Éditeur(s) : HAL CCSD Royal Society of Chemistry
Résumé : International audience
A series of graphene oxide (GO) and zinc partially substituted magnetite GO-Fe1-xZnxOy (0 ≤ x ≤ 0.285) catalysts were synthesised through a precipitation-oxidation method. The rate constants for the degradation of acid orange seven (AO7) proceeded at a significant faster rate under UV-irradiation (up to 670%) than the conventional heterogeneous Fenton-like reaction. The resultant catalysts were mesoporous, so there was no mass transfer limitation for AO7 to access active sites in the catalysts. Further, maximum increases of rate constant up to 220% occurred as the zinc molar concentration increased from x = 0 to x = 0.159. GO enhanced to incorporation of zinc into the combined metal oxide, whilst zinc limited crystal growth, thus forming smaller crystallite sizes. These features proved to be essential for the improved catalytic activity of the resultant catalysts. The optimised zinc molar value at x = 0.159 delivered the best catalytic activity. © The Royal Society of Chemistry 2016.
ISSN: 2046-2069

hal-01683215
https://hal.univ-antilles.fr/hal-01683215
DOI : 10.1039/c6ra04068c

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Convergent plate margins typically experience a transition from subduction to collision dynamics as massive continental blocks enter the subduction channel. Studies of high-pressure rocks indicate that tectonic fragments are rapidly exhumed from eclogite facies to mid-crustal levels, but the details of such dynamics are controversial. To understand the dynamics of a subduction channel we report the results of a petrochronological study from the central Sesia Zone, a key element of the internal Western Alps. This comprises two polymetamorphic basement complexes (Eclogitic Micaschist Complex and Gneiss Minuti Complex) and a thin, dismembered cover sequence (Scalaro Unit) associated with pre-Alpine metagabbros and metasediments (Bonze Unit). Structurally controlled samples from three of these units (Eclogitic Micaschist Complex and Scalaro-Bonze Units) yield unequivocal petrological and geochronological evidence of two distinct high-pressure stages. Ages (U-Th-Pb) of growth zones in accessory allanite and zircon, combined with inclusion and textural relationships, can be tied to the multi-stage evolution of single samples. Two independent tectono-metamorphic 'slices' showing a coherent metamorphic evolution during a given time interval have been recognized: the Fondo slice (which includes Scalaro and Bonze rocks) and the Druer slice (belonging to the Eclogitic Micaschist Complex). The new data indicate separate stages of deformation at eclogite-facies conditions for each recognized independent kilometer-sized tectono-metamorphic slice, between ∼85 and 60 Ma, with evidence of intermittent decompression (ΔP ∼ 0*5 GPa) within only the Fondo slice. The evolution path of the Druer slice indicates a different P-T-time evolution with prolonged eclogite-facies metamorphism between ∼85 and 75 Ma. Our approach, combining structural, petrological and geochronological techniques, yields field-based constraints on the duration and rates of dynamics within a subduction channel.
ISSN: 0022-3530

hal-01054335
https://hal.archives-ouvertes.fr/hal-01054335
DOI : 10.1093/petrology/egu029

Éditeur(s) : Springer
Résumé : The structure and summertime production of planktonic communities and the role of nondiatom planktonic cells were studied in coastal ponds, which are areas traditionally used for fattening and greening table-sized oysters. The abundance and biomass of nano-microplanktonic protists were determined at weekly intervals between February 1998 and February 1999 in a coastal pond without oysters in the French Atlantic coast near La Rochelle. The production of these microbiotas was determined in the summer period. The structure of plankton communities revealed the following observations: (1) microphytoplanktonic cells were mostly diatoms and dinoflagellates, (2) microzooplanktonic cells were mainly ciliates, and (3) nanoplanktonic cells were represented by pigmented (80-90% of the nanoplankton biomass) and colorless nanoflagellates. Diatoms were dominated by Naviculiineae. Dinoflagellates were dominated by Peridiniales. Oligotrichida were predominant in the ciliate community. Protist biomass levels were nine times higher from April to August (summer period 1033 mu g C L-1) than from September to March (winter period 114 mu g C L-1). Whatever the season, nanoflagellates were dominant in the water column (66 and 53% of the entire protist biomass in the summer and winter periods, respectively). Nanoflagellates represented the highest production of nano-microplanktonic communities (76% of carbon protist production) in the coastal pond in summer and showed the shortest generation time (7.1 h). Dinoflagellates came after nanoflagellates in production (19.5% of carbon protist production). Diatoms represented only a supplementary carbon resource available for higher trophic levels, whereas, until now, they were considered as the principal food of oysters in coastal ponds. Ciliates were a small source of carbon, but their growth rate was high. We suggest, first, that nanoflagellates represented the primary resource available in the pond and could constitute an important food resource for higher trophic levels, such as oysters, farmed in this type of pond. Overall, the system appeared to be more autotrophic than heterotrophic. Because inorganic nutrients are quickly exhausted in a semiclosed pond, pigmented flagellates dominated the carbon biomass, production and biomass of bacteria were high (thus, the microbial food web appeared to be active in this pond), and mixotrophy seemed to be an important trophic mode there.
Microbial Ecology (0095-3628) (Springer), 2007-05 , Vol. 53 , N. 4 , P. 537-548

Droits : 2007 Springer
http://archimer.ifremer.fr/doc/2007/publication-2641.pdf
DOI:10.1007/s00248-006-9087-z
http://archimer.ifremer.fr/doc/00000/2641/

Éditeur(s) : Elsevier
Résumé : The fining upward trend commonly described on levees of turbidite systems can be either attributed to changes in the sediment supply (external forcing = allocyclic) or changes in the spillover processes related to the growth of the levee (internal forcing = autocyclic). However the real causes remain speculative and difficult to demonstrate. Knowledge of vertical change in flow velocity (or grain size) in turbidity currents, of the turbidity current's height, as well as the growth rate of a levee are theoretically sufficient to describe the evolution of the grain size of a leveed turbidite sequence deposited by spillover processes. A piston core (MD99-2344) retrieved on the right levee of the Petit-Rhone neofan, sampled an 8.50 m long turbidite sequence containing more than one hundred turbidite beds and showing a marked fining upward trend. With the help of two profiles describing respectively the vertical velocity [Stacey, M. and Bowen, A.J., 1988b. The vertical structure of turbidity currents and a necessary condition for self-maintenance, Journal of Geophysical Research, pp. 3543-3553.] and the vertical grain size [Migeon, S., 2000. Dunes geantes et levees sedimentaires en domaine marin profond: approche morphologique, sismique et sedimentologique. PhD Thesis, Universite Bordeaux 1, Talence, France, 288 pp.] of a turbidity current, and a simple graphical method, we test several hypotheses on the height of the turbidity current and on the grain size at the bottom of the turbidity current and we attempt to reproduce the vertical fining upward trend. Our results show that the fining upward trend of the turbidite facies can be explained by the aggradation of the turbidite levee and the gradual confinement of the turbidity currents in the channel. This is, therefore, an autocyclical phenomenon. However a high frequency variability of the grain size overprinted on the trend cannot be explained by internal forcing and is believed to be allocyclical, depending on changes to the sediment input. The vertical grain-size profile allows more realistic flow conditions to be determined and shows that the vertical velocity profile does not describe the ability of turbidity current to transport sediment. This simple graphical method allows a better understanding and quantification of the forcing on turbidite deposits and improves description of the characteristics of the turbidity currents from the grain size of the deposits.
Marine Geology (0025-3227) (Elsevier), 2006-12 , Vol. 234 , N. 1-4 , P. 191-213

Droits : 2006 Elsevier
http://archimer.ifremer.fr/doc/2006/publication-2311.pdf
DOI:10.1016/j.margeo.2006.09.019
http://archimer.ifremer.fr/doc/00000/2311/

Éditeur(s) : Proceedings of the 6 th Annual Meeting of World Mariculture Society
Résumé : As no indigenous species of commercial penaeid shrimp live in the waters of French Po1ynesia, the pre1iminary step in deve10ping shrimp aquaculture was to obtain maturation and spawning in captivity. Five species have been investigated. Wi1d-caught juveni1es from the New Ca1edonia 1agoon (f. merguiensis, f. semisulcatus, ~. ensis) and post1arvae from the Ga1veston NMFS 1aboratory (P. aztecus) and Fujinaga Institute (f. japonicus) have been used to-obtain adu1t stock. Shrimps are reared in circu1ar tanks of 12 m3 with a continuous water circulation through a coral sand bed. Rate of exchange is from 1 to 3 times a day. Throughout the year water temperature is between 25 and 29 C, sa1inity around 34.5 ppt, and pH 8.2. Solar energy is reduced by shade covers. Artificial pellets of different composition are given as food. In these conditions we have obtained: 1) about 1,000 spawnings and two generations in captivity from September 1973 to September 1974 with f. merguiensis; 2) spawnings of ~. ensis in 1973; 3) four spawnings of f. japonicus in September 1974; 4) about 20 spawnings of P. aztecus, but only aftcr removing one eyestalk; 5) maturation signs in P. semizulcatus but no spawning. Experiments on larval rearing and growth of these species are in progress. [NOT CONTROLLED OCR]

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1975/acte-4406.pdf
http://archimer.ifremer.fr/doc/00000/4406/

Éditeur(s) : Pêche thonière et dispositifs de concentration de poissons, Caribbean-Martinique, 15-19 Oct 1999
Résumé : For most fisheries, increasing the local production of pelagic fish is the main objective of Fish Aggregating Devices (fads). This does not rule out the existence of a larger-scale impact, especially on the migratory behaviour of fish. The analysis of data collected during 25 experimental fishing surveys around Martinique between 1995 and 1997 has led to the hypothesis that fads influence the migratory behaviour of young dolphinfish. Unlike recent studies of dolphinfish migration in the Caribbean, which tend to show an annual migration pattern with a seasonal passage through the French West Indies, the experimental fishing surveys done over more than a year on a monthly basis on a single cohort, show that the migratory pattern of part of the regional stock could be disrupted. This analysis has made it possible to estimate an average growth rate for this species during the first year of life.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00042/15321/12635.pdf
http://archimer.ifremer.fr/doc/00042/15321/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : We conducted a rigorous test of tropical tree seedling microhabitat differentiation by examining microhabitat associations, survival and growth of established seedlings of ten tropical tree species representing a four-factor gradient in seed size. Eight microhabitat variables describing soil and light conditions were measured directly adjacent to each of 588 seedlings within twelve 10×100 m belt transects at Paracou, French Guiana, and at 264 reference points along the transects. From these measurements, we defined three principal components describing soil richness, soil softness and canopy openness. Six of ten species (in 9 of 30 total cases) were distributed non-randomly with respect to microhabitat along at least one principal component. However, few species demonstrated clear microhabitat specialization. All shifts in distribution relative to reference points were in the same direction (richer, softer soil). Furthermore, of 135 pairwise comparisons among the species, only 7 were significantly different. More than three-fourths of all seedlings (75.3%) survived over the 2-year monitoring period, but survival rates varied widely among species. In no case was the probability of survival influenced by any microhabitat parameter. Relative height growth rates for the seedlings over 2 years varied from -0.031 cm cm-1 year-1 (Dicorynia guianensis, Caesalpiniaceae) to 0.088 cm cm-1 year-1 (Virola michelii, Myristicaceae). In only 4 of 30 cases was height growth significantly associated with one of the three principal components. Because the conditions in this study were designed to maximize the chance of finding microhabitat differentiation among a group of species differing greatly in life history traits, the lack of microhabitat specialization it uncovered suggests that microhabitat partitioning among tropical tree species at the established seedling stage is unlikely to contribute greatly to coexistence among these species.
ISSN: 0029-8549

hal-01031928
https://hal.archives-ouvertes.fr/hal-01031928
DOI : 10.1007/s00442-004-1691-3

Éditeur(s) : Gauthier-Villars
Résumé : Echinoderms show phenotypic plasticity in which variation in environmental conditions elicit graded reaction norms of morphological change. With the sea urchin Strongylocentrotus purpuratus under laboratory conditions, decreases in available food caused decreases in dry weights of the gonad and gut coupled with increases in the mass of Aristotle's lantern and length of the demi-pyramids. Spine clipping caused increased spine growth as well as decreases in the gut and gonad masses. Survival rate remained unchanged over a range of feeding and clipping treatments. In the field, at Sunset Bay, Oregon, well-fed sea urchins, with relatively small demi-pyramids, showed survival rates similar to poorly fed sea urchins that had large demi-pyramids. The wide range of morphological change, coupled with the narrow range of-change in survival, suggests that morphological plasticity buffers survival and hence would increase fitness. Phenotypic plasticity shown by other sea urchins includes changes in the relative sizes of Aristotle's lantern in Diadema antillarum and Echinometra mathaei and seasonal variation in the density of pedicellariae in Echinus esculentus. Variation in body size of echinoids and asteroids in different habitats and variation in number of arms in crinoids also may be examples of adaptive plasticity. Seasonal atrophy of internal organs in the sea cucumber Parastichopus californicus has been interpreted as an adaptive response to food limitation but, given the nature of responses in other echinoderms, such an interpretation seems unlikely and the significance of seasonal atrophy of organs in holothurians remains unknown.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1996 , Vol. 19 , N. 3-4 , P. 347-355

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00094/20492/18187.pdf
http://archimer.ifremer.fr/doc/00094/20492/

Résumé : After 12 years of a difficult start, the sea bass (Dicentrarchus labrax) breeding projects are multiplying. Faced with the constraints presented by the sites used in the past, farming at sea seems to offer conditions more conducive to the growth and survival of the animals. The zootechnical data from the farm makes it possible to link the rate of growth and the thermal profile of the site. Risks and uncertainties still weigh heavily on aquafarming projects, but solutions such as insurance are helping to improve their economic feasibility. The economic and financial analysis comes up with good overall profitability of the project, even if the duration of the breeding cycle and the necessity to ensure a progressive increase in operating capacity make the start-up phase long and not very lucrative.
(OCR non controlé) Après 12 années d'un démarrage difficile, les projets d'élevage du loup (Dicentrarchus labrax) se multiplient. Face aux contraintes que présentent les sites utilisés par le passé, l'élevage en mer semble offrir des conditions plus favorables à la croissance et à la survie des animaux. Les données zootechniques de l'élevage permettent de mettre en relation la vitesse de croissance et le profil thermique du site. Risques et incertitudes pèsent encore lourdement sur les projets aquacoles, mais des solutions telles que l'assurance contribuent à améliorer leur faisabilité économique. L'analyse économique et financière conclut à une bonne rentabilité globale du projet même si la durée du cycle d'élevage et la nécessité d'assurer une montée en puissance progressive de l'exploitation rendent la phase de démarrage longue et peu rémunératrice.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/1989/rapport-2417.pdf
http://archimer.ifremer.fr/doc/00000/2417/

Éditeur(s) : PSIC 11 - 11th Pacific Science Inter-Congress : Pacific Countries and their Ocean: Facing Local and Global Changes / 2nd Symposium on French Research in the Pacific. March 2 - 6, 2009 Tahiti, French Polynesia.
Résumé : In aquaculture, Artemia nauplii are commonly used as live prey; and represent 40 % of the total aquaculture feed demands in the early stages. However, the production of Brine shrimp is very unstable from one year to another and in the late 90’s, only 20 % of the world aquaculture need was covered. An insufficient offer leads to higher prices of the Artemia cysts and consequently, the price of shrimp juveniles from hatchery. In New Caledonia, marine aquaculture is mainly based on the blue shrimp Litopenaeus stylirostris. From Zoea 3 to 10 days old post-larvae (P10), the shrimp are mainly fed with live preys. Eleven kilos of Artemia cyst are necessary for producing one million of P10. From a sanitary point of view, Artemia can be a virus carrier and Vibrio population increase is often detected in the larval rearing tank the day after the feeding with live prey. Up to now, Brine shrimp are delivered in excess but with the cost and sanitary problems, Saint-Vincent laboratory has started some experiments in order to optimise the use of Artemia in shrimp larval rearing. The first tests were conducted to determine the effect of the Artemia quantity on the growth and the survival rate at different post-larval stages (P8-P11, P5-P8 and M3-P3). It was shown that four to twelve times fold Artemia was necessary for P8-P11 compared to M3-P3. And it was also noticed that the “optimized”quantity of live food at M3-P3 was twice lower than the recommended amount of the hatchery feeding protocol in New Caledonia. A better knowledge of the real feed requirement in the early life of the blue shrimp will be helpful to decrease the cysts quantities used in shrimp hatcheries but also the associated sanitary impact. And further, these results will give data for developing formulated diets which will replace the live prey and will increase the biosecurity and the sustainability of the production of the blue juvenile shrimp in New Caledonia.
En aquaculture, les nauplii d’Artemia sont largement utilisés comme proies vivantes et représentent près de 40 % des besoins en aliments pour la production des stades précoces. Cependant, l’approvisionnement en Artemia peut fluctuer de façon importante d’une année sur l’autre. Ainsi vers la fin des années 90, la demande mondiale a pu être satisfaite seulement à hauteur de 20%. Les années avec une offre insuffisante correspondent à des augmentations importantes du cours mondial des cystes d’artemia avec des répercussions sur le prix des animaux juvéniles produits en écloserie. En Nouvelle-Calédonie, l’aquaculture marine est principalement basée sur la crevette bleue Litopenaeus stylirostris. Les larves de cette espèce, à partir du stade Zoé 3, se nourrissent essentiellement de proies vivantes. Ainsi pour produire un million de Post-larves de 10 jours il faut compter 11 kilos de cystes d’Artemia. Outre le problème posé par le coût, les artemii peuvent également représenter un risque sanitaire pour l’écloserie. En effet certaines souches sont infectées par des virus qui peuvent contaminer les crevettes et de façon plus générale l’introduction des artemii dans le volume d’élevage larvaire s’accompagne le plus souvent d’une flambée de la flore vibrionacée. Jusqu’à présent, les Artemii étaient distribuées en excès cependant du fait de leur coût et des risques sanitaires, le laboratoire de St Vincent a débuté un travail pour optimiser leur utilisation en production larvaire de crevette. Ainsi, nos premières expérimentation sur l’effet de la dose en artemii sur le développement et la survie des larves de crevettes ont permis de déterminer les rations optimales pour les stades larvaires P8-P11, P5-P8 et M3-P3. Nous avons ainsi montré que la ration de proies vivantes était 4 à 12 fois plus importante à P8-P11 qu’à M3-P3. Par ailleurs la dose optimale déterminée au cours de nos expérimentations était pour les stades M3-P3 deux fois moins élevée que celle préconisée par le protocole actuel des écloseries commerciales de Nouvelle-Calédonie. Nous voyons ainsi, qu’une meilleure compréhension des besoins alimentaires de la crevette au cours de son développement permettra de diminuer de façon substantielle les proies vivantes utilisées ainsi que le risque sanitaire associé. A terme, ces travaux donneront des bases au développement d’aliments inertes en remplacement des proies vivantes et à la production durable, en conditions de biosécurité, des crevettes bleues juvéniles pour la filière Calédonienne

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00198/30877/29245.pdf
http://archimer.ifremer.fr/doc/00198/30877/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Propagation energies for five examples of deformation bands in porous sandstones from four field sites in Nevada, Utah, and France were calculated by using the J-integral approach. Pure compaction bands that accommodate primarily closing displacements from the Valley of Fire (Nevada) site have a closing-mode band propagation energy of J I = 5.5 ± 1.6 kJ/m2. Shear-enhanced compaction bands having subequal amounts of normal (closing) and shear strains across them from the same site have propagation energies of J I = 6.11 ± 1.8 kJ/m2 and J II = 1.52 ± 0.5 kJ/m2 for closing and shearing modes respectively. Closing- and shearing-mode band propagation energies for shear-enhanced compaction bands from the Buckskin Gulch (Utah) site, 5.63 ± 1.7 and 1.91 ± 0.57 kJ/m2 and the Uchaux (France) site, 11.0 ± 3.3 and 2.35 ± 0.7 kJ/m2 respectively are comparable to the values for similar structures from the Valley of Fire site. Cataclastic deformation bands at the Orange (France) site accommodate significantly larger values of shear offset than do shear-enhanced compaction bands, with a ratio of shear to closing offset that exceeds 7. The calculated closing- and shearing-mode propagation energies for these shear bands, 17.8 ± 5.4 and 3.3 ± 1.0 kJ/m2 respectively are comparable to those for pure or shear-enhanced compaction bands deformed at approximately the same depth of burial. Strain softening of cataclastic compactional shear bands implies unstable shearing, whereas stable and perhaps strain-hardening shearing may be inferred for shear-enhanced compaction bands. Displacement-length scaling relations for shear-enhanced compaction bands of the form D∝L are consistent with the results and with suggestions of band thickening during growth obtained from bifurcation analyses and with field observations of shear zones in porous host rock.
ISSN: 0376-9429

hal-00750341
https://hal.archives-ouvertes.fr/hal-00750341
DOI : 10.1007/s10704-012-9730-2

Éditeur(s) : Université de Pau et des Pays de l'Adour
Résumé : In a context of decline of European eel (Anguilla anguilla L.) and search for biological markers of habitat use and quality, a multidisciplinary approach was engaged on the Adour estuary and its associated wetlands. Two axes were developed. The first axe aimed at highlighting the successive presence of the species in different ecosystems based on the otolith elemental composition. The second aimed at the evaluation of the chemical pressure underwent by eels based on the contaminant bioconcentration in soft tissues and the early molecular response to the chemical stress. With a view to the analyses of otolith elemental composition taking into account the 3D structure, the low elemental concentration in the matrix and keeping the finest spatial resolution, four micro sampling strategies and multi elemental analyses using femtosecond laser ablation ICP-MS were tested (crater, 1D scan, 2D scan, flash ablation). The strategy showing the best compromise according to the objectives (continuous recording, multi elemental approach) was applied on otolith of yellow eels from the Adour. The simultaneous use of Sr and Ba profiles, after validation, represents a new tool, easy, fast and reliable for the reconstruction of freshwater and brackish ecosystems use by eel avoiding misinterpretation due to vaterite inclusions. Three major behaviors were highlighted on the Adour: a residency in brackish water, a residency in freshwater and nomad behavior. The last one is illustrated by a shift to brackish water after three to four years spent in freshwater. Simultaneously, the study of inorganic and organic contamination of eel soft tissues showed that sampled wetlands are moderately contaminated. These results were confirmed by the first estimation, in wild conditions, of the early response to the chemical stress using the hepatic expression of CYP1A1 gene measured by real time RT-PCR. Conversely, in the downstream part of the Adour estuary, Hg loads in eels, especially methyl mercury, and PCBs analyses indicate values that need further investigations considering the European norms of consumption. The comparison of the different markers used (heavy metal and organochlorinated compounds contamination of soft tissues, condition index) support a lower quality of the estuary despite higher eel growth rate on this site. This study supports the use of numerous markers in integrated studies in order to understand and specify the relationships between eels and their continental growth zones.
Dans un contexte de déclin de l'anguille européenne (Anguilla anguilla L.) et de recherche de marqueurs biologiques retraçant la fréquentation des divers habitats et renseignant sur la qualité de ceux-ci, une approche pluridisciplinaire a été mise en place sur l'estuaire de l'Adour et ses zones humides. Deux axes ont été privilégiés. Le premier cherchait à visualiser la présence successive de l'espèce dans différents écosystèmes en se basant sur la composition élémentaire des otolithes. Le deuxième avait pour but d'évaluer la pression chimique inorganique et organique subie par l'anguille dans les zones d'études en s'appuyant sur la bioconcentration des contaminants dans les tissus mous et la réponse moléculaire précoce au stress chimique. En vue des analyses de la composition élémentaire des otolithes et pour répondre au mieux à la structure en trois dimensions, à la faible concentration des éléments dans la matrice tout en conservant une résolution spatiale la plus fine possible, quatre stratégies de micro-échantillonnage et d'analyses multiélémentaires par ablation laser femtoseconde ICP-MS ont été testées (cratère, scan 1D, scan 2D, ablation flash). La méthodologie présentant le meilleur compromis par rapport aux objectifs fixés (enregistrement continu, approche multiélémentaire) a ensuite été appliquée sur les otolithes d'anguilles jaunes du Bas-Adour. L'utilisation simultanée des profils continus de Sr et de Ba, après validation, constitue un outil facile d'utilisation, rapide et fiable pour reconstruire les historiques de fréquentation des différents écosystèmes estuariens et dulçaquicoles par l'anguille tout en s'affranchissant des problèmes potentiels liés aux inclusions de vatérite, un polymorphe du carbonate de calcium. Trois grands types de comportement ont pu être mis en évidence sur l'Adour : résidence en eau saumâtre, résidence en eau douce et nomadisme. Ce dernier est plus particulièrement illustré par un mouvement marqué vers l'eau saumâtre pour des individus ayant passé de trois à quatre ans dans l'eau douce. Parallèlement, l'étude de la contamination organique et inorganique des tissus mous de l'anguille a permis de déduire à la faible contamination des zones humides échantillonnées. La première estimation en condition naturelle de la réponse précoce au stress chimique par évaluation de l'expression hépatique du gène CYP1A1 par RT-PCR en temps réel confirme ces résultats. En revanche, dans la partie estuarienne aval de l'Adour, les niveaux en Hg, présent en majorité sous sa forme méthylée dans les anguilles, et l'analyse des PCBs indiquent des valeurs qui suscitent un examen plus approfondi au regard des normes européennes en vigueur. La confrontation des différents descripteurs (contamination des tissus mous par les métaux lourds et organochlorés, indice de condition) utilisés conforte la qualité moindre de la zone estuarienne malgré des performances de croissance de l'anguille favorisées sur ces sites. Ainsi, cette étude supporte l'intérêt de la mise en oeuvre de descripteurs multiples utilisés (niveaux de métaux lourds et organochlorés dans les tissus mous, réponse moléculaire au stress chimique, microchimie de l'otolithe, indice de condition, taux de croissance) dans des approches intégrées pour comprendre et préciser les relations existantes entre l'anguille et ses zones de croissance continentales.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2009/these-7381.pdf
http://archimer.ifremer.fr/doc/00000/7381/

Éditeur(s) : Elsevier Science Bv
Résumé : The main objective of this work was to establish the influence of sex, maturity and reproduction on the contamination of the demersal fish Merluccius merluccius by organochlorine compounds. Polychlorinated biphenyls (PCBs) and p,p'DDE were quantified in muscle, liver and gonads of female and male hakes collected in the Gulf of Lions in 2004 and 2005. Observed levels appeared higher than the population of the Bay of Biscay and lower than the population of the Thyrrenian Sea. Contaminant fingerprints were roughly constant whatever the studied organ and the hake biological condition. Concentrations varied significantly according to the sex and maturity of hakes. Mature specimens were more contaminated than immature, and males presented higher levels than females. This sex effect can be linked to a lower growth rate of males, and a contaminant elimination during female spawning. Gonadal contamination depends on the importance of lipid content and increases with the maturation degree. Although the main organ of energy and PCB storage is the liver, muscle appears as the main contributor to the gonad contamination. (C) 2009 Elsevier B.V. All rights reserved.
Science Of The Total Environment (0048-9697) (Elsevier Science Bv), 2009-12 , Vol. 408 , N. 2 , P. 304-311

Droits : 2009 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00000/11129/9317.pdf
DOI:10.1016/j.scitotenv.2009.10.004
http://archimer.ifremer.fr/doc/00000/11129/

Éditeur(s) : HAL CCSD Mineralogical Society of America
Résumé : International audience
To test if hydrogen incorporation by ionic diffusion can occur between a volatile-rich kimberlitic liquid and forsterite, results of high-pressure and high-temperature experiments using a piston-cylinder apparatus at 1200–1300 °C and 1 GPa for durations of 1 min, 5 h, and 23 h, are reported here. Kimberlitic liquid in the system CaO-MgO-Al2O3-SiO2-CO2-H2O and synthetic forsterite single crystals were chosen as a first simplification of the complex natural kimberlite composition. Unpolarized Fourier transform infrared spectroscopy was used to quantify the concentrations of OH in the crystallographically oriented forsterite. Scanning electron microscopy, electron backscattered diffraction, electron microprobe analyses, and transmission electron microscopy were performed to identify the run products. After 5 and 23 h, a forsterite overgrowth crystallized with the same orientation as the initial forsterite single crystal. The kimberlitic liquid has crystallized as micrometer-scale euhedral forsterite neocrystals with random crystallographic orientations, as well as a nanoscale aluminous phase and a calcic phase. Despite theoretical water-saturation of the system and long duration, none of the initial forsterite single crystals display signs of hydration such as hydrogen diffusion profile from the border toward the center of the crystal. Most likely, the presence of CO2 in the system has lowered the H2O fugacity to such an extent that there is no significant hydration of the starting forsterite single crystal or its overgrowth. Also, the presence of CO2 enhances rapid forsterite crystal growth. Forsterite growth rate is around 2 × 108 μm3/h at 1250 °C. These experimental results suggest a deep mantle origin of the high OH content found in natural mantle-derived xenoliths transported in kimberlites, as reported from the Kaapvaal craton. In agreement with previous studies, it also points out to the fact that significant hydration must take place in a CO2-poor environment.
ISSN: 0003-004X

hal-01217157
https://hal.archives-ouvertes.fr/hal-01217157
DOI : 10.2138/am-2015-5200

Éditeur(s) : EDP Sciences
Résumé : The degree to which larvae of the invasive American slipper limpet (Crepidula fornicata) and the Japanese oyster (Crassostrea gigas) may compete for food was examined during 2003 in the laboratory. Larval microalgae uptake, growth and mortality were compared for larvae fed each of six species of unicellular algae, ranging in length from 2 to 10 mu m. Tested diets included the two flagellates Tetraselmis chui (Prasinophyceae) and Isochrysis affinis galbana (T-ISO, Haptophyceae), one member of the Chlorophyceae (Nannochloris atomus), and three diatom species (Chaetoceros calcitrans forma pumilum, Chaetoceros gracilis, Skeletonema marino). We found that the limpet larvae ingested phytoplankton over a wider range of cell sizes and ate at higher rates on each diet than did the oyster larvae. For example, oyster larvae consumed 2216 cells h(-1) of N. atomus, while limpet larvae consumed the same phytoplankton cells at approximately twice that rate, 5159 cells h(-1), on the same diet. Larvae of both species grew more quickly on a mixture of flagellates than on any of the diatom alone (12 versus 7 mu m d(-1) for oyster larvae and 41 versus 28 mu m d(-1) for limpet larvae). Our results suggest that in the Bay of Mount Saint-Michel (France, Western Channel), where larvae of both species co-exist in the summer, intensive grazing by limpet larvae can potentially deplete phytoplankton concentrations to cause competition with oyster larvae, particularly for smaller sized phytoplankton species.
Compétition trophique chez les larves de mollusques marins Crepidula fornicata et Crassostrea gigas. En 2003, des expérimentations ont été menées en laboratoire pour évaluer la compétition trophique entre les larves de crépidules (Crepidula fornicata) et celles de l'huître japonaise (Crassostrea gigas). Les taux de consommation, de croissance et de mortalité sont comparés, en alimentant les larves de chaque mollusque avec six espèces d'algues unicellulaires, dont la taille varie de 2 à 10 μm, deux flagellées Tetraselmis chui (Prasinophycée) et Isochrysis affinis galbana (T-ISO, Haptophycée), une chlorophycée Nannochloris atomus, et trois diatomées : Chaetoceros calcitrans forma pumilum, Chaetoceros gracilis et Skeletonema marinoï. Contrairement aux larves d'huîtres, les larves de crépidules consomment toutes les cellules phytoplanctoniques quelles que soient leurs tailles, et ceci, à un taux plusélevé que celui des larves d'huîtres. Ainsi, une larve d'huître consomme 2216 cellules h−1 de N. atomus, tandis que la larve de crépidule en consomme 5159 cellules h−1, soit environ deux fois plus. Ces expériences mettent également en évidence que les larves des deux espèces grandissent plus vite quand elles sont nourries avec le mélange des algues flagellées plutôt qu'avec chacune des espèces de ces mêmes algues (12 contre 7 μm j−1 pour l'huître et 41 contre 28 μm j−1 pour la crépidule). Ainsi, en baie du Mont Saint-Michel (Manche ouest) où les larves des deux espèces apparaissent à la même période estivale, nos résultats suggèrent que la filtration des larves de crépidules abaisse notablement la concentration de phytoplancton, et tout spécialement celle des petites cellules algales, entraînant alors une compétition trophique avec les larves d'huîtres.
Aquatic Living Resources (0990-7440) (EDP Sciences), 2008-04 , Vol. 21 , N. 2 , P. 197-205

Droits : EDP Sciences, IFREMER, IRD 2008
http://archimer.ifremer.fr/doc/2008/publication-4703.pdf
DOI:10.1051/alr:2008025
http://archimer.ifremer.fr/doc/00000/4703/

Éditeur(s) : Inter-Research
Résumé : Situated in the north of the Mozambique Channel, Mayotte is the easternmost island of the Comoros Archipelago. From 1998 to 2005, Grande Saziley beach was monitored daily for green turtle Chelonia mydas nesting activity. Track surveys were monitored daily on 5 other adjacent beaches. Although nesting occurs throughout the year, nesting seasonality begins at the end of the wet season and intensifies during the dry season to reach an average nesting peak in June. In order to estimate the number of females nesting in the Saziley site and population trends over the study period, incubation success and number of nests per female and per season were estimated at 0.77 (±0.05 SD) and 3.03 (±0.37) respectively. With an average of 1545 nesting turtles per year (±439), the change in nesting numbers over the study period was so small that the population can be regarded as stable, with an estimated annual mean growth rate of 0.912, confirmation that this population is both stable and in good health. Added support for this argument is demonstrated by the fact that the annual carapace size distribution of nesting females is stable, meaning that the nesting green turtle population of Mayotte is not ageing or rejuvenating. After due consideration of data on other nesting sites in the southwest Indian Ocean, the data from Mayotte emphasizes the fact that the green turtle is not an endangered species in this region. Even if it is still illegally exploited and alterations occur in their different habitats, the green turtle populations of this region seem to have successfully survived all threats during the past century.
Endangered Species Research (1613-4796) (Inter-Research), 2007-10-10 , Vol. 3 , P. 273-282

Droits : 2007 Inter-Research
http://archimer.ifremer.fr/doc/00018/12916/9873.pdf
DOI:10.3354/esr00053
http://archimer.ifremer.fr/doc/00018/12916/

Résumé : Two batches of red drum larvae were air shipped from hatcheries in the U.S.A. and stocked in two intensive tank experiments at densities oc 7 :.nd 2-3 larvae per liter. Food items include live rotifers, copepods, brine shrimps. squid and commercial fish pellets. Growth rates were similar in both experiments up to day 20 (12-1" mm) but differences in feeding schedules and an infestation by the dinoflagelate Amyloodinium sp. affected the growth from day 20 to 43 in the second trial. Significant mortalities occurred in the tanks during the first feeding period (days 2 to 7) and again from days 17 to 20 as the result of cannibalism. Survival between day 2 and day 44 was 44% in the first trial. Abnormal inflation of the swim bladder and infection with Amyloodinium sp. reduced the survival to 6-19% in the second.
Deux lots de larves du tambour rouge ont été transportés par avion depuis des écloseries aux USA et stockés dans deux essais en bac intensif aux densités oc 7 : nd 2-3 larves le litre. L'alimentation comprend les rotifères vivants, les copépodes, les artémias, les encornets et les boulettes de poisson commerciales. Les taux de croissance étaient pareils dans les deux expériences jusqu'au jour 20 (12-1''mm) mais des différences dans les programmes d'alimentation et une infestation par le dinoflagellé Amyloodinium sp. ont modifié la croissance à partir du jour 20 jusqu'au jour 43 dans le deuxième essai. Des mortalités importantes se sont produites dans les bacs pendant la première période d'alimentation (jours 2 et 7) et encore du jour 17 jusqu'au 20 à la suite d'un cannibalisme. La survie entre le jour 2 et le jour 44 était de 44 % dans le premier essai. Un gonflement anormal de la vessie natatoire et une infection de l'Amyloodinium sp. ont réduit la survie de 6 ¿ 19 % dans le deuxième.

Droits : 1988 Ifremer, UAG, Orstom
http://archimer.ifremer.fr/doc/1998/rapport-1914.pdf
http://archimer.ifremer.fr/doc/00000/1914/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: The Hippo pathway regulates growth rate and organ size in fly and mouse, notably through control of cell proliferation. Molecular interactions at the heart of this pathway are known to have originated in the unicellular ancestry of metazoans. They notably involve a cascade of phosphorylations triggered by the kinase Hippo, with sub‑ sequent nuclear to cytoplasmic shift of Yorkie localisation, preventing its binding to the transcription factor Scalloped, thereby silencing proliferation genes. There are few comparative expression data of Hippo pathway genes in non‑ model animal species and notably none in non‑bilaterian phyla.Results: All core Hippo pathway genes could be retrieved from the ctenophore Pleurobrachia pileus and the hydro‑ zoan cnidarian Clytia hemisphaerica, with the important exception of Yorkie in ctenophore. Expression study of the Hippo, Salvador and Scalloped genes in tentacle " cellular conveyor belts " of these two organisms revealed striking differences. In P. pileus, their transcripts were detected in areas where undifferentiated progenitors intensely prolifer‑ ate and where expression of cyclins B and D was also seen. In C. hemisphaerica, these three genes and Yorkie are expressed not only in the proliferating but also in the differentiation zone of the tentacle bulb and in mature tentacle cells. However, using an antibody designed against the C. hemiphaerica Yorkie protein, we show in two distinct cell lineages of the medusa that Yorkie localisation is predominantly nuclear in areas of active cell proliferation and mainly cytoplasmic elsewhere.Conclusions: This is the first evidence of nucleocytoplasmic Yorkie shift in association with the arrest of cell prolifera‑ tion in a cnidarian, strongly evoking the cell division‑promoting role of this protein and its inhibition by the activated Hippo pathway in bilaterian models. Our results furthermore highlight important differences in terms of deployment and regulation of Hippo pathway genes between cnidarians and ctenophores.
ISSN: 2041-9139

Droits : http://creativecommons.org/licenses/by/
hal-01286578
http://hal.upmc.fr/hal-01286578
http://hal.upmc.fr/hal-01286578/document
http://hal.upmc.fr/hal-01286578/file/comparative.pdf
DOI : 10.1186/s13227-016-0041-y

Éditeur(s) : HAL CCSD Elsevier Science
Résumé : International audience
Some anthropogenic noise is now considered pollution, with evidence building that noise from human activities such as transportation, construction and exploration can impact behaviour and physiology in a broad range of taxa. However, relatively little research has considered the effects of repeated or chronic noise; extended exposures may result in habituation or sensitisation, and thus changes in response. We conducted a field-based experiment at Moorea Island to investigate how repeated exposure to playback of motorboat noise affected a coral reef fish (Dascyllus trimaculatus). We found that juvenile D. trimaculatus increased hiding behaviour during motorboat noise after two days of repeated exposure, but no longer did so after one and two weeks of exposure. We also found that naïve individuals responded to playback of motorboat noise with elevated ventilation rates, but that this response was diminished after one and two weeks of repeated exposure. We found no strong evidence that baseline blood cortisol levels, growth or body condition were affected by three weeks of repeated motorboat-noise playback. Our study reveals the importance of considering how tolerance levels may change over time, rather than simply extrapolating from results of short-term studies, if we are to make decisions about regulation and mitigation.
ISSN: 0013-9327

Droits : http://creativecommons.org/licenses/by/
hal-01357915
https://hal-univ-perp.archives-ouvertes.fr/hal-01357915
https://hal-univ-perp.archives-ouvertes.fr/hal-01357915/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01357915/file/1-s2.0-S0269749116304468-main.pdf
DOI : 10.1016/j.envpol.2016.05.058

Éditeur(s) : HAL CCSD MDPI
Résumé : International audience
Cyanobacteria are a component of public health hazards in freshwater environments because of their potential as toxin producers. Eutrophication has long been considered the main cause of cyanobacteria outbreak and proliferation, whereas many studies emphasized the effect of abiotic parameters (mainly temperature and light) on cell growth rate or toxin production. In view of the growing concerns of global change consequences on public health parameters, this study attempts to enlighten climate influence on cyanobacteria at regional scale in Brittany (NW France). The results show that homogeneous cyanobacteria groups are associated with climatic domains related to temperature, global radiation and pluviometry, whereas microcystins (MCs) occurrences are only correlated to local cyanobacteria species composition. As the regional climatic gradient amplitude is similar to the projected climate evolution on a 30-year timespan, a comparison between the present NW and SE situations was used to extrapolate the evolution of geographical cyanobacteria distribution in Brittany. Cyanobacteria composition should shift toward species associated with more frequent Microcystins occurrences along a NW/SE axis whereas lakes situated along a SW/NE axis should transition to species (mainly Nostocales) associated with lower MCs detection frequencies.
ISSN: 2072-6651

hal-01122236
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01122236
PUBMED : 24476711
DOI : 10.3390/toxins6020509
PUBMEDCENTRAL : PMC3942748