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Societal concerns over the potential impacts of recent global change have prompted renewed interest in the long-term ecological monitoring of large ecosystems. The deep sea is the largest ecosystem on the planet, the least accessible, and perhaps the least understood. Nevertheless, deep-sea data collected over the last few decades are now being synthesised with a view to both measuring global change and predicting the future impacts of further rises in atmospheric carbon dioxide concentrations. For many years, it was assumed by many that the deep sea is a stable habitat, buffered from short-term changes in the atmosphere or upper ocean. However, recent studies suggest that deep-seafloor ecosystems may respond relatively quickly to seasonal, inter-annual and decadal-scale shifts in upper-ocean variables. In this review, we assess the evidence for these long-term (i.e. inter-annual to decadal-scale) changes both in biologically driven, sedimented, deep-sea ecosystems (e.g. abyssal plains) and in chemosynthetic ecosystems that are partially geologically driven, such as hydrothermal vents and cold seeps. We have identified 11 deep-sea sedimented ecosystems for which published analyses of long-term biological data exist. At three of these, we have found evidence for a progressive trend that could be potentially linked to recent climate change, although the evidence is not conclusive. At the other sites, we have concluded that the changes were either not significant, or were stochastically variable without being clearly linked to climate change or climate variability indices. For chemosynthetic ecosystems, we have identified 14 sites for which there are some published long-term data. Data for temporal changes at chemosynthetic ecosystems are scarce, with few sites being subjected to repeated visits. However, the limited evidence from hydrothermal vents suggests that at fast-spreading centres such as the East Pacific Rise, vent communities are impacted on decadal scales by stochastic events such as volcanic eruptions, with associated fauna showing complex patterns of community succession. For the slow-spreading centres such as the Mid-Atlantic Ridge, vent sites appear to be stable over the time periods measured, with no discernable long-term trend. At cold seeps, inferences based on spatial studies in the Gulf of Mexico, and data on organism longevity, suggest that these sites are stable over many hundreds of years. However, at the Haakon Mosby mud volcano, a large, well-studied seep in the Barents Sea, periodic mud slides associated with gas and fluid venting may disrupt benthic communities, leading to successional sequences over time. For chemosynthetic ecosystems of biogenic origin (e.g. whale-falls), it is likely that the longevity of the habitat depends mainly on the size of the carcass and the ecological setting, with large remains persisting as a distinct seafloor habitat for up to 100 years. Studies of shallow-water analogs of deep-sea ecosystems such as marine caves may also yield insights into temporal processes. Although it is obvious from the geological record that past climate change has impacted deep-sea faunas, the evidence that recent climate change or climate variability has altered deep-sea benthic communities is extremely limited. This mainly reflects the lack of remote sensing of this vast seafloor habitat. Current and future advances in deep-ocean benthic science involve new remote observing technologies that combine a high temporal resolution (e.g. cabled observatories) with spatial capabilities (e.g. autonomous vehicles undertaking image surveys of the seabed).

Hydrothermal vent community dynamics over a ten year span was studied in the Logatchev area, 14 degrees 45'N on the Mid-Atlantic Ridge. On the SERPENTINE cruise in March 2007 with the RN Pourquoi pas? and the ROV Victor 6000 (IFREMER), composition, abundance and distribution of dominant megafauna at Logatchev were examined and compared to published data from 1997. Our results revealed notable changes in several community characteristics. The most significant changes evident in March 2007 compared to July 1997 were the increase up to by order of magnitude in the population density of predatory gastropods Phymorchynchus spp. at the site Irina-2 and disappearance of a live population of vesicomyids at the site Anya's Garden. Other notable differences between the two periods of observation were the overall increase in the abundance in 2007 of the mussel Bathymodiolus puteoserpentis and a high abundance of gravid females of the shrimp Rimicaris exoculata at Irina-2. It is suggested that the extinction of vesicomyids occurred owing to either a sediment slide at a steep slope of the Anya's Garden locality or instability of a biotope required for vesicomyids. Live vesicomyids were not found over a large area explored at Logatchev in 2007. Other changes observed in 2007 apparently were related to seasonal fluctuations in the community at Logatchev or fluctuations in the hydrothermal activity. Any successional stages over a decadal scale at Logatchev were not observed.

Research needs and interests on biodiversity have drastically increased since the Rio Conference (1992). The main conclusions from the Millennium Ecosystem Assessment (MEA, 2001) carried out by the UN and the demonstration of the critical role of biodiversity in maintaining ecosystems services have strengthened research interests on biodiversity. Moreover, the systemic approach generalization, complex system modeling, confluence of thematic prompting new scientific concepts, and multi-scalar – multifunctional approach have induced significant changes to the scientific context. A review of major advances on biodiversity monitoring and research resulting from Ifremer programs will be presented considering deep sea as well as coastal ecosystems and associated technologies. Development of benthic habitat mapping (e.g., REBENT), and data platforms and information systems on marine biodiversity (SINP, SIH, BIOCEAN) are all contributing to an improved spatial and temporal biodiversity observatory. Ifremer has already demonstrated its main interest in an active scientific strategy of cooperation through national research groups such as the IFB then FRB, ECCHIS GDR, European projects (HERMES), scientific coordination (REX MARBEF, Marine Genomics) as well as the European ERANETs (Biodiversa, Marinera, Marifish), and its involvement in the 'Census of Marine Life' international program. Beyond the next European Sea ERANET, an increased cooperation among scientific partners appears critical to address the three major scientific challenges regarding marine biodiversity: 1. explore and characterize marine biodiversity at various scales (landscapes, habitats, communities), 2. operational monitoring, and 3. development of functional biodiversity modeling to assess ecosystem resilience to the main trend changes of impact vectors., Les besoins en recherches dans le domaine de la biodiversité se sont accrus depuis la Conférence de Rio (1992) et les conclusions portées par le bilan mondial des Nations Unies concernant l'évaluation des services des écosystèmes et du rôle essentiel de la biodiversité dans leur maintien (MEA, 2001). La généralisation de l'approche systémique, la modélisation de systèmes complexes, la convergence de disciplines vers de nouveaux concepts et les approches multi-échelles et multi-fonctionnelles sont autant d'éléments d'évolution du contexte scientifique et technique dans ce domaine. Une revue des avancées de l'Ifremer dans le domaine de l'observation et de la recherche en biodiversité sera présentée depuis les travaux sur les écosystèmes des grands fonds jusqu'au domaine côtier tout en considérant les technologies associées. La réalisation de la cartographie des habitats benthiques (e.g., REBENT), le développement de plate-formes et de systèmes d'information sur la biodiversité marine (SINP, SIH, BIOCEAN) contribuent à une meilleure observation spatio-temporelle de celle-ci. La participation de l'Ifremer aux groupements de recherche nationaux (IFB puis FRB, GDR ECCHIS), aux projets européens (HERMES) et coordinations scientifiques (REX MARBEF, Marine Genomics), ainsi qu'aux ERANET (Biodiversa, Marinera, Marifish) et le rôle joué dans le programme international « Census of Marine Life » démontre l'importance que l'Institut accorde à une stratégie active de coopération scientifique en matière de biodiversité marine. Au delà du prochain ERANET « SEANET », l'amélioration de la coordination pluri-organismes de la recherche en biodiversité marine apparaît essentielle à court terme pour répondre aux trois enjeux de recherche que sont 1. l'exploration et la caractérisation de la biodiversité marine à différentes échelles (paysages, habitats, communautés), 2. la surveillance opérationnelle, 3. le développement de la modélisation fonctionnelle de la biodiversité pour l'étude de la résilience des écosystèmes face aux évolutions des vecteurs d'impact.

[1] Mid-ocean ridge volcanic activity is the fundamental process for creation of ocean crust, yet the dynamics of magma emplacement along the slow spreading Mid-Atlantic Ridge ( MAR) are largely unknown. We present acoustical, seismological, and biological evidence of a magmatic dike intrusion at the Lucky Strike segment, the first detected from the deeper sections (> 1500 m) of the MAR. The dike caused the largest teleseismic earthquake swarm recorded at Lucky Strike in > 20 years of seismic monitoring, and one of the largest ever recorded on the northern MAR. Hydrophone records indicate that the rate of earthquake activity decays in a nontectonic manner and that the onset of the swarm was accompanied by 30 min of broadband (> 3 Hz) intrusion tremor, suggesting a volcanic origin. Two submersible investigations of high-temperature vents located at the summit of Lucky Strike Seamount 3 months and 1 year after the swarm showed a significant increase in microbial activity and diffuse venting. This magmatic episode may represent one form of volcanism along the MAR, where highly focused pockets of magma are intruded sporadically into the shallow ocean crust beneath long-lived, discrete volcanic structures recharging preexisting seafloor hydrothermal vents and ecosystems.

A new species of scale-worm belonging to the sub-family Macellicephalinae, Levensteiniella iris sp. nov., is described. It was collected on the Mid-Atlantic Ridge, on the Lucky Strike and Rainbow vent sites, associated to the mussel Bathymodiolus azoricus on very low flow hydrothermal vents., Une nouvelle espèce de Polynoidae appartenant à la sous-famille des Macellicephalinae, Levensteiniella iris sp. nov., est décrite. Elle a été récoltée sur la dorsale médio-Atlantique, sur les sites hydrothermaux Lucky Strike et Rainbow, associée à des moulières à Bathymodiolus azoricus sur des évents tièdes à très faible flux.

Two new species of polychaetous annelids Prionospio unilamellata sp. nov. and Laonice asaccata sp. nov. (Spionidae) are described from samples collected at Mid-Atlantic hydrothermal vent fields close to the Azores Triple Junction and in the Snake Pit vent field. These two species are important components of the communities associated with active venting. Prionospio unilamellata differs from all other Prionospio species in the form of anterior notopodial lamellae. Laonice asaccata differs from other Laonice species by lacking interparapodial pouches., Deux nouvelles espèces d'annélides polychètes Prionospio unilamellata sp. nov. et Laonice asaccata sp. nov. (Spionidae) sont décrites à partir des collections recueillies par les submersibles sur les sources hydrothermales actives de la ride médio-atlantique, à proximité du point triple des Açores et dans le champ hydrothermal Snake Pit. Ces deux espèces sont fréquentes dans les communautés associées aux fluides hydrothermaux. Prionospio unilamellata sp. nov. diffère de toutes les espèces de ce genre par la forme de la lamelle notopodiale antérieure. Laonice asaccata sp. nov. diffère des autres espèces de ce genre par l'absence de poche inter-parapodiale.

As part of an ongoing examination of microbial diversity associated with hydrothermal vent polychaetes of the family Alvinellidae, we undertook a culture-independent molecular analysis of the bacterial assemblage associated with mucous secretions of the Northeastern Pacific vent polychaete Paralvinella palmiformis. Using a molecular 16S rDNA-based phylogenetic approach, clone libraries were constructed from two samples collected from active sulfide edifices in two hydrothermal vent fields. In both cases, clone libraries were largely dominated by epsilon-Proteobacteria. Phylotypes belonging to the Cytophaga-Flavobacteria and to the Verrucomicrobia were also largely represented within the libraries. The remaining sequences were related to the taxonomic groups Fusobacteria, Green non-sulfur bacteria, Firmicutes, gamma- and delta-Proteobacteria. To our knowledge, this is the first report of the presence of Verrucomicrobia, Fusobacteria and green non-sulfur bacteria on hydrothermal edifices. The potential functions of the detected bacteria are discussed in terms of productivity, recycling of organic matter and detoxification within the P. palmiformis microhabitat.

Introduction : The evolutionary age of some of the hydrothermal vent taxa have recently become a highly debated issue. Vestimentiferan worms (= siboglinid polychaetes) in particular, have been claimed to be as old as 430 million years based on the occurrence of fossilized tubes resembling those of currently known Vestimentifera (Little et al., 1997), while other authors, based on molecular data, have claimed they must be younger than 100 million years old (Black et al, 1997; Halanych et al., 1998). One explanation for this apparent discrepancy might be that tubes, such as those found in the Silurian fossil vent communities, did not belong to vestimentiferans, but rather to other tube-dwelling polychaetes. However, it is also possible that the choice of the molecular clock used to estimate the age of the vestimentiferan radiation from the molecular data, was simply not appropriate. Opportunities to accurately calibrate molecular clocks are relatively rare and cannot be generalized to all genes nor to all taxa. Such an opportunity appeared during a phylogeographic study of the hydrothermal-vent ampharetid polychaete Amphisamytha galapagensis Zottoli, 1983, which is widely distributed in the Eastern Pacific (Chevaldonne et al., in prep.). Originally described from the Galapagos Rift, this worm was later found at most vent sites of the East Pacific Rise (EPR), but also on the northeastern Pacific ridge systems (Desbruyeres, 1997). However, our ongoing molecular studies suggest that specimens from the northeastern ridges (Gorda, Juan de Fuca and Explorer ridges) should be assigned to a new cryptic sister-species that is distinct from A. galapagensis but very closely related (Chevaldonne et al., in prep.). These related worms occupy distinct ridge systems that formerly were part of the Farallon-Pacific Ridge, which was disrupted by subduction under the North-American Plate about 28.5 MYA (Atwater, 1989; Severinghaus & Atwater, 1990). Thus, they provide a unique opportunity to investigate the processes that lead to allopatric speciation events between vent assemblages of both ridge systems (Tunnicliffe, 1988), and to calibrate the rate of molecular evolution in deep-sea annelids.

A new species of scale-worm, Lepidonotopodium jouinae, belonging to the sub-family Lepidonotopodinae (Polychaeta: Polynoidae) has been found in samples collected on deep-sea hydrothermal vent fields at the Azores Triple Junction on the Mid-Atlantic Ridge. It is the first species of Polynoidae described from the Mid-Atlantic Ridge hydrothermal vents. Other species of the same genus have been described from hydrothermal vents of the Pacific Ocean., L. jouinae sp. nov., appartenant à la sous-famille des Lepidonotopodinae, a été trouvée dans des échantillons récoltés sur les sites hydrothermaux profonds du Point Triple des Açores sur la Dorsale Médio-Atlantique. C'est la première espèce de Polynoidae décrite provenant des sites actifs de la Dorsale Médio-Atlantique. D'autres espèces du même genre ont été décrites dans la faune des sources hydrothermales de l'Océan Pacifique.

The polychaete family Polynoidae (scale-worms) is well-represented at deep sea hydrothermal vents. Most species are free-living in a wide range of habitats: from high-temperature hydrothermal `chimney' walls to diffuse venting areas. Conversely, species of the genus Branchipolynoe live inside the mantle cavity of vent and seep mytilids. Specimens, morphologically close to Branchipolynoe seepensis, have been reported from all the known vent areas on the Mid-Atlantic Ridge (MAR), with varying infestation rates (0¿6 individuals per host). Reproductive tract, gametogenesis and population structures were examined for specimens from the Lucky Strike vent field (MAR) in order to test whether this species displays dwarf males, protandric hermaphroditism or differential mortality between males and females. Observations of histological sections reveal the presence of fully developed ovaries in females which originate ventrally in segments 7¿9 and of an unusual genital tract in which both sperm and mature oocytes are stored. Oogenesis is intraovarian and quasi-continuous. The vitellogenic oocytes are only free in the coelom at their terminal growing stage and are then transferred into an ovisac through spermathecae. The species displays an external sexual dimorphism in the number of genital papillae and the shape of the pygidial appendages. Sex ratios showed significant deviations from a 1:1 expected ratio, in favour of females. The modal decompositions of size¿frequency histograms show the occurrence of three modes in females and only two modes in males, indicating discrete breeding periods. The two first modes were not significantly different between males and females. These results indicate that B. seepensis forms heterosexual pairs and uses internal fertilization to reproduce during discrete spawning periods. Differential mortality between males and females is likely to shape size-histograms as observed by preventing males from reaching the female proportions. Such an observation could be a result of either cannibalism on larger males, small sizes facilitating the male escape, or natural predation when males move from one bivalve to another to breed.

A new species of scale-worm, Lepidonotopodium atalantae, belonging to the sub-family Lepidonotopodinae (Polychaeta: Polynoidae) has been found in samples collected on the deep-sea hydrothermal vent sites of 9 degrees N and 13 degrees N on the East Pacific Rise. It is mainly characterized by elytra, regularly ornamented on their posterior border, and very long anal cirri. This is the fifth species of Lepidonotopodium, all belonging to the deep-sea hydrothermal vent fauna., Lepidonotopodium atalantae sp. nov., appartenant à la sous-famille des Lepidonotopodinae, a été trouvée dans des échantillons récoltés sur les sites hydrothermaux profonds de 9°N et 13°N sur la dorsale du Pacifique oriental. Elle se distingue principalement par ses élytres portant des ornementations régulières sur leur bord postérieur et par de très longs cirres anaux. C'est la cinquième espèce de Lepidonotopodium, toutes appartenant à la faune des sources hydrothermales profondes.

The objective of this study is to describe the chemical and physical environment surrounding the vent organisms at the Genesis site (EPR, 2640 m). The main chimney is colonized by Riftia pachyptila, fishes Zoarcidae and crabs Bythograeidae. The top of the smoker is covered with tubes of polychaetes Alvinellidae, the frontier zone by limpet gastropods. Temperature measurements and water sampling were made on an axis along the chimney. The environment was characterized using relationships between chemical concentrations and temperature to provide a chemo-thermal model of the site. Discrete temperature ranges were 1-1.6 degrees C in sea water, 1.6-10 degrees C among Riftia plumes (up to 25 degrees C at the tube base), 7-91 degrees C close to the alvinellid tubes, fluid emission was 262-289 degrees C. This study describes the habitat of Alvinellidae emphasizing its chemical (Sigma S [H2S + HS- + S-2-] 3-300 mu mol l(-1), CO2 3.5-6 mmol l(-1), pH 5.7-7.5) and thermal specificities compared to the Riftia ones (Sigma S 4-12 mu mol l(-1); CO2 2-3.5 mmol l(-1;) pH 5.8-7.7). The size of Riftia allowed us to define its environment at the organism (temperature gradient along the tube 0.5-1 degrees C cm(-1)) and population scales (temperature difference between organisms from the same clump: 10-20 degrees C). Such spatial heterogeneity may play a significant role in the animal physiology and calls for further investigations., Le but de ce travail est de décrire l’environnement physico-chimique des organismes hydrothermaux sur le site Genesis (EPR, 2 640 m). La cheminée centrale est colonisée par iftia pachyptila, des poissons Zoarcidae et des crabes Bythograeidae. Le sommet du fumeur est couvert de polychètes Alvinellidae, la zone frontière par des gastéropodes patelliformes. Un modèle reliant la température et la concentration en ΣS et CO2 est proposé. Les valeurs discrètes de températures s’échelonnent depuis 1-1,6°C dans l’eau de mer, 1,6-10°C autour de l’organe branchial de Riftia et jusqu’à 25°C à la base des tubes. Elles atteignent 7-91°C à proximité des alvinellidés et 262-289°C pour le fluide pur. Un environnement spécifique pour chaque communauté d’organismes est présenté : autour des Alvinellidae ΣS 3-300 µmol 1-1, CO2 3,5-6 mmol 1-1, pH 5,7-7,5 ; autour de Riftia pachyptila ΣS 4-12 µmol 1-1, CO2 2-3,5 mmol 1-1, pH 5,8-7,7. La taille de R. pachyptila a permis de préciser cet environnement à l’échelle de l’organisme (gradient de 0,5-1°C cm-1 le long du tube) et de la communauté (différence de 10-20°C au sein d’un même bouquet d’individus). Les travaux ultérieurs devront porter sur le rôle physiologique de cette hérérogénéité spatiale.

On July 14, 1997, in the Gulf of Mexico, a dense population of polychaete worms dwelling in methane hydrates associated with cold seeps was discovered and sampled at 538 meters depth. The worms belong to the family Hesionidae and represent a new species of the genus Hesiocaeca. They differ from the two previously described species by the shape of the prostomium, the shape of the setae and the presence of anal cirri., Le 14 juillet 1997, dans le Golfe du Mexique et par 538 mètres de fond, une population très dense de vers polychètes a été découverte, colonisant la surface de dépôts d'hydrates de méthane situés à proximité des zones de suintements froids d'hydrocarbures. Les spécimens récoltés appartiennent à la famille des Hésionidés et à une nouvelle espèce du genre Hesiocaeca. Cette espèce diffère des deux espèces précédemment décrites par la forme du prostomium, celle des soies et la présence d'urites bien développés.

Alvinella pompejana is a polychaetous annelid that inhabits high temperature environments associated with active deep-sea hydrothermal vents along the East Pacific Rise. A unique and diverse epibiotic microflora with a prominent filamentous morphotype is found associated with the worm's dorsal integument. A previous study established the taxonomic positions of two epsilon proteobacterial phylotypes, 13B and 5A, which dominated a clone library of 16S rRNA genes amplified by PCR from the epibiotic microbial community of an A. pompejana specimen. In the present study deoxyoligonucleotide PCR primers specific for phylotypes 13B and 5A were used to demonstrate that these phylotypes are regular features of the bacterial community associated with A. pompejana. Assaying of other surfaces around colonies of A. pompejana revealed that phylotypes 13B and 5A are not restricted to A. pompejana. Phylotype 13B occurs on the exterior surfaces of other invertebrate genera and rock surfaces, and phylotype 5A occurs on a congener, Alvinella caudata. The 13B and 5A phylotypes were identified and localized on A. pompejana by in situ hybridization, demonstrating that these two phylotypes are, in fact, the prominent filamentous bacteria on the dorsal integument of A. pompejana. These findings indicate that the filamentous bacterial symbionts of A. pompejana are epsilon Proteobacteria which do not have an obligate requirement for A. pompejana.

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