Évaluation des facteurs associés à l'occurrence des cyanobactéries à la prise d'eau et modélisation de leur distribution spatio-temporelle

RÉSUMÉ La gestion des ressources en eau est un défi majeur compte tenu des menaces sur la qualité de l’eau. En effet, les cyanobactéries (CB) communément appelées algues bleu-vert prolifèrent fortement dans beaucoup de plans d’eau utilisés pour l’alimentation en eau potable. La gravité de ce phénomène, appelé «fleur d’eau», réside dans le fait que certaines espèces de cyanobactéries produisent des toxines qui peuvent traverser toutes les barrières du traitement conventionnel de l’eau (filtration, coagulation-floculation, sédimentation, désinfection). Plusieurs équipes de recherche à travers le monde travaillent sur cette question des «fleurs d’eau» afin de mieux comprendre ce phénomène en apportant des éléments explicatifs sur les principales causes. Cependant, la non-linéarité des facteurs impliqués (vent, température de l’eau, lumière, nutriments) ne facilite pas l’analyse des données recueillies afin de pouvoir :1) évaluer le risque d’occurrence associé à ces facteurs à une prise d’eau et 2) comprendre le rôle et l’interaction des différents mécanismes impliqués tels que l’advection et la flottabilité des cyanobactéries. L’advection dans un lac est souvent due au mouvement de l’eau induit par les effets des contraintes de vent à la surface du plan d’eau. La flottabilité des cyanobactéries est le résultat de leur changement de densité suite aux vésicules de gaz dont elles disposent et à la variation de leur contenu en glucides. C’est ainsi que cette étude a été entreprise à la suite des deux constatations relevées ci-dessus.----------ABSTRACT Cyanobacteria or blue green algae are a concern for water resources management as a result of their occurrence in many drinking water sources. Many cyanobacterial (CB) species produce toxins that can break through the conventional water treatment processes unmodified. Many studies have been conducted to understand the main causes leading to the phenomenon of CB blooms. However, the non-linearity of the controlling factors (wind, water temperature, light, nutrients) combined with the importance of the geographic position of the drinking water intake do not facilitate the analysis of data. Among the challenges are1) to estimate the risk that CB occurs at drinking water intake and 2) to understand the interactions between the physics and biology among transport mechanisms such as advection and CB buoyancy. Advection in a lake is often the transport induced by water movement under wind stress effects. CB buoyancy is the result of their change of density, due to variation in the content of aerotopes (gas vesicles) and denser-than-water carbohydrate storage products

Developing environmental flow targets for benthic macroinvertebrates in large rivers using hydraulic habitat associations and taxa thresholds

Holistic environmental flows frameworks are built on our understanding of key flow-ecology relationships that support sensitive taxa and critical ecosystem functions under different flow and water level scenarios. Most research on flow-ecology relationships has typically focused on small systems, with less known about flow as-sociations, indicator taxa, and environmental thresholds of assemblage change along hydraulic gradients of large non-wadeable rivers. We assessed benthic macroinvertebrate assemblage structure and applied Taxa Indicator Threshold ANalysis (TITAN) on biomonitoring data collected during a six-year period in the Wolastoq | Saint John River in Atlantic Canada. Flow velocity was strongly associated with the distribution and relative abundance of benthic macroinvertebrates in the river, and taxon associations reflected functional adaptations to flow. We identified 33 genus-level indicator taxa that were either positively or negatively associated with flow velocity. Weaker taxa responses were shown for the gradient in median substrate particle size where 22 negatively and positively responding taxa were identified. We predicted changes in indicator taxon abundance under different flow scenarios using a hydrodynamic model, and characterised the distribution and availability of suitable hydraulic habitat patches within a 20 km reach downstream of a large hydropower generating station. These observations set the stage for the development of ecologically-based flow targets to support holistic environmental flow management in large rivers

Systèmes à libération contrôlée pH-dépendants de principes actifs hydrophobes à partir d’oléogels

Les rhumatismes inflammatoires chroniques sont une cause importante d'invalidité dans le monde entier. De ce fait, les affections rhumatismales chroniques font peser une lourde charge sociale et économique sur toutes les sociétés, pas seulement sur celles où l’espérance de vie est élevée. L’objectif principal de ce travail était d’étudier le profil de libération pH-dépendante de principes actifs hydrophobes à partir d’oléogels oraux et/ou cutanés. La formulation des oléogels a été réalisée selon une méthode sol-gel, reproductible à grande échelle. La caractérisation et le suivi dans le temps ont montré une bonne stabilité des oléogels. Les valeurs de pH des oléogels étaient globalement acides (entre 4,3 et 5,8) et dépendaient de la quantité de gélifiant utilisée. Les études de libération du kétoprofène, principe actif hydrophobe, en fonction du pH des milieux de dissolution ont montré des profils de libération d’une cinétique du premier ordre d’équation =+. avec des coefficients de détermination proches de 1 (milieux à pH égal à 1,2 et 5,5). Une meilleure libération du kétoprofène a été obtenue dans un milieu intestinal simulé (pH égal à 6,8) pour les formulations qui présentaient déjà une saturation en milieu gastrique simulé (pH égal à 1,2). Cette étude qui a permis de formuler, d’évaluer et de modéliser le profil de libération du kétoprofène à partir d’oléogels peut constituer une étape importante dans un objectif de souveraineté thérapeutique des pays d’Afrique subsaharienne notamment le Sénégal.Mots clés : Oléogels, rhumatismes inflammatoires chroniques, kétoprofène, libération contrôlée, pH-dépendant.   English Title: pH-dependent controlled release systems of hydrophobic active pharmaceutical ingredients from oleogels Chronic inflammatory rheumatism is a major cause of disability around the world. As a result, chronic rheumatic diseases place a heavy social and economic burden on all societies, not just those with high life expectancy. The main objective of this work was to control the pH-dependent release of hydrophobic active pharmaceutical ingredients from oral and / or skin oleogels. The formulation of the oleogels was carried out using a sol-gel large-scale reproducible method. Characterization and monitoring over time have shown good stability of the oleogels. The pH values of the oleogels were overall acid (between 4.3 and 5.8) and depended on the amount of gelling agent used. The release studies of ketoprofen, a hydrophobic active pharmaceutical ingredient, as a function of the pH of the dissolution media have shown release profiles of first-order kinetics of equation =+. with coefficients of determination close to 1 (media at pH equal to 1.2 and 5.5). Better release of ketoprofen was obtained in simulated intestinal medium (pH equal to 6.8) for formulations which already exhibited saturation in simulated gastric medium (pH equal to 1.2). This study, which made it possible to formulate, evaluate and model the release profile of ketoprofen from oleogels, may constitute an important step in an objective of therapeutic sovereignty of the countries of sub-Saharan Africa, particularly Senegal.Keywords: oleogels - chronic inflammatory rheumatism - ketoprofen - controlled release – pH-dependent

Evaluation de l’état hydrique chez les patients hémodialysés chroniques : une étude transversale monocentrique: Assessment of the hydration status in chronic hemodialysis patients: a single-center cross-sectional study

Context and objective. For many practitioners, blood pressure is the main indicator of the hydration status of the chronic hemodialysis patient. The objective of this study was to assess the extent to which bioimpedance analysis (BIA) can assist in determining acute changes in fluid volume during the hemodialysis session. Methods. This was a 9-week longitudinal study. The total body water (TBW) was measured with a BIA analyzer, before and after 6 successive sessions. The ΔWeight was compared to the ΔTBW by calculating the P/V ratio (ΔWeight/ΔTBW) with the assumption that the dry weight is reached when P/V = 1. Results. The measurements made in 22 patients (46.6 years, 54.5% men, 92.3 months on dialysis) were reproducible. There was no statistically significant difference between ΔTBW and ΔWeight. However, at the individual level, significant differences had been observed. Using hypertension as a marker for a state of hyperhydration, a 31.8% agreement was noted between the P/V ratio and hypertension. Conclusion. Although the loss of water predicted by the BIA did not always correspond to the weight loss, BIA is a technique that can be used to assess the variations in TBW during the hemodialysis session in patients. Contexte et objectif. La pression artérielle est pour de nombreux praticiens, l’indicateur principal du statut hydrique du patient hémodialysé chronique. L’objectif de la présente étude était d’évaluer dans quelle mesure l’analyse d’impédance bioélectrique (BIA) pourrait aider à la détermination des variations aigues du volume hydrique au cours de la séance d’hémodialyse. Méthodes. Il s’agissait d’une étude de suivi longitudinal sur 9 semaines. Le volume total d’eau (VTE) a été mesuré par BIA, avant et après 6 séances. Le ΔPoids a été comparé au ΔVTE par le calcul du ratio P/V (ΔPoids / ΔVTE) dans l’hypothèse que le poids sec est atteint lorsque P/V = 1. Résultats. Les mesures faites chez 22 patients (46,6 ans, 54,5% hommes, 92,3 mois en dialyse) étaient reproductibles. Il n’y avait pas de différence statistiquement significative entre le ΔVTE et le ΔPoids. Cependant à l’échelon individuel des différences importantes étaient observées. En utilisant l’hypertension artérielle (HTA) comme marqueur d’un état d’hyperhydratation, une concordance de 31,8% était notée entre le ratio P/V et l’HTA. Conclusion. Bien que la perte d’eau prédite par la BIA ne corresponde pas toujours à celle du poids, la BIA est une technique qui peut être utilisée pour évaluer les variations du VTE au cours de la séance d’hémodialys

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Migration of Atlantic salmon (Salmo salar) smolts in a large hydropower reservoir

Migration rates, delay, timing, and success of acoustic-tagged Atlantic salmon (Salmo salar) presmolts (n = 120) and smolts (n = 57) are reported as they moved through the large Mactaquac Generating Station (MGS) reservoir and subsequently the lower Saint John River (SJR). The potential relationship between fish movements and the MGS operations was examined directly and via a hydrodynamic model. Migration rates were 15.4–29.3 km·day−1 within the river sections and 5.0–13.3 km·day−1 through the reservoir, a significant reduction of 32%–57%. Migratory timing was temporally mismatched with dam operations such that only a few (n = 3) smolts had the option of dam passage via spill. Migration success estimated as apparent survival was high through the reservoir (81%–100%), declined by 8%–32% during passage at the MGS, and additional losses (27%–55%) occurred during the migration to the lower SJR, such that overall survival to the estuary for the groups tagged as autumn presmolts was 61%–65%, and survival for those tagged as spring smolts was 6%–10%.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Developing environmental flow targets for benthic macroinvertebrates in large rivers using hydraulic habitat associations and taxa thresholds

Holistic environmental flows frameworks are built on our understanding of key flow-ecology relationships that support sensitive taxa and critical ecosystem functions under different flow and water level scenarios. Most research on flow-ecology relationships has typically focused on small systems, with less known about flow associations, indicator taxa, and environmental thresholds of assemblage change along hydraulic gradients of large non-wadeable rivers. We assessed benthic macroinvertebrate assemblage structure and applied Taxa Indicator Threshold ANalysis (TITAN) on biomonitoring data collected during a six-year period in the Wolastoq | Saint John River in Atlantic Canada. Flow velocity was strongly associated with the distribution and relative abundance of benthic macroinvertebrates in the river, and taxon associations reflected functional adaptations to flow. We identified 33 genus-level indicator taxa that were either positively or negatively associated with flow velocity. Weaker taxa responses were shown for the gradient in median substrate particle size where 22 negatively and positively responding taxa were identified. We predicted changes in indicator taxon abundance under different flow scenarios using a hydrodynamic model, and characterised the distribution and availability of suitable hydraulic habitat patches within a 20 km reach downstream of a large hydropower generating station. These observations set the stage for the development of ecologically-based flow targets to support holistic environmental flow management in large rivers

Assessing the vulnerability of urban drinking water intakes to water scarcity under global change: A bottom-up approach

Drinking water intakes (DWIs) face significant pressure due to global changes, including urbanization and climate change. The common approach relies mainly on climate projections generated by global climate models to simulate large scale hydroclimatic conditions. However, it is crucial to discern the impact of global changes on water scarcity at the local level, including in regions where available data are limited. This paper proposes an approach that focuses on studying the vulnerability of surface DWIs to low water levels and water demand in current and future climates within a cold-climate region.Low flows at DWIs were simulated using historical water level data obtained from hydrometric stations situated along the studied river. After defining four scenarios for climate change and anthropogenic activities affecting raw water withdrawals at DWIs, the full potential range of level variations was simulated. This study employed a combined water scarcity index derived from two sub-indices based on water level and water demand. The resulting index ranges from 0 to 1, where a higher value indicates a greater vulnerability to water scarcity. The simulation results demonstrate the vulnerability of water scarcity in both current and future climates.The calculated index, selecting the current vulnerability to water scarcity for the five studied DWIs, ranged from 0.61 to 0.76. The results for the vulnerability of these DWIs under future climate conditions exhibited significant variability across the different scenarios representing possible maximum daily withdrawal. These scenarios were defined to encompass a spectrum of options related to the government's policy for drinking water conservation strategy implementation. While exploring the full range of potential risks, the study's results demonstrated that the DWIs were especially vulnerable to anthropogenic changes affecting water demand.The framework developed in this study can provide a decision-support basis for municipalities and water managers to adapt to global change and achieve greater water supply resilience