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Biogeography and phenology of the jellyfish Rhizostoma pulmo (Cnidaria : Scyphozoa) in southern European seas
No full textAim: Global anthropogenic changes have altered biogeography and phenology of marine populations, thereby promoting a spatial reconfiguration in the functioning of marine ecosystems. Among these changes, massive proliferations of jellyfish in temperate latitudes warn of potential alterations in biogeochemical fluxes, ecosystems' structure and assets, and the services they provide to human welfare. Understanding driving factors shaping large-scale patterns of jellyfish proliferations is a pressing need in global ecology and sustainability science. Using a comprehensive dataset of the largest blooming scyphomedusae in southern European seas we test, over broad space-time scales, current hypotheses relating jellyfish dynamics to warming and eutrophication. Location: Southern European seas. Time period: 1875-2019. Major taxa studied: Rhizostoma pulmo. Methods: We have gathered historical and contemporaneous records of R. pulmo from the Mediterranean and Black Seas over the last two centuries (7,359 records). Generalized statistical models were used to assess the influence of thermal (latitudinal) and productivity (longitudinal) gradients on the biogeographical patterns, and the species' phenology at large and regional scales. Results: Rhizostoma pulmo abundance exhibited an enhanced magnitude and frequency in recent decades, concurrently with positive temperature anomalies. We found that the latitudinal temperature gradient, but not productivity, shaped long-term bloom intensity and biogeographical patterns of the species. Our analysis further uncovered a significant effect of the interannual variability of spring temperature on the species' phenology over the period 2008-2018, with warmer springs favouring an earlier start (c. 3 months) and a longer duration (from 5 to 7 months) of jellyfish season. Main conclusions: Among the current hypotheses linking jellyfish changes with anthropogenic disturbances, only the warming-based hypothesis gained support over wide space-time scales, while the eutrophication-based hypothesis mainly applied at local scales. Hence, biogeographical patterns of R. pulmo are shaped by the latitudinal temperature gradient, while the species bloom dynamics echo variations in ecoregion thermal regimes
Near-surface western boundary circulation off Northeast Brazil
No full textIn the tropical Atlantic Ocean, the North Brazil Undercurrent (NBUC) and the North Brazil Current (NBC) play important roles as near-surface northward paths for the Atlantic meridional overturning circulation. To investigate the meridional evolution of the near-surface western boundary circulation in that region, two surveys were carried out off Northeast Brazil during austral spring 2015 and fall 2017, periods that we show to be representative of typical conditions for the spring and fall seasons. Using conductivity temperature depth oxygen probe and ship-mounted acoustic Doppler current profiler measurements, altimetry data, and numerical reanalysis products, we examine the spatiotemporal variability of the NBUC, providing a comprehensive view of the circulation, including NBUC-NBC transition and the potential impact of mesoscale eddies. The NBUC originating south of 10 degrees S flows equatorward over the continental slope. NBUC mean velocity, transport and vertical extent of the velocity core were higher in spring 2015 (0.81 m s(-1), 15.6 Sv, and >400 m) than in fall 2017 (0.65 m s(-1), 11.0 Sv, and similar to 300 m). The upper limit of the NBUC velocity core rose slightly from 160 m at 9 degrees S to 105 m depth at 6 degrees S. This pattern is associated with a northward increase in current velocity from 0.7 m s(-1) at 9 degrees S to 1 m s(-1) at 5 degrees S. The orographic effect shifts the flow from northeastward south of 7.5 degrees S to northwestward north of 7.5 degrees S, following the shoreline. Besides, altimetry data show that this flow can be locally influenced by mesoscale activity. Farther north, at similar to 4.8 degrees S, data obtained in fall 2017 show that the central branch of the South Equatorial Current (cSEC) enters into the western boundary system where it coalesces with the NBUC to form the NBC, flowing toward the Caribbean Sea. Finally, in fall, the NBUC retroflection does not feed the South Equatorial Undercurrent (SEUC), which, instead originates from retroflections of the cSEC and the equatorial branch of the South Equatorial Current (eSEC)
Uranium retention on iron oxyhydroxides in post-mining environmental conditions
No full textInvestigating uranium migration mechanisms related to the weathering of waste rocks is essential for developing strategies that can address the potential environmental issues caused by uranium mining. This work is based on environmental samples containing 2 L ferrihydrite, lepidocrocite and goethite collected in the technosols from granitic waste rock piles, mine drainage conduits and mine waters. The results show the important role of iron oxyhydroxide in U immobilization and re-concentration. EXAFS spectroscopy combined with mineralogical and geochemical studies (Scanning electronic microscopy, Wavelength-dispersive X-ray spectroscopy microprobe, inductively coupled plasma - optical emission spectrometry/mass spectrometry and X-ray diffraction) allowed for the identification of uranyl ternary surface complexes at the ferrihydrite surface that were either composed of phosphate groups or organic matter. Moreover, goethite and lepidocrocite were also identified as a secondary trap for U immobilization. U(VI) is known to be mobile in oxidizing conditions. This study highlights the control of the uranyl mobility by various iron oxyhydroxides in supergene conditions
Evidence that seasonal malaria chemoprevention with SPAQ influences blood and pre-erythrocytic stage antibody responses of Plasmodium falciparum infections in Niger
No full textBackground In endemic areas, children develop slowly and naturally anti-Plasmodium antibodies and become semi-immune. Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine + amodiaquine (SPAQ) is a new strategy to reduce malaria morbidity in West African young children. However, SMC may impact on the natural acquisition of anti-Plasmodium immunity. This paper evaluates the effect of SMC with SPAQ on antibody concentration in young children from Niger. Methods This research was conducted in areas benefitting from SMC since 2014 (Zinder district), without SMC (Dosso district), and with 1 year of SMC since 2016 (Gaya district). To assess the relationship between SMC and Plasmodium falciparum IgG antibody responses, the total antibody concentrations against two P. falciparum asexual stage vaccine candidate antigens, circumsporozoite protein (CSP) and glutamate-rich protein R2 (GLURP-R2), in children aged 3 to 59 months across the three areas were compared. Antibody concentrations are quantified using an enzyme-linked immunosorbent assay on the elution extracted from positive and negative malaria Rapid Diagnostic Test cassettes. Results The analysis concerns two hundred and twenty-nine children aged from 3 to 59 months: 71 in Zinder, 77 in Dosso, and 81 in Gaya. In Zinder (CSP = 17.5 mu g/ml and GLURP-R2 = 14.3 mu g/ml) median antibody concentration observed are higher than in Gaya (CSP = 7.7 mu g/ml and GLURP-R2 = 6.5 mu g/ml) and Dosso (CSP = 4.5 mu g/ml and GLURP-R2 = 3.6 mu g/ml) (p < 0.0001). Conclusion The research reveals some evidences which show that seasonal malaria chemoprevention with SPAQ has an effect on blood stage antibody responses and pre-erythrocytic stage of P. falciparum infections in Niger. Increased antibody titres with increased SMC/SPAQ implementation. This contradicts hypothesis that SMC/SPAQ could reduce immunity to erythrocyte and liver-stage antigens. Further studies are necessary to provide better understanding of the SMC effect on malaria immunity
Enjeux démographiques en Afrique subsaharienne : promouvoir et confronter les sources statistiques
No full textLes enfants jumeaux comparativement aux singletons sont sujets à une mortalité plus élevée. Cette situation est d'autant plus préoccupante dans les pays d'Afrique subsaharienne, où la mortalité est déjà plus élevée que partout ailleurs dans le monde. Cela fait de la santé des jumeaux un défi supplémentaire de santé publique sur ce continent. Dans ce travail, nous apportons une contribution complémentaire à toutes celles qui existent déjà, mais en mobilisant d'autres types de données moins utilisées pour analyser la surmortalité des jumeaux : des données longitudinales provenant de 21 observatoires de population. Il compare les courbes de survie entre jumeaux et singletons sur la période 2010-2014, présente l'évolution dans le temps (de 1995 à 2014) de ces courbes et détermine l'âge auquel une différence de taux de mortalité entre jumeaux et singletons serait maintenue. Il étudie également les facteurs associés à la différence de survie entre les jumeaux et les singletons de moins de 5 ans. Les résultats obtenus montrent l'existence de disparités significatives entre les observatoires de population en termes de différentiel de survie entre jumeaux et singletons. Ils montrent également que le différentiel de survie entre jumeaux et singletons se réduit avec le temps. Nos analyses ont également montré qu'il n'y aurait pratiquement plus de surmortalité des jumeaux après l'âge de 5 ans. En outre, l'analyse des facteurs associés au différentiel de survie entre jumeaux et singletons a montré que les facteurs biomédicaux (en particulier le faible poids à la naissance et la prématurité) expliquent la majeure partie de ce différentiel
Validation of the D:A:D chronic kidney disease risk score in people living with HIV : the IeDEA West Africa Cohort Collaboration
No full textObjectives: A risk score for long-term prediction of chronic kidney disease (CKD) in people living with HIV (PLHIV) has been developed using data from the D:A:D cohort. We assessed the performance of the D:A:D risk score in a cohort of PLHIV in West Africa. Methods : Data from PLHIV starting antiretroviral treatment in four clinics in Burkina Faso, Côte d'Ivoire and Togo participating in the IeDEA West Africa collaboration were analysed. CKD was defined as two consecutive estimated glomerular filtration rates (eGFRs) of ≤ 60 mL/min/1.73 m2. The D:A:D score (short version) was calculated using age, gender, nadir CD4 and baseline eGFR and was categorized into low, medium, and high-risk groups. Results : In 14 930 participants (70% female, median age = 38 years; median nadir CD4 count = 183 cells/µL) followed for a median duration of 5.7 years, 660 (4.4%) progressed to CKD, with an incidence [95% confidence interval (CI)] of 7.8 (7.2-8.4) per 1000 person-years (PY). CKD incidence rates were 2.4 (2.0-2.8), 8.1 (6.8-9.6) and, 30.9 (28.0-34.1) per 1000 PY in the low-, medium- and high-risk groups, respectively. In the high-risk group, 14.7% (95% CI: 13.3; 16.3) had progressed to CKD at 5 years. Discrimination was good [C-statistics = 0.81 (0.79-0.83)]. In all, 79.4% of people who progressed to CKD were classified in the medium- to high-risk group at baseline (sensitivity) and 66.5% of people classified in the low risk group at baseline did not progress to CKD (specificity). Conclusions : These findings confirm the validity of the D:A:D score in identifying individuals at risk of developing CKD who could benefit from enhanced kidney monitoring in West African HIV clinic
Les mondes du surf : transformations historiques, trajectoires sociales, bifurcations technologiques
No full textMean spectral reflectance from bare soil pixels along a Landsat-TM time series to increase both the prediction accuracy of soil clay content and mapping coverage
No full textVisible, near-infrared and short wave infrared (VNIR/SWIR, 400-2500 nm) remote sensing imagery is a useful tool for topsoil property mapping, but limited to bare soils pixels. With the increasing amount of freely available VNIR/SWIR satellite imagery (e.g. Landsat TM, ETM+, OLI and Sentinel-2A/B), extensive time series data can be exploited to increase the spatial coverage of bare soil derived information. The objective of this study was to evaluate the benefits of using a bare soil image created from the mean spectral reflectance from bare soil pixels along a time series, compared to a single-date image. The benefits were analyzed in term of (i) proportion of soil mapping and (ii) accuracy of clay content prediction. The study was conducted over the Cap-Bon region (Northern Tunisia) which is a pedologically contrasted and cultivated area. To this end, 262 topsoil samples and three Landsat-TM images acquired during the summer season were used. Multiple linear regression (MLR) models based on the multi-date and single-date Landsat-derived spectral dataset were performed to quantify clay soil content. Our results have shown that (1) a bare soil image created from only mean spectral reflectance from common bare soil pixels along a time series provided the best accuracy of clay content prediction (i.e., coefficient of determination of validation (R-val(2)) of 0.75, a root mean square error of prediction (RMSEP) of 88 g/kg) with a moderate bare soil coverage (i.e., 23% of the study area); (2) a bare soil image created from a mix of mean spectral reflectance from common bare soil pixels along a time series and of spectral reflectance from bare soil pixels of single-date images provided acceptable accuracy of clay content prediction (i.e., R-val(2) = 0.64, RMSEP = 109 g/kg) with a relatively high bare soil coverage (i.e., 44% of the study area); and (3) all the bare soil images provided similar spatial structures of the clay content predictions. With the actual availability of the VNIR/SWIR satellite imagery for the entire globe, this study offer a simple and accurate method for delivering accurate soil property maps over large areas, to the geoscience community
Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails
No full textCryptic species can present a significant challenge to the application of systematic and biogeographic principles, especially if they are invasive or transmit parasites or pathogens. Detecting cryptic species requires a pluralistic approach in which molecular markers facilitate the detection of coherent taxonomic units that can then be analyzed using various traits (e.g., internal morphology) and crosses. In asexual or self-fertilizing species, the latter criteria are of limited use. We studied a group of cryptic freshwater snails (genus Galba) from the family Lymnaeidae that have invaded almost all continents, reproducing mainly by self-fertilization and transmitting liver flukes to humans and livestock. We aim to clarify the systematics, distribution, and phylogeny of these species with an integrative approach that includes morphology, molecular markers, wide-scale sampling across America, and data retrieved from GenBank (to include Old World samples). Our phylogenetic analysis suggests that the genus Galba originated ca. 22 Myr ago and today comprises six species or species complexes. Four of them show an elongated-shell cryptic phenotype and exhibit wide variation in their genetic diversity, geographic distribution, and invasiveness. The remaining two species have more geographically restricted distributions and exhibit a globose-shell cryptic phenotype, most likely phylogenetically derived from the elongated one. We emphasize that no Galba species should be identified without molecular markers. We also discuss several hypotheses that can explain the origin of cryptic species in Galba, such as convergence and morphological stasis