Éditeur(s) : HAL CCSD Seismological Society of America
Résumé : International audience
Abstract The continuous record of large surface-rupturing earthquakes along the Dead Sea fault brings unprecedented insights for paleoseismic and archaeoseismic research. In most recent studies, paleoseismic trenching documents the late Holocene faulting activity, while tectonic geomorphology addresses the long-term behavior (>10 ka), with a tendency to smooth the effect of individual earthquake rupture events (Mw >7). Here, we combine historical, archaeological, and paleoseismic investigations to build a consolidated catalog of destructive surface-rupturing earthquakes for the last 14 ka along the left-lateral Jordan Valley fault segment. The 120- km-long fault segment limited to the north and the south by major pull-apart basins (the Hula and the Dead Sea, respectively) is mapped in detail and shows five subsegments with narrow stepovers (width < 3 km). We conducted quantitative geomorphology along the fault, measured more than 20 offset drainages, excavated four trenches at two sites, and investigated archaeological sites with seismic damage in the Jordan Valley. Our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at Tell Saydiyeh, supplemented with a rich historical seismic record, document 12 surface-rupturing events along the fault segment with a mean interval of ∼1160 yr and an average 5 mm=yr slip rate for the last 25 ka. The most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr, with a median value of 790 yr, and suggests an episodic behavior for the Jordan Valley fault. Our study allows a better constraint of the seismic cycle and related short-term variations (late Holocene) versus long-term behavior (Holocene and late Pleistocene) of a major continental transform fault.
ISSN: 0037-1106

hal-00747401
https://hal.archives-ouvertes.fr/hal-00747401
DOI : 10.1785/0120100097

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
We use 3 yr of surface absolute gravity measurements at three sites on the Larzac plateau (France) to quantify the changes induced by topography and the building on gravity time-series, with respect to an idealized infinite slab approximation. Indeed, local topography and buildings housing ground-based gravity measurement have an effect on the distribution of water storage changes, therefore affecting the associated gravity signal. We first calculate the effects of surrounding topography and building dimensions on the gravity attraction for a uniform layer of water. We show that a gravimetric interpretation of water storage change using an infinite slab, the so-called Bouguer approximation, is generally not suitable. We propose to split the time varying gravity signal in two parts (1) a surface component including topographic and building effects (2) a deep component associated to underground water transfer. A reservoir modelling scheme is herein presented to remove the local site effects and to invert for the effective hydrological properties of the unsaturated zone. We show that effective time constants associated to water transfer vary greatly from site to site. We propose that our modelling scheme can be used to correct for the local site effects on gravity at any site presenting a departure from a flat topography. Depending on sites, the corrected signal can exceed measured values by 5-15 μGal, corresponding to 120-380 mm of water using the Bouguer slab formula. Our approach only requires the knowledge of daily precipitation corrected for evapotranspiration. Therefore, it can be a useful tool to correct any kind of gravimetric time-series data.
ISSN: 0956-540X

hal-00795590
https://hal.archives-ouvertes.fr/hal-00795590
DOI : 10.1093/gji/ggs007

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
Surface displacements due to temporal changes in environmental mass redistributions are observable in the coordinate time series of many Global Navigation Satellite System (GNSS) sites. In this study, we investigated the effect of loading on estimates of tectonic velocity computed from campaign-style GNSS observations. The study region is in the Pyrenees mountain range between France and Spain (ResPyr campaigns). In this area, seismic activity is continuous and moderate and the expected amplitude of the horizontal tectonic velocity is less than 0.5 mm/yr. In order to determine the velocity, 4 sparse GNSS campaigns were carried out from 1995 to 2010. Considering this small rate of deformation, loading phenomena can contribute a non-negligible artifact to the velocity computation that could affect our geodynamical interpretation. In this investigation, we specifically considered the atmospheric, hydrological, and non-tidal ocean loading phenomena. The computed loading deformations for this region show the horizontal displacements are dominated by the non-tidal ocean loading (maximum 4 mm for the North and 3.1 mm for the East components); the main vertical contributions are due to the atmospheric and continental water storage loading (maximum 14.3 for the atmosphere and 8.1 mm for the hydrology, respectively). We have found that the dominant loading effect on the horizontal velocity is the non-tidal ocean loading (mean of 0.11 mm/yr), whereas the vertical component is dominated by the hydrological loading (mean of 0.21 mm/yr). Since the study area is in a mountainous region, we also analyzed the difference between the atmospheric and the topography dependent atmospheric loading models at our GNSS campaign sites. We did not find any significant difference between the two atmospheric loading models in terms of horizontal velocity. Finally, we performed simulations to identify the optimum timing and frequency of future GNSS campaigns in this area that would minimize the loading effects on tectonic velocity estimates.
ISSN: 0039-3169

hal-00963629
https://hal.archives-ouvertes.fr/hal-00963629
DOI : 10.1007/s11200-012-0458-2

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages , we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk.
ISSN: 0962-8452

hal-01323255
https://hal.archives-ouvertes.fr/hal-01323255
DOI : 10.1098/rspb.2015.0418

Éditeur(s) : HAL CCSD Paris : Muséum national d'histoire naturelle
Résumé : International audience
Coral reefs are one of the most diverse ecosystems on Earth and sustain millions of people worldwide.However, coral reefs are temporally dynamic and fragile systems subject to ever increasing disturbancesof anthoropogenic and natural origins. Understanding the patterns and trajectories of changes through time isurgently needed to estimate the resilience of coral reefs. To ascertain these patterns, we depend on the availabilityof long-term datasets, which are seldom available. In this study, we present the data set which allowed us to analysethe long-term trends of coral and fish assemblages for the island of Moorea (French Polynesia) from 1983to 2014, a dataset spanning 32 years, comprising two Acanthaster planci outbreaks (1987 and 2006) and severalhurricanes (1982, 1983, 1991 and 2010), on three permanent monitoring sites (quadrats of 50 × 2 m2) located onboth fringing and barrier reefs as well as on the outer slope. Coral cover oscillated significantly over time, particularlyon the outer slope where it suffered greatly from the effects of A. planci outbreaks and hurricanes. Totalfish and commercial fish abundances varied significantly across the three habitats. Prior to 2000, both total fishand herbivorous fish abundances increased on the barrier reef while after this time, numbers began to drop significantlyalong the outer slope. Species richness for total, commercialized and herbivorous fish increased over thesampling period for all three habitats. There were varied responses amongst species to disturbances on the outerslope over the sampling period: while some tended to disappear for a while before reappearing, others showed apeak in abundance in the middle of the sampling period, and still others increased or decreased continuously orwere stable over time. Our results support the view that coral reefs are highly dynamic systems and that differentfunctional groups show different temporal trajectories. While disturbance is probably the major driver for coralcover dynamics, its impact is less obvious for fish, possibly due to their mobility and population dynamics whichmay mask the effect of disturbance.
Les récifs coralliens sont des systèmes dynamiques et diversifiés régulièrement soumis à des perturbationsnaturelles et anthropiques, sources d’hétérogénéité spatiale et temporelle dans la structure et la dynamique deces communautés d’organismes que sont, entre autres, les poissons et les coraux. Récemment, il a été démontréque les activités humaines pouvaient modifier les régimes naturels de perturbations des récifs coralliens en transformantles événements ponctuels en perturbations persistantes ou en stress chronique, soit en introduisant denouveaux types de perturbations, soit en ajoutant ou altérant certaines perturbations naturelles nécessaires au bonmaintien de la dynamique inhérente aux récifs. Dans cette étude, nous présentons la base de données qui nouspermettra d’analyser les tendances à long-terme des assemblages de poissons et de coraux de l’île de Moorea(Polynésie française) entre 1983 et 2014 sur une période de 32 ans, comprenant deux proliférations d’Acanthasterplanci (1987 et 2006) et plusieurs cyclones (1982, 1983, 1991 et 2010), sur trois sites de suivi permanents(quadrats de 50 × 2 m2) sur les récifs barrière et frangeant ainsi que sur la pente externe. La couverture corallienneprésente de fortes oscillations, en particulier sur la pente externe où elle a répondu fortement à la proliférationd’A. planci et des cyclones. Les abondances des poissons totaux et des poissons commercialisés montrent destendances contrastées sur les trois habitats, avec, plus particulièrement, une augmentation sur le récif barrière etune diminution sur la pente externe après 2000. Ces tendances se retrouvent chez les poissons herbivores dansces deux habitats. La richesse spécifique des poissons totaux, commerciaux et herbivores, augmente de façoncontinue au cours de la période d’étude dans les trois habitats. Des groupes particuliers d’espèces répondentdifféremment aux perturbations de la pente externe au cours du suivi : alors que certaines espèces ont tendanceà disparaître pendant quelques années avant de réapparaître, d’autres présentent un pic en terme d’abondanceen milieu de suivi ; d’autres espèces ont des abondances qui augmentent ou diminuent de façon continue, etd’autres encore montrent des abondances stables. Ceci indique que les récifs coralliens sont des systèmes trèsdynamiques dans lesquels les perturbations naturelles peuvent affecter les espèces de façon différente. Alors quele régime de perturbations naturelles semble être important pour la dynamique de la couverture corallienne danscertains habitats, cela se retrouve beaucoup moins pour les poissons. Cette atténuation des fluctuations spatialeset temporelles peut être due aux aptitudes de dispersion de nombreuses espèces de poissons, capables de chercherun autre habitat favorable en cas de perturbation de l’habitat corallien d’origine.
ISSN: 0399-0974

hal-01282378
https://hal-univ-perp.archives-ouvertes.fr/hal-01282378

Éditeur(s) : Elsevier Science Bv
Résumé : The biodynamic and saturation models offer promising lines of enquiry to predict the bioaccumulation of metals by aquatic organisms. However, in order to construct these models, the accumulation strategies have to be defined for each metal/organism couple in controlled conditions. This study aims at modelling the waterborne bioaccumulation of Ni and the influence of the water's geochemical properties on this process in a crustacean that is widely distributed in Europe, Gammarus pulex. In the laboratory, G. pulex was exposed to several Ni concentrations (from 0.001 to 100 mg L(-1)) in aquatic microcosms. Our results show that G. pulex is very tolerant to Ni (LC50(48 h) = 477 mg L(-1) Ni). Time course experiments enabled the construction of a biodynamic model by determining the uptake (k(u)) and elimination (k(e)) rate constants. When the exposure concentration exceeded 1 mg L(-1) Ni, the metal uptake reached a maximum due to a limited number of binding sites for Ni. Therefore, the organism's maximal capacity to accumulate the metal (B(max)) and the half-saturation constant (K) were determined to establish the saturation model. We showed that the two models are comparable for the lowest exposure concentrations (<1 mg L(-1) Ni), with k(u)/k(e) = B(max)/K. Then, the bioaccumulation of Ni was recorded in waters exhibiting various concentrations of three major ions (Na(+), Mg(2+) and Ca(2+)). Only Ca had an inhibitory effect on the Ni uptake. This study reports for the first time the bioaccumulation of Ni in G. pulex. Because of its high tolerance to Ni and its high capacity to accumulate this metal, this crustacean could be used as an indicator of Ni bioavailability in freshwaters. (C) 2011 Elsevier B.V. All rights reserved.
Aquatic Toxicology (0166-445X) (Elsevier Science Bv), 2011-08 , Vol. 104 , N. 3-4 , P. 161-167

Droits : 2011 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00041/15217/18005.pdf
DOI:10.1016/j.aquatox.2011.04.011
http://archimer.ifremer.fr/doc/00041/15217/

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Plant litter diversity effects on decomposition rates are frequently reported, but with a strong bias towards temperate ecosystems. Altered decomposition and nutrient recycling with changing litter diversity may be particularly important in tree species-rich tropical rainforests on nutrient-poor soils. Using 28 different mixtures of leaf litter from 16 Amazonian rainforest tree species, we tested the hypothesis that litter mixture effects on decomposition increase with increasing functional litter diversity. Litter mixtures and all single litter species were exposed in the field for 9 months using custom-made microcosms with soil fauna access. In order to test the hypothesis that the long-term presence of tree species contributing to the litter mixtures increases mixture effects on decomposition, microcosms were installed in a plantation at sites including the respective tree species composition and in a nearby natural forest where these tree species are absent. We found that mixture decomposition deviated from predictions based on single species, with predominantly synergistic effects. Functional litter diversity, defined as either richness, evenness, or divergence based on a wide range of chemical traits, did not explain the observed litter mixture effects. However, synergistic effects in litter mixtures increased with the long-term presence of tree species contributing to these mixtures as the home field advantage hypothesis assumes. Our data suggest that complementarity effects on mixed litter decomposition may emerge through long-term interactions between aboveground and belowground biota.
ISSN: 0029-8549

hal-01032393
https://hal.archives-ouvertes.fr/hal-01032393
DOI : 10.1007/s00442-011-1966-4

Éditeur(s) : HAL CCSD
Résumé : Karstic aquifers represent the most important fresh water reservoirs in many regions of the world like the Mediterranean Basin. However, because of complex processes of karstification, those aquifers are highly heterogeneous at all spatial scales and vulnerable to contamination. In this dissertation, we studied the potential of gravimetry and ambient seismic noise for hydrological modeling in karstic areas.The dolomitic area surrounding the “GEK” observatory in the Durzon catchment on the Larzac plateau, in France, is the preferred site for these studies. Inside the observatory, a superconducting gravimeter dedicated to hydrology has continuously measured gravity changes since 2011 with high precision, undertaken for the first time on a karst. From this gravity monitoring, we made conceptual hydrological models which laid the foundation of 1-D flow physical models. Indeed, gravimetry is an integrative hydro-geophysical method which allows 1) to consider the epikarst, locally heterogeneous as an equivalent tabular medium and 2) to define the types of transfer (fast & slow) occurring at the site. Especially, the lack of fast transfer through the GEK epikarst was precisely quantified for the first time at the field scale (~100m). Gravity-driven water mass balance with local meteorological data (evapotranspiration from a flux tower and precipitation) allowed setting the bottom outlet of the model to 1 mm.day-1. This flow has proved to be representative of the low-flow discharge at the only spring which represents all groundwater outflows from the catchment. This result supposes the homogeneity of the dolomitic epikarst almost at the basin scale. Model parameters were next calibrated using one year of ambient seismic noise monitored at two stations. Phase velocity changes obtained by cross-correlating the noise between 6 and 8 Hz were used as a ”timer” to follow the water infiltration between a depth of 30 and 60 meters. Thus, monitoring seismic velocity changes using ambient seismic noise demonstrates great potential for the study of deep and complex critical zones and could fill the instrumental gap currently existing in hydrology.Time-lapse gravity measurements with a spring-based portable gravimeter have also demonstrated the different behavior of two epikarsts and their variability at the scale of a few hundred meters. Monthly measurements around the observatory revealed the spatial homogeneity of this dolomitic epikarst: all the stations showed the same water storage changes. On the contrary, seasonal surface to depth gravity measurements along the underground passage of the Saint-Ferréol sinkhole, in limestone, have shown fast transfer and strong spatial variability of water storage. Lithology is then expected to play a part in the epikarst capacity to retain water. The precision needed to measure the weak hydrological induced signals during those surveys required robust methodology and an ambient temperature effect on measurements with spring-based gravimeter was observed in the field and quantified in the laboratory.
Les aquifères karstiques représentent des ressources en eau essentielles dans de nombreuses régions du monde comme le bassin Méditerranéen. Cependant, de par les processus complexes de karstification, ces aquifères sont hétérogènes à de nombreuses échelles et vulnérables. Dans cette thèse, nous étudions le potentiel de la gravimétrie et du bruit sismique ambiant pour la modélisation hydrologique en milieu karstique.Le site dolomitique de l’observatoire « GEK », sur le bassin du Durzon dans le Larzac, est le site d’étude privilégié de ces travaux. Dans l’observatoire, un gravimètre supraconducteur dédié à l’hydrologie mesure depuis 2011 les variations de gravité en continu et à une très haute précision, pour la première fois sur un karst. Des modèles hydrologiques conceptuels ont été réalisés à partir de cette surveillance gravimétrique et ont permis de poser les bases de modèles physiques d’écoulements 1-D. En effet la gravimétrie, intégratrice, permet 1) de considérer l’épikarst localement hétérogène comme un milieu tabulaire équivalent et 2) de définir les types de transfert à l’œuvre sur le site. En particulier, l’absence de transfert rapide dans l’épikarst a été quantifiée avec précision pour la première fois à l’échelle du terrain (~100m). A l’aide de données météorologiques locales, un bilan de masse précis a permis de définir le flux en limite inférieure du modèle à 1 mm.jour-1. Ce flux s’est montré représentatif du débit de basses-eaux de la source drainant l’ensemble du bassin. Ce résultat suppose une homogénéité de l’épikarst dolomitique quasiment à l’échelle du bassin. Les paramètres des modèles physiques ont ensuite pu être calibrés à l’aide d’un an d’intercorrélation du bruit sismique ambiant entre deux stations. Les variations de vitesses de phase obtenues entre 6 et 8Hz nous ont servi de « chronomètre » pour suivre l’infiltration entre 30 et 60m de profondeur. La surveillance passive des variations de vitesses sismiques par intercorrélation du bruit sismique ambiant montre ainsi un fort potentiel pour l’étude des zones critiques profondes et complexes à l’échelle du terrain et peut combler la lacune instrumentale qui existe actuellement en hydrologie.Des campagnes répétées de mesures avec un gravimètre portable à ressort ont également mis en évidence le fonctionnement différent de deux épikarsts et leur variabilité à l’échelle de la centaine de mètres. Des mesures mensuelles autour de l’observatoire ont mis en évidence l’homogénéité spatiale de cet épikarst dolomitique : toutes les stations ont les mêmes variations temporelles de stock d’eau. Au contraire, des mesures saisonnières en surface et en profondeur le long de la galerie souterraine calcaire de l’abîme de Saint-Ferréol ont montré une variabilité spatiale forte du stockage ainsi que du transfert rapide. La lithologie de l’épikarst est donc suspectée de jouer un rôle dans sa capacité de stockage. Lors de ces campagnes, la faiblesse du signal recherché a nécessité une méthodologie précautionneuse et un effet de température sur les mesures des gravimètres relatifs à ressort a été observé sur le terrain et quantifié en laboratoire.
https://tel.archives-ouvertes.fr/tel-01649606

NNT : 2016MONTT128
tel-01649606
https://tel.archives-ouvertes.fr/tel-01649606
https://tel.archives-ouvertes.fr/tel-01649606/document
https://tel.archives-ouvertes.fr/tel-01649606/file/2016_FORES_archivage.pdf

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

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

Éditeur(s) : HAL CCSD Inter-Research
Résumé : International audience
Ecological connectivity is important for effective marine planning and biodiversity conservation. Our aim was to identify factors important in influencing variation in benthic community structure on shallow rocky reefs in 2 regions of the Mediterranean Sea with contrasting oceanographic regimes. We assessed beta (β) diversity at 146 sites in the littoral and shallow sub-littoral from the Adriatic/Ionian Seas (eastern region) and Ligurian/Tyrrhenian Seas (western region) using a null modelling approach to account for variation in species richness. The distance decay relationship between species turnover within each region and geographic distance by sea was determined using generalised linear models. Mantel tests were used to examine correlations between β diversity and connectivity by ocean currents, estimated from Lagrangian dispersal simulations. Variation in β diversity between sites was partitioned according to environmental and spatial components using a distance-based redundancy approach. Species turnover along a gradient of geographic distance was greater by a factor of 3 to 5 in the western region than the eastern region, suggesting lower con-nectivity between sites. β diversity was correlated with connectivity by ocean currents at both depths in the eastern region but not in the western region. The influence of spatial and environmental predictors of β diversity varied considerably between regions, but was similar between depths. Our results highlight the interaction of oceanographic, spatial and environmental processes influencing benthic marine β diversity. Persistent currents in the eastern region may be responsible for lower observed β diversity compared to the western region, where patterns of water circulation are more variable.
Marine Ecology Progress Series

Droits : http://creativecommons.org/licenses/by/
hal-01357935
https://hal-univ-perp.archives-ouvertes.fr/hal-01357935
https://hal-univ-perp.archives-ouvertes.fr/hal-01357935/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01357935/file/m553p001.pdf
DOI : 10.3354/meps11783

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé :  
In this paper, we report a study of the mating system and gene flow of Symphonia globulifera, a hermaphroditic, mainly bird-pollinated tree species with a large geographic distribution in the tropical Americas and Africa.Using three microsatellites, we analysed 534 seeds of 28 open pollinated families and 164 adults at the experimental site 'Paracou' in French Guiana. We observed, compared to other tropical tree species, relatively high values for the effective number of alleles. Significant spatial genetic structure was detected, with trees at distances up to 150 m more genetically similar than expected at random. We estimated parameters of the mating system and gene flow by using the mixed mating model and the TwoGener approach. The estimated multilocus outcrossing rate, tm, was 0.920. A significant level of biparental inbreeding and a high proportion of full-sibs were estimated for the 28 seed arrays. We estimated mean pollen dispersal distances between 27 and 53 m according to the dispersal models used. Although the adult population density of S. globulifera in Paracou was relatively high, the joint estimation of pollen dispersal and density of reproductive trees gave effective density estimates of 1.6 and 1.3trees/ha. The parameters of the mating system and gene flow are discussed in the context of spatial genetic and demographic structures, flowering phenology and pollinator composition and behaviour.
ISSN: 0018-067X

hal-01032178
https://hal.archives-ouvertes.fr/hal-01032178
DOI : 10.1038/sj.hdy.6800560

Éditeur(s) : HAL CCSD Ecological Society of America
Résumé : Line transect surveys are widely used in neotropical rainforests to estimate the population abundance of medium- and large-sized vertebrates. The use of indices such as Encounter Rate has been criticized because the probability of animal detection may fluctuate due to the heterogeneity of environmental conditions among sites. In addition, the morphological and behavioral characteristics (biological traits) of species affect their detectability. In this study, we compared the extent to which environmental conditions and species' biological traits bias abundance estimates in terra firme rainforests in French Guiana. The selected environmental conditions included both physical conditions and forest structure covariates, while the selected biological traits included the morphological and behavioral characteristics of species. We used the distance sampling method to model the detection probability as an explicit function of environmental conditions and biological traits and implemented a model selection process to determine the relative importance of each group of covariates. Biological traits contributed to the variability of animal detectability more than environmental conditions, which had only a marginal effect. Detectability was best for large animals with uniform or disruptive markings that live in groups in the canopy top. Detectability was worst for small, solitary, terrestrial animals with mottled markings. In the terra firme rainforests which represent ~80% of the Amazonia and Guianas regions, our findings support the use of relative indices such as the encounter rate to compare population abundance between sites in species-specific studies. Even though terra firme rainforests may appear similar between regions of Amazonia and the Guianas, comparability must be ensured, especially in forests disturbed by human activity. The detection probability can be used as an indicator of species' vulnerability to hunting and, thus, to the risk of local extinction. Only a few biological trait covariates are required to correctly estimate the detectability of the majority of medium- and large-sized vertebrates. Thus, a biological trait model could be useful in predicting the detection probabilities of rare, uncommon or localized species for which few data are available to fit the detection function.
ISSN: 1051-0761

hal-01555267
https://hal.archives-ouvertes.fr/hal-01555267
DOI : 10.1002/eap.1549
PRODINRA : 396614
PUBMED : 28419598

Résumé : La connaissance des facteurs qui influent sur les populations de tiques et en particulier sur leurs distributions est un préalable indispensable à l’étude des maladies qu’elles transmettent. Parmi eux, l’importance des facteurs biotiques et en particulier celle de la compétition interspécifique est peu connue et souvent négligée. L’objectif de ce travail était d’évaluer le rôle de la compétition interspécifique sur la distribution de deux espèces de tiques d’importance vétérinaire, Amblyomma variegatum et A. hebraeum. Alors que seule A. variegatum favorise la transmission de la dermatophilose, une maladie de peau débilitante pour les ruminants, les deux espèces sont vectrices de la cowdriose, maladie due à une bactérie Ehrlichia ruminantium qui représente une contrainte économique majeure pour l’élevage. L’impact de l’espèce vectrice dans l’épidémiologie de la cowdriose (différences de souches circulantes, sévérité des cas,…) est inconnu bien qu’ayant potentiellement des conséquences en termes de surveillance (risque épidémiologique à l’introduction d’animaux) et de contrôle (développement de vaccin régional adapté aux souches circulantes) de la maladie. Ces deux espèces ont une distribution contiguë en Afrique australe avec peu de chevauchement (distribution parapatrique) suggérant une préférence environnementale différentielle ou une compétition exclusive entre elles. Une revue des données de la littérature a permis de mettre en évidence un chevauchement de leur niche trophique, climatique, et temporelle, et une interférence comportementale via la production de leurs phéromones. Les deux espèces pourraient donc rentrer en compétition directement par interférence communicative ou reproductive (hybridation stérile), ou indirectement via le partage de ressources, prédateurs ou pathogènes communs. Le rôle des facteurs biotiques et abiotiques sur le maintien de la parapatrie de ces deux espèces a été analysée (i) d’une part par la comparaison de leur niche environnementale réalisée en Afrique australe, et aux deux zones de contact au Zimbabwe et Mozambique, par des méthodes d’ordination et de modèles de niche (Maxent) ; (ii) et d’autre part par l’étude de leurs distributions et de leurs interactions (distribution sur les hôtes, croisements hétérospécifiques) dans la zone de contact au Mozambique. Globalement les résultats montrent qu’en Afrique Sud-Est et au Zimbabwe les deux espèces occupent des niches environnementales distinctes, celle d’A. hebraeum incluant des zones plus chaudes et plus sèches que celle d’A. variegatum. Au contraire au Mozambique les deux niches se chevauchent considérablement. L’enquête de terrain dans cette zone montre que les deux espèces y sont moins souvent trouvées en sympatrie que les données prédites, suggérant une distribution en partie déterminée par des interactions biotiques. Dans les rares sites avec présence des deux espèces, A. variegatum et A. hebraeum partagent les mêmes sites de fixation sur les animaux et forment un pourcentage relativement élevé de couples hétérospécifiques. Ce pourcentage, bien que similaire entre les femelles A. variegatum et A. hebraeum, semble impliquer des processus de discrimination spécifique propres aux deux espèces intervenant au niveau de l’agrégation, de la fixation et du contact des individus. Nos résultats suggèrent l’existence d’une compétition exclusive entre les deux espèces, due à une compétition sexuelle probablement associée à une compétition indirecte. La frontière parapatrique semble occuper une position stable le long d’un gradient environnemental au Zimbabwe mais pas au Mozambique. Les conditions entrainant la coexistence ou l’exclusion des deux espèces avec formation d’une frontière parapatrique sont discutés à l’aide de modèles théoriques de compétition.
Studying the factors that influence tick populations and their distributions is an essential pre-requisite to understanding the dynamics of the diseases they transmit. The relative importance of biotic factors such as interspecific competition is not well known and often neglected. The objective of this study was to assess the influence of interspecific competition on the distribution of two tick species of veterinary importance, Amblyomma variegatum and A. hebraeum. Whereas only A. variegatum is known to favor dermatophilosis, a debilitating skin disease of ruminants, both species are good vectors of Ehrlichia ruminantium, the bacteria causing heartwater, a fatal disease of ruminants that presents a major constraint for livestock development in Africa. The impact of vector species in heartwater epidemiology (differences of circulating strains, severity of clinical cases…) is poorly known but may have important implications for surveillance (epidemiological risk of imported animals) and control (adapting regional vaccine programs to circulating strains) of the disease. These two ticks have abutting and marginally overlapping (i.e. parapatric) distributions in southern Africa, suggesting either differential environmental preferences or exclusive competition between the two species. A review of published data highlighted an important overlap of their trophic, climatic and seasonal niche, and existence of chemical behavior interference through pheromone production. Therefore, the two species might compete either directly by communicative or reproductive interference (sterile hybridization), or indirectly by sharing the same resources, predators or pathogens. The role of biotic and abiotic factors in determining parapatry of these species was assessed by (i) comparing their realized environmental niche in southern Africa, and at contact zones in Zimbabwe and Mozambique, using ordination techniques and environmental niche modeling (Maxent); (ii) studying their distributions and their interactions (distribution on co-infested host, heterospecific mating) at the contact zone in Mozambique. Globally, the results indicated the two species occupied distinctly different environmental niches in southern Africa and at the contact zone in Zimbabwe, with the niche of A. hebraeum including both hotter and drier areas than that of A. variegatum. However, in Mozambique their niches overlapped considerably. Field studies within this zone showed that sympatry was observed less frequently than predicted by niche models, suggesting an importance of biotic interactions. At the rare sites where both species were present, A. variegatum and A. hebraeum were observed to share the same preference sites on hosts and formed a high percentage of heterospecific pairs. Though this cross-mating rate was not significantly different between A. variegatum and A. hebraeum females, our observations suggest different mechanism of species discrimination involved for the two species acting at the aggregation, fixation and partner contact level. Our results strongly suggest exclusive competition between these species may arise from sexual competition probably interacting with other indirect forms of competition. The parapatric boundary apparently occupies a stable location along an environmental gradient at the contact zone in Zimbabwe but not in Mozambique. Conditions inducing coexistence or exclusion of both species with the formation of parapatric distributions are discussed in relation to theoretical models of competition. When sexual competition is introduced in these models, the relative frequency of two species is determined by their endogenous fitness (a function of environmental conditions), density dependent effects of competitive interactions, historical distributions and dispersal rates: survival of the first prevails when the immigration rate of a fitter invading species remains lower than an invasion threshold.

http://www.theses.fr/2014AGUY0705/document

Éditeur(s) : HAL CCSD Endocrine Society
Résumé : International audience
Transcriptional regulation by the estrogen receptor-alpha(ER) has been investigated mainly in breast cancer cell lines, but estrogens such as 17 beta-estradiol (E2) exert numerous extrareproductive effects, particularly in the liver, where E2 exhibits both protective metabolic and deleterious thrombotic actions. To analyze the direct and early transcriptional effects of estrogens in the liver, we determined the E2-sensitive transcriptome and ER cistrome in mice after acute administration of E2 or placebo. These analyses revealed the early induction of genes involved in lipid metabolism, which fits with the crucial role of ER in the prevention of liver steatosis. Characterization of the chromatin state of ER binding sites (BSs) in mice expressing or not ER demonstrated that ER is not required per se for the establishment and/or maintenance of chromatin modifications at the majority of its BSs. This is presumably a consequence of a strong overlap between ER and hepatocyte nuclear factor 4 alpha BSs. In contrast, 40% of the BSs of the pioneer factor forkhead box protein a (Foxa2) were dependent upon ER expression, and ER expression also affected the distribution of nucleosomes harboring dimethylated lysine 4 of Histone H3 around Foxa2 BSs. We finally show that, in addition to a network of liver-specific transcription factors including CCAAT/enhancer-binding protein and hepatocyte nuclear factor 4 alpha, ER might be required for proper Foxa2 function in this tissue.
ISSN: 0888-8809

hal-01357623
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01357623
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01357623/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01357623/file/Changes%20in%20gene%20expression%201%20and%20Estrogen%20Receptor_accepted.pdf
DOI : 10.1210/me.2015-1311

Éditeur(s) : HAL CCSD
Résumé : Integrating ecological connectivity into marine ecosystem management and planning is important, especially in a global context of severe fish stocks depletion and growing habitat degradation. Environmental tools such as Marine Protected Areas have been proposed to protect biodiversity, restore damaged ecosystems, sustain fisheries, and rebuild overexploited stocks. The effectiveness of marine protected areas depends in part on the maintenance of connectivity between marine populations, linked by ecological processes such as larval dispersal. In this thesis, we applied a biophysical model driven by ocean currents derived from satellite altimetry to evaluate connectivity between Western Indian Ocean reefs and across the current MPA system in the Mediterranean Sea. We applied different methods of analysis such as graph-theoretic and clustering. In the Western Indian Ocean, marine connectivity analyses show that the number of connections between reefs increases with fish pelagic larval duration. It also highlights a low connectivity across the region and a high interconnectivity within several regions (Mozambique Channel, Mascarene archipelago). In the Mediterranean Sea, connectance is globally low at the regional scale. This connectance is more important in Western than Eastern Mediterranean. Moreover, the marine connectivity analyses revealed high domestic connectivity rates. Depending on the study area, priority reefs or sites for MPA implementation are proposed. Finally, implications for transboundary marine policies and regional cooperation are discussed.
Intégrer les connaissances sur la connectivité écologique dans la gestion des écosystèmes marins est essentiel, surtout dans un contexte d'appauvrissement des ressources marines et de dégradation des habitats côtiers à l'échelle mondiale. Des outils environnementaux, tels que les Aires Marines Protégées ont été mises en œuvre pour protéger la biodiversité, restaurer les écosystèmes endommagés, soutenir les pêcheries et reconstituer les stocks surexploités. Leur efficacité dépend en partie du maintien de la connectivité entre les populations marines, assurée à travers divers processus écologiques dont la dispersion larvaire. Dans le cadre de ce travail de thèse, un modèle biophysique intégrant des données de courants, issues de mesures d'altimétrie par satellite, a été utilisé pour évaluer la connectivité entre les récifs de l'océan Indien d'une part, et à travers le réseau d'AMP de Méditerranée d'autre part. Différentes méthodes d'analyse ont été utilisées, telles que la théorie des graphes et le clustering. Dans l'océan Indien occidental, l'analyse des connectivités marines montre que le nombre de connexions entre les récifs augmente avec la durée de vie larvaire des poissons. Elle met également en évidence une faible connectivité à l'échelle de la région, mais une forte inter-connectivité au sein de plusieurs sous-régions (Canal du Mozambique, Mascareignes). En Méditerranée, la connectance est globalement faible à l'échelle régionale, bien que plus importante dans le bassin occidental que le bassin oriental. L'analyse des connectivités marines montre également un taux de connectivité élevé à l'échelle d'un même pays. Selon le cas d'étude, une liste de récifs ou de sites prioritaires dans la mise en œuvre des AMP a été proposée. Enfin, les implications de ces résultats en termes de politiques transfrontalières et de coopération régionale sont discutées.
https://tel.archives-ouvertes.fr/tel-01269631

NNT : 2015LARE0003
tel-01269631
https://tel.archives-ouvertes.fr/tel-01269631
https://tel.archives-ouvertes.fr/tel-01269631/document
https://tel.archives-ouvertes.fr/tel-01269631/file/2015lare0003_ECrochelet.pdf

Éditeur(s) : HAL CCSD Wiley
Résumé : [b]1.[/b] Plant functional traits, in particular specific leaf area (SLA), wood density and seed mass, are often good predictors of individual tree growth rates within communities. Individuals and species with high SLA, low wood density and small seeds tend to have faster growth rates.[br/][br/][b]2.[/b] If community-level relationships between traits and growth have general predictive value, then similar relationships should also be observed in analyses that integrate across taxa, biogeographic regions and environments. Such global consistency would imply that traits could serve as valuable proxies for the complex suite of factors that determine growth rate, and, therefore, could underpin a new generation of robust dynamic vegetation models. Alternatively, growth rates may depend more strongly on the local environment or growth–trait relationships may vary along environmental gradients.[br/][br/][b]3.[/b] We tested these alternative hypotheses using data on 27 352 juvenile trees, representing 278 species from 27 sites on all forested continents, and extensive functional trait data, 38% of which were obtained at the same sites at which growth was assessed. Data on potential evapotranspiration (PET), which summarizes the joint ecological effects of temperature and precipitation, were obtained from a global data base.[br/][br/][b]4.[/b] We estimated size-standardized relative height growth rates (SGR) for all species, then related them to functional traits and PET using mixed-effect models for the fastest growing species and for all species together.[br/][br/][b]5.[/b] Both the mean and 95th percentile SGR were more strongly associated with functional traits than with PET. PET was unrelated to SGR at the global scale. SGR increased with increasing SLA and decreased with increasing wood density and seed mass, but these traits explained only 3.1% of the variation in SGR. SGR–trait relationships were consistently weak across families and biogeographic zones, and over a range of tree statures. Thus, the most widely studied functional traits in plant ecology were poor predictors of tree growth over large scales.[br/][br/][b]6.[/b] Synthesis. We conclude that these functional traits alone may be unsuitable for predicting growth of trees over broad scales. Determining the functional traits that predict vital rates under specific environmental conditions may generate more insight than a monolithic global relationship can offer.
ISSN: 0022-0477

hal-01204226
https://hal.archives-ouvertes.fr/hal-01204226
DOI : 10.1111/1365-2745.12401
PRODINRA : 307144

Éditeur(s) : HAL CCSD
Résumé : Staphylococcus aureus is an opportunistic pathogen of humans and warm-blooded animals. It is foundin healthy carriage and can cause a wide range of infections in its hosts. The epithelial surface is theprincipal site of staphylococcal infection. The pathogens have evolved sophisticated mechanisms tohijack the main function of the host cells, thus promoting their invasion and colonization. Amongstthese effects are, alteration of host cell apoptosis, promotion of cell proliferation or conversely,inhibition of cell growth. Using human cervix cancer HeLa and mammary gland bovine MAC-Tepithelial cells, we studied the cytopathic effect of S. aureus and its ability to affect host cell cycle.Using microscopic examination, we found that S. aureus induced the cytopathic effect resulting in theenlargement of the host cells 72 hours post infection. Our experiments showed that the proliferationrate of the epithelial cells was slowed down in S. aureus-infected culture. Three different S. aureusstrains from human and animal origins were used and showed similar effect on both human and bovinecells. Microscopic analysis of DAPI-stained cells revealed huge decrease of mitotic indexes in infectedHeLa and Mac-T cells, synchronized by Double Thymidine Block. Using flow cytometry analysis, wefound that S. aureus induces G2/M phase delay in synchronous HeLa cells. By Western blot analysis,we showed that the G2/M phase delay was associated with accumulation of inactive phosphorylatedcyclin-dependent kinase Cdk1/cdc2, a key inducer of mitosis entry, and dephosphorylation of corehistone H3, an important component of the epigenetic landscape.These results suggest that the delay in G2/M phase transition of the infected epithelial cells may beone of the mechanisms employed by S. aureus to survive and to propagate inside the host. A fullcomprehension of the mechanisms associated to S. aureus-host cell interactions will undoubtedly helpto discover novel targets to treat staphylococcal infections.
EMBO
Villars sur Ollon, Switzerland

hal-01454214
https://hal.archives-ouvertes.fr/hal-01454214
PRODINRA : 171657

Éditeur(s) : Université des Antilles Études caribéennes
Résumé : The tropical coast of Queensland, Australia is experiencing rapid population and tourism growth. Heavy development pressure is being placed on the biophysical environment, which includes the largest sand island in the world (World Heritage listed), Fraser Island. Despite the existence of State planning legislation oriented towards environmental sustainability, it is apparent that little, if any, regard is being paid to the long-term effects of resort and canal-estate development on the underlying biophysical environment of the coast and islands. While the remarkable surface features of the tropical coastal environment such as the surf beaches, the unique dune lakes, and the coastal vegetation, as well as the prolific wildlife, are used as selling points for new settlement and above all tourism, little is known or apparently of major concern with respect to the long term environmental impact of coastal development. While the crowding effect of large numbers of visitors and their impact on the natural environment - through significant degradation, site hardening or lack of proper on-site management – has been identified as a particular problem in certain areas, there is little knowledge of impacts on the underlying coastal geomorphology. In particular, developmental choices are often made in ignorance of, or disregard of, the widespread existence of tropical acid sulfate soils in that coastal environment. Reactive soils such as these can, and do, greatly affect the biophysical outcomes of a development if they are exposed. This paper documents such impacts in the form of a case study of the acid sulfate soil problem in relation to the development of tourist resorts, and suggests that part of the solution is for the State Government to insist on enforceable standards relating to their development for tourism in the coastal zone. These would reduce the use by many resort owners of fancy golf course developments as an environmental cover up to make it look as if they put a lot of effort into protecting the environment….
La côte tropicale du Queensland est confrontée à un accroissement rapide de la population. Les fortes pressions anthropiques pèsent sur le milieu biophysique, qui comprend notamment a plus grande île de sable du monde, un site classé Patrimoine de l’Humanité, Port Hinchinbrook et Fraser Island. Malgré l’existence d’une législation nationale orientée vers la préservation de l’environnement, il est manifeste que peu d’attention est accordée aux effets à long terme des sites touristiques et du développement de l’urbanisation sur ces franges côtières sensibles. L’aspect massif des flux de visiteurs et leurs impacts sur le milieu naturel a été identifié comme un sujet d’inquiétude particulier dans certaines régions. La connaissance des impacts sur la géomorphologie côtière souterraine est très réduite et les choix de développement sont souvent faits dans l’ignorance ou au mépris de la présence répandue de terrains de sulfate d’acide dans ce milieu côtier. Des sols réactifs comme ceux-là peuvent affecter, et affectent, grandement les résultats géophysiques d’un développement lorsqu’ils sont connus. Des études de cas sur le problème des sols de sulfate d’acide suggèrent qu’une partie de la solution pour le gouvernement de l’Etat du Queensland est d’imposer des normes obligatoires pour le développement du tourisme dans la zone côtière.
Australie
Queensland

Droits : info:eu-repo/semantics/openAccess
urn:doi:10.4000/etudescaribeennes.1272
http://journals.openedition.org/etudescaribeennes/1272

Éditeur(s) : HAL CCSD Oldendorf/Luhe
Résumé : International audience
Large filamentous sulfur-oxidizing bacteria belonging to the Beggiatoacae family can cover large portions of shallow marine sediments surrounding mangroves in Guadeloupe (French West Indies). In order to assess the importance of Beggiatoa mats as an infaunal food source, observations were conducted of the area within mats and at increasing distances from mats. We used natural isotopic compositions and a C-13 enrichment study. Both revealed an ingestion of bacterial mats by associated meiofauna, dominated by rotifers and to a smaller extent by small polychaetes and nematodes. Compared to adjacent sites, sediment covered by bacterial mats presented a higher abundance of diatoms, whereas the total biomass of bacteria did not vary. This constant bacterial abundance suggests that the proportion of organic matter represented by sulfur bacteria is limited compared to the fraction of total bacteria. There was no significant difference in infaunal abundance in mats, suggesting that the availability of this chemosynthetic food resource had a limited local effect. Grazers presented a delta C-13 value increasing with distance from the mat. However, isotopic composition of phospholipid-derived fatty acids specific for diatoms and bacteria revealed that this change is related to modifications of delta C-13 dietary components rather than to changes in diet composition. These complementary methods revealed that the occurrence of sulfur-oxidizing bacterial mats does not necessarily affect grazer abundance and importance of bacteria in their diet. Despite its wide occurrence, Beggiatoa mats would consequently have a minor influence on the structure of the mangrove food web.
ISSN: 0171-8630

hal-01545912
https://hal.archives-ouvertes.fr/hal-01545912
DOI : 10.3354/meps11035

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Saline aquifers in deep sedimentary formations are considered the primary candidates for geological storage of CO2, due to their large volumetric capacity that would be sufficient to meet the needs for CCS storage space in a global scale. In comparison to depleted oil and gas reservoirs the deep saline aquifers are, however, less investigated as there has previously been little economic interest in them. Effective methods for characterizing the storage aquifers are crucial for a successful implementation of any CCS project and therefore being developed and transferred from other applications in a various CCS projects.The objective of EU FP7 funded project MUSTANG project (A multiple space and time scale approach for the quantification of deep saline formations for CO2 storage, www.co2mustang.eu) has been to develop methods for characterizing saline aquifers and for understanding their properties. An essential part of this was establishment of a CO2 injection site at Heletz, Israel, where small-scale scientifically motivated injection experiments are planned to be carried out in presently ongoing continuation projects TRUST (http://trust-co2.org/) and CO2QUEST (www.co2quest.eu).While a large number of publications has been already produced based on the work in the MUSTANG project and its successors, and published in different journals, including this one, the objective of this Special Edition has been to gather some of the concluding work in the same journal issue. The focus has in particular been in summarizing the site characterization work carried out at the Heletz site, thereby providing readers an easy overview of the findings and characteristics of the site. In addition, some related work from some of the other sites investigated in MUSTANG project is also included, namely work from the sites Hontomin, Maguelone and a natural analog site in the North Sea. The results are intended to add to our understanding on relevant properties of geological formations as candidates for CO2 geological storage.
ISSN: 1750-5836

hal-01356326
https://hal.archives-ouvertes.fr/hal-01356326
DOI : 10.1016/j.ijggc.2016.02.007