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 30 m 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

Évolution de l’occupation et de l’utilisation du sol entre 1973 et 2010 dans la zone agropastorale du lac de Guiers (Sénégal)

Cette étude traite de l’évolution de l’occupation et de l’utilisation du sol dans la région du lac de Guiers. Elle contribue à la caractérisation des principales entités spatiales de la zone entre 1973 et 2010. Les techniques cartographiques basées sur les analyses d’images satellites multidates ont été utilisées et complétées par des vérifications sur le terrain. Sur la période étudiée, il a été observé une augmentation des étendues d’eau de 14,9 % ; de la végétation aquatique de 17,5 %, des exploitations agricoles industrielles et privées 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 d’occupation du sol se sont manifestés principalement par la substitution de la steppe arbustive par une steppe herbeuse entre 1973-1988 (avant l’édification des barrages de Diama et Manantali sur le fleuve Sénégal), et l’extension des aménagements agricoles et de la végétation aquatique, entre 1988 à 2010 (après les barrages). L’utilisation du sol en 2010 est marquée par le développement de l’agriculture irriguée qui occupe 42 % de la zone étudiée. L’importante extension des exploitations agricoles irriguées est source de nombreux conflits fonciers. Il est essentiel de revoir le développement de la région dans son ensemble dans le cadre de la politique nationale en matière d’aménagement du territoire et de développement 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

Évolution de l’occupation et de l’utilisation du sol entre 1973 et 2010 dans la zone agropastorale du lac de Guiers (Sénégal)

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

Effet d’un dispositif biomécanique sur la récupération des sols salés et la culture du riz dans le bassin fluvio-marin du Sine-Saloum à Ndoff (Sénégal)

Objectif: La salinisation est l’un des principaux facteurs de dégradation chimique des sols au Sénégal. Les terres salées de la zone du Sine Saloum augmentent constamment et représentent environ 33% des terres émergées, selon Chauvin (2013). Pour faire face à cette contrainte, la présente étude expose les effets d’undispositif biomécanique sur les sols salés et la culture du riz à Ndoff dans le bassin fluviomarin du Sine-Saloum.Méthodologie et résultats: Le dispositif expérimental est en split plot avec 3 répétitions. Le facteur principal est l'espèce de reboisement (fixation des diguettes) avec 3 variantes (Gossypium hirsutum L. (GH), Andropogon gayanus. Kunt. (AG) et un témoin). Le facteur secondaire est la variété de riz avec 3 variantes (« Rock 5 », « WAR 77 » et « Diayi »). Le nombre de répétitions est de 3. La caractérisation des sols du site expérimental a permis d’identifier un seul type de sol qui est hydromorphe minéral, salé, sulfaté acide, sur matériau sableux alluvio-colluvionnaire. Une baisse significative de la conductivité électrique (CE) et une augmentation du pH montrent que le dispositif biomécanique mis en place a fortement amélioré les caractéristiques physico-chimiques du sol. La variété locale de riz Diayi, en présence d’une 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 épis et la longueur des épis. Le rendement grain de la première campagne a été nul à cause d’un déficit pluviométrique mais celui de la biomasse a été encourageant (10,96 t.ha-1).Conclusion et application des résultats: Ainsi, l’aménagement biomécanique des sols, accompagné d’une bonne fertilisation organo-minérale et de bonnes pratiques culturales et d’un choix de variétés adaptées est un procédé efficace pour la récupération et valorisation des terres salées dans la vallée de Ndoff. Toutefois, cette expérience mériterait d’être menée avec d’autres variétés de riz améliorées à cycle court.Mots clés: Fatick, Ndoff, salinité, acidité, biomécanique, récupération, 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 27.2 % 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 resources’ 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 Park’s 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 bodies’ 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 bodies’ 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

Particularités de la perturbation de l’identité chez les émigrés sénégalais - À propos de 3 cas

Dans la migration, la culture se « reconstruit », puisqu’elle n’est pas un état mais un processus dynamique. La condition de migrant expose souvent à des conditions de vie nouvelles. Le sujet doit faire des efforts permanents d’adaptation du moins au début, pour annihiler le décalage culturel. L’échec de cette opération risque de conférer un caractère agressif au flot envahissant des stimuli étrangers. Cette étude souligne quelques particularités de la perturbation de l’identité culturelle chez des émigrés sénégalais qui ont trait à l’usage exclusif d’attribut traditionnel dans un but expiatoire et de référence anxieuse à des chefs religieux

The Rock-Eval® 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-Eval® 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−1 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 (R² = 0.98) and in the protected shrubby savanna (R² = 0.97). They are also correlated significantly in cultivated soils receiving organic wastes (R² = 0.82), manure (R² 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-Eval® 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

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