Hydrocarbon influence on denitrification in bioturbated Mediterranean coastal sediments

An in situ experiment has been carried out inbioturbated Mediterranean coastal marine sediments (Gulfof Fos) in order to study the influence of hydrocarbons ondenitrification after 1, 4 and 6 months. In theabsence of hydrocarbons in the control sediments, the presenceof macrofauna stimulated denitrificationby 160%. This stimulation is induced by sediment reworkingthat favours both direct NO-3 supply fromthe water column and the penetration of O{2}, which in turnstimulated nitrification, the other source ofNO-3 in sediment. The presence of hydrocarbons in theexperimental sediments either stimulated orinhibited the denitrification. The denitrification response tothe presence of hydrocarbon is dependent onthe quantity of matter buried by the macrofauna activity. Insmall quantities, the organic matter relatedto hydrocarbons 120% enhanced the denitrification compared tothe controls. On the other hand, whenburied hydrocarbon concentrations were higher (>100 mgsaturated hydrocarbon fraction kg-1 drysediment), the denitrification was inhibited.On the basis of the results obtained, a descriptive model ofthe patterns of denitrification in relation to the presence ofmacrofauna and the distribution of hydrocarbons in sediments is proposed

Adaptive Element-Free Galerkin method applied to the limit analysis of plates

The implementation of an h-adaptive Element-Free Galerkin (EFG) method in the framework of limit analysis is described. The naturally conforming property of mesh- free approximations (with no nodal connectivity required) facilitates the implementation of h-adaptivity. Nodes may be moved, discarded or introduced without the need for complex manipulation of the data structures involved. With the use of the Taylor expansion technique, the error in the computed displacement field and its derivatives can be estimated throughout the problem domain with high accuracy. A stabilized conforming nodal integration scheme is extended to error estimators and results in an efficient and truly meshfree adaptive method. To demonstrate its effectiveness the procedure is then applied to plates with various boundary conditions

The deep-sea macrobenthos on the continental slope of the northwestern Mediterranean Sea: a quantitative approach

As part of the ECOMARGE operation (J.G.O.F.S. France), macrobenthic assemblages in the Toulon Canyon were described and quantified on the basis of sampling carried out between 250 and 2000 m depth on the Mediterranean continental slope. Results show that Mediterranean bathyal assemblages are made up mainly of continental shelf eurybathic species. The qualitative and quantitative composition of populations varies with depth on the slope and also varies with station position at equivalent depth, whether on the flanks or in the canyon channel. Various analyses have provided evidence on the factors responsible for this population distribution pattern. No single factor emerges as predominant, but rather a group of factors, which are related to the nature and origin of sediments and more particularly their grain size distribution, geochemical composition and mode of transportation and sedimentation (benthic nepheloid or originating from the water column), act in conjunction to determine the pattern. Comparison with ocean continental slopes shows that in the Mediterranean Sea the absence of tidal current modifies the trophic structure of the macrobenthic assemblages, which are characterized by a dominance of surface and subsurface deposit feeders as compared to a dominance of suspension feeders and carnivores in the upper and median part of the slope in the ocean. Surface dumping of dredge spoil at the canyon head and channelling of waste induces an increase of organic matter and pollutant concentrations in sediment from the upper part of the canyon channel but does not give rise to any marked population degradation

Quelques observations sur An. moucheti S.l. : différences morphologiques d'une population d'An. moucheti issue de Ebogo : rapport de mission effectuée du 12 au 14 novembre 1991 à Ebogo (Nyong et So'o)

1- Observations sur la composition du genre Anopheles au sein des différentséchanrillonnages.Le genre Anopheles est essentiellement composé par l'espèce An.moucheti. Sur976 identifications, nous avons observé 1 An. paludis issu de capture sur homme àl'extérieur des maisons et 1 An. gambiae issu de capture sur homme à l'intérieur d'unemaison de Soo-Assi.Tous les Anopheles capturés par les pièges lumineux étaient desAn.mouchetì.Conclusion: compte-tenu de la composition du genre Anopheles échantillonné à Ebogo,on ne peut pas retenir ce village comme station expérimentale pour tester les différentsadulticides OMS. La prospection d'un village où les captures sont composées par An.gambiae doit se poursuivre autour de Yaoundé.2-Observations sur les différences morphologiques d'une population d'An.moucheti.morphologiques qui interviennent dans l'identification et la différenciation des 2 sousespèces d'An.mouchetì et d'An.bewoetsi. An.bervoetsi est très proche d'An.mouchetì:on le retrouve assez souvent dans les collections d'An.moucheti. Pour chaque critère dedifférenciation, nous précisons quelles ont été nos observations pour la souche"Ebogo".En ce qui concerne les pattes, Gillies et de Meillon (1968) proposent pour :- An. moucheti moucheti Evans, 1925: tous les tarses, sauf le 5ème de toutes les pattes etle 4ème des pattes antérieures, avec une bande apicale claire Ctroite mais visible. - variations: des prélèvement issus d'Ouganda présentaient des tarses 4 antérieurs avecune petite tache apicale.- An.moucheti nìgeriensìs Evans, 1931: pas de différence avec An. mouchetì moucheti. - An.bervoetsi DHaenens, 1961: tarses antérieurs 4 avec une bande claire bien visible àl'apex

Révision des Neomelaniconion Newstead (Diptera : Culicidae) de Madagascar : espèces présentes et description de cinq nouvelles espèces

International audienceRevision of the Neomelaniconion Newstead (Diptera: Culicidae) form Madagascar: recorded species and decription of fi ve new species. The authors carry out a review of the genus Neomelaniconion Newstead in Madagascar. They confi rm the presence of Neomelaniconion circumluteolus (Theobald 1908). They question the presence of Neomelaniconion palpalis (Newstead 1907) and they describe fi ve new species for world fauna: Neomelaniconion albiradius sp. nov., Neomelaniconion belleci sp. nov., Neomelaniconion fontenillei sp. nov., Neomelaniconion nigropterum sp. nov., Neomelaniconion sylvaticum sp. nov. They fi nally propose the creation of Circumluteolus and Sylvaticum groups. Résumé. Les auteurs effectuent une révision du genre Neomelaniconion Newstead à Madagascar. Ils confi rment la présence de Neomelaniconion circumluteolus (Theobald 1908), mettent en doute la présence de Neomelaniconion palpalis (Newstead 1907) et décrivent 5 nouvelles espèces pour la faune mondiale : Neomelaniconion albiradius sp. nov., Neomelaniconion belleci sp. nov., Neomelaniconion fontenillei sp. nov., Neomelaniconion nigropterum sp. nov., Neomelaniconion sylvaticum sp. nov. Ils proposent enfi n la création des groupes Circumluteolus et Sylvaticum

Prevalence and risk factors for avian influenza and Newcastle disease viruses in domestic poultry in seven African countries with outbreaks of H5N1 HPAI

The distribution of H5N1 highly pathogenic avian influenza (HPAI) outbreaks in domestic poultry has been previously studied in Asia, and within Egypt and Nigeria in Africa. However, no studies have yet explored across multiple African countries how local conditions may relate to HPAI H5N1 outbreaks distribution, and to the general prevalence of avian influenza (AI) and Newcastle disease (ND) viruses. A cross-sectional survey was conducted between February and May 2008 in 43 sites located in seven countries (Burkina Faso, Cameroon, Egypt, Ivory Coast, Niger, Nigeria and Sudan) which had previously experienced outbreaks of H5N1 HPAI. Twenty-two sites corresponded to locations where H5N1 outbreaks had occurred, and 21 sites corresponded to non-infected sites in the same surveillance zone as the outbreak sites. Information on poultry management, trade practices, environment, and presence of wild birds was collected in each site and analysed by univariate and multivariate methods including logistic regression, principal component analysis, distance matrices, Mantel test, and linear model. Biological samples (tracheal and cloacal swabs, sera) were also collected in each site from a number of birds sufficient to detect a 5% or more prevalence with a 95% confidence. Samples were collected from a total number of 3 672 birds and tested by RRT-PCR for the detection of AI and APMV1 viruses, ELISA and/or hemagglutination inhibition (HI) tests for the detection of antibodies against type A influenza, H5 and H7 AI strains, and APMV1 virus. The comparison of HPAI H5N1 infected and non-infected sites found that sites where routine ND vaccination was practiced, wild bird mortality had been observed, or a permanent pond was present, were more likely to have been infected. However, these results should be treated cautiously because of the non-random selection of non-infected sites and the lack of statistical power preventing testing multiple factors simultaneously. None of the swabs tested (3641 tracheal, 3627 cloacal) was positive for AI RRT-PCR, but 26.4% of the 3539 sera tested were positive for ELISA AI (19.9% when only considering birds non-vaccinated against HPAI), with 3.1% also positive for HI H5 and 0% positive for HI H7. 0.7% of the 3641 tracheal swabs and 0.4% of the 3627 cloacal were positive for APMV1 RRT-PCR, and 34.0% of the 3519 sera tested were positive for HI APMV1 (25.5% when only considering birds non-vaccinated against ND). AI seroprevalence was much more spatially structured than ND seroprevalence and was correlated to the poultry composition of the site. A statistical association was found between individual AI serological results and age and species, and between individual ND serological status and species. These results represent the first large-scale survey of AI and ND in African domestic poultry and enabled to identify putative risk factors both qualitatively and quantitatively. (Texte integral

Ecoéthologie des vecteurs et transmission du paludisme dans la région rizicole de basse altitude de Mandritsara, Madagascar

International audienceTo evaluate the determining factors of the malaria transmission in the northwest region of Madagascar, transversal studies were carried out through one year, from March 1997 to April 1998, in two villages located near Mandritsara, at less than 300 meters above sea level. The rice-growingregion forms an intermediate zone between the central highlands with epidemic and instable malaria and the coastal zone with endemic and stable malaria. Mosquitoes were collected when landing on humans during the night and by pyrethrum spray catches as regards endophilic mosquitoes. Three vectors were identified : Anopheles arabiensis, An.gambiae and An. funestus. An. arabiensis and An. gambiae were exophagic and zoophilic.An.funestus was endo-exophagic and anthropophilic but this species shows also a zoophilic trophic deviation. In both villages, An. funestus is the main vector of human malaria. Malaria transmission was estimated to be around 50 and 70 infective bites/person/year in each village.Pour évaluer les facteurs qui déterminent la transmission du paludisme dans la région nord-est de Madagascar, des enquêtes entomologiques ont été menées d’avril 1997 à mars 1998 dans deux villages situés dans la région de Mandritsara, à moins de 300 mètres d’altitude. Cette région est une zone rizicole importante et fait partie de la zone intermédiaire entre les Hautes terres à paludisme instable, épidémique et la région côtière à paludisme stable endémique.Les moustiques ont été récoltés par des captures sur hommes volontaires et par des collectes matinales des moustiques endophiles. Les vecteurs ont été Anopheles arabiensis, An. gambiae et An. funestus. An. funestus a été le vecteur majeur du paludisme; il n'a pas présenté d'aptitude particulière pour l'endophagie ou l'exophagie; il a essentiellement présenté une anthropophilie mais avec une tendance zoophile marquée. Le taux entomologique d’inoculation a été d’environ 50 piqûres infectantes par homme et par an dans le premier village et 70 dans le deuxième