Éditeur(s) : Public Library Science
Résumé : Like hydrothermal vents along oceanic ridges, cold seeps are patchy and isolated ecosystems along continental margins, extending from bathyal to abyssal depths. The Atlantic Equatorial Belt (AEB), from the Gulf of Mexico to the Gulf of Guinea, was one focus of the Census of Marine Life ChEss (Chemosynthetic Ecosystems) program to study biogeography of seep and vent fauna. We present a review and analysis of collections from five seep regions along the AEB: the Gulf of Mexico where extensive faunal sampling has been conducted from 400 to 3300m, the Barbados accretionary prism, the Blake ridge diapir, and in the Eastern Atlantic from the Congo and Gabon margins and the recently explored Nigeria margin. Of the 72 taxa identified at the species level, a total of 9 species or species complexes are identified as amphi-Atlantic. Similarity analyses based on both Bray Curtis and Hellinger distances among 9 faunal collections, and principal component analysis based on presence/absence of megafauna species at these sites, suggest that within the AEB seep megafauna community structure is influenced primarily by depth rather than by geographic distance. Depth segregation is observed between 1000 and 2000m, with the middle slope sites either grouped with those deeper than 2000m or with the shallower sites. The highest level of community similarity was found between the seeps of the Florida escarpment and Congo margin. In the western Atlantic, the highest degree of similarity is observed between the shallowest sites of the Barbados prism and of the Louisiana slope. The high number of amphi-atlantic cold-seep species that do not cluster according to biogeographic regions, and the importance of depth in structuring AEB cold-seep communities are the major conclusions of this study. The hydrothermal vent sites along the Mid Atlantic Ridge (MAR) did not appear as "stepping stones" for dispersal of the AEB seep fauna, however, the south MAR and off axis regions should be further explored to more fully test this hypothesis.
Plos One (1932-6203) (Public Library Science), 2010-08 , Vol. 5 , N. 8 , P. 1-11

Droits : © 2010 Olu et al.
http://archimer.ifremer.fr/doc/00011/12207/8975.pdf
DOI:10.1371/journal.pone.0011967
http://archimer.ifremer.fr/doc/00011/12207/

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : Deep-sea bivalves found at hydrothermal vents, cold seeps and organic falls are sustained by chemosynthetic bacteria which ensure part or all of their carbon nutrition. These symbioses are of prime importance for the functioning of the ecosystems. Similar symbioses occur in other bivalve species living in shallow and coastal reduced habitats worldwide. In recent years, several deep-sea species have been investigated from continental margins around Europe, West Africa, East America, the Gulf of Mexico, and from hydrothermal vents on the Mid-Atlantic Ridge. In parallel, numerous more easily accessible shallow marine species were studied. We here provide a summary of the current knowledge available on chemosymbiotic bivalves in the area ranging west-to-east from the Gulf of Mexico to Marmara Sea, and north-to-south from the Arctic to the Gulf of Guinea. Characteristics of symbioses in 51 species from the area are summarized for each of the five bivalve families documented to harbor chemosynthetic symbionts (Mytilidae, Vesicomyidae, Solemyidae, Thyasiridae and Lucinidae), and compared among families with special emphasis on ecology, life cycle, and connectivity. Chemosynthetic symbioses are a major adaptation to ecosystems and habitats exposed to reducing conditions, yet relatively little is known regarding their diversity and functioning apart from a few "model species" on which effort has focused over the last 30 yr. In the context of increasing concern about biodiversity and ecosystems, and increasing anthropogenic pressure on Oceans, we advocate for a better assessment of bivalve symbioses diversity in order to evaluate the capacities of these remarkable ecological and evolutionary units to withstand environmental change
Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2013 , Vol. 10 , N. 5 , P. 3241-3267

Droits : Author(s) 2012. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00133/24417/22431.pdf
DOI:10.5194/bg-10-3241-2013
http://archimer.ifremer.fr/doc/00133/24417/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Transport of liquid and gaseous hydrocarbons through focused fluid flow systems is a widespread process in continental margins and sedimentary basins, which is gaining increased attention in the assessment of geohazards, environment conservation, and securing fossil energy resources. Studying the abundance, distribution and drivers for this process is crucial for understanding its role in 1) the dynamics of gas hydrate accumulation and destabilization, 2) submarine slope stability and related tsunamis, 3) the plethora of chemosynthetic benthic ecosystems that develop in deep seep sites, and 4) the input of greenhouse gases (e.g. methane) into the ocean/atmosphere system, which may influence the atmospheric carbon budget and Earth's paleo- and present climate. New ocean exploration tools provide ever more data and improve our understanding of these systems. However, the subject still suffers from a lack of interdisciplinary knowledge dissemination. The ongoing international debate about the timing and the processes that control fluid expulsion in sedimentary basins is fuelled by their implications for structural and petroleum geology. Because fluids expelled at cold seeps originate at depth they represent open windows into the underlying petroleum systems and are valuable indicators for the reservoir systems. They may also help in deciphering past and predicting future climate change because worldwide release of large amounts of fluids may have an impact on the chemistry of the ocean and atmosphere.
ISSN: 0025-3227

hal-00772472
https://hal.archives-ouvertes.fr/hal-00772472
DOI : 10.1016/j.margeo.2012.10.012

Résumé : The MEDECO Leg 2 cruise followed the MEDECO Leg 1 cruise that had crossed the Mediterranean Sea from the west to the east to study benthic communities of the Var canyon, deep corals found on the Calabrian Margin and cold seep ecosystems of the Mediterranean Ridge. The main objective of the MEDECO Leg 2 cruise was to study and compare, using a multidisciplinary approach, the structure and dynamics of deep-sea ecosystems at various active cold seep sites from the Nile deep sea fan and the Calabrian Arc, in the Eastern Mediterranean sea. During MEDECO Legs 1 & 2, a multiscale strategy was promoted to integrate (1) a high resolution cartography of geological structures (km2 scale), (2) a detailed mapping, including video imagery, of smaller-scale areas (scale 100 to 300 m2), (3) the physical, chemical and sedimentary characteristics of the habitat (multiscale), (4) the structure and functioning of faunal communities, including microbes, in terms of composition, diversity and biomass (multiscale), (5) small scale studies of interactions between organisms and their environment (scale < m2), (6) detailed ecophysiological studies at the organism scale on invertebrates. The use of the ROV “Victor 6000” and of various equipments for in situ and ex situ observations and measurements has helped reaching our objectives. The MEDECO cruise represented the key-Mediterranean cruise of the HERMES project “Hotspot Ecosystem Research on the Margins of European Seas” (P.I. P. Weaver, NOC-Southampton). The cruise was organized to follow the objectives of the HERMES program to better understand the functioning of deep ecosystems of the continental margins aiming at obtaining: (1) the description and quantification of the natural drivers (geological, hydrological, chemical factors) that control the distribution of ecosystems on margins; (2) the characterization and quantification of biodiversity, from bacteria to megafauna, as well as the knowledge of ecosystem functioning; (3) the study of ecosystems dynamics including the biology/physiology of key-species. Specific objectives. Colonization experiments conducted in the frame of two European programs, Diwoo and Chemeco, have given the opportunity to recover the fauna installed in the devices deployed during the Bionil cruise (2006) and to deploy new ones at the same site located in the pockmark area of the central province of Nile deep sea fan.

Droits : 2008 Insu, Cnrs, Locean
http://archimer.ifremer.fr/doc/00134/24550/22583.pdf
http://archimer.ifremer.fr/doc/00134/24550/

Éditeur(s) : Public Library Science
Résumé : Subsurface sediments of the Sonora Margin (Guaymas Basin), located in proximity of active cold seep sites were explored. The taxonomic and functional diversity of bacterial and archaeal communities were investigated from 1 to 10 meters below the seafloor. Microbial community structure and abundance and distribution of dominant populations were assessed using complementary molecular approaches (Ribosomal Intergenic Spacer Analysis, 16S rRNA libraries and quantitative PCR with an extensive primers set) and correlated to comprehensive geochemical data. Moreover the metabolic potentials and functional traits of the microbial community were also identified using the GeoChip functional gene microarray and metabolic rates. The active microbial community structure in the Sonora Margin sediments was related to deep subsurface ecosystems (Marine Benthic Groups B and D, Miscellaneous Crenarchaeotal Group, Chloroflexi and Candidate divisions) and remained relatively similar throughout the sediment section, despite defined biogeochemical gradients. However, relative abundances of bacterial and archaeal dominant lineages were significantly correlated with organic carbon quantity and origin. Consistently, metabolic pathways for the degradation and assimilation of this organic carbon as well as genetic potentials for the transformation of detrital organic matters, hydrocarbons and recalcitrant substrates were detected, suggesting that chemoorganotrophic microorganisms may dominate the microbial community of the Sonora Margin subsurface sediments.
Plos One (1932-6203) (Public Library Science), 2014-08 , Vol. 9 , N. 8 , P. e104427

Droits : This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
http://archimer.ifremer.fr/doc/00203/31408/29801.pdf
DOI:10.1371/journal.pone.0104427
http://archimer.ifremer.fr/doc/00203/31408/

Éditeur(s) : Université de Bretagne Occidentale
Résumé : The major objectives of this thesis were to study the structure, functioning and dynamics of different faunal assemblages associated with cold seep ecosystems in the eastern Mediterranean Sea. We focused our study on three main sites: the Marmara Sea, the Mediterranean ridge and the Nile deep sea fan. This thesis aims at determining the environmental signature of Mediterranean sites and the characteristics of the associated fauna at European and global scales. The specific objectives were to (1) determine the composition, diversity, density, biomass of invertebrate assemblages, (2) characterize biogeochemical conditions within different microhabitats in the vicinity of organisms, (3) to define the trophic relationships amongst seep fauna using stable isotope analyses (collaboration) and lastly, (4) to compare the spatial distribution and assemblage characteristics at different spatial scales (local, structure-scale, regional). The results show that (1) the Napoli mud volcano is the richest structure in terms of numbers of taxa while the Nile deep-sea fan sites need additional sampling, (2) a high variability is observed both between the different microhabitats but also within a single microhabitat, (3) the methane and oxygen gradients as well as substratum type are the main structuring factors explaining the distribution of the fauna and (4) the characteristics of the microhabitats, rather than the study area, influence the structure of benthic communities associated with Mediterranean cold seeps.
Les objectifs principaux de cette thèse sont d’étudier la structure, le fonctionnement et la dynamique de différents assemblages de faune associée aux émissions de fluides froids de Méditerranée orientale. Trois principaux sites ont été étudiés : la mer de Marmara, la ride méditerranéenne et le delta profond du Nil. Cette thèse tente de déterminer la « signature environnementale » des sites méditerranéens et les caractéristiques de la faune qui y est associée dans un contexte de marges européennes et mondiale. Les objectifs spécifiques sont (1) de déterminer la composition, la diversité, la densité et la biomasse des assemblages d'invertébrés ; (2) de caractériser les conditions biogéochimiques au sein des différents microhabitats à proximité des organismes; (3) de caractériser les relations trophiques sur les différents assemblages de faune par une approche isotopique (en collaboration) et finalement, (4) de comparer la distribution spatiale et les caractéristiques des assemblages à différentes échelles spatiales (locale, à l’échelle d’une structure géologique, régionale). Les résultats montrent que : (1) le volcan de boue Napoli est le site le plus riche en taxons alors que les sites du delta du Nil nécessiteraient un échantillonnage plus approfondi ; (2) il existe une grande variabilité entre les microhabitats ainsi qu’au sein d’un même microhabitat ; (3) les gradients en méthane, en oxygène ainsi que la nature du substrat sont les principaux facteurs abiotiques expliquant la distribution de la faune, (4) les caractéristiques des microhabitats, plutôt que la zone d’étude, influencent la structure des communautés benthiques associées aux écosystèmes de fluides froids méditerranéens.

Droits : 2010 The Author, UBO
http://archimer.ifremer.fr/doc/00020/13138/10178.pdf
http://archimer.ifremer.fr/doc/00020/13138/

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Bathymodiolin mussels occur at hydrothermal vents and cold seeps, where they thrive thanks to symbiotic associations with chemotrophic bacteria. Closely related genera Idas and Adipicola are associated with organic falls, ecosystems that have been suggested as potential evolutionary 'stepping stones' in the colonization of deeper and more sulphide-rich environments. Such a scenario should result from specializations to given environments from species with larger ecological niches. This study provides molecular-based evidence for the existence of two mussel species found both on sunken wood and bones. Each species specifically harbours one bacterial phylotype corresponding to thioautotrophic bacteria related to other bathymodiolin symbionts. Phylogenetic patterns between hosts and symbionts are partially congruent. However, active endocytosis and occurrences of minor symbiont lineages within species which are not their usual host suggest an environmental or horizontal rather than strictly vertical transmission of symbionts. Although the bacteria are close relatives, their localization is intracellular in one mussel species and extracellular in the other, suggesting that habitat choice is independent of the symbiont localization. The variation of bacterial densities in host tissues is related to the substrate on which specimens were sampled and could explain the abilities of host species to adapt to various substrates.
ISSN: 0950-1193

hal-00755293
https://hal.univ-antilles.fr/hal-00755293
DOI : 10.1098/rspb.2008.1101

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
Mussels of the subfamily Bathymodiolinae thrive around chimneys emitting hot fluids at deep sea hydrothermal vents, as well as at cold seeps and on sunken organic debris (sunken wood, whale falls). Despite the absence of light-driven primary production in these deep-sea ecosystems, mussels succeed reaching high biomasses in these harsh conditions thanks to chemosynthetic, carbon-fixing bacterial symbionts located in their gill tissue. Since the discovery of mussel symbioses about three decades ago our knowledge has increased, yet new findings are published regularly regarding their diversity, role and evolution. This article attempts to summarize current knowledge about symbiosis in Bathymodiolinae, focusing on mussel species for which information is available regarding both hosts and symbionts. Moreover, new data obtained from small mussels inhabiting sunken woods around the Philippines are provided. Indeed, mussel species from organic falls remain poorly studied compared to their vent and seep relatives despite their importance for the understanding of the evolution of symbiosis in the subfamily Bathymodiolinae.
ISSN: 1631-0691

hal-00750422
https://hal.univ-antilles.fr/hal-00750422

Éditeur(s) : Wiley-blackwell
Résumé : The history of colonization and dispersal in fauna distributed among deep-sea chemosynthetic ecosystems remains enigmatic and poorly understood because of an inability to mark and track individuals. A combination of molecular, morphological and environmental data improves understanding of spatial and temporal scales at which panmixia, disruption of gene flow or even speciation may occur. Vestimentiferan tubeworms of the genus Escarpia are important components of deep -sea cold seep ecosystems, as they provide long-term habitat for many other taxa. Three species of Escarpia, Escarpia spicata [Gulf of California (GoC)], Escarpia laminata [Gulf of Mexico (GoM)] and Escarpia southwardae (West African Cold Seeps), have been described based on morphology, but are not discriminated through the use of mitochondrial markers (cytochrome oxidase subunit 1; large ribosomal subunit rDNA, 16S; cytochrome b). Here, we also sequenced the exon-primed intron-crossing Haemoglobin subunit B2 intron and genotyped 28 microsatellites to (i) determine the level of genetic differentiation, if any, among the three geographically separated entities and (ii) identify possible population structure at the regional scale within the GoM and West Africa. Results at the global scale support the occurrence of three genetically distinct groups. At the regional scale among eight sampling sites of E. laminata (n=129) and among three sampling sites of E. southwardae (n=80), no population structure was detected. These findings suggest that despite the patchiness and isolation of seep habitats, connectivity is high on regional scales.
Molecular Ecology (0962-1083) (Wiley-blackwell), 2013-08 , Vol. 22 , N. 16 , P. 4147-4162

Droits : 2013 John Wiley & Sons Ltd
http://archimer.ifremer.fr/doc/00152/26354/24515.pdf
DOI:10.1111/mec.12379
http://archimer.ifremer.fr/doc/00152/26354/

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Six morphotypes of small mussels (Bivalvia: Mytilidae) were found attached to naturally sunken wood collected in the Bohol Sea (Philippines). These specimens are related to the large Bathymodiolus mussels that are found worldwide at cold seeps and hydrothermal vents. In these habitats, the mytilids harbour sulphur- and methane-oxidizing endosymbionts in their gills and depend on the energy and carbon provided by the symbionts. In this study, bacteria associated with the gills of wood-associated mussels are characterized using molecular and microscopic techniques. The existence of bacteria in the lateral zone of gill filaments in all specimens is demonstrated. Comparative analyses of 16S rRNA gene and adenosine 5′-phosphosulphate (APS) reductase gene sequences indicate that the bacteria are closely related to sulphur-oxidizing endosymbionts of Bathymodiolus. FISHs using specific probes confirm that sulphur oxidizers are by far the most abundant, if not the only bacteria present. Electron micrographs displayed mostly extracellular bacteria located between microvilli at the apical surface of host gill epithelial cells all along the lateral zone of each gill filament. In some specimens, occasional occurrence of intracellular bacteria with similar morphology was noted. This study provides the first molecular evidence for the presence of possible thiotrophic symbiosis in sunken wood ecosystems. With their epibiotic bacteria, wood-associated mussels display a less integrated type of interaction than described in their seep, vent and whale fall relatives.
ISSN: 0168-6496

hal-00715244
https://hal.univ-antilles.fr/hal-00715244
DOI : 10.1111/j.1574-6941.2008.00438.x

Éditeur(s) : HAL CCSD
Résumé : International audience
Seven individuals of a single morphotype of mussels (Bivalvia: Mytilidae) were found attached to a naturally sunken whale intervertebral disk collected in Guadeloupe (Caribbean) at 800 m depth. These specimens resemble small Idas mussels which are found worldwide at cold seeps and hydrothermal vents, and typically harbor ectosymbiotic bacteria on their gills upon which they depend for nutrition. Based on multi-locus gene sequencing, these specimens appear to belong to a new species closely related to two species now included within the genus Terua. Unexpectedly, its closest relatives are found in the Pacific, questioning how this species has reached the Antilles arc. Based on marker gene sequence analysis, electron and fluorescence microscopy, Terua n. sp. harbors two distinct and abundant extracellular bacterial symbionts located between microvilli at the apical surface of host gill epithelial cells. One is a sulfur-oxidizing bacterium similar to the symbionts previously identified in several deep-sea mussels, while the other is related to Colwellia species, a group of cold-adapted heterotrophic bacteria able to degrade organic compounds. This study provides the first evidence for the existence of a dual symbiosis in mussels from whale fall ecosystems in the Caribbean. The evolutionary history of Terua n. sp. and potential role of its Colwellia symbionts are discussed.
Deep Sea Research Part I: Oceanographic Research Papers

hal-01336943
http://hal.upmc.fr/hal-01336943
http://hal.upmc.fr/hal-01336943/document
http://hal.upmc.fr/hal-01336943/file/Duperron_Colwellia_and.pdf
DOI : 10.1016/j.dsr.2016.05.012

Éditeur(s) : Springer
Résumé : The Håkon Mosby mud volcano is a 1.5-km-diameter geological structure located on the Southwest Barents Sea slope at a water depth of 1,270 m. High-definition seabed mapping of the mud volcano has been carried out in 2003 and 2006. A comparative analysis of the bathymetry and backscatter maps produced from the two surveys shows subtle morphological changes over the entire crater of the mud volcano, interpreted to be the consequence of mud eruption events. Mud temperature measurements point to a persistently warm mud at shallow depth in the crater. This is explained by upward fluid advection, rather than conductive cooling of mud flows. The small-scale spatial variability in the temperature distribution may be related to mud outflows or changes in the fluid flow regime. Furthermore, the locations of free gas venting observed in 2006 were found to differ from those of 2003. Our observations of overall similar topographic profiles across the mud volcano in 2003 and 2006 suggest that eruption events would have been modest. Nevertheless, the data bring evidence of significant change in activity even over short time intervals of only 3 years. This may be a characteristic shared by other submarine mud volcanoes, notably those considered to be in a quiescent stage.
Geo-marine Letters (0276-0460) (Springer), 2010-06 , Vol. 30 , N. 3-4 , P. 157-167

Droits : Springer-Verlag 2010
http://archimer.ifremer.fr/doc/00004/11527/10261.pdf
DOI:10.1007/s00367-010-0193-z
http://archimer.ifremer.fr/doc/00004/11527/