23 research outputs found
Fine-scale vertical structure of sound-scattering layers over an east border upwelling system and its relationship to pelagic habitat characteristics
Understanding the relationship between sound-scattering layers (SSLs) and pelagic habitat characteristics is a substantial step to apprehend ecosystem dynamics. SSLs are detected on echo sounders representing aggregated marine pelagic organisms. In this study, SSL characteristics of zooplankton and micronekton were identified during an upwelling event in two contrasting areas of the Senegalese continental shelf. Here a cold upwelling-influenced inshore area was sharply separated by a strong thermal boundary from a deeper, warmer, stratified offshore area. Mean SSL thickness and SSL vertical depth increased with the shelf depth. The thickest and deepest SSLs were observed in the offshore part of the shelf. Hence, zooplankton and micronekton seem to occur more frequently in stratified water conditions rather than in fresh upwelled water. Diel vertical and horizontal migrations of SSLs were observed in the study area. Diel period and physicochemical water characteristics influenced SSL depth and SSL thickness. Although chlorophyll-a concentration insignificantly affected SSL characteristics, the peak of chlorophyll a was always located above or in the middle of the SSLs, regularly matching with the peak of SSL biomass. Such observations indicate trophic relationships, suggesting SSLs to be mainly composed of phytoplanktivorous zooplankton and micronekton. Despite local hypoxia, below 30âm depth, distribution patterns of SSLs indicate no vertical migration boundary. The results increase the understanding of the spatial organization of mid-trophic species and migration patterns of zooplankton and micronekton, and they will also improve dispersal models for organisms in upwelling regions.publishedVersio
Ăvolution de lâoccupation et de lâutilisation du sol entre 1973 et 2010 dans la zone agropastorale du lac de Guiers (SĂ©nĂ©gal)
Cette Ă©tude traite de lâĂ©volution de lâoccupation et de lâutilisation du sol dans la rĂ©gion du lac de Guiers. Elle contribue Ă la caractĂ©risation des principales entitĂ©s spatiales de la zone entre 1973 et 2010. Les techniques cartographiques basĂ©es sur les analyses dâimages satellites multidates ont Ă©tĂ© utilisĂ©es et complĂ©tĂ©es par des vĂ©rifications sur le terrain. Sur la pĂ©riode Ă©tudiĂ©e, il a Ă©tĂ© observĂ© une augmentation des Ă©tendues dâeau de 14,9 % ; de la vĂ©gĂ©tation aquatique de 17,5 %, des exploitations agricoles industrielles et privĂ©es respectivement de 207,5 et 5508,8 % et une diminution des superficies des steppes arbustives et herbeuses de 69,9 et 64,3 %. Les changements dâoccupation du sol se sont manifestĂ©s principalement par la substitution de la steppe arbustive par une steppe herbeuse entre 1973-1988 (avant lâĂ©dification des barrages de Diama et Manantali sur le fleuve SĂ©nĂ©gal), et lâextension des amĂ©nagements agricoles et de la vĂ©gĂ©tation aquatique, entre 1988 Ă 2010 (aprĂšs les barrages). Lâutilisation du sol en 2010 est marquĂ©e par le dĂ©veloppement de lâagriculture irriguĂ©e qui occupe 42 % de la zone Ă©tudiĂ©e. Lâimportante extension des exploitations agricoles irriguĂ©es est source de nombreux conflits fonciers. Il est essentiel de revoir le dĂ©veloppement de la rĂ©gion dans son ensemble dans le cadre de la politique nationale en matiĂšre dâamĂ©nagement du territoire et de dĂ©veloppement local participatif.This study encapsulates the evolution of the occupation and land use in the region of the Lake of Guiers. It also contributes to the characterization of the main spatial entities of the zone between 1973 and 2010. Satellite based mapping techniques have been used and complemented by field verifications, During the period under review, we have witnessed an increase in stretches of water by 14,9 %, aquatic vegetation by 17,5 %, industrial and private agricultural holdings respectively by 207,5 and 5508,8 % and a decrease of shrub-steppe and grassy-steppe of 69,9 and 64,3 %. Modifications in land occupation have become apparent mainly through the substitution of shrub steppe by grassy-steppe between 1973 and 1988 (before the construction of the dams in Diama and Manantali on River Senegal) and the extension of managed agricultural land and aquatic vegetation between 1988 and 2010 (after the construction of dams). Land use in 2010 is marked by the development of irrigated agriculture by 42 % on the zone under review. The important extension of irrigated agricultural land is the source of numerous conflicts over land. In this regard, it is important to update the development of the region as a whole through the frame of national policies of land-use planning and participative local development
Ăvolution de lâoccupation et de lâutilisation du sol entre 1973 et 2010 dans la zone agropastorale du lac de Guiers (SĂ©nĂ©gal)
This study encapsulates the evolution of the occupation and land use in the region of the Lake of Guiers. It also contributes to the characterization of the main spatial entities of the zone between 1973 and 2010. Satellite based mapping techniques have been used and complemented by field verifications, During the period under review, we have witnessed an increase in stretches of water by 14,9Â %, aquatic vegetation by 17,5Â %, industrial and private agricultural holdings respectively by 207,5 and 5508,8Â % and a decrease of shrub-steppe and grassy-steppe of 69,9 and 64,3Â %. Modifications in land occupation have become apparent mainly through the substitution of shrub steppe by grassy-steppe between 1973 and 1988 (before the construction of the dams in Diama and Manantali on River Senegal) and the extension of managed agricultural land and aquatic vegetation between 1988 and 2010 (after the construction of dams). Land use in 2010 is marked by the development of irrigated agriculture by 42Â % on the zone under review. The important extension of irrigated agricultural land is the source of numerous conflicts over land. In this regard, it is important to update the development of the region as a whole through the frame of national policies of land-use planning and participative local development
Effet dâun dispositif biomĂ©canique sur la rĂ©cupĂ©ration des sols salĂ©s et la culture du riz dans le bassin fluvio-marin du Sine-Saloum Ă Ndoff (SĂ©nĂ©gal)
Objectif: La salinisation est lâun des principaux facteurs de dĂ©gradation chimique des sols au SĂ©nĂ©gal. Les terres salĂ©es de la zone du Sine Saloum augmentent constamment et reprĂ©sentent environ 33% des terres Ă©mergĂ©es, selon Chauvin (2013). Pour faire face Ă cette contrainte, la prĂ©sente Ă©tude expose les effets dâundispositif biomĂ©canique sur les sols salĂ©s et la culture du riz Ă Ndoff dans le bassin fluviomarin du Sine-Saloum.MĂ©thodologie et rĂ©sultats: Le dispositif expĂ©rimental est en split plot avec 3 rĂ©pĂ©titions. Le facteur principal est l'espĂšce de reboisement (fixation des diguettes) avec 3 variantes (Gossypium hirsutum L. (GH), Andropogon gayanus. Kunt. (AG) et un tĂ©moin). Le facteur secondaire est la variĂ©tĂ© de riz avec 3 variantes (« Rock 5 », « WAR 77 » et « Diayi »). Le nombre de rĂ©pĂ©titions est de 3. La caractĂ©risation des sols du site expĂ©rimental a permis dâidentifier un seul type de sol qui est hydromorphe minĂ©ral, salĂ©, sulfatĂ© acide, sur matĂ©riau sableux alluvio-colluvionnaire. Une baisse significative de la conductivitĂ© Ă©lectrique (CE) et une augmentation du pH montrent que le dispositif biomĂ©canique mis en place a fortement amĂ©liorĂ© les caractĂ©ristiques physico-chimiques du sol. La variĂ©tĂ© locale de riz Diayi, en prĂ©sence dâune plantation de G. hirsutum L. (GH) sur les diguettes, a obtenu la moyenne la plus importante pour le nombre total de talles productives, le nombre de plants avec Ă©pis et la longueur des Ă©pis. Le rendement grain de la premiĂšre campagne a Ă©tĂ© nul Ă cause dâun dĂ©ficit pluviomĂ©trique mais celui de la biomasse a Ă©tĂ© encourageant (10,96 t.ha-1).Conclusion et application des rĂ©sultats: Ainsi, lâamĂ©nagement biomĂ©canique des sols, accompagnĂ© dâune bonne fertilisation organo-minĂ©rale et de bonnes pratiques culturales et dâun choix de variĂ©tĂ©s adaptĂ©es est un procĂ©dĂ© efficace pour la rĂ©cupĂ©ration et valorisation des terres salĂ©es dans la vallĂ©e de Ndoff. Toutefois, cette expĂ©rience mĂ©riterait dâĂȘtre menĂ©e avec dâautres variĂ©tĂ©s de riz amĂ©liorĂ©es Ă cycle court.Mots clĂ©s: Fatick, Ndoff, salinitĂ©, aciditĂ©, biomĂ©canique, rĂ©cupĂ©ration, rizEnglish AbstractObjective: The main factors of chemical soil degradation in Senegal is salinization (Sadio 1991). The saline lands of the Sine Saloum area are constantly increasing and represent about 33% of the land surface, according to Chauvin (2013). To address this constraint, the present study exposes the effects of biomechanical design on saline soils and rice cultivation in the Sine-Saloum fluviomarine basin.Methodology and results: The experimental design is a split plot with the species factor of small bunds fixation with three variants (main factor) and the variety factor with three variants (secondary factor). The three rice varieties used are: Diayi (local variety), the War 77 and Rock5 (new varieties). The three plant species for fixing the bunds are: Gossypium hirsutum L. (GH), Andropogon gayanus. Kunt (AG) and Vetiveria zizanioides L. (VZ). The number of repetitions is 3. The results of the experimental site soil characterization revealed that the ground on which the test was conducted is a mineral, salty, acid, sulfated hydro-morph soil, on sandy alluvial-colluvial material. A significant decrease in the electrical conductivity (EC) and an increase in pH show that the established biomechanical device has greatly improved the physical and chemical soil characteristics. Local rice variety (Diayi) in the presence of a plantation of G. hirsutum L. (GH) on the bunds, received the largest average for the total number of productive suckers, the number of plants with ears and the length of the ears. The grain yield of the first season was zero because of a rainfall deficit but that of the biomass was encouraging (10, 96 t.ha-1) Thus, soil biomechanical design, accompanied by a good organo-mineral fertilizers and good agricultural practices is an effective method for the reclamation and valorization of saline lands. However, this experience deserves to be experienced with other short cycle improved rice varieties.Keywords: Fatick, Ndoff, salinity, acidity, biomechanics, recovery, ric
Recombinant Helicobacter pylori Vaccine Delivery Vehicle: A Promising Tool to Treat Infections and Combat Antimicrobial Resistance
Antimicrobial resistance (AMR) has become a global public health threat. Experts agree that unless proper actions are taken, the number of deaths due to AMR will increase. Many strategies are being pursued to tackle AMR, one of the most important being the development of efficient vaccines. Similar to other bacterial pathogens, AMR in Helicobacter pylori (Hp) is rising worldwide. Hp infects half of the human population and its prevalence ranges from <10% in developed countries to up to 90% in low-income countries. Currently, there is no vaccine available for Hp. This review provides a brief summary of the use of antibiotic-based treatment for Hp infection and its related AMR problems together with a brief description of the status of vaccine development for Hp. It is mainly dedicated to genetic tools and strategies that can be used to develop an oral recombinant Hp vaccine delivery platform that is (i) completely attenuated, (ii) can survive, synthesize in situ and deliver antigens, DNA vaccines, and adjuvants to antigen-presenting cells at the gastric mucosa, and (iii) possibly activate desired compartments of the gut-associated mucosal immune system. Recombinant Hp vaccine delivery vehicles can be used for therapeutic or prophylactic vaccination for Hp and other microbial pathogens
Prolifération de Cissus quadrangularis L. dans le Parc National des Iles-de-la-Madeleine, Sénégal
National parks are representative protected areas of natural ecosystems of a country. The introduction of alien plants in natural systems present a risk to biodiversity conservation, particularly where protected areas are islands. In the past few years , Cissus quadrangularis, a plant species from Indo-Malaysian, introduced in Senegal around 19th century, has developed signs that warry the authorities of Madeleine Islands National Park (MINP) of over 45 hectares. The present work was undertaken to evaluate the status on the distribution of C. quadrangularis and provide the information on the impact of that species on the ecosystems in this country part. The phytosociological surveys highlighted eight plant communities. From digital image (Quickbird) of 1 meter resolution, the main facies of occupancy were mapped and the areas occupied by C. quadrangularis were estimated. The surface of occurrency (5.7 ha) of plant stands population represent 27.2Â % of the total area of the islands (20.9 ha). This plant is threats to biodiversity of the Park. It is urgent to find and implement appropriate measures to control the spread of the plant in the park
Water Resources Dynamics and Vulnerability in Rusizi National Park (Burundi) from 1984 to 2015, in the Context of Climate Change and Global Warming
The study of water resourcesâ dynamics and vulnerability in Rusizi national Park aimed to achieve the following objectives: (1) to identify, characterize and map water bodies, (2) to analyze and explain their periodical evolutions and (3) to analyze the spatial transformation processes affecting them. It is a contribution to the knowledge of the Parkâs water resources for the development of monitoring systems and the sustainability of their functions as strategic ecosystems. It is based on the diachronic analysis of land cover from multi-date Landsat images of years 1984, 1990 and 2011 (TM), 2000 (ETM+) and 2015 (OLI-TIRS), landscape ecology tools and socio-economic and climate data. Supervised classification of images allowed the identification of 9 to 10 land cover classes including water bodies, according to years. A total number of 17 water bodies were detected from 1984 to 2015. During this period, regularly detected and dried up water bodies represent 18.2% and 54.6% respectively. The rates of water bodiesâ drying up were 69.2% in 2000 and 64.2% in 2015. Water bodies are experiencing a great deterioration in number, size and stability. The Park's water coverage has decreased from 3.56% in 1984 to 2.43% in 2015. This corresponds to a decline of 31.2%. The water bodiesâ stability, which was 75.70% between 1984 and 1990, represents only 42.78% between 1984 and 2015. The stability of individual water bodies is decreasing as well while low spatial connectivities are being observed between some close water bodies. The spatial transformation processes carrying these dynamics are patch enlargement, patch creation, patch attrition and patch dissection, depending on the period. Global warming, rainfall variability and farming activities like land drainage and irrigation are the most important threats to water resources
ParticularitĂ©s de la perturbation de lâidentitĂ© chez les Ă©migrĂ©s sĂ©nĂ©galais - Ă propos de 3 cas
Dans la migration, la culture se « reconstruit », puisquâelle nâest pas un Ă©tat mais un processus dynamique. La condition de migrant expose souvent Ă des conditions de vie nouvelles. Le sujet doit faire des efforts permanents dâadaptation du moins au dĂ©but, pour annihiler le dĂ©calage culturel. LâĂ©chec de cette opĂ©ration risque de confĂ©rer un caractĂšre agressif au flot envahissant des stimuli Ă©trangers. Cette Ă©tude souligne quelques particularitĂ©s de la perturbation de lâidentitĂ© culturelle chez des Ă©migrĂ©s sĂ©nĂ©galais qui ont trait Ă lâusage exclusif dâattribut traditionnel dans un but expiatoire et de rĂ©fĂ©rence anxieuse Ă des chefs religieux
The Rock-EvalÂź signature of soil organic carbon in arenosols of the Senegalese groundnut basin. How do agricultural practices matter?
(IF 5.57; Q1)International audienceSoil organic carbon (SOC) ensures soil quality and productivity of cultivated systems in the Sahelian region. This study uses Rock-EvalÂź pyrolysis to examine how cultural practices impact the quantity of SOC and quality of SOM in cultivated sandy soils in the Senegal groundnut basin. This cost-effective method provides information on SOC thermal stability, which has been shown to be related qualitatively to biogeochemical stability of SOC. We sampled soils within two villages in agricultural plots representative of local agricultural systems, and in two local preserved areas (tree plantation and shrubby savanna). SOC concentrations ranged from 1.8â18.5 g.kgâ1 soil in the surface layer (0â10 cm) and from 1.5â11.3 g.kgâ1 soil in the 10â30 cm layer. SOC contents of cultivated soils decreased significantly (p-value addition of manure > millet residues left after harvest > no organic input. We found that the quantity and the quality of SOC are linked, and that both depend on land-use and agricultural practices, especially upon the type of organic inputs. Quantity of SOC and quality of SOM are correlated strongly in the tree plantation (RÂČ = 0.98) and in the protected shrubby savanna (RÂČ = 0.97). They are also correlated significantly in cultivated soils receiving organic wastes (RÂČ = 0.82), manure (RÂČ from 0.74 and 0.91), or millet residues (R2 = 0.91) but not in soils that receive no organic inputs. Indexes based upon Rock-EvalÂź pyrolysis were represented in an I/R diagram that illustrates the level of SOC stabilization. The indexes of the studied soils were plotted against comparable results from literature. Thermal signatures of the Senegalese Arenosols show an inversion of I and the R indexes compared to data from the literature. This result highlights SOC stabilization as a function of soil depth. Indeed, the refractory pool in the studied soils (where refractory pool ranged from 7.7â21.3 % in the 0â10 cm layer, and from 12.5â24.3 % in the 10â30 cm) was more abundant than in Ferralsols in natural conditions, where refractory pool ranged from 2 to 9%. The soil organic matter in these Arenosols while positively affected by organic inputs, is dominated by more or less labile forms that mineralize quickly: a quality that is excellent for productivity of these agrosystems, but not for mitigation of climate change in the long term
The Rock-Eval (R) signature of soil organic carbon in arenosols of the Senegalese groundnut basin : how do agricultural practices matter ?
Soil organic carbon (SOC) ensures soil quality and productivity of cultivated systems in the Sahelian region. This study uses Rock-Eval (R) pyrolysis to examine how cultural practices impact the quantity of SOC and quality of SOM in cultivated sandy soils in the Senegal groundnut basin. This cost-effective method provides information on SOC thermal stability, which has been shown to be related qualitatively to biogeochemical stability of SOC. We sampled soils within two villages in agricultural plots representative of local agricultural systems, and in two local preserved areas (tree plantation and shrubby savanna). SOC concentrations ranged from 1.8-18.5 g.kg soil in the surface layer (0 - 10 cm) and from 1.5-11.3 g.kg(-1) soil in the 10 - 30 cm layer. SOC contents of cultivated soils decreased significantly (p-value addition of manure > millet residues left after harvest > no organic input. We found that the quantity and the quality of SOC are linked, and that both depend on land-use and agricultural practices, especially upon the type of organic inputs. Quantity of SOC and quality of SOM are correlated strongly in the tree plantation (R-2 = 0.98) and in the protected shrubby savanna (R = 0.97). They are also correlated significantly in cultivated soils receiving organic wastes (R-2 = 0.82), manure (R-2 from 0.74 and 0.91), or millet residues (R-2 = 0.91) but not in soils that receive no organic inputs. Indexes based upon Rock-Eval (R) pyrolysis were represented in an I/R diagram that illustrates the level of SOC stabilization. The indexes of the studied soils were plotted against comparable results from literature. Thermal signatures of the Senegalese Arenosols show an inversion of I and the R indexes compared to data from the literature. This result highlights SOC stabilization as a function of soil depth. Indeed, the refractory pool in the studied soils (where refractory pool ranged from 7.7-21.3 % in the 0-10 cm layer, and from 12.5-24.3 % in the 10 - 30 cm) was more abundant than in Ferralsols in natural conditions, where refractory pool ranged from 2 to 9%. The soil organic matter in these Arenosols while positively affected by organic inputs, is dominated by more or less labile forms that mineralize quickly: a quality that is excellent for productivity of these agrosystems, but not for mitigation of climate change in the long term