The BLLAST field experiment: Boundary-Layer late afternoon and sunset turbulence

Due to the major role of the sun in heating the earth's surface, the atmospheric planetary boundary layer over land is inherently marked by a diurnal cycle. The afternoon transition, the period of the day that connects the daytime dry convective boundary layer to the night-time stable boundary layer, still has a number of unanswered scientific questions. This phase of the diurnal cycle is challenging from both modelling and observational perspectives: it is transitory, most of the forcings are small or null and the turbulence regime changes from fully convective, close to homogeneous and isotropic, toward a more heterogeneous and intermittent state. These issues motivated the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign that was conducted from 14 June to 8 July 2011 in southern France, in an area of complex and heterogeneous terrain. A wide range of instrumented platforms including full-size aircraft, remotely piloted aircraft systems, remote-sensing instruments, radiosoundings, tethered balloons, surface flux stations and various meteorological towers were deployed over different surface types. The boundary layer, from the earth's surface to the free troposphere, was probed during the entire day, with a focus and intense observation periods that were conducted from midday until sunset. The BLLAST field campaign also provided an opportunity to test innovative measurement systems, such as new miniaturized sensors, and a new technique for frequent radiosoundings of the low troposphere. Twelve fair weather days displaying various meteorological conditions were extensively documented during the field experiment. The boundary-layer growth varied from one day to another depending on many contributions including stability, advection, subsidence, the state of the previous day's residual layer, as well as local, meso- or synoptic scale conditions. Ground-based measurements combined with tethered-balloon and airborne observations captured the turbulence decay from the surface throughout the whole boundary layer and documented the evolution of the turbulence characteristic length scales during the transition period. Closely integrated with the field experiment, numerical studies are now underway with a complete hierarchy of models to support the data interpretation and improve the model representations.publishedVersio

Impact of salinity on early life history traits of three estuarine fish species in Senegal

International audienceThe adaptive mechanisms on the early life stages of fishes to hypersaline stress are still poorly understood and probably determine the resistance of a population to disruption, compared with other less plastic species. The Casamance River in Senegal is an ideal location to test the adaptation to salinity as a dam was built in 1998 to exclude saline water intrusion. This lowered the salinity from 70 to 5 upstream and 60 downstream. The salinity influence on the growth in the early life of three West African fish species (Ethmalosa fimbriata, Sarotherodon melanotheron, and Tilapia guineensis) was studied using the width of microstructures in the otoliths and the individual migratory behaviour analysed from strontium (Sr) to calcium (Ca) ratios in the otoliths. The Sr:Ca ratio was quantified along individual transects measured from the posterior edge of the otolith to the core. The fishes were sampled on both sides of the dam that separated water with low salinity upstream from metahaline and hyperhaline water downstream. The results showed that salinity has different influence on the growth of each species. Ethmalosa fimbriata has the highest growth during the first 180 days in the freshwaters, indicating growth inhibition in the hyperhaline areas. For the two other species no growth difference were found. The Sr/Ca ratio varied widely, in Tilapia and Sarotherodon from below the dam. Individual life histories were more heterogeneous than upstream and showed a crossing of the dam for some individuals which could reach half of the fishes analysed. On the contrary in E. fimbriata, despite the large range of salinity, identical Sr/Ca profiles were found both upstream and downstream. This indicated that Sr/Ca ratio was not appropriate to evaluate life history patterns linked to salinity for this specie

Mise en place d'un Système d'Information Géographique appliqué à la reconnaissance archéologique de l'agglomération antique d'Epomanduodurum (Mandeure, Mathay, Doubs)

International audienceThis work took place in an archaeological research project. Its aim is to try out new methods for the survey of the ancient city of Epomanduodurum and its territory (Mathay-Mandeure, Doubs). On sites of great spatial extent (more than 300 hectares in our case), archaeological survey requires important data processing which generally comes from various methods. The synthesis of this data appears essential for understanding elaborated and extended sites.Réalisé dans le cadre d'un projet collectif de recherche, ce travail a pour objectif d'expérimenter les méthodes nouvelles pour la reconnaissance de l'agglomération d'Epomanduodurum et de son territoire (Mathay-Mandeure, Doubs). Sur les sites archéologiques de très grande étendue (plus de 300 hectares dans notre cas), la prospection correspond à une phase importante d'acquisition des données qui met généralement en oeuvre un grand nombre de méthodes. Ces opérations aboutissent à la collecte d'une masse considérable d'informations, dont la synthèse s'avère indispensable pour progresser dans la compréhension générale de sites complexes et étendus

Mise en place d'un Système d'Information Géographique appliqué à la reconnaissance archéologique de l'agglomération antique d'Epomanduodurum (Mandeure, Mathay, Doubs)

International audienceThis work took place in an archaeological research project. Its aim is to try out new methods for the survey of the ancient city of Epomanduodurum and its territory (Mathay-Mandeure, Doubs). On sites of great spatial extent (more than 300 hectares in our case), archaeological survey requires important data processing which generally comes from various methods. The synthesis of this data appears essential for understanding elaborated and extended sites.Réalisé dans le cadre d'un projet collectif de recherche, ce travail a pour objectif d'expérimenter les méthodes nouvelles pour la reconnaissance de l'agglomération d'Epomanduodurum et de son territoire (Mathay-Mandeure, Doubs). Sur les sites archéologiques de très grande étendue (plus de 300 hectares dans notre cas), la prospection correspond à une phase importante d'acquisition des données qui met généralement en oeuvre un grand nombre de méthodes. Ces opérations aboutissent à la collecte d'une masse considérable d'informations, dont la synthèse s'avère indispensable pour progresser dans la compréhension générale de sites complexes et étendus

Implication of the Type IV Secretion System in the Pathogenicity of Vibrio tapetis, the Etiological Agent of Brown Ring Disease Affecting the Manila Clam Ruditapes philippinarum

International audienceVibrio tapetis is a Gram-negative bacterium that causes infections of mollusk bivalves and fish. The Brown Ring Disease (BRD) is an infection caused by V. tapetis that primarily affects the Manila clam Ruditapes philippinarum . Recent studies have shown that a type IV secretion system (T4SS) gene cluster is exclusively found in strains of V. tapetis pathogenic to clams. However, whether the T4SS is implicated or not during the infection process remains unknown. The aim of this study was to create and characterize a V. tapetis T4SS null mutant, obtained by a near-complete deletion of the virB4 gene, in order to determine the role of T4SS in the development of BRD. This study demonstrated that the T4SS is neither responsible for the loss of hemocyte adhesion capacities, nor for the decrease of the lysosomal activity during BRD. Nevertheless, we observed a 50% decrease of the BRD prevalence and a decrease of mortality dynamics with the Δ virB4 mutant. This work demonstrates that the T4SS of V. tapetis plays an important role in the development of BRD in the Manila clam

Nouvelles données sur l'agglomération antique d'Epomanduodurum - Mandeure (Doubs): Fonctionnement alluvial et aménagements anthropiques dans la boucle du Doubs et ses abords

Bulletin de la Société d'Émulation de Montbéliard

Nouvelles données sur l'agglomération antique d'Epomanduodurum - Mandeure (Doubs): Fonctionnement alluvial et aménagements anthropiques dans la boucle du Doubs et ses abords

Bulletin de la Société d'Émulation de Montbéliard

Evolution morphosédimentaire de la plaine alluviale et aménagements anthropiques aux abords du sanctuaire-théâtre

International audienceLes investigations conduites aux abords du complexe monumental théâtre/sanctuaire d’Epomanduodurum (Mandeure–Mathay, Doubs) ont permis de mettre en évidence l’empreinte de plusieurs incisions mineures holocènes dans l’épanchement fluviatile de la basse terrasse würmienne Fy sur laquelle l’agglomération antique est en partie édifiée. La morphologie des lits fossiles repérés montre la coexistence de différents styles fluviaux. L’analyse du remplissage d’un des bras morts du Doubs a permis d’individualiser sept phases majeures d’évolution avec plusieurs remises en eau occasionnées par des crues plus ou moins importantes de la rivière. Des traces d’une occupation protohistorique pouvant être antérieures au IVème siècle ont été reconnues dans les couches supérieures scellant le comblement du chenal. Parallèlement, un ensemble de structures inédites (enceintes, temples, bâtiments, fosses et voies) a été détecté aux abords du complexe monumental par les prospections géophysiques. La nature de ces découvertes renouvelle complètement la perception de l’organisation spatiale des vestiges et le schéma de l’urbanisation de cette partie de l’agglomération antique

Chemical profiles in otoliths from 3 fish species along the Moroccan coast: accumulation and migration patterns

International audienceThe Canary Current Large Ecosystem is characterized by a major, nutrient-rich up-welling of deep, cold oceanic waters, which stimulates high biological productivity that results in an abundance of both pelagic and demersal fishery resources. In this area, the Moroccan coast is also under direct anthropogenic activities influences such as phosphates industries. Several observations indicate that variations of the upwelling activities observed in the recent years would generate the remobilization of the contaminants. Our study deals with the metallic concentrations in the otoliths of 3 fish species of economic interest ( Merlucius merlucius, Pagellus acarne, Sardina pilchardus) along the Moroccan coast. The fishes were collected in markets in june 2012 for the northern part of Morocco (during the maximum of the upwelling activity) and in November 2012 for the southern part. Concentrations were measured by ICP-MS on transects from nucleus to the edge of otoliths to characterize environmental variations or accumulations linked to ecophases and growth. For each species, 5 fishes were analyzed in 7 locations from North to south of the Moroccan Atlantic coast. First results indicate that the concentrations are highly variable in hake transects, and on the other hand, transects in seabreams seem very stable regardless of location. Transects in sardines indicate different patterns depending on the locations and, some of them, clearly show the upwelling signature