The siliceous sponges and crinoids from the Chénier Ravine (France, Lower Callovian) are used here as biological markers to characterize the palaeoenvironment of the adjacent and contemporaneous La Voulte Lagerstätte that is remarkable for its unique soft-bodied fauna (e.g. worms, cirrate octopods, vampire squids). Sponges are abundant with dominant hexactinellids (80%) and lithistids (20%). Four lines of fossil evidence, supported by Recent analogues, indicate that this sponge community inhabited deepwater setting under dysphotic or aphotic conditions: (1) the dominance of hexactinellids; (2) the prevalence of cone shaped and erect morphologies that usually characterize Recent bathyal sponges; (3) the close similarities with Recent hexactinellids from the continental slope and; (4) the lack of encrustation by photophilic organisms. Attachments of sponges on hard substrate (e.g. crystalline basement) and their preservation in soft sediments (e.g. muds) indicate heterogeneous bottom conditions. The Chénier fauna also contains small stalked, asymmetric cyrtocrinid crinoids that are known to live on hard substrates in bathyal environments such as the SW Pacific steep seamounts. Convergent palaeoenvironmental clues obtained from both crinoids and siliceous sponges support the notion that the La Voulte area, including the La Voulte Lagerstätte, was situated in the upper part of the bathyal zone near the slope-basin transition with a water depth most probably exceeding 200 m. Supporting evidence from heterogeneous substrates and complex fault systems indicate a depositional environment along the external part of the slope where steep topographies and blocks usually favour the settlement of cyrtocrinid crinoids and hexactinellid sponges. La Voulte may therefore be one of the rare and extremely precious Mesozoic Lagerstätten to have fossilized a deep marine environment.

CALSUB, MUSORSTOM 6

The following results are deduced from radiocarbon and oxygen 18 curve datings obtained in Quaternary hemipelagic deposits cored off SW and SE slopes surrounding New-Caledonia: _ the radiometric age of total sediment (periplatform ooze + calcareous planctonic remains) exceeds that derived from the 8(18)0 curve yielded by Orbulina universa; _the rate of sedimentation strongly decreases, principally off southwestern coasts, during the last 16,000 years. This is a probable consequence of the screen-effect of the reefal Quaternary belt, enhanced by the Flandrian transgression.

BIOCAL, BIOGEOCAL

Submarine slopes and basins off New-Caledonia (South-Western Pacifie); morphology, biosedimentary environments, sedimentation During the Biocal deep-sea cruise off New-Caledonia, fauna and sediments were sampled and Seabeam maps were drawn. The first geological results are as follows: - block-faulting determines the morphology of the slopes, their erosion and the transport of sediments along them towards the Loyalty basin plain; - erosion is predominant in the studied areas of the western Caledonian slopes and along the slopes off Lifou island where the canyons are broad and scattered, whereas in front of the "passe de Thio", through the reefal barrier, a relatively high detritic influx transits through several narrow canyons; - the Loyalty basin has been explored along the Thio-Lifou transect; it exhibits a flat bottom and is fed mainly from the eastern Caledonian slopes by calcareous and argilaceous turbidites, which spread eastward over nearly 50 km and interfinger with hemipelagites; - the sediments are constituted by 5 distinct components: 15 to 50% of detritics from New-Caledonia (mainly clay minerais, iron oxydes and silicate minerais); 15 to 25% bioclastic silts and sands derived from the reefal ring and from the lagoon; mixed bioclasts ( 1 to 20%) furnished by benthonic communities living on the slopes and in the basin; planktonic debris (30 to 75%) with a dominant fraction composed of foraminifers and pteropods; and volcanic debris (0,5 to 10%). A sedimentation rate of about 6cm/1000 years (between 16000 and 5000 years B.P.)has been estimated from the explored sector of the Loyalty basin.

BIOCAL

Submarine slopes and basins off New-Caledonia (South-Western Pacifie); morphology, biosedimentary environments, sedimentation During the Biocal deep-sea cruise off New-Caledonia, fauna and sediments were sampled and Seabeam maps were drawn. The first geological results are as follows: - block-faulting determines the morphology of the slopes, their erosion and the transport of sediments along them towards the Loyalty basin plain; - erosion is predominant in the studied areas of the western Caledonian slopes and along the slopes off Lifou island where the canyons are broad and scattered, whereas in front of the "passe de Thio", through the reefal barrier, a relatively high detritic influx transits through several narrow canyons; - the Loyalty basin has been explored along the Thio-Lifou transect; it exhibits a flat bottom and is fed mainly from the eastern Caledonian slopes by calcareous and argilaceous turbidites, which spread eastward over nearly 50 km and interfinger with hemipelagites; - the sediments are constituted by 5 distinct components: 15 to 50% of detritics from New-Caledonia (mainly clay minerais, iron oxydes and silicate minerais); 15 to 25% bioclastic silts and sands derived from the reefal ring and from the lagoon; mixed bioclasts ( 1 to 20%) furnished by benthonic communities living on the slopes and in the basin; planktonic debris (30 to 75%) with a dominant fraction composed of foraminifers and pteropods; and volcanic debris (0,5 to 10%). A sedimentation rate of about 6cm/1000 years (between 16000 and 5000 years B.P.) has been estimated from the explored sector of the Loyalty basin. Oceanologica Acta, 1989, 11, 2, 131-140.

BIOCAL

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.

PANGLAO 2005

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. To cite this article: S. Duperron et al., C. R. Biologies 332 (2009). (C) 2008 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

PANGLAO 2005, SANTO 2006

The Lansdowne Bank is a partly drowned, isolated carbonate platform of around 4000 km2 located 300 km west of New Caledonia, in the SW Pacific Ocean, in water depths of 20 to 100 m. New multibeam bathymetric data, high resolution seismic reflection profiles and sediment gravity cores have been acquired on the bank top and adjacent slopes. This dataset reveals an almost continuous 4 km wide outer reef rim located in ca. 50 m water depth, surrounding a gently deepening inner platform, reaching up to 100 m water depth. The bank is bordered by very steep slopes showing numerous erosional morphologies such as canyons, channels and gullies. Along with these bypass features, spectacular bank margin collapses and slope failures are evidenced by up to 20 kmwide bank edge and intraslope failure scars, respectively, resulting in a typical “scalloped” geometry of the bank margin. These failure scars can lead to a complete collapse of the outer reef rim and impact subsequent reef development. Bank margin collapses are evidenced by hectometer to kilometer-scale blocks and debris shed on the slope, likely emplaced by rock fall/avalanching processes originating from the brittle failure of early cemented bank edge and upper slope sediments. In turn, failures triggered on the un-cemented mud-prone middle to lower slopes likely generate more cohesive, submarine debris flows that could be at the origin of erosive morphologies within the debris fields. Estimated individual failure volumes can reach up to 3 km3. Quaternary sea-level lowstands, that would have led to platform exposure, fracturing and karstification, and the development of an erosional sea cliff, as well as subsequent rising sea-level are believed to play a significant role in mass wasting event emplacement, yet “bottom up” submarine processes such as the upslope propagation of bypass morphologies by retrogressive headward erosion cannot be ruled out. In terms of geomorphic and stratigraphic constraints, the documented bank margin collapses affect a terrace located in 70 m water depth around the bank, which, depending on its age and origin, could provide a minimum age for collapse events. Finally, considering the shallow water depth of failure headscarps, the volumes of material involved in the slides as well as their vicinity to the nearby main island of New Caledonia, numerical simulations of the tsunamigenic potential of submarine slides have been performed. They showed that these slides would have been able to produce a meter-scale wave that would reach the northern coast of the island in less than an hour.

SEDLAB

This preliminary study deals with deep-sea biogenic traces and bioturbation off New Caledonia. All the data were obtained during the Biocal multidisciplinary (biology/geology) cruise aboard the oceanographie vessel Jean-Charcot (summer 1985). The studied area was chiefly along a transect extending from Thio to Lifou across the Loyalty basin. An initial inventory of superficial biogenic traces and sorne reflections concerning their distribution are given. Certain traces correspond to ichnogenera rarely or not found on modern oceanic floors but weil known in deep-sea fossil deposits (Paleodictyon, Urohelminthoida). In contrast with plain pelagie environments, the bioturbation is very variable. Indeed, the benthic life is frequently disturbed by turbidites and mud flows. Bioturbation is closely dependent on these sedimentary perturbations, and seems to be conditioned by the thickness and frequency of turbiditic deposits, size and shape of particles, and occurrence of a predepositional erosive phase. The effects of bioturbation have been analysed in connection with the obliteration of contacts between hemipelagites and turbidites and with the progressive disappearance of sorne thin turbiditic deposits. These observations and corresponding conclusions underline the interest of studying bioturbation for the analysis of fossil deposits containing hemipelagites and turbidites.

BIOCAL

BIOCAL, BIOGEOCAL

L'intérêt paléoenvironnemental des traces fossiles est bien connu des géologues. De même, l'importance de la bioturbation ou de la biocorrosion, dont elles sont l'expression, est considérable dans la dynamique sédimentaire. Or l'interprétation correcte de ces objets et de ces phénomènes ne peut progresser sans une meilleure connaissance de leurs équivalents actuels ou récents. Bien connus en milieu littoral, ils le sont beaucoup moins en milieu marin profond. D'où l'intérêt du programme ENVIMARGES qui a permis de multiples observations sur les pentes et dans les bassins au large de la Nouvelle Calédonie, dans un intervalle bathymétrique de moins de 100 m à plus de 3000 m. Les moyens d'investigation utilisés ont été nombreux et complémentaires. Les traces biologiques de surface ont ainsi été étudiées par observation directe depuis la soucoupe Cyana (CALSUB), par photographie automatique avec une caméra ponctuelle (BIOGEOCAL) ou commandée depuis la soucoupe (CALSUB), par film vidéo (CALSUB) et même par carottage grande surface Usnel (BIOCAL, BIOGEOCAL). Certaines traces profondes et les sédiments bioturbés ou biocorrodés ont été prélevés par carottage Usnel ou Kullenberg, dragage et chalutage (BIOCAL, BIOGEOCAL) ou directement par le bras préhensile de la soucoupe (CALSUB). Le but de ce travail est de rassembler les principales observations réalisées au cours des différentes campagnes et de présenter d'une manière synthétique et très simplifiée quelques résultats d'intérêt général.

BIOCAL, BIOGEOCAL, CALSUB

The deep-sea floor off New Caledonia was investigated during three successive multidisciplinary (biology/geology) cruises from 1985 to 1989: BIOCAL, BIOGEOCAL, and CALSUB. The main study area is the Loyalty Basin, which comprises a deep (2300 m) trough with a flat bottom and steep slopes topped by coral reefs. This basin is filled by a thick sequence of Recent hemipelagic muds and turbiditic sands, silts and muds. The slopes, which are strongly eroded, are locally covered by a thin layer of recent hemipelagic muds. Many biogenic traces occur in all muddy deposits. The trace assemblages of the basin bottom characterizes typical deep-sea ichnofacies with burrows, mounds, tracks, trails, and fecal castings. Two main ichnofacies are evidenced: a deep slope ichnofacies and a deep plain ichnofacies. The distribution of biogenic traces is probably controlled by the greater food supply on the slopes. The main trace makers that could be identified are holothurians and enteropneusts. Some traces, sampled by boxcoring, correspond to ichnogenera that are well known in fossil deposits (e.g., Paleodictyon and Urohelminthoida. One novel trace occurs on bathyal slopes, at depths exceeding 1300 m. It is made up of one mound and several holes forming a horseshoe ("Fer d Cheval") = the FC trace. It is strictly restricted to the slope, oriented according to the declivity, and very common between 1600 and 2000 m. So, this trace provides a very good environmental index. Bioturbation and erosion strongly hinder the preservation of these biogenic traces. Rapid burial by slightly or non destructive distal turbidites seems to be the only possible fossilization process.

BIOCAL, BIOGEOCAL, CALSUB

Bivalves belonging to the genera Idas and Adipicola were collected from wood fall environments in the west Pacific (Vanuatu islands) between 300 and 890 m depths in 2004. Bacterial symbionts were checked by three complementary techniques: histological and DAPI staining, in situ hybridization (FISH), and TEM. No bacteria were detected inside the gills of the two species, rejecting the endosymbiosis hypothesis. However, results from our study demonstrated the existence of ectosymbionts colonizing microvilli differentiated at the apical surface of the cells constituting the lateral zone of gill filaments. These ectosymbionts are gamma-Proteobacteria due to their strong hybridization with the specific probe GAM42; in contrast no hybridization was obtained from either gills or other host tissues by using the oligonucleotide probes specific to alpha- beta- and delta-Proteobacteria. Based on TEM observations, these Gram-negative bacterial symbionts are not methanotrophic due to the lack of concentric stacking of intracellular membranes in their cytoplasm. Such ectosymbionts may represent thioautotrophic bacteria as already described in various Mytilidae from hydrothermal vents and cold seeps. Unfortunately, no phylogenetic analysis could be done in this study to compare their DNA sequence to that of other marine invertebrate symbionts described to date.

BOA0

Wood falls in the deep sea have recently become the focus of studies showing their importance as nutrients on the deep-sea floor. In such environments, Crustaceans constitute numerically the second-largest group after Mollusks. Many questions have arisen regarding their trophic role therein. A careful examination of the feeding appendages, gut contents, and gut lining of Munidopsis andamanica caught with wood falls revealed this species as a truly original detritivorous species using wood and the biofilm covering it as two main food sources. Comparing individuals from other geographic areas from substrates not reported highlights the galatheid crab as specialist of refractory substrates, especially vegetal remains. M. andamanica also exhibits a resident gut microflora consisting of bacteria and fungi possibly involved in the digestion of wood fragments. The results suggest that Crustaceans could be full-fledged actors in the food chains of sunken-wood ecosystems and that feeding habits of some squat lobsters could be different than scavenging.

BOA1, KARUBAR, MUSORSTOM 10, MUSORSTOM 3, SALOMONBOA 3, SANTO 2006

Squat lobsters of the deep-sea genus Munidopsis are among the most regularly reported crustaceans associated with deep-sea wood falls. They are often thought to indirectly use these substrates for preying or scavenging wood-associated molluscs or annelids, albeit the species M. andamanica has been recently highlighted as a xylophagous specialist. In this work, we examined the feeding appendages, gut contents and gut lining of M. nitida, M. bispinoculata and M. pilosa specimens from natural sunken woods and compared them with specimens of the same species having survived and grown on different hard-to-digest substrates (i.e. woods, turtle shells and whale bones) experimentally submerged in the deep South Pacific. In both cases, all three species directly ingest large wood fragments deeply degraded by microorganisms, but M. nitida also feeds on experimentally submerged whale bone and turtle shell fragments. Munidopsis nitida is also the only species to host a resident gut microflora, but the bacterial morphotypes vary according to the ingested substrate. The results suggest that the three species are most probably opportunistic, bacterivorous detritivores and that M. nitida could be at the beginning of an evolutionary process towards xylophagy within the genus Munidopsis.

BOA1, CONCALIS, Restreint, SALOMONBOA 3, SANTO 2006

Sunken woods are abundant in deep oceanic environments, housing a huge faunal diversity. Studies on that substrate firstly focused on the associated organisms, but since a few years, identification of wood is a further aim. The purpose is to appreciate its degradation state, diversity, geographical origin and to identify specific associations between colonizing organisms and substrates. The first determinations were made on sunken woods from Taiwan/Philippines, the Vanuatu Archipelago, and the Mediterranean Sea. Samples' identification was based on histological studies. Different preparation techniques were used, depending on their degradation state. Detailed anatomy descriptions were made and compared to the native flora and the introduced species. Wood samples were well preserved. Diversified species were encountered, seemingly originating from local floras. In situ settlements of known wood species will enhance the knowledge of degradation and colonization degrees.

BOA0, MUSORSTOM 3, TAIWAN 2002

BOA0, SANTO 2006

When deposited in marine sediments, sunken wood and large animal remains can undergo sufficiently steady decay for oxygen to be depleted, attracting anaerobic living forms. Chemosynthetically living communities have recently been identified around whale skeletons and sunken woods. The phylogenetic resemblance and overlap in species of metazoans living in these habitats with those of highly reduced environments like hydrothermal vents and vent seeps has led to the hypothesis that deep-sea organic rich matter deposits could play a major role in the adaptation and evolution of chemoautotrophic communities at the ocean basin. Until present little attention has been paid to the free-living microbial diversity and activities in large organic falls like sunken woods and whale bones. In this communication we outline a series of methods to quantitatively study microbial biodiversity and degradation processes in sunken wood. Cellulose is the most abundant component of plant material and it can only be degraded by fungi and bacteria. We present results from cellulolytic activities in a long-term ex-situ experiment on samples from naturally and experimentally immersed sunken wood. We also have developed methods to quantitatively measure microbial cell numbers in wood chips. Further studies at the molecular level in combination with the methods reported here will broad our narrow knowledge on the microbial biofilms that develop on and within sunken woods and give clues on the ecological importance of these deep-sea organic islands.

BOA0

BOA0

During the CALSUB cruise, bathyal environments were explored off the New Caledonia corallian platfdrms (southwestern Pacific). Green algae were observed down to a depth of 1 IO m, and red algae down to 145 m. Algal blocks, pebbles and sands contribute to sedimentation to a depth of 400 m and beyond, and are mixed with autochthonous fossils and bioclasts produced by bathyal benthos. Epibathyal fauna suggests similarities with Jurassic and Cretaceous fauna of Tethyan margins (Nautilus, pleurotomarian gastropods, sponges, brachiopods and crinoids…). Richness and abundance of the benthos are the highest in areas where currents are frequent between 300 m and 700 m (sometimes 10 to 20 terebratulid brachiopods per m2 or dense populations of echinoderms entirely covering the substrate). Such currents induce erosion of' substrate or bioclastic accumulations. Biocorrosion seems to be very active in erosion processes, especially on hard grounds. Burrows and traces show the importance of sediment bioturbation on slopes. The occurrence on bathyal slope of some taphonomic processes previously known from geological series and generally considered as closely related lo shallow-water environments should be emphasized.

CALSUB

L'exploration de la faune profonde de NouvelleCalédonie a débuté par des campagnes d'essai de 1977 à 1979 sur des fonds de 200 m à 1000 m au large de la Grande Terre, de l'île des Pins et des îles Loyauté (Intès, 1978). A partir de 1985, elle s'est élargie et intensifiée avec les campagnes MUSORSTOM 4 à 6 et CHALCAL (Richer de Forges, 1990), BIOCAL, BIOGEOCAL et SMIB, complétées par des observations directes à l'aide de la soucoupe plongeante Cyana lors de la campagne CALSUB. Nous ne donnerons ici que les grands traits de l'étagement de la macrofaune et de la mégafaune benthique en insistant sur les observations directes insitu lors de la campagne CALSUB et sur la liaison avec les caractères du milieu.

CALSUB