Clara F.; Leger, Nelly; Szafranski, Kamil; Decker, Carole; Olu, Karine; Gaudron, Sylvie M.
Fauna from deep-sea cold seeps worldwide is dominated by chemosymbiotic metazoans. Recently, investigation of new sites in the Gulf of Guinea yielded numerous new species for which symbiosis was strongly suspected. In this study, symbioses are characterized in five seep-specialist metazoans recently collected from the Guiness site located at ∼600 m depth. Four bivalve and one annelid species belonging to families previously documented to harbor chemosynthetic bacteria were investigated using bacterial marker gene sequencing, fluorescence in situ hybridization, and stable isotope analyses. Results support that all five species display chemosynthetic, sulfur-oxidizing γ-proteobacteria. Bacteria are abundant in the gills of bivalves, and in the trophosome of...
Tipo: Text
Palavras-chave: Acharax; Calyptogena; Chemosynthesis; Cold seeps; Elenaconcha; Gulf of Guinea; Lamellibrachia; Symbiosis; Thyasira.
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00133/24418/22432.pdf

Occurrence of Chromadorita regabi sp nov (Nematoda: Adenophorea), a nematode egg predator of Alvinocaris muricola (Crustacea: Decapoda: Caridea: Alvinocarididae) from a deep cold seep area of the Gulf of Guinea
Provedor de dados: 5
Autores: Baldrighi, Elisa; Vanreusel, A.; Zeppilli, Daniela; Sandulli, R.; Segonzac, Michel.
Several individuals belonging to a new species of the genus Chromadorita (Nematoda: Adenophorea) were collected in a cold-seep area in the Gulf of Guinea during two French cruises: BIOZAIRE 2 (2001) and BIOZAIRE 3 (2003-2004) on board the R/V L'Atalante. In this area, rich chemosynthetic benthic communities have been discovered at 3150 m depth in the large pockmark field named Regab. Chromadorita regabi sp. nov. was found among the eggs in ovigerous specimens of the shrimp Alvinocaris muricola. The combination of long size (1500-2200 mu m), nine strong preanal papillae and relatively small dorsal tooth with weak musculature distinguishes this species from all known congeneric ones. An identification key to all known species of Chromadorita is provided.
Tipo: Text
Palavras-chave: Chromadorita regabi; Cold seep; Gulf of Guinea; Alvinocaris muricola.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00454/56599/58271.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

Eastern Tropical Atlantic Mixed Layer Depth: Assessment of Methods from In Situ Profiles in the Gulf of Guinea from Coastal to High Sea
Provedor de dados: 5
Autores: N’guessan, Benjamin Kouadio; Kouassi, Aka Marcel; Trokourey, Albert; Toualy, Elisée; Kanga, Desiré Kouamé; Brehmer, Patrice.
To assess the eastern Atlantic tropical mixed layer depth (MLD) at 4°W in the Gulf of Guinea, water temperature and density profiles from over five hundred historical observational Conductivity – Temperature - Depth (CTD) data were used. These data, obtained from key oceanographic survey databases covering 60 years (1956 to 2016) were used for a numerical and visual determination of the MLD. The numerical approach consists of the use of the algorithms of three methods; while the visual estimation of the MLD were made on both temperature and density profiles. The numerical approaches were evaluated by comparing their results on the determination of tropical MLD with those of the visual inspections by means of statistical and graphical analysis in order to...
Tipo: Text
Palavras-chave: Mixed layer depth; Gulf of Guinea; Atlantic Ocean; Density; Temperature.
Ano: 2020
URL: https://archimer.ifremer.fr/doc/00599/71115/75615.pdf

Deep-sea environment and biodiversity of the West African Equatorial margin
Provedor de dados: 5
Autores: Sibuet, Myriam; Vangriesheim, Annick.
The long-term BIOZAIRE multidisciplinary deep-sea environmental program on the West Equatorial African margin organized in partnership between Ifremer and TOTAL aimed at characterizing the benthic community structure in relation with physical and chemical processes in a region of oil and gas interest. The morphology of the deep Congo submarine channel and the sedimentological structures of the deep-sea fan were established during the geological ZAIANGO project and helped to select study sites ranging from 350 to 4800 m water depth inside or near the channel and away from its influence. Ifremer conducted eight deep-sea cruises on board research vessels between 2000 and 2005. Standardized methods of sampling together with new technologies such as the ROV...
Tipo: Text
Palavras-chave: Cold coral; Cold seep communities; Benthos diversity; Turbidity current; Congo canyon; Gulf of Guinea.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-7349.pdf

Large Vesicomyidae (Mollusca: Bivalvia) from cold seeps in the Gulf of Guinea off the coasts of Gabon, Congo and northern Angola
Provedor de dados: 5
Autores: Von Cosel, Rudo; Olu, Karine.
Two new genera and three new species of large Vesicomyidae are described from cold-seep sites on pockmarks and other sulfide-rich environments in the Gulf of Guinea (tropical east Atlantic) off Gabon, Congo (Brazzaville) and northern Angola, from 500 to 4000 m depth: "Catyptogena" (s.l.) regab n. sp., Wareniconcha (n.g.) guineensis (Thiele and Jaeckel 1931), Elenaconcha guiness n.g. n. sp., and Isorropodon atalantae n. sp. For two other species already taken by the R/V Valdivia in 1898, Calyptogena valdiviae (Thiele and Jaeckel 1931) and Isorropodon striatum (Thiele and Jaeckel 1931) new localities were discovered, and the species are rediscussed. E. guiness n.g. n.sp. is also recorded from off Banc d'Arguin, Mauritania, collected by commercial fishing...
Tipo: Text
Palavras-chave: New Taxa; Systematics; Eastern Atlantic; Gulf of Guinea; Cold seeps; Vesicomyidae.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-7443.pdf

Remotely forced biweekly deep oscillations on the continental slope of the Gulf of Guinea
Provedor de dados: 5
Autores: Guiavarc'H, Catherine; Treguier, Anne-marie; Vangriesheim, Annick.
Current meter measurements on the continental slope of the Gulf of Guinea (at 7 degrees 20'S and 1300 m depth) have revealed biweekly oscillations of the currents, bottom intensified and oriented along the bathymetry. We develop a three-dimensional primitive equation model of the Gulf of Guinea to study the oscillations and their forcing mechanism. The high resolution (1/12 degrees) regional model reproduces remarkably well the main characteristics of the deep currents on the continental slope. Experiments with different forcings demonstrate that the biweekly variability at 1300 m depth is remotely forced by equatorial winds. Deep Yanai waves generated by the wind propagate eastward along the equator. Upon reaching the African coast, the energy propagates...
Tipo: Text
Palavras-chave: Gulf of Guinea; Numerical modeling; Coastal trapped waves.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4476.pdf

Deep-sea habitat heterogeneity influence on meiofaunal communities in the Gulf of Guinea
Provedor de dados: 5
Autores: Van Gaever, Saskia; Galeron, Joelle; Sibuet, Myriam; Vanreusel, Ann.
To estimate the degree of spatial heterogeneity of benthic deep-sea communities, we carried out a multiple-scale (from m's to 200km) investigation in the Congo-Angola margins (Equatorial West African margin, 3150-4800 m) in which we examined the metazoan meiofauna at a variety of habitats along the Congo Channel system and in the associated cold seep. We investigate the structure, density, vertical distribution patterns in the sediment and biomass of meiofaunal communities in the Gulf of Guinea and how they are controlled by hydrologic and biogeochemical processes The meiofaunal. communities in the Gulf of Guinea were shaped by heterogeneous conditions on the margin, and reflect the multiple-scale spatial variability that corresponds with the different...
Tipo: Text
Palavras-chave: Gulf of Guinea; Nematodes; Meiofauna; Cold seep; Congo canyon; West equatorial Africa margin deep sea.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-7483.pdf

Macrobenthic communities on the continental shelf of Cote-d'Ivoire. Seasonal and diel cycles in relation to hydroclimate
Provedor de dados: 5
Autores: Le Loeuff, P; Intes, A.
Benthic communities of the shrimp (Penaeus notialis) grounds off Grand-Bassam, Cote-d'Ivoire, exhibit distinct variations, correlated to annual changes in hydroclimate, characterized by warm and cold (upwelling) seasons. These changes appear to be the result of the well-defined reproduction periods of many short-living benthic species, as clearly shown by the peaks of abundance in the samples, at different times of the year, but quite often at the end of the cold and the beginning of the warm seasons (September-November). Many species show marked diel rhythms, either diurnal (pagurids, brachyurans) or nocturnal (macrurans, brachyurans, molluscs), so that the species composition displays distinct differences between day and night samples (February 1970...
Tipo: Text
Palavras-chave: Faune benthique; Golfe de Guinée; Cycle saisonnier; Cycle circadien; Perturbation; Benthic fauna; Gulf of Guinea; Seasonal cycle; Diel cycle; Perturbation.
Ano: 1999
URL: http://archimer.ifremer.fr/doc/00325/43601/43985.pdf

Spatial variability in autumnal equatorial upwelling intensity within the Gulf of Guinea as inferred from in situ measurements
Provedor de dados: 5
Autores: Nubi, O. A.; Oyatola, O.o; Bonou, F.
In attempt to study the spatial differences in autumnal equatorial upwelling intensity relative to bio-productivity in the eastern equatorial Atlantic, oceanographic in situ data along regions 10°W, 0°E, 2.5°E and 6°E, collected in the Gulf of Guinea during autumn cruise carried out in September 2007 were analyzed. The surface mean values for temperature along 10°W, 0°E, 2.5°E and 6°E are 25.02, 26.15, 26.88 and 25.60°C, respectively. There was eastward weakening of the equatorial undercurrent from 10°W until its complete disappearance at 6°E. The highest concentration of nitrate recorded at the surface at 10°W was attributed to the shoaling pycnocline observed at this region. The surface mean values for nitrate along 10°W, 0°E, 2.5°E and 6°E are 0.37,...
Tipo: Text
Palavras-chave: Vertical mixing; Zonal advection; Equatorial undercurrent; Equatorial upwelling; Gulf of Guinea; Nutrients; Phytoplankton biomass; Surface enrichment.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00621/73318/72485.pdf

The influence of Congo River discharges in the surface and deep layers of the Gulf of Guinea
Provedor de dados: 5
Autores: Vangriesheim, Annick; Pierre, C; Aminot, Alain; Metzl, N; Baurand, F; Caprais, Jean-claude.
The main feature of the Congo-Angola margin in the Gulf of Guinea is the Congo (ex-Zaire) deep-sea fan composed of a submarine canyon directly connected to the Congo River, a channel and a [sediment] lobe area. During the multi-disciplinary programme called BIOZAIRE conducted by Ifremer from 2000 to 2005, two CTD-O2 sections with discrete water column samples were performed (BIOZAIRE3 cruise: 2003-2004) to study the influence of the Congo River discharges, both in the surface layer and in the deep and near-bottom layers. The surface layer water is greatly diluted with river water that has a heavy particle load. The deep layer is affected by episodic turbidity currents that flow in the deep Congo channel and reach deep areas far from the coast. Previous...
Tipo: Text
Palavras-chave: DIC; Stable isotopes; Nutrient anomaly; Oxygen anomaly; Congo canyon; Gulf of Guinea.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-6737.pdf

Dynamical contribution to sea surface salinity variations in the eastern Gulf of Guinea based on numerical modelling
Provedor de dados: 5
Autores: Berger, Henrick; Treguier, Anne-marie; Perenne, Nicolas; Talandier, Claude.
In this study, we analyse the seasonal variability of the sea surface salinity (SSS) for two coastal regions of the Gulf of Guinea from 1995 to 2006 using a high resolution model (1/12°) embedded in a Tropical Atlantic (1/4°) model. Compared with observations and climatologies, our model demonstrates a good capability to reproduce the seasonal and spatial variations of the SSS and mixed layer depth. Sensitivity experiments are carried out to assess the respective impacts of precipitations and river discharge on the spatial structure and seasonal variations of the SSS in the eastern part of the Gulf of Guinea. In the Bight of Biafra, both precipitations and river runoffs are necessary to observe permanent low SSS values but the river discharge has the...
Tipo: Text
Palavras-chave: Gulf of Guinea; Salinity; Modelling; Congo; Bight of Biafra; Mixed layer budget.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00194/30493/29215.pdf

Contribution to the knowledge of the coastal marine fishes of São Tomé Island (Gulf of Guinea)
Provedor de dados: 20
Autores: Porteiro, F.M.; Barreiros, J.P.; Afonso, P.; Santos, R.S.; Worms, J.; Wirtz, P.
Little is known about the ichthyofauna of the São Tomé and Príncipe archipelago. Since the early works of Osório, at the turn of the century, only few attempts were made to update and complete existing knowledge on fish systematics and biodiversity from this area. Over the past few years, however, several surveys made it possible to start an inventory of the coastal fishes for the archipelago. These are mainly based on specimens that where captured or observed whilst diving and also on fishes landed on beaches by local artisanal fishermen. A total of 124 species belonging to 108 genera and 61 families was identified. Some specimens, including Serranidae, Gobiidae and Labridae probably belong to undescribed species and are currently being studied.
Tipo: Journal Contribution
Palavras-chave: Fishes; Gulf of Guinea; São Tomé e Principe; Checklist; Marine fish; Ichthyofauna.
Ano: 1999
URL: http://hdl.handle.net/1834/704