Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
Rainbow is a dome-shaped massif at the 36°14′N nontransform offset along the Mid-Atlantic Ridge. It hosts three ultramafic-hosted hydrothermal sites: Rainbow is active and high temperature; Clamstone and Ghost City are fossil and low temperature. The MoMARDREAM cruises (2007, 2008) presented here provided extensive rock sampling throughout the massif that constrains the geological setting of hydrothermal activity. The lithology is heterogeneous with abundant serpentinites surrounding gabbros, troctolites, chromitites, plagiogranites, and basalts. We propose that a W dipping detachment fault, now inactive, uplifted the massif and exhumed these deep-seated rocks. Present-day deformation is accommodated by SSW-NNE faults and fissures, consistent with oblique teleseismic focal mechanisms and stress rotation across the discontinuity. Faults localize fluid flow and control the location of fossil and active hydrothermal fields that appear to be ephemeral and lacking in spatiotemporal progression. Markers of high-temperature hydrothermal activity (∼350°C) are restricted to some samples from the active field while a more diffuse, lower temperature hydrothermal activity (<220°C) is inferred at various locations through anomalously high As, Sb, and Pb contents, attributed to element incorporation in serpentines or microscale-sulfide precipitation. Petrographic and geochemical analyses show that the dominant basement alteration is pervasive peridotite serpentinization at ∼160–260°C, attributed to fluids chemically similar to those venting at Rainbow, and controlled by concomitant alteration of mafic-ultramafic units at depth. Rainbow provides a model for fluid circulation, possibly applicable to hydrothermalism at oceanic detachments elsewhere, where both low-temperature serpentinization and magmatic-driven high-temperature outflow develop contemporaneously, channeled by faults in the footwall and not along the detachment fault.
ISSN: 1525-2027

hal-01115281
https://hal.archives-ouvertes.fr/hal-01115281
https://hal.archives-ouvertes.fr/hal-01115281/document
https://hal.archives-ouvertes.fr/hal-01115281/file/Andreani_et_al-2014-Geochemistry%2C_Geophysics%2C_Geosystems.pdf
DOI : 10.1002/2014GC005269

Éditeur(s) : HAL CCSD Elsevier
Résumé : The seismic characteristics of focused fluid-related features such as pockmarks and carbonate build-ups on the Nigerian continental slope have been investigated using complementary seismic data sets (reprocessed 3D exploration data and 2D Very High Resolution hull-mounted and near-bottom seismic data) coupled with the results of previous studies (sedimentological, geotechnical and geochemical analyses).The results show different types of fluid-related features within the hemipelagic phase of long duration (∼1 Myr) Turbidite/Hemipelagic cycles. They are the product of the disturbance of the hosting sediments following two main distinct processes: (1) no or low sediment deposition caused by fluid escape associated with seafloor settlement (benthic fauna, carbonate precipitation, gas hydrate formation) and (2) post-depositional erosion, caused either by fluid release (dewatering from underlying features such as channels and upward migration from a deep source) or by collapse (destabilisation of gas hydrates). The temporal evolution reveals a decrease in fluid flow during the hemipelagic deposition as witnessed by the decrease in methanogenic activity and by gas hydrate destabilisation. The spatial distribution of fluid-related features seems to be controlled by the type of fault (small fault or structural lineament).
ISSN: 0264-8172

hal-01685513
https://hal.archives-ouvertes.fr/hal-01685513
DOI : 10.1016/j.marpetgeo.2017.10.004

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 0040-1951

hal-00843380
https://hal-mines-paristech.archives-ouvertes.fr/hal-00843380
DOI : 10.1016/j.tecto.2013.05.043

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Understanding how communities respond to natural disturbances is fundamental to assess the mechanisms of ecosystem resistance and resilience. However, ecosystem responses to natural disturbances are rarely monitored both through space and time, while the factors promoting ecosystem stability act at various temporal and spatial scales. Hence, assessing both the spatial and temporal variations in species composition is important to comprehensively explore the effects of natural disturbances. Here, we suggest a framework to better scrutinize the mechanisms underlying community responses to disturbances through both time and space. Our analytical approach is based on beta diversity decomposition into two components, replacement and biomass difference. We illustrate this approach using a 9-year monitoring of coral reef fish communities off Moorea Island (French Polynesia), which encompassed two severe natural disturbances: a crown-of-thorns starfish outbreak and a hurricane. These disturbances triggered a fast logistic decline in coral cover, which suffered a 90% decrease on all reefs. However, we found that the coral reef fish composition remained largely stable through time and space whereas compensatory changes in bio-mass among species were responsible for most of the temporal fluctuations, as outlined by the overall high contribution of the replacement component to total beta diversity. This suggests that, despite the severity of the two disturbances, fish communities exhibited high resistance and the ability to reorganize their compositions to maintain the same level of total community biomass as before the disturbances. We further investigated the spatial congruence of this pattern and showed that temporal dynamics involved different species across sites; yet, herbivores controlling the proliferation of algae that compete with coral communities were consistently favored. These results suggest that compensatory changes in bio-mass among species and spatial heterogeneity in species responses can provide further
ISSN: 1932-6203

hal-01212344
https://hal-univ-perp.archives-ouvertes.fr/hal-01212344
https://hal-univ-perp.archives-ouvertes.fr/hal-01212344/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01212344/file/journal.pone.0138696.pdf
DOI : 10.1371/journal.pone.0138696

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The detailed morphology and internal structure of the Calabrian accretionary wedge and adjacent Eastern Sicily margin are imaged in unprecedented detail by a combined dataset of multi-beam bathymetry and high-resolution seismic profiles. The bathymetric data represent the results of 6 recent marine geophysical surveys since 2010 as well as a compilation of earlier surveys presented as a 2 arc-sec (60 m) grid. Several distinct morpho-tectonic provinces are identified including: the deeply incised Malta–Hyblean Escarpment, numerous submarine canyons, broad regions of relatively flat seafloor dominated by fields of sediment waves, the gently undulating anticlinal fold-and-thrust belts of the external Calabrian accretionary wedge and the adjacent portion of the Western Mediterranean Ridge. The Calabrian arc can be divided into 4 domains (from SE to NW): 1) the undeformed Ionian abyssal plain, 2) the external evaporitic wedge, 3) the internal clastic wedge, 4) the Calabrian backstop (Variscan crystalline basement). The Calabrian accretionary wedge can also be divided laterally into two major lobes, the NE- and the SW lobes, and two minor lobes. The kinematics of the limit between the two major lobes is investigated and shown to be sinistral in the external (evaporitic) wedge. A network of radial slip lines within the southernmost external wedge unequivocally demonstrate ongoing dextral displacement of a rigid indenter (representing the corner of the clastic wedge) into the evaporitic wedge thereby confirming the geodynamic model of an active lateral slab tear fault here off eastern Sicily. The slab tear produces a series of major sub-parallel dextral strike-slip faults offshore Mt. Etna and south of the Straits of Messina consistent with the relative motions between Calabria and the Peloritan domain (NE Sicily). Abundant strike-slip faulting, and wide-spread folding and thrusting observed throughout the entire accretionary wedge, indicate regional shortening between the Ionian abyssal plain (foreland) and the Calabrian–Peloritan backstop caused by active subduction.
ISSN: 0012-821X

hal-01523990
https://hal.archives-ouvertes.fr/hal-01523990
DOI : 10.1016/j.epsl.2016.12.020

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : International audience
After the January 12, 2010, Haiti earthquake, we deployed a mainly offshore temporary network of seismologic stations around the damaged area. The distribution of the recorded aftershocks, together with morphotectonic observations and mainshock analysis, allow us to constrain a complex fault pattern in the area. Almost all of the aftershocks have a N‐S compressive mechanism, and not the expected left‐lateral strike‐slip mechanism. A first‐order slip model of the mainshock shows a N264°E north‐dipping plane, with a major left‐lateral component and a strong reverse component. As the aftershock distribution is sub‐parallel and close to the Enriquillo fault, we assume that although the cause of the catastrophe was not a rupture along the Enriquillo fault, this fault had an important role as a mechanical boundary. The azimuth of the focal planes of the aftershocks are parallel to the north‐dipping faults of the Transhaitian Belt, which suggests a triggering of failure on these discontinuities. In the western part, the aftershock distribution reflects the triggering of slip on similar faults, and/or, alternatively, of the south‐dipping faults, such the Trois‐Baies submarine fault. These observations are in agreement with a model of an oblique collision of an indenter of the oceanic crust of the Southern Peninsula and the sedimentary wedge of the Transhaitian Belt: the rupture occurred on a wrench fault at the rheologic boundary on top of the under‐thrusting rigid oceanic block, whereas the aftershocks were the result of the relaxation on the hanging wall along pre‐existing discontinuities in the frontal part of the Transhaitian Belt.
ISSN: 0094-8276

insu-00643489
https://hal-insu.archives-ouvertes.fr/insu-00643489
https://hal-insu.archives-ouvertes.fr/insu-00643489/document
https://hal-insu.archives-ouvertes.fr/insu-00643489/file/GRL-haiti.2011.pdf
DOI : 10.1029/2011GL049799

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
The newly-desribed Centropyge cocosensis has long been considered a variant of the lemonpeel pygmy angelfish C. flavissima because of their overall similarity in color patterns. DiBattista and co-authors [J. Hered. 107 (2016) 647–653] recently contested the validity of C. cocosensis, based on arguments that are challenged here.
ISSN: 0022-1503

ird-01525431
http://hal.ird.fr/ird-01525431
http://hal.ird.fr/ird-01525431/document
http://hal.ird.fr/ird-01525431/file/Letter%20to%20Editor_JHered%20p%20haL.pdf
DOI : 10.1093/jhered/esx008

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Ciguatera Fish Poisoning (CFP) is a non-bacterial seafood poisoning well characterized in the remote archipelagos of French Polynesia, yet poorly documented in the Society archipelago, most notably on Moorea, the second most populated island in French Polynesia, which counts a high proportion of fishermen fishing on a regular basis. To address this knowledge gap, a holistic study of the ciguatera issue was conducted on Moorea. First, ciguatera risk was analysed in terms of incidence rate, fish species most commonly involved and risk stratification in Moorea lagoon based on 2007–2013 epidemiological data. A mean incidence rate of 8 cases per 10,000 inhabitants for the study period and an average under-reporting rate of 54% were found. Taking into account hospitalization and medication fees, and loss of productive days, the health-related costs due to CFP were estimated to be USD $1613 and $749 for each reported and unreported case, respectively, with an overall cost of USD $241,847 for the study period. Comparison of the present status of CFP on Moorea with a risk map established in the late 1970’s showed that the spatial distribution of the risk has stayed relatively stable in time, with the north shore of the island remaining the most prone to ciguatera. Evaluation of the current knowledge on CFP among different populations groups, i.e. fishermen, residents and visitors, was also conducted through direct and indirect interviews. About half of the fishermen interviewed were actually able to identify risky fishing areas. While, overall, the CFP risk perception in the fishing community of Moorea seemed accurate, although not scientifically complete, it was sufficient for the safe practice of their fishing activities. This may be due in part to adaptive responses adopted by 36% of the fishermen interviewed, such as the avoidance of either high-risk fishing sites or toxic species. At the residents and visitors’ level, the study points out a striking lack of awareness of the CFP issue among visitors, as compared to local residents. Indeed, less than 25% of Moorea visitors vs. an average of 98% in residents were aware of CFP or of its presence on the island. Interestingly, evaluation of the fish consumption preferences showed that 70% of visitors do not consume lagoon fish during their stay, not for fear of CFP, but mainly due to the lack of availability of these species in recreational facilities or because they have nutritional preference for pelagic fish. This lack of awareness, along with the report by several CFP patients of the consumption of fish species yet banned for sale, stress the need for improved communication efforts on this critical issue among both residents and visitors on Moorea. The implementation of a public outreach strategy is proposed, based on both existing information networks and low-cost communication actions through information displays at various strategic locations, e.g. Tahiti-Faa’a international airport, the ferry boat station, recreational facilities, as well as the major trading points on Moorea Island.
ISSN: 1568-9883

hal-01391648
https://hal-univ-perp.archives-ouvertes.fr/hal-01391648
DOI : 10.1016/j.hal.2016.10.003

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : International audience
A sediment core encompassing 3500 years of continuous sedimentation has been collected from a coastal lagoon located on the southwestern French Mediterranean coast. Lead concentrations and stable isotopes show that the sediments have recorded the three major periods of Pb pollution: the Etruscan-Greek-Roman period (650 BC to AD 50), the medieval period (AD 650 to AD 1450), and the modern period (from around AD 1850 to the present). These periods were separated by low pollution periods during the Dark Ages (between AD 50 and 650) and during the 16th century. From the end of the 19th century to the 1960s, Pb pollution increased exponentially. Coal combustion was the major source of Pb in the lagoon in the second half of the 20th century. Both the decrease in coal consumption and the ban on leaded gasoline resulted in a decrease in Pb pollution by a factor of 1.5 between 1973 and 1995. From 1991, sewage treatment plants and incinerators could be the major source of Pb. The average baseline Hg concentration from 1525 BC to AD 900 was 0.017 ± 0.003 μg g(-1) (n = 54). The Hg concentrations profile shows three major peaks: in AD 1150, AD 1660, and AD 1969, with the concentrations being respectively 8, 5, and 34 times higher than the baseline levels. The medieval peak (AD 1150) is attributed the medical use of Hg in the town of Montpellier and/or the burning of soil and vegetation. Noticeable Hg pollution was also detected during the 17th century in relation to gold and silver amalgamation in Europe. From the end of the 19th century, Hg concentrations increased exponentially until 1969. This modern pollution is attributed to the burning of coal.
ISSN: 0013-936X

halsde-00639280
https://hal.archives-ouvertes.fr/halsde-00639280

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
AimEcological connectivity is currently considered to be essential to enhance biodiversity conservation efforts and benefit adjacent areas. We evaluate the spatial structure of vulnerable marine benthic invertebrate populations based on connectivity to improve the placement of marine protected areas.LocationGulf of Lions, NW Mediterranean Sea.MethodsWe used a spatially explicit metapopulation model to explore how larval dispersal affects marine benthic invertebrate dynamics at local and regional scales. Minimum recruitment success (the proportion of larvae that settle in a site and survive between spawning and first reproduction, which is required to ensure species persistence) is proposed as a measure of vulnerability. Three contrasting simulations were constructed: closed versus connected populations, habitat loss versus recruitment failure disturbances and varying patterns of oceanographic connectivity. The rescue factor (the ratio of minimum recruitment success in connected and closed populations) quantified the decrease in vulnerability because of oceanographic connectivity.ResultsIn the Gulf of Lions, connectivity reduced population vulnerability by a rescue factor of 5.3. The minimum recruitment success for regional persistence decreased from 3% to 0.2% when species' life expectancies increased from 2 to 50 years. Connectivity enabled the spread of individuals over the entire region, but there were higher densities in sink sites, where low retention rates do not allow for local persistence (western tip of the gulf). Source sites, defined as those sites bringing metapopulation resistance to recruitment failure and stresses from habitat loss, were located in the centre of the gulf.Main conclusionsConnectivity drives the spatial structure of population density distribution and population vulnerability in the absence of any other structuring factor. In the Gulf of Lions, marine protected areas are located in population sinks; however; if protection measures were taken in the central part, populations would benefit throughout the region via the rescue effect.
ISSN: 1366-9516

hal-01341743
https://hal-univ-perp.archives-ouvertes.fr/hal-01341743
DOI : 10.1111/ddi.12254

Éditeur(s) : HAL CCSD
Résumé : International audience
Cumulative human impacts have led to the degradation of marine ecosystems and thedecline of biodiversity in the European and contiguous seas. Effective conservationmeasures are urgently needed to reverse these trends. Conservation must entail societalchoices, underpinned by human values and worldviews that differ between the countriesbordering these seas. Social, economic and political heterogeneity adds to the challenge ofbalancing conservation with sustainable use of the seas. Comprehensive macro-regionalcoordination is needed to ensure effective conservation of marine ecosystems andbiodiversity of this region. Under the European Union Horizon 2020 framework programme,the MarCons COST action aims to promote collaborative research to support marinemanagement, conservation planning and policy development. This will be achieved bydeveloping novel methods and tools to close knowledge gaps and advance marineconservation science. This action will provide support for the development of macro-regional and national policies through six key actions: to develop tools to analysecumulative human impacts; to identify critical scientific and technical gaps in conservationefforts; to improve the resilience of the marine environment to global change and biologicalinvasions; to develop frameworks for integrated conservation planning across terrestrial,freshwater, and marine environments; to coordinate marine conservation policy acrossnational boundaries; and to identify effective governance approaches for marine protectedarea management. Achieving the objectives of these actions will facilitate the integration ofmarine conservation policy into macro-regional maritime spatial planning agendas for theEuropean and contiguous seas, thereby offsetting the loss of biodiversity and ecosystemservices in this region.
Research Ideas and Outcomes

hal-01474085
https://hal-univ-perp.archives-ouvertes.fr/hal-01474085
https://hal-univ-perp.archives-ouvertes.fr/hal-01474085/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01474085/file/RIO_article_11884.pdf
DOI : 10.3897/rio.3.e11884

Éditeur(s) : HAL CCSD Wiley-VCH Verlag
Résumé : International audience
Bacterial biofilm development is conditioned by complex processes involving bacterial attachment to surfaces, growth, mobility, and exoproduct production. The marine bacterium Pseudoalteromonas sp. strain D41 is able to attach strongly onto a wide variety of substrates, which promotes subsequent biofilm development. Study of the outer-membrane and total soluble proteomes showed ten spots with significant intensity variations when this bacterium was grown in biofilm compared to planktonic cultures. MS/MS de novo sequencing analysis allowed the identification of four outer-membrane proteins of particular interest since they were strongly induced in biofilms. These proteins are homologous to a TonB-dependent receptor (TBDR), to the OmpW and OmpA porins, and to a type IV pilus biogenesis protein (PilF). Gene expression assays by quantitative RT-PCR showed that the four corresponding genes were upregulated during biofilm development on hydrophobic and hydrophilic surfaces. The Pseudomonas aeruginosa mutants unable to produce any of the OmpW, OmpA, and PilF homologues yielded biofilms with lower biovolumes and altered architectures, confirming the involvement of these proteins in the biofilm formation process. Our results indicate that Pseudoalteromonas sp. D41 shares biofilm formation mechanisms with human pathogenic bacteria, but also relies on TBDR, which might be more specific to the marine environment.
ISSN: 1615-9853

hal-00864093
https://hal.archives-ouvertes.fr/hal-00864093
DOI : 10.1002/pmic.201100644

Éditeur(s) : HAL CCSD
Résumé : International audience
ISSN: 0248-076X

hal-01324138
https://hal-univ-perp.archives-ouvertes.fr/hal-01324138

Éditeur(s) : HAL CCSD AGU and the Geochemical Society
Résumé : International audience
Hydrothermal circulation at ultramafic-hosted sites supports a large variety of high-and low-temperature hydrothermal vents and associated ecosystems. The discovery of abundant fossil vesicomyid and thyasirid shell accumulations at the ridge crest, approximately 2.5 km east of the active Rainbow vent field on the Mid-Atlantic Ridge (MAR, 36 degrees 13'N), increased our knowledge regarding the diversity of vent communities at slow spreading ridges. Bivalve molluscs of the family Vesicomyidae were represented by the genus Phreagena. Here we present the first record of this genus in the Atlantic Ocean. This second vesicomyid species known from the MAR, Phreagena sp., was found to be associated with a Thyasira species that is affiliated with T. southwardae (at the Logatchev vent field on the MAR) and with T. vulcolutre (in the Gulf of Cadiz). These two clams have close relationships with seep taxa along the continental margin, and were likely associated with sedimented vent fields. delta O-18 and delta C-13 analyses of the shells suggested that the burrowing bivalve Thyasira could incorporate isotopically light carbon, derived from the oxidation of methane in the sediment, while the signature of Phreagena sp. shells denoted a different carbonate source. C-14 dating of the shells denoted that the hydrothermal activity in the Rainbow area began at least similar to 25.5 kyr BP, which is similar to the model of the hydrothermal vent field distribution that was proposed for the Logatchev hydrothermal site. The results provide new insight regarding the diversity of chemosynthetic fauna on the MAR over geologic time. Ultramafic-hosted, on-axis sedimented vent fields extend the range of habitats for chemosynthetic communities, underlying the need to further explore the geology of these types of environments on slow-spreading ridges and to determine their role in the ecology of deep-sea vent communities.
ISSN: 1525-2027

hal-00523467
https://hal.archives-ouvertes.fr/hal-00523467
https://hal.archives-ouvertes.fr/hal-00523467/document
https://hal.archives-ouvertes.fr/hal-00523467/file/G3-Lartaud-_-al.pdf
DOI : 10.1029/2010GC003079

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Fish mucus has important biological and ecologicalroles such as defense against fish pathogens andchemical mediation among several species. A non-targetedliquid chromatography–mass spectrometry metabolomicapproach was developed to study gill mucus of eight butterflyfishspecies in Moorea (French Polynesia), and theinfluence of several fish traits (geographic site and reefhabitat, species taxonomy, phylogeny, diet and parasitismlevels) on the metabolic variability was investigated. Abiphasic extraction yielding two fractions (polar and apolar)was used. Fish diet (obligate corallivorous, facultativecorallivorous or omnivorous) arose as the main driver ofthe metabolic differences in the gill mucus in both fractions,accounting for 23% of the observed metabolic variabilityin the apolar fraction and 13% in the polar fraction.A partial least squares discriminant analysis allowed us toidentify the metabolites (variable important in projection,VIP) driving the differences between fish with differentdiets (obligate corallivores, facultative corallivores andomnivorous). Using accurate mass data and fragmentationdata, we identified some of these VIP as glycerophosphocholines,ceramides and fatty acids. Level of monogeneangill parasites was the second most important factor shapingthe gill mucus metabolome, and it explained 10% of themetabolic variability in the polar fraction and 5% in theapolar fraction. A multiple regression tree revealed that themetabolic variability due to parasitism in the polar fractionwas mainly due to differences between non-parasitized andparasitized fish. Phylogeny and butterflyfish species werefactors contributing significantly to the metabolic variabilityof the apolar fraction (10 and 3%, respectively) buthad a less pronounced effect in the polar fraction. Finally,geographic site and reef habitat of butterflyfish species didnot influence the gill mucus metabolome of butterflyfishes.
ISSN: 0722-4028

hal-01563312
https://hal-univ-perp.archives-ouvertes.fr/hal-01563312
DOI : 10.1007/s00338-017-1554-0

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Seabirds concentrate nutrients from large marine areas on their nesting islands playing an important ecological role in nutrient transfer between marine and terrestrial ecosystems. Here we investigate the role of guano on corals reefs across scales by analyzing the stable nitrogen isotopic (delta N-15) values of the scleractinian coral Pocillopora damicornis on fringing reefs around two Pacific remote islets with large seabird colonies. Marine stations closest to the seabird colonies had higher nitrate + nitrite concentrations compared to more distant stations. Coral and zooxanthellae delta N-15 values were also higher at these sites, suggesting that guano-derived nitrogen is assimilated into corals and contributes to their nitrogen requirements. The spatial extent of guano influence was however restricted to a local scale. Our results demonstrate that seabird-derived nutrients not only spread across the terrestrial ecosystem, but also affect components of the adjacent marine ecosystem. Further studies are now needed to assess if this nutrient input has a positive or negative effect for corals. Such studies on remote islets also open fresh perspectives to understand how nutrients affect coral reefs isolated from other anthropogenic stressors.
ISSN: 2045-2322

hal-01681575
https://hal.archives-ouvertes.fr/hal-01681575
DOI : 10.1038/s41598-017-03781-y

Éditeur(s) : HAL CCSD
Résumé : International audience
The Socotra Island belongs to the southern rifted margin of the Gulf of Aden and occupied in Neoproterozoic times a key position to constrain the age and the nature of the largely hidden Neoproterozoic rocks of the Arabian plate. Our integrated field, petrographic, geochemical and geochrono- logical study in the Neoproterozoic rocks recognises three main successive events: (a) high-temperature ductile defor- mation and metamorphism forming probably in a compressive or transpressive regime; (b) mafic to intermediate intrusions as vertical sheets, kilometre-scale gabbro laccoliths, mafic dike swarm and lavas which present mainly a depleted arc signature with some evidences of evolution from an enriched-arc signature; (c) felsic intrusions mainly composed of highly potassic calc-alkaline and pinkish granites dated between 840 and 780 Ma. Relationships between the various petrographic types and U-Pb data suggest that these events occurred during a relatively short time span (80 Ma at max). Earlier high-temperature-low-pressure metamorphism stage as well as geochemical signature of mafic rocks show that development of Cryogenian formations of Socotra were controlled successively by an Andean-arc and a back-arc setting. These features cannot be easily reconciled with those of the Arabian-Nubian shield to the west of Socotra and of the Mozambique Belt to the south. We propose that the Socotra basement was developed at an active margin close to the India block in Cryogenian times.
Arabian Journal of Geoscience

hal-00647487
https://hal.archives-ouvertes.fr/hal-00647487
DOI : 10.1007/s12517-011-0476-3

Éditeur(s) : HAL CCSD International Phycological Society
Résumé : International audience
We studied a group of monoraphid diatom species (Bacillariophyceae, Achnanthidiaceae) found in the marine coastal environment of tropical islands of the Caribbean Sea, western Atlantic Ocean, Indian Ocean, South Pacific Ocean, the Adriatic Sea and the Black Sea. Based on light and electron microscope examination, Madinithidium was formally described as a genus new to science with the generitype defined as Madinithidium undulatum. The characteristic features of the valve structure are a strongly developed sternum and raphe sternum, transapical striae formed by a single areola (macroareolae) positioned in small depressions, elevated virgae and coaxial internal central raphe endings. Furthermore, the striae of both raphe and sternum valves are closed by finely perforated hymenes. Madinithidium and Achnanthidium species are difficult to identify correctly with light microscopy since their valves are small and finely structured. Four species recently described from the western Indian Ocean and assigned to Achnanthidium sensu lato – Achnanthidium capitatum, A. flexuistriatum, A. pseudodelicatissimum and A. scalariforme – possessed morphological features permitting their placement into Madinithidium gen. nov. The above-mentioned species were formally transferred to the new genus.
ISSN: 2330-2968

hal-01333391
https://hal-univ-perp.archives-ouvertes.fr/hal-01333391
DOI : 10.2216/14-21R2

Éditeur(s) : HAL CCSD National Academy of Sciences
Résumé : International audience
Among the deep-sea hydrothermal vent sites discovered in thepast 30 years, Lost City on the Mid-Atlantic Ridge (MAR) isremarkable both for its alkaline fluids derived from mantle rockserpentinization and the spectacular seafloor carbonate chimneysprecipitated from these fluids. Despite high concentrations ofreduced chemicals in the fluids, this unique example of a serpentinite-hosted hydrothermal system currently lacks chemosyntheticassemblages dominated by large animals typical of high-temperaturevent sites. Here we report abundant specimens of chemosymbioticmussels, associated with gastropods and chemosymbioticclams, in approximately 100 kyr old Lost City-like carbonates fromthe MAR close to the Rainbow site (36 °N). Our finding shows thatserpentinization-related fluids, unaffected by high-temperaturehydrothermal circulation, can occur on-axis and are able to sustainhigh-biomass communities. The widespread occurrence of seafloorultramafic rocks linked to likely long-range dispersion of ventspecies therefore offers considerably more ecospace for chemosyntheticfauna in the oceans than previously supposed
ISSN: 0027-8424

insu-01352929
https://hal-insu.archives-ouvertes.fr/insu-01352929
https://hal-insu.archives-ouvertes.fr/insu-01352929/document
https://hal-insu.archives-ouvertes.fr/insu-01352929/file/PNAS-2011-Lartaud-7698-703.pdf
DOI : 10.1073/pnas.1009383108

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Different marine habitats are characterised by different soundscapes. How or which differences may be representative of the habitat characteristics and/or community structure remains however to be explored. A growing project in passive acoustics is to find a way to use soundscapes to have information on the habitat and on its changes. In this study we have successfully tested the potential of two acoustic indices, i.e. the average sound pressure level and the acoustic complexity index based on the frequency spectrum. Inside and outside marine protected areas of Moorea Island (French Polynesia), sound pressure level was positively correlated with the characteristics of the substratum and acoustic complexity was positively correlated with fish diversity. It clearly shows soundscape can be used to evaluate the acoustic features of marine protected areas, which presented a significantly higher ambient sound pressure level and were more acoustically complex than non-protected areas. This study further emphasizes the importance of acoustics as a tool in the monitoring of marine environments and in the elaboration and management of future conservation plans. Coral reef ecosystems are among the most biologically diverse and complex marine ecosystems worldwide. In addition to their biological and ecological importance, coral reefs support major economic and physical functions (e.g. food production, tourism, biotechnology development and coastal protection) that are essential for many countries 1. Unfortunately, coral reefs are severely threatened: 20% of coral reefs can no longer be defined as such, another 25% are currently endangered and another 25% will be endangered by 2050 2. The frequency and severity of natural perturbations (e.g. cyclone, outbreaks of predators, particularly the crown-of-thorns starfish [COTS] Acanthaster planci) and anthropogenic perturbations (e.g. ocean acidification, pesticides, rising seawater temperatures) on coral reefs have greatly increased worldwide in the last three decades, and, as a consequence, reef communities (fish, coral and benthic invertebrates) have suffered unprecedented levels of decline 3,4
ISSN: 2045-2322

hal-01370610
https://hal-uvsq.archives-ouvertes.fr/hal-01370610
https://hal-uvsq.archives-ouvertes.fr/hal-01370610/document
https://hal-uvsq.archives-ouvertes.fr/hal-01370610/file/2016%20Sci.Rep.pdf
DOI : 10.1038/srep33326