The Congolobe project, a multidisciplinary study of Congo deep-sea fan lobe complex: Overview of methods, strategies, observations and sampling

Type Article
Date 2017-08
Language English
Author(s) Rabouille C.1, Olu Karine2, Baudin F.3, Khripounoff AlexisORCID2, Dennielou BernardORCID4, Arnaud-Haond SophieORCID5, Babonneau Nathalie6, Bayle Christophe2, Beckler J.7, Bessette Sandrine5, Bombled B., Bourgeois S.8, Brandily Christophe2, Caprais Jean-Claude2, Cathalot CecileORCID1, Charlier K.9, Corvaisier R.10, Croguennec Chantal4, Cruaud Perrine5, Decker Carole2, Droz L.6, Gayet Nicolas2, Godfroy AnneORCID5, Hourdez S.11, Le Bruchec J.2, Saout Johan4, Le Saout Marie-Helene6, Lesongeur Francoise5, Martinez P.9, Mejanelle L.8, Michalopoulos P.12, Mouchel Olivier2, Noel Philippe2, Pastor Lucie2, Picot M.6, Pignet Patricia5, Pozzato L.1, Pruski A. M.8, Rabiller Manuella2, Raimonet M.10, Ragueneau O.10, Reyss J. L.1, Rodier Philippe2, Ruesch Blandine4, Ruffine Livio4, Savignac F.3, Senyarich C.8, Schnyder J.3, Sen Arunima2, Stetten E.3, Sun Ming Yi13, Taillefert M.7, Teixeira S.14, Tisnerat-Laborde N.1, Toffin Laurent5, Tourolle JulieORCID2, Toussaint F.1, Vetion G.8, Jouanneau J. M.9, 12, Bez M.12, 15
Affiliation(s) 1 : Univ Paris Saclay, CEA, CNRS, Lab Sci Climat & Environm,UVSQ 8212 & IPSL, Ave Terrasse, F-91190 Gif Sur Yvette, France.
2 : IFREMER, Ctr Bretagne, Lab Environm Profond, REM EEP LEP, F-29280 Plouzane, France.
3 : UPMC, Sorbonne Univ, CNRS, Inst Sci Terre Paris,UMR 7193, Case 117,4 Pl Jussieu, F-75252 Paris 05, France.
4 : IFREMER, Dept REM, Unite Rech Geoscie Marines, F-29280 Plouzane, France.
5 : IFREMER, CNRS, Lab Microbiol Environm Extremes, Technopele Brest Iroise,UMR UBO 6197, F-29280 Plouzane, France.
6 : Inst Univ Europeen Mer, Lab Domaines Ocean, CNRS, UMR UBO 6538, F-29280 Plouzane, France.
7 : Georgia Inst Technol, Sch Earth & Atmospher Sci, 311 Ferst Dr, Atlanta, GA 30332 USA.
8 : Sorbonne Univ, UPMC, CNRS, Lab Ecogeochim Environm Benth,UMR 8222,Observ Oce, Banyuls Sur Mer, France.
9 : Univ Bordeaux, Environm & Paleoenvironm Ocean & Continentaux, UMR 5805, Allee Geoffroy St Hilaire, F-33615 Pessac, France.
10 : Inst Univ Europeen Mer, CNRS, Lab Sci Environm Marin, UMR UBO, F-29280 Plouzane, France.
11 : UPMC, CNRS, Equipe Ecophysiol Adaptat & Evolut Mol, Stn Biolog Roscoff,UMR 7144, F-29680 Roscoff, France.
12 : Hellen Ctr Marine Res, POB 712,PC 19013, Anavyssos Attiki, Greece.
13 : Univ Georgia, Dept Marine Sci, Athens, GA 30602 USA.
14 : Univ Algarve, CIMAR, Ctr Marine Sci, Campus Gambelas, P-8005139 Faro, Portugal.
15 : Total Ctr Scientif & Tech Jean Feger, Ave Larribau, F-64018 Pau, France.
Source Deep-sea Research Part Ii-topical Studies In Oceanography (0967-0645) (Pergamon-elsevier Science Ltd), 2017-08 , Vol. 142 , P. 7-24
DOI 10.1016/j.dsr2.2016.05.006
WOS© Times Cited 20
Keyword(s) Chemosynthetic habitats, Congo deep-sea fan, Fine sediment, Sedimentation rate, Seafloor morphology, Turbidite, Vesicomyidae
Abstract 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 geology, organic and inorganic geochemistry, and micro- and macro-biology of the terminal lobes of the Congo deep-sea fan. Using this multidisciplinary approach, the morpho-sedimentary features of the lobes were characterized along with the origin and reactivity of organic matter, the recycling and burial of biogenic compounds, the diversity and function of bacterial and archaeal communities within the sediment, and the biodiversity and functioning of the faunal assemblages on the seafloor. Six different sites were selected for this study: Four distributed along the active channel from the lobe complex entrance to the outer rim of the sediment deposition zone, and two positioned cross-axis and at increasing distance from the active channel, thus providing a gradient in turbidite particle delivery and sediment age.

This paper aims to provide the general context of this multidisciplinary study. It describes the general features of the site and the overall sampling strategy and provides the initial habitat observations to guide the other in-depth investigations presented in this special issue. Detailed bathymetry of each sampling site using 0.1 m to 1 m resolution multibeam obtained with a remotely operated vehicle (ROV) shows progressive widening and smoothing of the channel-levees with increasing depth and reveals a complex morphology with channel bifurcations, erosional features and massive deposits. Dense ecosystems surveyed in the study area gather high density clusters of two large-sized species of symbiotic Vesicomyidae bivalves and microbial mats. These assemblages, which are rarely observed in sedimentary zones, resemble those based on chemosynthesis at cold-seep sites, such as the active pockmarks encountered along the Congo margin, and share with these sites the dominant vesicomyid species Christineconcha regab. Sedimentation rates estimated in the lobe complex range between 0.5 and 10 cm yr−1, which is 2-3 orders of magnitude higher than values generally encountered at abyssal depths. The bathymetry, faunal assemblages and sedimentation rates make the Congo lobe complex a highly peculiar deep-sea habitat driven by high inputs of terrigenous material delivered by the Congo channel-levee system.
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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. (2017). The Congolobe project, a multidisciplinary study of Congo deep-sea fan lobe complex: Overview of methods, strategies, observations and sampling. Deep-sea Research Part Ii-topical Studies In Oceanography, 142, 7-24. Publisher's official version : https://doi.org/10.1016/j.dsr2.2016.05.006 , Open Access version : https://archimer.ifremer.fr/doc/00335/44580/