Éditeur(s) : HAL CCSD American Chemical Society
Résumé : International audience
Semivolatile organic compounds (SVOCs) are ubiquitous contaminants in indoor environments, emanating from different sources and partitioning among several compartments, including the gas phase, airborne particles, and settled dust. Nevertheless, simultaneous measurements in the three compartments are rarely reported. In this study, we investigated indoor concentrations of a wide range of SVOCs in 30 French dwellings. In settled dust, 40 out of 57 target compounds were detected. The highest median concentrations were measured for phthalates and to a lesser extent for bisphenol A, synthetic musks, some pesticides, and PAHs. Di(2-ethylhexyl)phthalate (DEHP) and diisononyl phthalate (DINP) were the most abundant compounds. A total of 34 target compounds were detected both in the gas phase and airborne particles. The highest concentrations were measured for diisobutyl phthalate (DiBP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and synthetic musks in the gas phase and for DEHP, DiBP, DBP, and DINP in the airborne particles. This is the first study on the indoor concentrations of a wide range of SVOCs in settled dust, gas phase, and airborne particles collected simultaneously in each dwelling.
ISSN: 0013-936X

hal-01118577
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01118577
PUBMED : 24588211
DOI : 10.1021/es405269q

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Over the last decades, numerous studies have emphasized the role of serpentinites in the subduction zone geodynamics. Their presence and role in subduction environments are recognized through geophysical, geochemical and field observations of modern and ancient subduction zones and large amounts of geochemical database of serpentinites have been created. Here, we present a review of the geochemistry of serpentinites, based on the compilation of ~ 900 geochemical data of abyssal, mantle wedge and exhumed serpentinites after subduction. The aim was to better understand the geochemical evolution of these rocks during their subduction as well as their impact in the global geochemical cycle. When studying serpentinites, it is essential to determine their protoliths and their geological history before serpentinization. The geochemical data of serpentinites shows little mobility of compatible and rare earth elements (REE) at the scale of hand-specimen during their serpentinization. Thus, REE abundance can be used to identify the protolith for serpentinites, as well as magmatic processes such as melt/rock interactions before serpentinization. In the case of subducted serpentinites, the interpretation of trace element data is difficult due to the enrichments of light REE, independent of the nature of the protolith. We propose that enrichments are probably not related to serpentinization itself, but mostly due to (sedimentary-derived) fluid/rock interactions within the subduction channel after the serpentinization. It is also possible that the enrichment reflects the geochemical signature of the mantle protolith itself which could derive from the less refractory continental lithosphere exhumed at the ocean-continent transition. Additionally, during the last ten years, numerous analyses have been carried out, notably using in situ approaches, to better constrain the behavior of fluid-mobile elements (FME; e.g. B, Li, Cl, As, Sb, U, Th, Sr) incorporated in serpentine phases. The abundance of these elements provides information related to the fluid/rock interactions during serpentinization and the behavior of FME, from their incorporation to their gradual release during subduction. Serpentinites are considered as a reservoir of the FME in subduction zones and their role, notably on arc magma composition, is underestimated presently in the global geochemical cycle.
ISSN: 0024-4937

hal-00903601
https://hal.archives-ouvertes.fr/hal-00903601
DOI : 10.1016/j.lithos.2013.05.019

Éditeur(s) : Elsevier Science Bv
Résumé : Fluid escape structures on the Nile Deep Sea Fan were investigated during the MEDIFLUX MIMES expedition in 2004. Mud volcanoes, pockmarks and authigenic carbonate structures were surveyed for the first time with a high-resolution deep-towed 75 kHz sidescan sonar and a 2-8 kHz Chirp sediment echosounder. In combination with existing multibeam bathymetry and detailed seafloor in situ geological observations, these new data allowed detailed seep analyses. About 60 gas flares were detected acoustically in the water column from the sidescan sonar raw data at water depths from 770 to 1700 m. These gas flares coincide at the seabed with 1) the centres of the mud volcanoes where mud is also extruded, 2) the borders of the mud volcanoes where the emitted gases contribute to the precipitation of authigenic carbonates, and 3) to the edges of broad sheets of authigenic carbonates. Subsurface sediments are commonly disturbed by ascending fluids throughout the delta, with an abundance of seep-related carbonate structures on the seafloor. The feeder channels below mud volcanoes, similar to the gas conduits below the widespread carbonate crust structures and pockmarks, are relatively narrow and, for the vast majority of them, do not exceed a few metres in diameter. The seeps on the Nile Deep Sea Fan clearly follow lineations on the seafloor that we can relate to faults. (C) 2010 Elsevier B.V. All rights reserved.
Marine Geology (0025-3227) (Elsevier Science Bv), 2010-09 , Vol. 275 , N. 1-4 , P. 1-19

Droits : 2010 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00013/12457/9766.pdf
DOI:10.1016/j.margeo.2010.04.003
http://archimer.ifremer.fr/doc/00013/12457/

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 :  
Previous studies in lowland tropical rainforests of French Guiana showed that, among non-N2-fixing trees, two groups of late successional species contrasting in their leaf 15N natural abundance coexist, suggesting two different main ways of nitrogen acquisition. Two abundant late-successional species typically co-occurring in rainforests in French Guiana, namely Eperua falcata and Dicorynia guianensis, were chosen as representative of each group. Stable isotope techniques and measurements of potentials of microbial N transformation were performed to assess to what extent leaf 15N natural abundance of these species could be related to (i) d15N signatures of soil mineral N sources and (ii) the capacity of soil to express nitrification and denitrification (both processes being directly involved in the balance between NH4 + and NO3 - ). Soil d15N-NH4 + was roughly similar to leaf d15N of D. guianensis (around 3.5%), suggesting a preferential use of NH4 +, whereas in E. falcata, leaf d15N values were closer to root d15N-NO3 _ values (0.2 and _2.0%, respectively), suggesting a preferential use of NO3 _. These differences in N source utilization were not accompanied by differences in availability in soil NO3 _ or in intensity of microbial functions responsible for soil N mineral evolution. However, (i) under both tree species, these functions showed clear spatial partitioning, with denitrification occurring potentially in soil and nitrification in the litter layer, and (ii) E. falcata fine roots colonized the litter layer much more strongly than D. guianensis fine roots. This strongly suggests that (i) the contrasted leaf d15N values found in the two late-successional species reveal distinct N acquisition strategies and (ii) the ability of roots to predominantly exploit the litter layer (E. falcata) or the soil (D. guianensis) may constitute an important explanation of the observed differences. A complementarity between tree species, based on mineral N resource partitioning (itself resulting from a spatially structured location of the microbial functions responsible for the balance between NH4 + and NO3 - ), can thus be supposed.
ISSN: 0038-0717

hal-01032035
https://hal.archives-ouvertes.fr/hal-01032035
DOI : 10.1016/j.soilbio.2007.09.011

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
Haplognathia ruberrima is a cosmopolitan gnathostomulid species found in sulfur bacterial mats in mangroves in Guadeloupe (French West Indies). Haplognathia ruberrima presents a d13C value lower than all measured meiofaunal grazers and lower than the available measured food sources of this environment. This low d13C value can not be due to specific ingestion of 13C-depleted methanogenic bacteria because abundances of those bacteria are reduced in surficial and deep sediments as revealed by d13C of bacterial fatty acid. According to scanning electron microscope observations, no bacterial ectosymbionts were observed at the surface of the gnathostomulids, and transmission electronmicroscope views revealed the absence of bacterial endosymbionts. Energy-dispersive X-ray spectroscopy analysis detected low levels of sulfur (0.32%+-0.8) in biological tissues of H. ruberrima, confirming the absence of thioautotrophic bacterial symbionts in these animals. Consequently, the low d13C value of H. ruberrima can not be due to the presence of sulfur-oxidizing symbionts but more probably to the selective and exclusive consumption of free-living, sulfuroxidizing bacteria
ISSN: 0173-9565

hal-01253239
https://hal.archives-ouvertes.fr/hal-01253239
DOI : 10.1111/maec.12296

Éditeur(s) : Pergamon-elsevier Science Ltd
Résumé : Metazooplankton abundance, biomass (<80 mu m, 200-500 mu m and >500 mu m) and community structure in the Ahe atoll were studied together with their relationships with environmental factors (temperature, salinity, wind) and trophic factors (phytoplankton, bacteria, heterotrophic nanoflagellates (HNF) and ciliates) during three periods in 2008-2009. Meroplankton, mainly bivalve and gastropod larvae, was dominant. Holoplankton was dominated by copepods, the main species being Oithona spp., Paracalanus parvus, Clausocalanus spp., Corycaeus spp., Acartia fossae and Undinula vulgaris. The results suggest a clear wind influence on the structure and horizontal distribution of the zooplankton communities. The metazooplankton appeared to be controlled mainly by food resources, suggesting a bottom-up control. The low nanophytoplankton biomass in contrast to the high abundance of picophytoplankton, HNF and nano-particle grazers (mainly Oithona spp., Paracalanus and bivalve larvae) highlighted the importance of the microbial loop in the food web. (C) 2012 Elsevier Ltd. All rights reserved.
Marine Pollution Bulletin (0025-326X) (Pergamon-elsevier Science Ltd), 2012 , Vol. 65 , N. 10-12 , P. 538-548

Droits : 2012 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00101/21207/19419.pdf
DOI:10.1016/j.marpolbul.2012.01.025
http://archimer.ifremer.fr/doc/00101/21207/

Éditeur(s) : HAL CCSD National Academy of Sciences
Résumé : International audience
Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of similar to 12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 size-fractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.
ISSN: 0027-8424

hal-01545320
https://hal.archives-ouvertes.fr/hal-01545320
DOI : 10.1073/pnas.1509523113

Éditeur(s) : Inter-research
Résumé : Ecosystem-based management (EBM) requires more extensive information than single-species management. Active underwater acoustic methods provide a means of collecting a wealth of ecosystem information with high space-time resolution. Worldwide fisheries institutes and agencies are carrying out regular acoustic surveys covering many marine shelf ecosystems, but these data are underutilized. In addition, more and more acoustic data collected by vessels of opportunity are becoming available. To encourage their use for EBM, we provide a brief introduction to acoustic and complementary data collection methods in the water column, and review current and potential contributions to monitoring population abundance and biomass, spatial distributions, and predator-prey relationships. Further development of acoustics-derived indicators is needed. We review and propose indicators for assessing and monitoring zooplankton, population dynamics of fish and other nekton, and changes in diversity and food-web functioning. Acoustic methods have the potential to make a strong contribution to EBM. Evaluation of new indicators and suitable reference points in different ecosystems are the current challenges.
Marine Ecology-progress Series (0171-8630) (Inter-research), 2011 , Vol. 442 , P. 285-301

Droits : 2011 Inter-research
http://archimer.ifremer.fr/doc/00073/18445/15972.pdf
DOI:10.3354/meps09425
http://archimer.ifremer.fr/doc/00073/18445/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Despite the impact of soil millipedes on litter fragmentation in tropical forests, there have been few studies dealing with factors determining their habitat preference in these ecosystems. In a natural secondary dry forest of Guadeloupe on Leptosol, two complementary studies were carried out in order to test the hypothesis that litter N-content strongly influences millipede distribution. Millipede abundance and species richness were described in the field under two tree species, Bursera simaruba and Pisonia subcordata, and were related to the chemical characteristics of their foliage. In addition, a laboratory experiment was done in order to assess millipede feeding preferences regarding the chemical characteristics of leaves from various species. Millipede abundance and species richness were significantly higher under P. subcordata than under B. simaruba, probably due to the higher N content of P. subcordata leaves. Moreover, millipedes fed preferentially on N-rich leaves. The present study confirms that there was a close correlation between the preferred food, its chemical composition and the local distribution of millipede populations.
ISSN: 0178-2762

hal-00495211
https://hal.archives-ouvertes.fr/hal-00495211
https://hal.archives-ouvertes.fr/hal-00495211/document
https://hal.archives-ouvertes.fr/hal-00495211/file/BFSO-D-08-00133-1.pdf
DOI : 10.1007/s00374-008-0321-3

Éditeur(s) : HAL CCSD Elsevier
Résumé : Hot collisional orogens are characterized by abundant syn-kinematic granitic magmatism that profoundly affects their tectono-thermal evolutions. Voluminous granitic magmas, emplaced between 360 and 270 Ma, played a visibly important role in the evolution of the Variscan Orogen. In the Limousin region (western Massif Central, France), syntectonic granite plutons are spatially associated with major strike-slip shear zones that merge to the northwest with the South Armorican Shear Zone. This region allowed us to assess the role of magmatism in a hot transpressional orogen. Microstructural data and U/Pb zircon and monazite ages from a mylonitic leucogranite indicate synkinematic emplacement in a dextral transpressional shear zone at 313 +/- 4 Ma. Leucogranites are coeval with cordierite-bearing migmatitic gneisses and vertical lenses of leucosome in strike-slip shear zones. We interpret U/Pb monazite ages of 315 +/- 4 Ma for the gneisses and 316 +/- 2 Ma for the leucosomes as the minimum age of high-grade metamorphism and migmatization respectively. These data suggest a spatial and temporal relationship between transpression, crustal melting, rapid exhumation and magma ascent, and cooling of high-grade metamorphic rocks.;Some granites emplaced in the strike-slip shear zone are bounded at their roof by low dip normal faults that strike N-S, perpendicular to the E-W trend of the belt. The abundant crustal magmatism provided a low-viscosity zone that enhanced Variscan orogenic collapse during continued transpression, inducing the development of normal faults in the transpression zone and thrust faults at the front of the collapsed orogen.
ISSN: 0040-1951

hal-00445260
https://hal.archives-ouvertes.fr/hal-00445260
DOI : 10.1016/j.tecto.2009.03.022

Éditeur(s) : HAL CCSD SpringerLink
Résumé : Trinucleotide microsatellites have proven to be the markers of choice in human genetic analysis because they are easier to genotype than dinucleotides. Their development can be more time-consuming due to their lower abundance in the genome. We isolated trinucleotide microsatellites in Norway spruce (Picea abies K.) using an enrichment procedure for the genomic-library construction. Here we report on the characterisation of 85 ATC microsatellite-containing clones, from which 39 markers were developed. Many of the clones showed the occurrence of tandem repeats of higher order than the trinucleotide ones, often resembling minisatellite repeats. The sequencing of a sample of the alleles at one of the loci revealed size homoplasy due to base substitutions within the microsatellite region. The presence of ATC motifs within repetitive sequence families was observed. We found a significant relationship between the level of polymorphism and the length of the microsatellite. The levels of variability for ATC trinucleotide markers were lower than those for dinucleotides, both when tested on all loci in a set of six individuals and on a subset of loci in four natural populations. This difference is most likely attributable to lower mutation rates for trinucleotide than for dinucleotide loci. The availability of markers with different mutation rates allows one to select the proper marker set to investigate population processes on different time scales.
Theoretical and Applied Genetics

hal-01032029
https://hal.archives-ouvertes.fr/hal-01032029
DOI : 10.1007/s00122-002-0986-1

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
This paper aims to decipher the thermal evolution of the Montagne Noire Axial Zone (MNAZ,southern French Massif Central) gneiss core and its metasedimentary cover through determination ofP–T paths and temperature gradients. Migmatitic gneiss from the core of the dome record a clock-wise evolution culminating at 725 25 °C and 0.8 0.1 GPa with partial melting, followed by adecompression path with only minor cooling to 690 25° C and 0.4 0.1 GPa. Field structuralanalyses as well as detailed petrological observations interpreted in a petrogenetic grid indicate thatthe cover sequence experienced LP-HT metamorphism at <0.4 GPa. Apparent thermal gradientswithin the cover were determined with garnet–biotite thermometry and Raman Spectroscopy on Car-bonaceous Matter. High-temperature apparent gradients (e.g. 530 °C km1 along one transect) areexplained by late brittle–ductile extensional shearing evidenced by phyllonites that post-date peakmetamorphism. In areas where normal faults are less abundant and closely spaced, gradients of 20to 50 °C km1 are calculated. These gradients can be accounted for by a combination of domeemplacement and ductile shearing (collapse of isotherms), without additional heat input. Finally, thethermal evolution of the MNAZ is typical for many gneiss domes worldwide as well as with otherLP-HT terranes in the Variscides.
ISSN: 0263-4929

Droits : http://creativecommons.org/licenses/by-nc-nd/
insu-01290388
https://hal-insu.archives-ouvertes.fr/insu-01290388
https://hal-insu.archives-ouvertes.fr/insu-01290388/document
https://hal-insu.archives-ouvertes.fr/insu-01290388/file/jmg12188.pdf
DOI : 10.1111/jmg.12188

Éditeur(s) : HAL CCSD IOP Publishing
Résumé : Radioactive pollutants are naturally present in microelectronic device materials and can be an issue for the reliability of devices. The main concern is alpha emitters that produce high-energy particles (a few MeV) that ionize the semiconductor and then trigger soft errors. The question is to know what kinds of radionuclides are present in the device, their location in the device and the abundance of each species. In this paper we describe tools that are required to address the issue of radioactive pollutants in electronic devices.
ISSN: 0268-1242

hal-01504448
https://hal.archives-ouvertes.fr/hal-01504448
DOI : 10.1088/1361-6641/aa5479

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
In the Caribbean, Pterocarpus officinalis swamp forest, a coastal freshwater wetland, has been locally transformed by human activities into Colocasia esculenta monoculture (under the swamp forest) or pasture (where deforestation has occurred). The aim of this study was to evaluate the impact of three land uses of this tropical wetland (swamp forest, C. esculenta monoculture and pasture) on soil abiotic and biological features. We hypothesized that increasing the level of ecosystem alteration by agricultural intensification would negatively impact soil chemical characteristics, soil fauna diversity and carbon mineralization. As expected, land use significantly affected soil characteristics and changes followed the increasing intensity of land use. The ‘undisturbed system’, that is swamp forest, was characterized by a large soil organic matter content, a high level of soil moisture, a small phosphorus content and a slightly lower pH. These characteristics were correlated with a small faunal abundance and diversity and slow carbon (C) mineralization. The ‘low disturbance system’, that is C. esculenta monoculture, was the closest to swamp forest characteristics and changes between the both systems principally concerned a very slight decrease in organic matter content and very small increase in C mineralization and Coleoptera diversity. By contrast, all parameters (soil chemical characteristics, C mineralization and faunal abundance and diversity) were impacted in the most intensive land-use, pasture. Our study confirmed that agricultural practices have an influence on soil fauna and C mineralization processes in wetlands. Moreover, our study suggested that a C. esculenta traditional agroecosystem under swamp forest cover could be considered as an ‘eco-friendly’ agricultural practice.
ISSN: 0266-0032

hal-01562423
https://hal.archives-ouvertes.fr/hal-01562423
DOI : 10.1111/sum.12273

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : There is broad consensus that the diversity of functional traits within species assemblages drives several ecological processes. It is also widely recognized that rare species are the first to become extinct following human-induced disturbances. Surprisingly, however, the functional importance of rare species is still poorly understood, particularly in tropical species-rich assemblages where the majority of species are rare, and the rate of species extinction can be high. Here, we investigated the consequences of local and regional extinctions on the functional structure of species assemblages. We used three extensive datasets (stream fish from the Brazilian Amazon, rainforest trees from French Guiana, and birds from the Australian Wet Tropics) and built an integrative measure of species rarity versus commonness, combining local abundance, geographical range, and habitat breadth. Using different scenarios of species loss, we found a disproportionate impact of rare species extinction for the three groups, with significant reductions in levels of functional richness, specialization, and originality of assemblages, which may severely undermine the integrity of ecological processes. The whole breadth of functional abilities within species assemblages, which is disproportionately supported by rare species, is certainly critical in maintaining ecosystems particularly under the ongoing rapid environmental transitions.
ISSN: 0962-8452

hal-01532639
https://hal.archives-ouvertes.fr/hal-01532639
DOI : 10.1098/rspb.2016.0084
PRODINRA : 384617

Éditeur(s) : HAL CCSD Paris : Muséum national d'histoire naturelle
Résumé : International audience
The decline of meso-predators such as reef sharks is a concern as such species can have importantecological roles in maintaining reef ecosystem resilience. Two field trips conducted in August 2010 and November2011 to the Chesterfield archipelago (Coral Sea) allowed us to assess the abundances and average sizes ofmedium-bodied Carcharhinidae with a specific focus on grey reef shark (Carcharhinus amblyrhynchos), throughfishing (46 hours of accumulated effort) and underwater visual censuses (25 hours of accumulated effort). Wefound low abundance and small average total length (TL) for all reef shark species, and in the case of the greyreef shark, an average abundance of 2.1 individuals/dive with the majority of animals less than 110 cm TL. Wecompared our findings with historical data and, given our low sampling effort, we so far hypothesise that a generalstrong decline in the reef shark populations may have occurred in this area, probably due to recent overfishing.The enforcement of conservation measures is strongly recommended among these remote reefs as well ascomplementary studies for confirming this hypothesis.
Le déclin de méso-prédateurs tels que les requins de récif pose problème dans la mesure où ces espèces peuventavoir un rôle important dans le maintien de la résilience des écosystèmes coralliens. Deux missions conduitesen août 2010 et novembre 2011 dans l’archipel des Chesterfield (mer de Corail) nous ont permis d’évaluer lesabondances et longueurs totales (LT) moyennes de Carcharhinidae côtiers, en particulier du requin gris (Carcharhinusamblyrhynchos), à partir de sessions de pêche (46 heures au total) et de comptages sous-marins (25 heuresau total). Nous avons globalement trouvé de très faibles abondances et tailles moyennes avec, spécifiquementpour le requin gris, une abondance moyenne de 2,1 individus/plongée et une majorité d’animaux avec des LTinférieures à 110 cm. Nous avons comparé ces résultats à des données historiques et, étant donné certaines limitesde notre échantillonnage, nous nous cantonnons à poser l’hypothèse d’un déclin généralisé des populationsde requins de récifs dans cette zone, probablement dû à la surpêche. La mise en oeuvre effective de mesures deconservation est fortement recommandée au sein de ces récifs éloignés, de même que des études complémentairespour confirmer cette hypothèse.
ISSN: 0399-0974

hal-01281158
https://hal-univ-perp.archives-ouvertes.fr/hal-01281158

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Highly siderophile element concentrations (HSE: Re and platinum-group elements (PGE)) are presented for gabbros, gabbroic eclogites and basaltic eclogites from the high-pressure Zermatt-Saas ophiolite terrain, Switzerland. Rhenium and PGE (Os, Ir, Ru, Rh, Pt, Pd) abundances in gabbro- and eclogite-hosted sulphides, and Re-Os isotopes and elemental concentrations in silicate phases are also reported. This work, therefore, provides whole rock and mineral-scale insights into the PGE budget of gabbroic oceanic crust and the effects of subduction metamorphism on gabbroic and basaltic crust. Chondrite-normalised PGE patterns for the gabbros are similar to published mid-ocean ridge basalts (MORB), but show less inter-element fractionation. Mean Pt and Pd contents of 360 and 530 pg/g, respectively, are broadly comparable to MORB, but gabbros have somewhat higher abundances of Os, Ir and Ru (mean: 64, 57 and 108 pg/g). Transformation to eclogite has not significantly changed the concentrations of the PGE, except Pd which is severely depleted in gabbroic eclogites relative to gabbros (similar to 75% loss). In contrast, basaltic eclogites display significant depletion of Pt (>= 60%), Pd (>85%) and Re (50-60%) compared with published MORB, while Os, Ir and Ru abundances are broadly comparable. Thus, these data suggest that only Pt, Pd and Re, and not Os, Ir and Ru, may be significantly fluxed into the mantle wedge from mafic oceanic crust. Re-Os model ages for gabbroic and gabbroic eclogite minerals are close to age estimates for igneous crystallisation and high-pressure metamorphism, respectively, hence the HSE budgets can be related to both igneous and metamorphic behaviour. The gabbroic budget of Os, Ir, Ru and Pd (but not Pt) is dominated by sulphide, which typically hosts >90% of the Os, whereas silicates account for most of the Re (with up to 75% in plagioclase alone). Sulphides in gabbroic eclogites tend to host a smaller proportion of the total Os (10-90%) while silicates are important hosts, probably reflecting Os inheritance from precursor phases. Garnet contains very high Re concentrations and may account for >50% of Re in some samples. The depletion of Pd in gabbroic eclogites appears linked, at least in part, to the loss of Ni-rich sulphide. Both basaltic and gabbroic oceanic crust have elevated Pt/Os ratios, but Pt/Re ratios are not sufficiently high to generate the coupled Os-186-Os-187 enrichments observed in some mantle melts, even without Pt loss from basaltic crust. However, the apparent mobility of Pt and Re in slab fluids provides an alternative mechanism for the generation of Pt- and Re-rich mantle material, recently proposed as a potential source of Os-187-Os-186 enrichment.
ISSN: 0016-7037

hal-00420072
https://hal.archives-ouvertes.fr/hal-00420072
DOI : 10.1016/j.gca.2008.11.036

Éditeur(s) : NRC
Résumé : We studied relationships between tropical tunas (albacore (Thunnus alalunga), bigeye (Thunnus obesus), and yellowfin (Thunnus albacares)) and their biotic and abiotic environments through simultaneous acoustic observations of tunas and their prey, experimental longline catch, and oceanographic data in French Polynesia. Vertical habitat limits were estimated based on temperature and dissolved oxygen at capture data. We then studied tuna-micronekton relationships to better understand how tuna occupy the pelagic space, At a regional scale, tunas were more abundant in areas rich in prey with favourable hydrological conditions. Inside such areas, at the scale of a longline set, however, the longline catches were maximal only when prey were not distributed in dense patches (except for yellowfin tuna). We interpreted this result by considering that areas with high prey abundance attract tunas, but at a small scale, if prey are patchy distributed, tunas are more inclined to feed on them rather than on longline baits. The effect of patches on yellowfin tuna catch per unit effort (CPUE) does not appear likely because this species also feeds on the mixed layer, where patch density was very low. Not only hydrological characteristics, but also prey density and prey patch characteristics, should be taken into account for interpreting longline CPUE data.
Thunnus obesus, et thon à nageoires jaunes, Thunnus albacares) à leurs environnements biotique et abiotique. Pour ce faire, nous avons réalisé simultanément, en Polynésie Française, des observations acoustiques des thons et de leurs proies, des pêches à l'aide d'une palangre instrumentée et des mesures hydrologiques. Des limites d'habitat vertical des thons calculées sur la base de données de température et d'oxygène dissous sont proposées. Nous étudions ensuite les relations thons-micronecton afin de mieux comprendre la stratégie d'occupation de l'espace des thons. A une échelle régionale, les thons sont plus abondants dans des zones riches en proies avec des conditions hydrologiques favorables. Cependant, à l'intérieur de telles zones, les captures sont maximales lorsque les proies ne sont pas distribuées sous forme de patchs (sauf pour le thon à nageoires jaunes). Nous interprétons ces résultats en considérant que les zones de fortes abondances en proies attirent les thons mais, qu'à une échelle fine, si les proies sont distribuées sous la forme de patchs denses, les thons s'en nourrissent préférentiellement, au détriment des appâts de la palangre. Ces patchs ne semblent pas influencer les prises par unité d'effort (PUE) des thons à nageoires jaunes, probablement parce que cette espèce se nourrit également dans la couche homogène où la densité en patchs est très faible. Les caractéristiques hydrologiques, mais également la densité en proies et leur type de distribution, devraient donc être pris en compte pour l'interprétation des données de PUE.
Canadian journal of fisheries and aquatic sciences (0706-652X) (NRC), 2002-06 , Vol. 59 , N. 6 , P. 1002-1013

Droits : 2002 NRC Canada
http://archimer.ifremer.fr/doc/2002/publication-733.pdf
DOI:10.1139/F02-073
http://archimer.ifremer.fr/doc/00000/733/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Geographical distribution of parasite species can provide insights into the evolution and diversity of parasiticcommunities. Biogeography of marine parasites is poorly known, especially because it requires anunderstanding of host-parasite interactions, information that is rare, especially over large spatial scales.Here, we have studied the biogeographical patterns of dactylogyrid parasites of chaetodontids, one of themost well-studied fish families, in the tropical Indo-west Pacific region. Dactylogyrid parasites were collectedfrom gills of 34 butterflyfish species (n = 560) at nine localities within an approximate area of62 million km2. Thirteen dactylogyrid species were identified, with richness ranging from 6 to 12 speciesat individual localities. Most dactylogyrid communities were dominated by Haliotrema angelopterum orHaliotrema aurigae, for which relative abundance was negatively correlated (q = !0.59). Parasite richnessand diversity were highest in French Polynesia and the Great Barrier Reef (Australia) and lowest in Palau.Three biogeographic regions were identified based on dactylogyrid dissimilarities: French Polynesia,characterised by the dominance of H. angelopterum, the western Pacific region dominated by H. aurigae,and Ningaloo Reef (Australia), dominated by Euryhaliotrema berenguelae. Structure of host assemblageswas the main factor explaining the dissimilarity (turnover and nestedness components of the Bray-Curtis dissimilarity and overall Bray-Curtis dissimilarity) of parasite communities between localities,while environment was only significant in the turnover of parasite communities and overall dissimilarity.Spatial structure of localities explained only 10% of the turnover of parasite communities. The interactionof the three factors (host assemblages, environment and spatial structure), however, explained the highestamounts of variance of the dactylogyrid communities, indicating a strong colinearity between the factors.Our findings show that spatial arrangement of chaetodontid dactylogyrids in the tropical Indo-westPacific is primarily characterised by the turnover of the main Haliotrema spp., which is mainly explainedby the structure of host assemblages.
ISSN: 0020-7519

hal-01562156
https://hal-univ-perp.archives-ouvertes.fr/hal-01562156
DOI : 10.1016/j.ijpara.2017.01.006