Éditeur(s) : HAL CCSD MDPI
Résumé : International audience
The decline in children's Blood Lead Levels (BLL) raises questions about the ability of current lead poisoning screening criteria to identify those children most exposed. The objectives of the study were to evaluate the performance of current screening criteria in identifying children with blood lead levels higher than 50 µg/L in France, and to propose new criteria. Data from a national French survey, conducted among 3831 children aged 6 months to 6 years in 2008-2009 were used. The sensitivity and specificity of the current criteria in predicting blood lead levels higher than or equal to 50 µg/L were evaluated. Two predictive models of BLL above 44 µg/L (for lack of sufficient sample size at 50 µg/L) were built: the first using current criteria, and the second using newly identified risk factors. For each model, performance was studied by calculating the area under the ROC (Receiver Operating Characteristic) curve. The sensitivity of current criteria for detecting BLL higher than or equal to 50 µg/L was 0.51 (0.26; 0.75) and specificity was 0.66 (0.62; 0.70). The new model included the following criteria: foreign child newly arrived in France, mother born abroad, consumption of tap water in the presence of lead pipes, pre-1949 housing, period of construction of housing unknown, presence of peeling paint, parental smoking at home, occupancy rates for housing and child's address in a cadastral municipality or census block comprising more than 6% of housing that is potentially unfit and built pre-1949. The area under the ROC curve was 0.86 for the new model, versus 0.76 for the current one. The lead poisoning screening criteria should be updated. The risk of industrial, occupational and hobby-related exposure could not be assessed in this study, but should be kept as screening criteria
ISSN: 1660-4601

hal-01239804
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01239804
DOI : 10.3390/ijerph121214989
PUBMED : 26633457

Éditeur(s) : HAL CCSD
Résumé : International audience
Afro-­ Caribbean sprinters often reach high performance levels at an early age. Adolescence is a time of morphological and physiological changes. This study was designed to analyze the evolution in parameters of short sprint performance during adolescence in Afro-­Caribbean boys, especially the stride number/body height ratio (SN/BH), which is at the interface of technical and morphological factors. Seventy-­‐‑ one 13-­‐‑ year-­‐‑ old boys performed vertical jumps and short sprint races. The races were filmed with a view to determine stride variables. Anthropometric parameters were also measured. The same tests were performed two years later. Body height and SN/BH were the main predictors of sprint performance. The delta of performance was principally explained by stride length and stride number. Although deterioration in technical parameters was expected, the parameters related to body size and stride length were the main sprint performance predictors rather than explosive force. These results could be useful in developing tests to detect sprint potential in youth.
Journal of Human Kinetics

hal-01143539
https://hal.univ-antilles.fr/hal-01143539

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : Three methods for automatic detection of mesoscale coherent structures are applied to Sea Level Anomaly (SLA) fields in the South Atlantic. The first method is based on the wavelet packet decomposition of the SLA data, the second on the estimation of the Okubo-Weiss parameter and the third on a geometric criterion using the winding-angle approach. The results provide a comprehensive picture of the mesoscale eddies over the South Atlantic Ocean, emphasizing their main characteristics: amplitude, diameter, duration and propagation velocity. Five areas of particular eddy dynamics were selected: the Brazil Current, the Agulhas eddies propagation corridor, the Agulhas Current retroflexion, the Brazil-Malvinas confluence zone and the northern branch of the Antarctic Circumpolar Current (ACC). For these areas, mean propagation velocities and amplitudes were calculated. Two regions with long duration eddies were observed, corresponding to the propagation of Agulhas and ACC eddies. Through the comparison between the identification methods, their main advantages and shortcomings were detailed. The geometric criterion presents the best performance, mainly in terms of number of detections, duration of the eddies and propagation velocities. The results are particularly good for the Agulhas Rings, which have the longest lifetimes of all South Atlantic eddies.
Ocean Science (1812-0784) (Copernicus Gesellschaft Mbh), 2011 , Vol. 7 , N. 3 , P. 317-334

Droits : Author(s) 2011. This work is distributed under the Creative Commons Attribution 3.0 License. EGU
http://archimer.ifremer.fr/doc/00039/15051/12378.pdf
DOI:10.5194/os-7-317-2011
http://archimer.ifremer.fr/doc/00039/15051/

Éditeur(s) : HAL CCSD Wiley
Résumé : 1- We examined among- and within-species effects of seed mass for seedling establishment from seed to 5 years of age in a field experiment at Paracou, French Guiana. 2- Six seeds of each of eight species were weighed and planted into each of 120 plots (1 m2) throughout closed-canopy forest along 12 100-m transects in 1998. 3- We described the microhabitat of each planting site using principal components derived from measurements of light availability, soil moisture, carbon and nitrogen content, and soil phosphorus availability. Although both survival and relative growth rate (RGR) increased with increasing light availability, no other microhabitat variable significantly affected seedling performance. Nor did the magnitude of microhabitat effects on survival or RGR differ among species. 4- Larger-seeded species were more likely to survive from germination to 1 year as well as from 1 to 5 years of age. RGR for seedling height during the first year post-germination was not related to seed mass, but smaller-seeded species did grow slightly faster thereafter. Path analyses revealed that correlations between seed mass and performance were explained in part because larger seeds produced larger initial seedlings, which tended to survive better but grow more slowly. 5- We also analysed within-species effects of seed mass for the larger-seeded Eperua grandiflora and Vouacapoua americana (both Caesalpiniaceae). Larger seeds produced larger seedlings in both species, but larger seeds survived better only for Eperua. Larger seedlings grew more slowly in both species, but did not offset the early (Eperua) and later (Vouacapoua) positive direct effects of seed mass on RGR that may represent contrasting strategies for reserve deployment. 6- Our results demonstrate that seed size influences performance within and among species in part because of indirect effects of initial seedling size. However, we suggest that traits tightly correlated with seed mass at the species level, such as specific leaf area, leaf longevity and photosynthetic capacity, may also contribute to interspecific performance differences.
ISSN: 0022-0477

hal-01031089
https://hal.archives-ouvertes.fr/hal-01031089
DOI : 10.1111/j.1365-2745.2005.01041.x

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : L’expansion de la microfinance en Haïti ne semble pas correspondre au développement réel des entreprises financées. Dans cet article, nous analysons dans quelle mesure les conditions de microfinancement déterminent la performance financière des microentreprises emprunteuses. À partir d’un échantillon de soixante-deux microentrepreneurs, nous avons estimé un modèle économétrique qui met en relation le chiffre d’affaires et 6 variables explicatives : taux d’intérêt, montant crédit, délai de remboursement, niveau d’éducation, localisation de l’entreprise, genre-associé. Selon nos résultats, les variables explicatives des résultats financiers des microentrepreneurs sont le délai de remboursement, le genre féminin et la localisation. Il est donc confirmé qu’un délai de remboursement long améliore les résultats financiers des microentreprises bénéficiaires de la microfinance. Par contre, un taux d’intérêt faible ne garantit pas nécessairement de meilleurs résultats financiers puisque le taux d’intérêt n’est pas corrélé significativement au chiffre d’affaires des entreprises.
The expansion of microfinance in Haiti does not seem to correspond to the actual development of microentreprises borrowing from microfinance organizations. In this article, we analyze the extent to which microfinance methodology determine the financial performance of borrowers. Based on a sample of 62 microentrepreneurs, we estimated an econometric model linking turnover and 6 explanatory variables: interest rate, credit amount, repayment period, education level, location, partner’s gender. According to our results, the variables explaining the microentrepreneurs' financial results are: the repayment period, the female gender of partner, and the location. It is therefore confirmed that a long repayment period improves the financial results of microenterprises benefiting from microfinance. On the other hand, a low interest rate does not necessarily guarantee better financial results since the interest rate is not significantly correlated with the turnover of the microentreprises.
Haïti

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.10381
http://journals.openedition.org/etudescaribeennes/10381

Éditeur(s) : Elsevier
Résumé : In the Gulf of Gabes (Tunisia, Eastern Mediterranean sea), the grooved carpet shell Ruditapes decussatus has been seen to contain persistent levels of gymnodimine (GYM) for several years. The present experimental work represents the first attempt to assess detoxification kinetics of fast-acting toxins (FAT) in marine molluscs fed specific diets of non-toxic algae (Isochrysis galbana). To find an optimal detoxification method, two experiments were performed in which clams were first fed the toxic dinoflagellate Karenia selliformis to artificially contaminate them with GYM, thus simulating the effect of natural toxic episodes. As a second step, the same clams were fed a non-toxic algae, I. galbana. to speed up the detoxification process. Changes in toxin content over the whole experiment were assessed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis. The first results revealed (i) faster detoxification rates in digestive gland (DG) when clams were fed on L galbana compared with a starved control (no food) and (ii) a typical detoxification pattern, i.e. a rapid drop in toxin content within the first days followed by a secondary slower decrease. GYM levels could be reduced approximately to less than 5% within 7-8 days in clams fed I. galbana, according to the initial toxin levels of 1400 and 9400 mu g GYM/kg of DG, respectively. At the end of the second experiment, DSP mouse bioassay was negative when GYM was less than 100 mu g/kg DG. (C) 2009 Elsevier B.V. All rights reserved.
Harmful Algae (1568-9883) (Elsevier), 2010-02 , Vol. 9 , N. 2 , P. 200-207

Droits : 2010 Elsevier Ltd All rights reserved.
http://archimer.ifremer.fr/doc/2010/publication-7488.pdf
DOI:10.1016/j.hal.2009.10.002
http://archimer.ifremer.fr/doc/00000/7488/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
During the treatment process of drinking water, disinfectants (chlorine, ozone, chlorine dioxide) react on water containing organic matter and bromide to produce disinfection by-products at trace levels. Among them, five of the nine existing halo-acetic acids (HAAs) are commonly found in drinking water (monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), monobromoacetic acid (MBAA), dibromoacetic acid (DBAA), and Trichloroacetic acid (TCAA)), including four classified in the 2B IARC group of potential carcinogens (BCAA, DBAA, DCAA, TCAA). With respect to drinking water quality, guidelines are proposed by WHO (2006) and water quality standards are imposed in many countries such as less than 100 μg/L for the sum of the five HAAs by US EPA (1998) and Canadian Health Department (2008). For this purpose, two analytical methods are commonly used, GC/MS with derivatization and LC/MS, UV or conductivity. A new method, based on two-dimensional ion chromatography (IC 2D) with suppressed conductivity is proposed. This method presents the main advantage of offering a quick implementation compared to GC or LC methods: direct injection, slight maintenance, lower cost of investment, by leading to good performances (specificity and sensitivity). The use of two different selectivity columns, and the fractionation on the first dimension canceling interferences, improves the specificity. The sensitivity is enabled by interfacing a preconcentration column between the two different internal diameter columns. The analytical conditions are optimized for the analysis of nine HAAs. The performances of the method are evaluated. The optimized method applied to natural water samples demonstrates its ability to quantify HAAs at trace levels in drinking water.
Microchemical Journal

hal-00877151
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00877151
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00877151/document
DOI : 10.1016/j.microc.2013.07.012

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
BACKGROUND: An association between education and preterm delivery has been observed in populations across Europe, but differences in methodology limit comparability. We performed a direct cross-cohort comparison of educational disparities in preterm delivery based on individual-level birth cohort data. METHODS: The study included data from 12 European cohorts from Denmark, England, France, Lithuania, the Netherlands, Norway, Italy, Portugal, and Spain. The cohorts included between 2434 and 99 655 pregnancies. The association between maternal education and preterm delivery (22-36 completed weeks of gestation) was reported as risk ratios, risk differences, and slope indexes of inequality with 95% confidence intervals (CIs). RESULTS: Singleton preterm live delivery proportion varied between 3.7% and 7.5%. There were large variations between the cohorts in the distribution of education and maternal characteristics. Nevertheless, there were similar educational differences in risk of preterm delivery in 8 of the 12 cohorts with slope index of inequality varying between 2.2 [95% CI 1.1, 3.3] and 4.0 [95% CI 1.4, 6.6] excess preterm deliveries per 100 singleton deliveries among the educationally most disadvantaged, and risk ratio between the lowest and highest education category varying from 1.4 [95% CI 1.1, 1.8] to 1.9 [95% CI 1.2, 3.1]. No associations were found in the last four cohorts. CONCLUSIONS: Educational disparities in preterm delivery were found all over Europe. Despite differences in the distributions of education and preterm delivery, the results were remarkably similar across the cohorts. For those few cohorts that did not follow the pattern, study and country characteristics did not explain the differences.
ISSN: 0269-5022

hal-01146842
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01146842
DOI : 10.1111/ppe.12185
PUBMED : 25808200

Éditeur(s) : Co-tutelle Al Centro de Investigaciones Biológicas del Noroeste - Université de Bretagne occidentale
Résumé : The interest in probiotics for aquaculture is increasing rapidly. In the present work we evaluated the potential of some yeast to induce the larvae gut maturation in sea bass larvae Dicentrarchus labrax. The production of polyamines putrescine, spermidine and spermine was quantified in ten yeast strains using high performance liquid chromatography (HPLC). Afterwards, fluorescently labelled yeast adhesion to the intestine of sea bass larvae and the spotted sand bass (Paralabrax maculatofasciatus) was evaluated by fluorescent microscopy. Two of them, CBS 8339 strain (Debaryomyces hansenii) and X2180 strain (Saccharomyces cerevisiae) produce the polyamines of our interest. The same strains showed the best adhering capabilities to the sea bass and spotted sand bass intestine. Both strains were selected and introduced by pulverization into the diet of larvae. The larvae fed with CBS 8339 strain, increase survival in 8.3% but not in their weight. The secretion of trypsin and amylase as well as those from the brush border membrane: alkaline phosphatase, maltase and leucine aminopeptidase, are incresed at 27 days after hatching (dah). At 42 dah difference in the enzyme activity of the different groups does not exist, suggesting a maturation of the digestive system in early stages of larval development. A second experiment was carried out to know the effect of different levels of incorporation into the diet of CBS 8339 strain: 1.1% and 5.7%. The minimum level, 1.1% of yeast produce best growth and survival rates, as well as lower deformed larvae than those obtained by 5.7% and the control one. Both level of yeast inclusion favored the trypsin secretion and lipase activity at 26 dah. Whereas mRNA levels for trypsin and amylase were influenced by both yeast concentrations at 26 and 36 dah, which suggest a development of digestive capacity of larvae as a result of the presence of polyamines secreted by the yeast.
Les probiotiques ont été définis comme des préparations microbiennes vivantes utilisées comme additif alimentaire, et qui ont une action bénéfique sur l'animal hôte en améliorant la digestion et l'hygiène intestinale. L'application de tels traitements aux productions aquacoles suscite un intérêt qui s'accroît rapidement. Dans ce travail, nous avons étudié l'effet de souches de levures sur la maturation de l'intestin des larves du bar Dicentrarchus labrax. Ces souches produisent des polyamines qui sont impliquées dans la réplication et la différentiation cellulaire, ainsi que dans la synthèse des protéines et des acides nucléiques. Dix souches de levures ont été testées pour leur production de polyamines (putrescine, spermidine et spermine), et pour leur adhérence à la paroi intestinale du bar et la cabrilla (Paralabrax maculatofasciatus). La production des polyamines a été analysée en utilisant la chromatographie liquide à haute performance (HPLC). Les levures selectionées ont été marquées avec un composé fluorescent pour tester leur adhérence a l'intestin de larves de bar et de juvéniles de cabrilla. L'adhérence a pu ainsi être evaluée par observation microscopique en épifluorescence. Les souches CBS 8339 (Debaryomyces hansenii) et X2180 (Saccharomyces cerevisiae) ont été choisies pour leur forte production de spermidine et de spermine, respectivement, et pour leur capacité d'adhérence à l'intestin du bar et de la cabrilla. Les deux souches ont été ajoutées par pulvérisation au régime des larves. Nous avons observé une augmentation de 8.3% du taux de survie avec les larves alimentées avec la souche CBS 8339, mais le poids moyen de ces larves était inférieur à celui obtenu sans ajout de levure. Une augmentation de l'activité de la trypsine et de l'amylase, aussi bien que des activités enzymatiques dans la bordure en brosse, aminopeptidase, phosphatase alkaline et maltase, ont été observées dans les larves âgées de 27 jours alimentées avec la souche CBS 8339. Au jour 42, il n'existait plus de différence d'activité enzymatique entre les larves traitées ou non avec la levure. Ces résultats suggèrent que la maturation du système digestif a été accélérée chez les larves nourries avec la levure, la maturation étant achevée chez les larves de 42 jours, qu'elles aient reçu l'un ou l'autre régime. Une deuxième expérience a été effectuée pour étudier l'effet de différents niveaux d'incorporation dans le régime contenant 1,1% et 5,7% de levure CBS 8339. L'incorporation de 1,1% a induit une augmentation du poids moyen et du taux de survie des larves, ainsi qu'une réduction du taux de malformation de la colonne vertébrale, par rapport aux résultats obtenus avec 0 ou 5,7% de levure. Les deux niveaux d'incorporation de la levure ont favorisé l'activité de la trypsine et de la lipase au jour 26. Les niveaux d'ARNm codant pour la synthèse de la trypsine et de l'amylase ont été influencés par les deux doses de levure aux jours 26 et 36. Ces résultats suggèrent qu'une faible dose de levure améliore le développement et la capacité digestive des larves, et nous formulons l'hypothèse que cette efficacité est due à la production de polyamines in situ. Le rôle des polyamines est particulièrement important pendant les phases de forte croissance comme les stades larvaires, mais elles peuvent être toxiques à dose trop élevée. L'incorporation de levure dans l'aliment destiné aux larves semble donc une excellente méthode pour délivrer les polyamines chez l'animal hôte.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2002/these-103.pdf
http://archimer.ifremer.fr/doc/00000/103/

Éditeur(s) : Copernicus Gesellschaft Mbh
Résumé : During the GWADASEIS cruise (Lesser Antilles volcanic arc, February-March 2009) a very high resolution (VHR) seismic-reflection survey was performed in order to constrain Late Quaternary to Present faulting. The profiles we obtained evidence frequent "ponding" of reworked sediments in the deepest areas, similar to the deposition of Mediterranean "homogenites". These bodies are acoustically transparent (few ms t.w.t. thick) and are often deposited on the hanging walls of dominantly normal faults, at the base of scarps. Their thickness appears sufficient to compensate (i.e. bury) co-seismic scarps between successive earthquakes, resulting in a flat and horizontal sea floor through time. In a selected area (offshore Montserrat and Nevis islands), piston coring (4 to 7m long) was dedicated to a sedimentological analysis of the most recent of these particular layers. It corresponds to non-stratified homogenous calcareous silty sand (reworked calcareous plankton and minor volcanoclastics). This layer can be up to 2 m thick, and overlies fine-grained hemipelagites. The upper centimeters of the latter represent the normal RedOx water/sediment interface. Pb-210 and Cs-137 activities lack in the massive sands, while a normal profile of unsupported Pb-210 decrease is observed in the hemipelagite below, together with a Cs-137 peak corresponding to the Atmospheric Nuclear Experiments (1962). The RedOx level was thus capped by a recent instantaneous major sedimentary event considered as post-1970 AD; candidate seismic events to explain this sedimentary deposits are either the 16 March 1985 earthquake or the 8 October 1974 one (M-w = 6.3 and M-w = 7.4, respectively). This leads to consider that the syntectonic sedimentation in this area is not continuous but results from accumulation of thick homogenites deposited after the earthquakes (as observed in the following weeks after Haiti January 2010 event, McHugh et al., 2011). The existence of such deposits suggests that, in the area of study, vertical throw likely results from cumulated effects of separated earthquakes rather than from aseismic creep. Examination of VHR profiles shows that all major co-seismic offsets are recorded in the fault growth sequence and that co-seismic offsets can be precisely estimated. By using a sedimentation rate deduced from Pb-210 decrease curve (0.5 mmyr(-1)) and taking into account minor reworking events detected in cores, we show that the Redonda system may have been responsible for five > M-6 events during the last 34 000 yr. The approach presented in this work differs from fault activity analyses using displaced sets of isochronous surfaces and postulating co-seismic offsets. Combining VHR seismic imagery and coring we can decipher co-seismic vs. slow continuous displacement, and thus actually estimate the amplitude and the time distribution of major co-seismic offsets.
Natural Hazards And Earth System Sciences (1561-8633) (Copernicus Gesellschaft Mbh), 2012 , Vol. 12 , N. 5 , P. 1755-1767

Droits : Author(s) 2012. CC Attribution 3.0 License.
http://archimer.ifremer.fr/doc/00089/20040/21990.pdf
DOI:10.5194/nhess-12-1755-2012
http://archimer.ifremer.fr/doc/00089/20040/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Leg ulcer is a disabling complication in patients with sickle cell anemia (SCA) but the exact pathophysiological mechanisms are unknown. The aim of this study was to identify the hematological and hemorheological alterations associated with recurrent leg ulcers. Sixty-two SCA patients who never experienced leg ulcers (ULC-) and 13 SCA patients with a positive history of recurrent leg ulcers (ULC+) - but with no leg ulcers at the time of the study - were recruited. All patients were in steady state condition. Blood was sampled to perform hematological, biochemical (hemolytic markers) and hemorheological analyses (blood viscosity, red blood cell deformability and aggregation properties). The hematocrit-to-viscosity ratio (HVR), which reflects the red blood cell oxygen transport efficiency, was calculated for each subject. Patients from the ULC+ group were older than patients from the ULC- group. Anemia (red blood cell count, hematocrit and hemoglobin levels) was more pronounced in the ULC+ group. Lactate dehydrogenase level was higher in the ULC+ group than in the ULC- group. Neither blood viscosity, nor RBC aggregation properties differed between the two groups. HVR was lower and RBC deformability tended to be reduced in the ULC+ group. Our study confirmed increased hemolytic rate and anemia in SCA patients with leg ulcers recurrence. Furthermore, our data suggest that although systemic blood viscosity is not a major factor involved in the pathophysiology of this complication, decreased red blood cell oxygen transport efficiency (i.e., low hematocrit/viscosity ratio) may play a role.
ISSN: 1932-6203

inserm-00922105
http://www.hal.inserm.fr/inserm-00922105
http://www.hal.inserm.fr/inserm-00922105/document
http://www.hal.inserm.fr/inserm-00922105/file/2013_Connes_-_Decreased_Hematocrit.pdf
DOI : 10.1371/journal.pone.0079680

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Increasingly, health risk assessment is addressing multiple pathway exposures to multiple contaminants. We reviewed aggregated exposure and cumulative risk approaches for contemporary and ubiquitous semivolatile organic compounds (SVOC). We identified 22 studies aggregating exposure pathways, and 31 cumulating risk. Exposure aggregation is based on the addition of pathway-specific doses, using kinetic modeling where it exists, and classic external dose equations otherwise. In most cases, exposure is dominated by a single route or source of exposure - mainly the oral pathway - via dietary or non-dietary exposure. Preferential routes and sources of exposure are influenced by SVOC physical-chemical properties such as vapor pressure. The cumulative risk approach for contaminants is based on dose addition. Simple sum of hazard quotient (Hazard Index: HI) is the most commonly used cumulative risk assessment approach, while Relative Potency Factor (RPF) appeared to the best suited – although this calls for a level of toxicological information that limits the number of compounds that can be studied simultaneously. Where both were performed, moving from HI to more refined approach produced similar results. In conclusion, both approaches - exposure aggregation and cumulative risk - rely on simple assumptions. Nevertheless, they allow uncertainty to be reduced, in comparison with source-by-source or chemical-by-chemical approaches.
ISSN: 0013-9351

hal-01635759
https://hal.archives-ouvertes.fr/hal-01635759
https://hal.archives-ouvertes.fr/hal-01635759/document
https://hal.archives-ouvertes.fr/hal-01635759/file/Pelletier%202017%20Review%20%20rev2.pdf
DOI : 10.1016/j.envres.2017.06.022

Éditeur(s) : Université de Bretagne Occidentale
Résumé : The objective of the present work is to study the formation of the passive continental margins of the Central Segment of the South Atlantic, most particularly the Congo and Angola margins. We propose a combined approach, which integrates structural constraints based on geological cross-sections (based on seismic data) and global constraints based on plate kinematic reconstructions. The structural study is based on : i) MCS and refraction data collected during the ZaiAngo programme (a joint project conducted by Ifremer and Total) ; ii) proprietary, industrial seismic data (courtesy of Total) from the Angola margin and iii) on all available seismic lines from the Africa and Brazil conjugated margins, between Walvis Ridge and the Equatorial Fracture Zones. Based on theses data, three structural domains (continental, transitional and oceanic) have been defined, the major characteristics of which are : Crustal thinning occurs abruptly, mostly below the continental slope, over a lateral distance of less than 50 km. The top of the crust deepens as the Moho shallows. Only a few extensional structures are observed ; tilted blocks are very few (one or two, depending on the profile), found only on the upper part of the slope and sealed by a discordance prior to salt deposition. The transitional domain is characterized by the existence of a pre-salt basin lying over a thin crustal layer. No tilted blocks are observed in this domain and reflectors within the pre-salt sediment series are parallel to the base of the Aptian salt, over distances greater than 100 km, precluding the possibility of any significant deformation that would imply large horizontal motions. Two types of crust are observed in the transitional domain. "Type I" crust is found below the undeformed pre-salt sediment series located below the eastern part of the basin ; it is characterized by an upper layer of thickness greater than 5 km and a abnormal velocity layer (7.2 - 7.6 km/s), up to 6 km thick. "Type II" crust is less than 5 km thick and found below the salt compressive front that affects the western part of the basin. The salt cover is continuous (no erosion surface is observed), from the continental shelf to the western termination of the basin. Salt was not deposited in a confined environment (like in the Mediterranean), but in a shallow water, lagunal environment. This imposes the zero-level and constrains the paleo-bathymetry at the time of salt deposition, which dates the latest stage of margin formation. Understanding the formation of a margin cannot be approached without studying the homolog margin. Therefore, it is of major importance to reconstruct the closure of the ocean bordered by these homolog margins and take into account the constraints imposed by the kinematic reconstructions on the lateral motions of the lithospheric plates. In order to assess the relative position of the plates at the ocean closure (prior to crustal thinning), a global study was thus performed, integrating all geophysical and geological constraints, in the ocean and on land. The role of african intra-plate deformation and its limits and their consequences have been thoroughly studied. To juxtapose the margins of the central segment of the Southern Atlantic, it is all the margins bordering the Equatorial Atlantic that need to be adjuste precisely. The kinematic study of this last region shows that the reconstruction obtained are reliable, unambiguous with a quantifiable precision The best fitting poles (obtained using the PLACA software), show that it is impossible to close the margins beyond the superposition of the salt fronts, from the Angola and Brazil margins. The geological cross-sections based on seismic data from the homolog margins indicate that a 330 km wide basin with thin (< 12 km) crust was present at the time of the fit. This basin cannot result from horizontal movement related to pure stretching or simple shear, or any model implying conservative volume. This conclusion is consistent with the existence of presalt reflectors parallel to the salt layer wich extends to the platform: the formation of the pre-salt basin must be related to vertical motions. The scenario that we propose for the evolution of the Congo-Angola margin consist in four stages: the first phase corresponds to extensional deformation limited to the few tilted blocks observed on the upper part of the slope. During the second phase, the main crustal thinning occurs, vertical motions prevailes, resulting in the formation of the continental slope and in the subsidence of the basin. The third phase corresponds to the first stress striction: deformation is concentrated in a limited section of the basin, which corresponds to the salt compression front. A proto-oceanic crust is formed, probably composed of thinned continental crust intruded by mantle material. The second stress striction corresponds to the finale phase, resulting in oceanisation senso stricto. The evolution described shows that we can not apply conservative models for margin formation (such as McKenzie and Wernicke or any of their avatars). In order to explain this thinning, one should investigate non-conservative models (implying geochemical transformation, small scale convection, intrusion...) such as those proposed in marginal or continental basins with no horizontal movments.
Ce travail de thèse aborde la formation des marges continentales passives dans le segment central de l'océan Atlantique Sud (plus particulièrement au Congo et en Angola), en intégrant une étude en coupe (étude structurale à partir des coupes sismiques) et une étude en plan (étude cinématique). L'étude structurale de la marge a été réalisée à partir des données de sismique réflexion et réfraction de la campagne Zaïango et d'une compilation de données sismiques réflexion existantes sur toutes les marges africaine et brésilienne entre les zones de fracture équatoriales et la ride de Walvis. L'interprétation de ces données a permis d'individualiser la structure de la marge en trois domaines : continental, transitionnel et océanique et de déterminer quelques points majeurs sur la structuration de la marge. L'amincissement est abrupt, localisé dans la zone de pente continentale et restreint à 50 km. La marge montre peu de structures distensives : seuls un ou deux blocs basculés sont observés en haut de pente continentale. Le domaine transitionnel est caractérisé par la géométrie particulière de la sédimentation anté-salifère, l'absence de blocs basculés et la faible épaisseur de croûte. La couche sédimentaire anté-salifère montre des réflecteurs plans jusqu'à la base du sel, continus sur 100 km, éliminant toutes possibilités de déformation du socle pendant et après son dépôt. La croûte du domaine transitionnel peut-être divisée en deux types : une croûte de type I sur laquelle se déposent les sédiments non déformés, et une croûte de type II sur laquelle se superposent les limites du « front compressif salifère » bien exprimé dans les séries postsalifères. Enfin le sel, que l'on observe depuis la plate-forme jusqu'au bassin profond, ne se dépose pas dans un bassin confiné (comme en Méditerranée) mais à un niveau proche de 0 m (ressemblant probablement à un dépôt de type lagunaire) et donne la paléo-bathymétrie au moment de son dépôt qui marque la fin de la période de formation de la marge. La compréhension de la genèse d'une marge ne peut être approchée sans son homologue. Cette simple constatation, cette évidence, montre toute l'importance que l'on doit apporter à la reconstruction cinématique initiale de l'océan qui borde ces marges homologues et aux contraintes imposées par les reconstructions cinématiques sur les mouvements horizontaux des plaques lithosphériques. Afin d'étudier la position des marges au moment de cette fermeture, c'est-à-dire avant amincissement, une étude globale intégrant l'ensemble des données disponibles, géophysiques et géologiques, océaniques et continentales, a été réalisée. Le rôle de la déformation intraplaque africaine, ses limites et leurs conséquences a, en particulier, été l'objet d'une attention poussée. Pour juxtaposer les marges du segment central, ce sont toutes les marges de l'océan Atlantique Equatorial qui doivent être ajustées précisément. L'étude cinématique réalisée de la région équatoriale montre que l'on obtient une reconstruction fiable et sans ambiguïté, avec une précision que l'on peut quantifier. Les pôles issus de cette étude (et calculés avec le Logiciel PLACA) indiquent qu'il est impossible d'obtenir une fermeture plus serrée que celle qui conduit à la superposition des fronts salifères brésilien et angolais : les coupes issues de la sismique réflexion des deux marges indiquent qu'il subsiste un bassin aminci, large de plus de 330 km et dont la croûte n'excède jamais 13 kilomètres d'épaisseur. La formation de ce bassin ne peut résulter de mouvements horizontaux, ce qui exclut un amincissement par étirement (pure stretching) ou par l'existence d'une faille de détachement (simple shear) ou par quelque modèle conservatif que ce soit. Cette constatation corrobore l'observation de la présence d'horizons anté-salifère parallèles, entre eux et au sel, couche salifère que l'on retrouve sur la plate-forme : la création de ce bassin anté-salifère ne peut être que liée à un mouvement vertical. Le schéma d'évolution que nous proposons à partir des données structurales et des contraintes cinématiques présente quatre étapes : le premier stade correspond à une phase de déformation distensive limitée aux quelques rares blocs basculés observés en haut de pente continentale. C'est durant la deuxième étape que se déroule la phase d'amincissement principal, les mouvements verticaux prévalent, aboutissant à la formation de la pente continentale et à la subsidence du bassin. La troisième phase correspond à une première striction des contraintes : la déformation se concentre sur une partie réduite du bassin, coïncidant avec le front salifère compressif. Une proto-croûte océanique se forme, probablement composée de croûte continentale amincie et intrudée de matériel mantellique. La seconde striction correspond à la phase finale de formation de la marge et aboutit à l'océanisation sensu stricto. L'étude cinématique et la description de l'évolution de la marge à partir des données sismiques montre donc que l'on ne peut envisager l'application d'un modèle de genèse des marges avec conservation de volume (type McKenzie ou Wernicke et leurs avatars) : pour expliquer l'amincissement du bassin, il faudrait probablement nous intéresser aux modèles non-conservatifs (impliquant transformation, convection à petite échelle, ...) qui sont déjà invoqués pour la formation des bassins marginaux ou continentaux, sans mouvements horizontaux.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2003/these-82.pdf
http://archimer.ifremer.fr/doc/00000/82/

Résumé : After a period of rapid development of the sites (an increase in both reared surface area and production), tropical shrimp aquaculture is currently being faced with critical problems due to economical and ecological constraints. In many countries with favourable conditions for shrimp aquaculture such as indonesia or Vietnam, sites are often badly selected and/or over-exploited. This conducts to sorne extent to decreases or collapses in the production due to the difficulty in predicting the maximum production capacity of the sites. Furthermore, it appears that production sustainability depends on many factors among which socio-economy and ecolo gy are of prime importance. The STD3 project titled « Assessment of tropical shrimp aquaculture impact on the environment in tropical countries using hydrobiology, ecology and remote sensing as helping tools for diagnosis )) was initiated in 1994, with the aim to study the sustainability of marine shrimp aquaculture in tropical areas, main! y Indonesia and Vietnam, through the following tasks: (i) improve site selection and study the impact of aquaculture on marine environments presenting a variable sensitivity to organic sewage, (ii) analyse the socio-economical aspects and profitability of the aquaculture industry and of common resources (iii) use remote sensing and geographical data bases for diagnosis and monitoring of site degradation (iv) reinforce the capacity of Asian scientists through training. Severa! aquaculture sites have been investigated in the Lampung region (South Sumatra, Indonesia), the Mekong delta (Vietnam) and on the West coast of New-Caledonia, providing a large range of typical ecosystems encountered in Asia and in the Pacifie, from coralline sites to coastal plains with mangrove and deltaic areas. The study concerned the spatial structure and seasonal influence of these ecosystems, the temporal variation during the course of the project (3 years) and the relation between the ecological structure and farm productions. Remote sensing provides a synoptic vision over large land expanses. Severa! scenes were processed for landuse mapping using conventional classification techniques. Concerning water quality assessment, a general relation for the Java sea was found between image and field data in terms of total suspended matter. Applying this relation to a new site in Sumatra has provided an initial approach to water type and, together with land use mapping, a preliminary assessment of the suitability of the area to shrimp aquaculture development. Socio-economic research has been focused on the identification ofneeds for collective action, including public policy, in the perspective of shrimp farming sustainability. The main concern is in the regulation of shrimp farming intensification and extensification at the scale of coastal ecosystemic entities in a common property resource management perspective. The common considered here is coastal water quality. Comparing the local development profiles and the institutional grounds for the design and implementation of collective management rules shows that variables such as land tenure system, farm owner socio-economic profile, social homogeneity or heterogeneity of the farmers are key factors to analyse the potential for sustainability. The defmition of water quality and the possible means to ensure its collective management are discussed. The main conclusion is that the economie incentives to farming development are strong but there is no significant difference among traditional, semi-intensive and intensive systems in terms of economie efficiency or wealth distribution. The description of the functioning of the different kinds of ecosystems make it possible to give an advice concerning the positioning of the activity inside the ecosystem, and furthermore to have a reference state in order to determine the impact of the activity on the coastal environnement. This impact can be summarized as an increase in the concentration of total suspended matt€?r, of particulate organic matter and of sulfate reducing bacterias. This organic ma~.er is either issued from rearing activities or from telluric origine, due to mangrove eradication when building the ponds. An evaluation of the relationship existing between productivity and characteristics of each ecosystem bas been conducted by correlating ecological indicators data (concentration of total suspended matter, particulate organic matter, chlorophyll, percentage of pheopigments in total pigments and cyanobacteria and sulfatereducing bacteria in water and sediments) with the average production of the farms. This comparison lead to the compilation of a scale of observed production integrating the range of these environmental parameters with shrimp production levels, bound to facilitate the positioning of shrimp farming in relation with the confmement leve! of each ecosystem. Lastly, ali geographie data originated from the various compartments of the study have been geo-referenced and loaded into a geographical information system. This allows to display any query made on spatial variables and their related statistical data, including the ir variations over the last few years and to reveal patterns and phenomena otherwise not obvious.
Le programme mis en oeuvre par la DRV (Paris, CREMA-L'Houmeau, DELIAO Brest, COP Tahiti, GIE/RA Nouvelle Calédonie), dans le cadre d'un projet européen STD3 «(Sciences et Technique au Service du Développement», en collaboration avec l'Université de Montpellier II, l'Ecole Nationale d'Agronomie de Rennes, l'ITC (Hollande), l'Institut Océanographique de Nha Trang (Vietnam), le BADC de Jepara et le BPPT de Jakarta (Indonésie), avait pour but la mise au point de méthodes permettant d'améliorer la sélection des sites ainsi que le suivi du développement et de l'impact de l'aquaculture des crevettes Péneides en milieu tropical pour éviter la surexploitation. Quatre axes de recherche ont été défmis : a) identifier la nature et quantifier les rejets de déchets issus de ce type d'aquaculture, b) définir les caractéristiques écologiques des écosystèmes susceptibles d'accueillir l'activité aquacole et suivre leur évolution sous l'influence des rejets, c) déterminer l'influence de la gestion des fermes et des ressources (aspects économiques) sur les performances de productivité, d) déterminer la capacité de la télédétection comme outil de diagnostic d'impact à l'échelle de la région, e) mener un programme de formation d'étudiants et jeunes chercheurs Vietnamiens et Indonésiens.

Droits : 1998 Ifremer
http://archimer.ifremer.fr/doc/00132/24357/22357.pdf
http://archimer.ifremer.fr/doc/00132/24357/

Éditeur(s) : University of Tasmania, Université de Bretagne Occidentale
Résumé : Empirical evidence and the theoretical literature both point to stock sustainability and the protection of marine biodiversity as important fisheries management issues. Decision-support tools are increasingly required to operationalize the ecosystem-based approach to fisheries management. These tools need to integrate (i) ecological and socio-economic drivers of changes in fisheries and ecosystems; (ii) complex dynamics; (iii) deal with various sources of uncertainty; and (iv) incorporate multiple, rather than single objectives. The stochastic co-viability approach addresses the trade-offs associated with balancing ecological, economic and social objectives throughout time, and takes into account the complexity and uncertainty of the dynamic interactions which characterize exploited ecosystems and biodiversity. This thesis proposes an application of this co-viability approach to the sustainable management of mixed fisheries, using two contrasting case studies: the French Bay of Biscay (BoB) demersal mixed fishery and the Australian Northern Prawn Fishery (NPF). Both fisheries entail direct and indirect impacts on mixed species communities while also generating large economic returns. Their sustainability is therefore a major societal concern. A dynamic bio-economic modelling approach is used to capture the key biological and economic processes governing these fisheries, combining age- (BoB) or size- (NPF) structured models of multiple species with recruitment uncertainty, and multiple fleets (BoB) or fishing strategies (NPF). Economic uncertainties relating to input and output prices are also considered. The bioeconomic models are used to investigate how the fisheries can operate within a set of constraints relating to the preservation of Spawning Stock Biomasses (BoB) or Spawning Stock Size Indices (NPF) of a set of key target species, maintenance of the economic profitability of various fleets (BoB) or the fishery as a whole (NPF), and limitation of fishing impacts on the broader biodiversity (NPF), under a range of alternative scenarios and management strategies. Results suggest that under a status quo strategy both fisheries can be considered as biologically sustainable, while socio-economically (and ecologically in the NPF case) at risk. Despite very different management contexts and objectives, viable management strategies suggest a reduction in the number of vessels in both cases. The BoB simulations allow comparison of the trade-offs associated with different allocations of this decrease across fleets. Notably, co-viability management strategies entail a more equitable allocation of effort reductions compared to strategies aiming at maximizing economic yield. In the NPF, species catch diversification strategies are shown to perform well in controlling the levels of economic risk, by contrast with more specialized fishing strategies. Furthermore analyses emphasize the importance to the fishing industry of balancing global economic performance with inter-annual economic variability. Promising future developments based on this research involve the incorporation of a broader set of objectives including social dimensions, as well as the integration of ecological interactions, to better address the needs of ecosystem-based approaches to the sustainable harvesting of marine biodiversity.
L’objectif général de la thèse est de modéliser les principaux processus biologiques et économiques régissant des pêcheries multi-espèces et multi-flottilles afin de proposer des stratégies viables pour la gestion durable de ces pêcheries mixtes, dans un contexte stochastique et multiobjectif. Plus spécifiquement, cette thèse utilise des analyses de co-viabilité stochastique pour étudier les arbitrages entre des objectifs contradictoires de gestion (conservation, et viabilité économique et sociale) des pêcheries mixtes. Deux pêcheries mixtes sont analysées dans cette thèse: la pêcherie française mixte démersale du golfe de Gascogne et la pêcherie crevettière australienne du Nord (NPF). Ces deux pêcheries sont multi-espèces, et utilisent des stratégies multiples de pêche, induisant des impacts directs et indirects sur les écosystèmes. Cette thèse propose une application de la co-viabilité stochastique à ces deux cas, en prenant en compte leur histoire, leur contexte socio-politique et les différences dans les stratégies et objectifs de gestion. Les résultats suggèrent que le status quo peut être considéré comme une stratégie biologiquement durable mais socio économiquement à risque dans les deux pêcheries (ainsi qu’à risque écologique dans le cas de la pêcherie australienne). Les simulations réalisées pour le golfe de Gascogne permettent de comparer les arbitrages associés à différentes réductions de capacités par flottille et de montrer qu’il existe des solutions de gestion permettant la co-viabilité du système (viabilité biologique des différentes espèces considérées et viabilité socio-économique des flottilles) contrairement à des stratégies de gestion mono-spécifiques ou basées sur la maximisation de la rente. Dans la pêcherie crevettière australienne, l’analyse montre que les stratégies de diversification permettent de limiter le risque économique contrairement aux stratégies plus spécialisées.

Droits : UBO, Univ. Tasmania
http://archimer.ifremer.fr/doc/00206/31731/30134.pdf
http://archimer.ifremer.fr/doc/00206/31731/

Éditeur(s) : HAL CCSD Human Kinetics
Résumé : International audience
The purpose of the present experiment was to examine whether the use of self-handicapping strategies influences participants' anxiety levels before athletic performance. Seventy-one competitive basketball players participated in the study. A repeated measures design was used, such that state cognitive and somatic anxiety intensity and direction were measured before and after participants were given the opportunity to self-handicap. Overall, participants reported their cognitive anxiety to be more facilitating after they had the opportunity to self-handicap. Thus, participants who were given the opportunity to self-handicap (i.e., use claimed and behavioral self-handicaps), reported greater increases in perceptions of cog-nitive anxiety as facilitating their performance. This study shows the importance of looking at anxiety direction, and not just anxiety intensity, when examining self-handicapping's effects on anxiety. Implications for sport psychologists are proposed.
ISSN: 1543-2793

Droits : info:eu-repo/semantics/OpenAccess
hal-01343255
https://hal.univ-antilles.fr/hal-01343255
https://hal.univ-antilles.fr/hal-01343255/document
https://hal.univ-antilles.fr/hal-01343255/file/TSP%2007-54.%20Final%20Manuscript.Self-handicapping%20and%20Anxiety%20in%20Sport%20HAL.pdf
DOI : 10.1123/tsp.22.3.304

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé :  
1. Despite considerable interest in the application of plant functional traits to questions of community assembly and ecosystem structure and function, there is no consensus on the appropriateness of sampling designs to obtain plot-level estimates in diverse plant communities. 2. We measured 10 plant functional traits describing leaf and stem morphology and ecophysiology for all trees in nine 1-ha plots in terra firme lowland tropical rain forests of French Guiana (N = 4709). 3.We calculated, by simulation, the mean and variance in trait values for each plot and each trait expected under seven sampling methods and a range of sampling intensities. Simulated sampling methods included a variety of spatial designs, as well as the application of existing data base values to all individuals of a given species. 4. For each trait in each plot, we defined a performance index for each sampling design as the proportion of resampling events that resulted in observed means within 5% of the true plot mean, and observed variance within 20%of the true plot variance. 5. The relative performance of sampling designs was consistent for estimations of means and variances. Data base use had consistently poor performance for most traits across all plots, whereas sampling one individual per species per plot resulted in relatively high performance. We found few differences among different spatial sampling strategies; however, for a given strategy, increased intensity of sampling resulted in markedly improved accuracy in estimates of trait mean and variance. 6. We also calculated the financial cost of each sampling design based on data from our 'every individual per plot' strategy and estimated the sampling and botanical effort required. The relative performance of designs was strongly positively correlated with relative financial cost, suggesting that sampling investment returns are relatively constant. 7. Our results suggest that trait sampling for many objectives in species-rich plant communities may require the considerable effort of sampling at least one individual of each species in each plot, and that investment in complete sampling, though great, may be worthwhile for at least some traits.
Functional Ecology

hal-01032175
https://hal.archives-ouvertes.fr/hal-01032175
DOI : 10.1111/j.1365-2435.2009.01600.x

Éditeur(s) : HAL CCSD
Résumé : While often criticized, independence remains the ultimate criterion for evaluating board composition, whether for regulators or shareholder activists. In this study, we examine the relationship between board independence and firm operating performance in a panel of French listed companies, paying particular attention to heterogeneity and endogeneity concerns. We take advantage of an original database, with a time-series dimension that can be used to mitigate heterogeneity and dynamic endogeneity issues through GMM estimators. In addition, this database can be disaggregated at the individual (director) level. This design enables us to introduce firm fixed effects and individual fixed effects in (firm) performance equations, thereby controlling for heterogeneity at the firm and individual levels. To our knowledge, this is the first paper so far to provide a systematic account on this issue for France. Our main result is to document a significant negative relationship between accounting performance and the independence status (irrespective of the person). This result supports the argument of an information gap suffered by independent board members, as developed by Adams and Ferreira (2007).
https://hal.archives-ouvertes.fr/hal-00919408

hal-00919408
https://hal.archives-ouvertes.fr/hal-00919408
https://hal.archives-ouvertes.fr/hal-00919408v2/document
https://hal.archives-ouvertes.fr/hal-00919408/file/cahier_de_recherche_2014-01.pdf

Éditeur(s) : HAL CCSD
Résumé : International audience
Mylonite bodies are exhumed extensions at depth of shallow structural level brittle faults. They are characterised by intense strain localisation involving large volumes of middle to lower continental crust. The analysis of shear zone geometry and microstructures is a useful tool to decipher deformation kinematics, though finite strain estimation is still relatively qualitative. Timing of the deformation has also been the focus of numerous studies using the complete spectrum of geochronometers. However, only rare examples provide geochronological data that can be unambiguously interpreted and cooling, recrystallisation and neocrystallisation are difficult to tell from each other. Thus, time-scales over which major mylonite zones develop and remain active under ductile conditions as well as their strain rate often remain poorly documented. We investigated two sections across the South-Armorican Shear Zone (SASZ), a crustal-scale pluri-km thick dextral shear zone active during a single tectonic event of late-Variscan age and associated with syntectonic granite emplacement.. Finite strain profiles on these cross-sections, quantified from average Quartz grain-size in 34 samples, show a strong deformation partitioning towards the center of the SASZ, with a decrease, for each section, from 150µm in slightly deformed zones to less than 7-5 µm in the core of the ultramylonite. Furthermore, toward the core of the SASZ, development of a penetrative shear band network progressively eliminates lenses of less deformed rocks and results in homogenisation of the Quartz grain sizes. In parallel, we performed in-situ UV-laser Ar/Ar dating on the fabric-forming white micas. White micas population can be decomposed into inherited muscovites carried by the folation and newly-formed, syn-tectonic substituted phengites located along the shear bands yielding 2 age groups for each sample. Along the profiles, the difference between these two ages evolves from 10-15 Ma in weakly deformed domains to zero toward the SASZ core. In addition, mylonite-forming phengites yielded the same age irrespectively of their position on the section or of the rock strain.. On the regional point of view, this study brings deformation-ages for the late-orogenic evolution of the South Armorican domain. Strain accumulated along the SASZ in a time-span extending to 300-298 Ma, i.e. contemporaneously with the activity of nearby major extensional shear zones. These results support a new model of crustal-scale shear zone activity, where the whole body of the shear zone is active throughout its history (defined as the largest age difference through the section), i.e. the actively deforming zone does not get progressively narrower. The strain distribution nevertheless evolves with time, with an increasingly large fraction partitioned in the ultramylonitic core.
EGU General Assembly
Vienne, Austria

insu-00839320
https://hal-insu.archives-ouvertes.fr/insu-00839320
BIBCODE : 2010EGUGA..12.9881A

Résumé : Bacteriological study of abyssal sediments: During the Demeraby mission of the N/O Jean Charcot in the western Atlantic Ocean, a study of the microflora of the digestive tracts of echinoderms (Holothuroidea of various genera, Asteroidea, Echinoidea) was compared with that of the surrounding sediment. The bacterial concentration observed in the digestive tracts of all the animals studied is higher than that in the surrounding sediments. The largest numbers were always found in the most anterior part of the digestive tracts of the holothurians. In some cases, the increase is considerable (7.10 versus 5.2. 10 cells per millilitre): It indicates a proliferation of bacterial cells in the anterior part of the digestive tract. As the sediment moves through the digestive tract, the bacterial level progressively decreases. In the most posterior part, the concentration is, however, always clearly greater than that in the surrounding sediment. In the case of the holothurian of the genus Deima, analysis according to the Adamsonian principle of comparison shows that the microflora isolated from the various parts of the digestive tract is composed of taxonomic groups showing little resemblance to those isolated from the sediment. In the case of the holothurian of the genus Pseudostichopus, no specialisation of the microflora from digestive tract contents appears with respect to that of the ingested sediment. Examination of metabolic activities suggests a juxtaposition of two types of communities: Free sediment - sediment in transit that complement one other in their enzymatic and nutritional behaviour Indeed, the strains of free sediment seem to be rather suitable for hydrolysing and using carbohydrates, while those of enteric communities prefer the hydrolysis of lipids and proteins and the assimilation of fatty acids, dicarboxylic acids, hydroxylic acids and certain amino acids. Moreover, the enteric microflorae possess a greater nutritional versatility that, linked with its total numbers, has a sizeable catabolic potential. .../... -2- Measurements of heterotrophic activity done by means of 14 C glucose tracers make it possible to show that the metabolic activities of the bacterial communities of superficial abyssal sediments vary according to zones. In the Amazon Cone, a clear glucose mineralization gradient over a distance of a few kilometres can be observed. In the abyssal plain of Demerara heterotrophic activities are slowed in relation to those of the superficial sediments of the Cone of the Amazon, even though the bacterial numbers and the depths are of the same order of magnitude in the two zones. The abundant microflorae associated with the various divisions of digestive tract contents of the Deima abyssal holothurian manifest little metabolic activity as regards the glucose. However, the bacterial communities of Pseudostichopus and Psychropotes manifest very strong heterotrophic activities, increasing from the oesophagus towards the cloaca. Current results are too fragmentary to allow us to observe possible physiological specialisation of enteric bacterial communities enabling the facilitation of digestion processes in the host. Conclusion: In the abyssal environment, characterised by poorly developed bacterial communities, microflorae associated with the digestive tract contents of echinoderms have considerably greater cellular concentrations. By means of their enzymatic equipment, these enteric communities, which complement those of the free microflorae of superficial sediments, can participate in the transformation of organic matter in the abyssal area. Study of the dynamics of microbial communities and their heterotrophic activities in shellfish farms: From experiments done on the water in the Arcachon basin, trials to quantify and describe the reactivity potential of bacterial communities were performed. Bacterial communities were defined by direct counts, counts after setting them up for cultivation, structure and diversity of these communities, dosage of AMP, ADP, ATP. Two opposite ecological conditions were considered: Autumn conditions (high temperature) and a winter conditions (low temperature). Tubs of sea water of 6 and 60 litres were enriched either with ammonium chloride or a mixture of amino acids, at about 500 uAtg N.L. The experiments lasted 24 hours, with sampling every 3 hours. The autumn community reacted rapidly (6 hours), the response to the enrichment in organic nitrogen being the highest. The structure of the community has unstable immature stages. On the contrary, during the winter experiment, no response could be perceived. This may mean that the latency phase is greater than 24 hours. The structure of this community has mature stages. In conclusion, bacterial communities react in the same way as macroscopic communities. Stable communities are diversified and correspond to mature stages of the ecosystem; the immature stages are unstable and less diversified. This type of experiment has made it possible to bring to light the rapidity of response of bacterial populations, and can be used to define the stability of a bacterial community in a precise biotope.
ETUDE BACTERIOLOGIQUE DES SEDIMENTS ABYSSAUX RESUME Au cours de la mission DEMERABY du n/o Jean CHARCOT en atlantique occidental , une étude de la microflore des tractus digestifs d'Echinodermes (Holothurides de différents genres, Astérides, Echinides) a été comparée à celle du sédiment environnant. La concentration bactérienne observée dans les tractus digestifs de tous les animaux étudiés est supérieure à celle des sédiments environnants. Les effectifs les plus importants sont toujours observés dans la partie la plus antérieure des tractus digestifs des holothuries. Dans certains cas, l'accroissement est considérable (7.10 contre 5,2. 10 cellules/ml) : il indique une prolifération des cellules bactériennes dans la partie antérieure du tractus digestif. Au.cours de la progression du sédiment dans le tractus digestif, la charge bactérienne décroit progressivement. Dans la partie la plus postérieure, la concentration est cependant toujours nettement supérieure à celle du sédiment environnant-. Dans le cas d'une holothurie du genre Deima, l'analyse selon le principe adansonien de comparaison montre que la microflore isolée des différentes parties du tractus digestif est constituée de groupes taxonomiques présentant peu de ressemblance avec ceux isolés du sédiment. Dans le cas d'une holothurie du genre Pseudostichopus il n'apparait pas de spécialisation de la microflore du contenu du tractus digestif par rapport à celle du sédiment ingéré. ¿ ¿ . L'étude des activités métaboliques suggère une juxtaposition de deux types de communautés : sédiment libre-sédiment en transit qui se complètent dans leur comportement enzymatique et nutritionnel. En effet les souches du sédiment libre semblent être plutôt aptes à hydrolyser et à utiliser les glucides, tandis que celles des communautés entériques portent leur préférence sur l'hydrolyse des lipides et protéines et 1'assimilation des acides gras, acides dicarboxyl iques, hydro'xy-acides et certains acides aminés. D'autre part les microflores entériques possèdent une versatilité nutritionnelle plus importante qui, liée à leurs effectifs, offre une potentialité catabolique non négligeable. .../... -2- Les mesures d'activité hétérotrophe effectuées au moyen de traceurs glucose 14 C permettent de montrer que les activités métaboliques des communautés bactériennes des sédiments abyssaux superficiels varient selon les zones. Dans le Cone de l'Amazone on observe un net gradient de minéralisation du glucose sur une distance de quelques kilomètres. Dans la plaine abyssale de Demerara les activités hétérotrophessont ralenties par rapport à celles des sédiments superficiels du Cone de l'Amazone, bien que les effectifs bactériens et les profondeurs soient du même ordre de grandeur dans ces deux zones. Les abondantes microflores associées aux différentes fractions du contenu du tractus digestif de l'holothurie abyssale Deima ne manifestent que peu d'activités métaboliques vis à vis du glucose. Par contre les communautés . bactériennes de Pseudostichopus et P syahropotes manifestent des activités hétérotrophes très fortes, croissant de 1'oesophage vers le cloaque. Les résultats actuels sont trop fragmentaires pour permettre d'observer une éventuelle spécialisation physiologique des communautés bactériennes entëriques permettant de faciliter les processus de digestion chez l'hôte. Conclusion: dans le milieu abyssal, caractérisé par des communautés bactériennes faiblement développées, les microflores associées aux contenus de tractus digestif des Echinodermes présentent des concentrations cellulaires considérablement plus importantes. Par leurs équipements enzymâtiques ces communautés entëriques complémentaires de ceux des microflores libres des sédiments superficiels, peuvent participer à la transformation des matières organiques du domaine abyssal. ETUDE DE LA DYNAMIQUE DES COMMUNAUTES MICROBIENNES ET DE LEURS ACTIVITES HETEROTROPHES DANS LES PARCS CONCHYLICOLES RESUME A partir d'expérimentations effectuées sur l'eau du bassin d'Arcachon, des essais de quantification et qualification du potentiel de réactivité des communautés bactériennes ont été effectuées. Les communautés bactériennes ont été définies par comptage directs, comptages après mise en culture, structure et diversité de ces communautés, dosage des AMP, ADP, ATP. Deux situations écologiques opposées ont étées considérées . Une situation automnale (température élevée) et une situation hivernale (température faible). Des bacs d'eau de mer de 6 et 60 litres ont été enrichis , soit avec du chlorure d'ammonium, soit avec un mélange d'acides aminés, à environ 500 uAtg N.l" . Les expériences ont duré 24 heures, avec des prélèvements toutes les 3 heures. La communauté automnale réagit rapidement (6 heures), la ' réponse à l'enrichissement en azote organique étant la plus importante. La structure de la communauté présente des stades immatures instables. Au contraire, au cours de l'expérimentation hivernale, aucune réponse n'a pu être perçue. Ceci peut signifier que la phase de latence est supérieure à 24 heures. La structure . de cette communauté présente des stades matures. En Conclusion, les communautés bactériennes réagissent de la même façon que les communautés macroscopiques. Les communautés stables sont diversifiées et correspondent à des stades matures de l'écosystème, les stades immatures sont instables et moins diversifiés. Ce type d'expérience a permi de mettre en évidence la rapidité de réponse des populations bactériennes, et peut être utilisé pour définir la stabilité d'une communauté bactérienne dans un biotope précis.

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http://archimer.ifremer.fr/doc/1981/rapport-1926.pdf
http://archimer.ifremer.fr/doc/00000/1926/