Le fleuve Sénégal / 2 : Flux continentaux de matières dissoutes à l'embouchure

Les événements géochimiques majeurs à l'embouchure du Sénégal sont liés aux phénomènes de la remontée cyclique des eaux marines dans la vallée du fleuve. La première partie de cette étude précise les variations saisonnières de la salinité et l'évolution de la composition chimique des eaux dans le milieu estuarien. A partir du bilan de l'érosion mécanique et de l'altération chimique, de nouvelles propositions sont formulées pour appréhender l'acquisition des charges particulaires et dissoutes et préciser dans les hydrogrammes annuels les contributions respectives des eaux de ruissellement et des eaux souterraines

Importance and trees management of Senegalia senegal on soil fertility and yield of associated crops in northern Senegal

Trees are usually eliminated in field due their possible competition with crops for water and nutrients. Our work aimed to investigate how to manage S. senegal trees to optimize their association with crops. A field trial was conducted under natural conditions in a S. senegal plantation 10 years old. Investigations were conducted during two years to evaluate the effect of S. senegal trees management on gum arabic yield, associated cowpea yield, soil mycorrhizal fungi spores density and enzymes activities reflecting soil fertility such as fluorescein diacetate (FDA), acid phosphatase and dehydrogenase. Four treatments of pruning were applicated (control, shoots, roots, shoots and roots pruning) and tapped in november. Soil samples were collected during dry and wet seasons at 0-25 cm layer. Cowpeas were sown at the beginning of rainy season in rows 0.5 m apart. Results showed that shoots pruning significantly increased gum arabic while a negative effect of roots pruning was noted. The presence of S. senegal increased soil fertility and cowpea yield. Any significant effect of treatments was noted on pods yield during the first year. However, shoots pruning, shoot and roots pruning increased significantly pods yield during the second year. Shoots and roots pruning seemed to decrease FDA and spores density depending on the season. Our results showed that shoots and roots pruning increased the positive effect on soil fertility and the association of S. senegal with annual crops

Adaptation to climate change in coastal communities: findings from seven sites on four continents

Climate change is causing wide-ranging effects on ecosystem services critical to coastal communities and livelihoods, creating an urgent need to adapt. Most studies of climate change adaptation consist of narrative descriptions of individual cases or global synthesis, making it difficult to formulate and test locally rooted but generalizable hypotheses about adaptation processes. In contrast, researchers in this study analyzed key points in climate change adaptation derived from coordinated fieldwork in seven coastal communities around the world, including Arctic, temperate, and tropical areas on four continents. Study communities faced multiple challenges from sea level rise and warmer ocean temperatures, including coastal erosion, increasing salinity, and ecological changes. We analyzed how the communities adapted to climate effects and other co-occurring forces for change, focusing on most important changes to local livelihoods and societies, and barriers to and enablers of adaptation. Although many factors contributed to adaptation, communities with strong self-organized local institutions appeared better able to adapt without substantial loss of well-being than communities where these institutions were weak or absent. Key features of these institutions included setting and enforcing rules locally and communication across scales. Self-governing local institutions have been associated with sustainable management of natural resources. In our study communities, analogous institutions played a similar role to moderate adverse effects from climate-driven environmental change. The findings suggest that policies to strengthen, recognize, and accommodate local institutions could improve adaptation outcomes.Ye

A METAGENOMIC ASSESSMENT OF BACTERIAL CONTAMINATION OF DUST EVENTS IN SENEGAL

Previous work in the Caribbean and West Africa have shown that air samples taken during dust events contain microorganisms (bacteria, fungi, viruses), including human pathogens that can cause many respiratory diseases. To better understand the potential downstream effect of bacteria dust on human health and public ecosystems, it is important to characterize the source population. In this study, we aimed to explore the bacterial populations of African dust samples collected between 2013-2017. The dust samples were collected using the spatula method, then the hypervariable regions (V3 and V4) of the 16S rRNA gene were amplified using PCR followed byMiSeq Illumina sequencing. Analysis of the sequencing data were performed using MG-RAST. At the phylum level, the proportions of Actinobacteria (22%), Firmicutes (20%), Proteobacteria (19%), and Bacteroidetes (13%) were respectively predominant in all dust samples. At the genus level, Bacillus(16%), Pseudomonas(10%), Nocardiodes and Exiguobacterium (5%) are the most dominated genera in African dust samples collected in this study.The study showed that molecular characterization of dust microbial population remains a very efficient method, also applicable to the search for viruses and fungi in this type of sample. It is important to note that the majority of microorganisms identified in this study can cause respiratory diseases.</jats:p

Crues et inondations dans la basse vallée du fleuve Sénégal

Les inondations récentes de la ville de Saint-Louis du Sénégal posent avec acuité le problème de sa protection en période de hautes-eaux. Cet article analyse la variabilité interannuelle des niveaux de crue du fleuve Sénégal à son embouchure pour comprendre le pourquoi des inondations actuelles malgré la sécheresse qui sévit dans cette région depuis une trentaine d’année. Les conditions hydroclimatiques Les crues exceptionnelles des siècles derniers Les récits des voyageurs, les documents his..

Le Bassin du Sénégal à l'embouchure, flux continentaux dissous et particulaires invasion marine dans la vallée du fleuve: contribution à l'hydrologie fluviale en milieu tropical humide et à la dynamique estuairienne en domaine Sahélien

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