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Extreme rainfall events alter the trophic structure in bromeliad tanks across the Neotropics
No full textChanges in global and regional precipitation regimes are among the most pervasive components of climate change. Intensification of rainfall cycles, ranging from frequent downpours to severe droughts, could cause widespread, but largely unknown, alterations to trophic structure and ecosystem function. We conducted multi-site coordinated experiments to show how variation in the quantity and evenness of rainfall modulates trophic structure in 210 natural freshwater microcosms (tank bromeliads) across Central and South America (18 degrees N to 29 degrees S). The biomass of smaller organisms (detritivores) was higher under more stable hydrological conditions. Conversely, the biomass of predators was highest when rainfall was uneven, resulting in top-heavy biomass pyramids. These results illustrate how extremes of precipitation, resulting in localized droughts or flooding, can erode the base of freshwater food webs, with negative implications for the stability of trophic dynamics. The amount and frequency of rainfall structures aquatic food webs. Here the authors show that in tropical tank bromeliads, lower trophic levels are more abundant in stable rainfall conditions, while biomass pyramids are inverted in conditions with periodic droughts
IPSL-CM5A2-an Earth system model designed for multi-millennial climate simulations
No full textBased on the fifth phase of the Coupled Model Intercomparison Project (CMIP5)-generation previous Institut Pierre Simon Laplace (IPSL) Earth system model, we designed a new version, IPSL-CM5A2, aiming at running multi-millennial simulations typical of deep-time paleoclimate studies. Three priorities were followed during the setup of the model: (1) improving the overall model computing performance, (2) overcoming a persistent cold bias depicted in the previous model generation and (3) making the model able to handle the specific continental configurations of the geological past. These developments include the integration of hybrid parallelization Message Passing Interface - Open Multi-Processing (MPI-OpenMP) in the atmospheric model of the Laboratoire de Meteorologic Dynamique (LMDZ), the use of a new library to perform parallel asynchronous input/output by using computing cores as "I/O servers" and the use of a parallel coupling library between the ocean and the atmospheric components. The model, which runs with an atmospheric resolution of 3.75 degrees x 1.875 degrees and 2 to 0.5 degrees in the ocean, can now simulate similar to 100 years per day, opening new possibilities towards the production of multi-millennial simulations with a full Earth system model. The tuning strategy employed to overcome a persistent cold bias is detailed. The confrontation of a historical simulation to climatological observations shows overall improved ocean meridional overturning circulation, marine productivity and latitudinal position of zonal wind patterns. We also present the numerous steps required to run IPSL-CM5A2 for deep-time paleoclimates through a preliminary case study for the Cretaceous. Namely, specific work on the ocean model grid was required to run the model for specific continental configurations in which continents are relocated according to past paleogeographic reconstructions. By briefly discussing the spin-up of such a simulation, we elaborate on the requirements and challenges awaiting paleoclimate modeling in the next years, namely finding the best trade-off between the level of description of the processes and the computing cost on supercomputers
Migrations africaines au Maghreb et au Moyen-Orient
No full textEn faisant dialoguer deux terrains de recherche conduits au Maroc et en Tunisie selon une démarche anthropologique, nous mettrons en lumière les questions que la migration africaine pose aujourd'hui aux institutions chrétiennes, catholique et protestante. Quelles reconfigurations religieuses la présence des migrants induit-elle ? D'un côté, les Églises ' historiques ' présentes dans les grandes villes, en tant qu'héritières des Églises officielles, ont augmenté le nombre de leurs fidèles et de leurs offices. De l'autre, les Églises pentecôtistes et charismatiques ont fait leur apparition dans les quartiers périphériques. Nous décrirons dans cet article, d'une part, les dynamiques nouvelles entre Églises catholique et protestante au Maroc et en Tunisie, et d'autre part, nous analyserons les manières différenciées dont les autorités ecclésiastiques des deux pays composent avec les orientations distinctes au sein du protestantisme entre les cultes historique et pentecôtiste. Notre hypothèse est que l'histoire des congrégations religieuses chrétiennes au Maghreb, implantées depuis le milieu du XIXe siècle, continue d'influer sur les équilibres actuels
Evapotranspiration partition using the multiple energy balance version of the ISBA-A-g(s) land surface model over two irrigated crops in a semi-arid Mediterranean region (Marrakech, Morocco)
No full textThe main objective of this work is to question the representation of the energy budget in soil-vegetation-atmosphere transfer (SVAT) models for the prediction of the turbulent fluxes in the case of irrigated crops with a complex structure (row) and under strong transient hydric regimes due to irrigation. To this end, the Interaction between Soil, Biosphere, and Atmosphere (ISBA-A-g(s)) is evaluated at a complex open olive orchard and, for the purposes of comparison, on a winter wheat field taken as an example of a homogeneous canopy. The initial version of ISBA-A-g(s) based on a composite energy budget (hereafter ISBA-1P for one patch), is compared to the new multiple energy balance (MEB) version of ISBA that represents a double source arising from the vegetation located above the soil layer. In addition, a patch representation corresponding to two adjacent, uncoupled source schemes (hereafter ISBA-2P for two patches) is also considered for the olive orchard. Continuous observations of evapotranspiration (ET), with an eddy covariance system and plant transpiration (T-r) with sap flow and isotopic methods were used to evaluate the three representations. A preliminary sensitivity analyses showed a strong sensitivity to the parameters related to turbulence in the canopy introduced in the new ISBA-MEB version. For wheat, the ability of the single- and dual-source configuration to reproduce the composite soil-vegetation heat fluxes was very similar; the root mean square error (RMSE) differences between ISBA-1P, ISBA-2P and ISBA-MEB did not exceed 10 W M-2 for the latent heat flux. These results showed that a composite energy balance in homogeneous covers is sufficient to reproduce the total convective fluxes. The two configurations are also fairly close to the isotopic observations of transpiration in spite of a light underestimation (overestimation) of ISBA- 1P (ISBA-MEB). At the olive orchard, contrasting results are obtained. The dual-source configurations, including both the uncoupled (ISBA-2P) and the coupled (ISBA-MEB) representations, outperformed the single-source version (ISBA-1P), with slightly better results for ISBA-MEB in predicting both total heat fluxes and evapotranspiration partition. Concerning plant transpiration in particular, the coupled approach ISBA-MEB provides better results than ISBA-1P and, to a lesser extent, ISBA-2P with RMSEs of 1.60, 0.90, and 0.70 mm d(-1) and R-2 of 0.43, 0.69, and 0.70 for ISBA-1P, ISBA-2P and ISBA-MEB, respectively. In addition, it is shown that the acceptable predictions of composite convective fluxes by ISBA-2P for the olive orchard are obtained for the wrong reasons as neither of the two patches is in agreement with the observations because of a bad spatial distribution of the roots and a lack of incoming radiation screening for the bare soil patch. This work shows that composite convection fluxes predicted by the SURFace EXternalisee (SURFEX) platform and the partition of evapotranspiration in a highly transient regime due to irrigation is improved for moderately open tree canopies by the new coupled dualsource ISBA-MEB model. It also points out the need for further local-scale evaluations on different crops of various geometry (more open rainfed agriculture or a denser, intensive olive orchard) to provide adequate parameterisation to global database, such as ECOCLIMAP-II, in the view of a global application of the ISBA-MEB model
L'anthropologie impliquée à l'hôpital en contexte d'épidémie de covid-19 pour accompagner les fins de vie et les décès hospitaliers
No full textA second population-based cohort study in Cameroon confirms the temporal relationship between onchocerciasis and epilepsy
No full textTo confirm our earlier evidence of a temporal and dose-response relationship between onchocerciasis and epilepsy, we conducted another cohort study in a different setting in Cameroon. Individuals whose Onchocerca volvulus microfilarial density (Ov-MFD) was measured in 1992-1994 when they were children were revisited in 2019 to determine if they acquired epilepsy. With reference to individuals with no microfilariae in 1992-1994, the relative risks of acquiring epilepsy were 0.96, 2.76, 3.67, and 11.87 in subjects with initial Ov-MFD of 1-7, 8-70, 71-200, and > 200 microfilariae per skin snip, respectively. This study further demonstrates reproducibility using the Bradford Hill's criteria for causality
Freshwater fish diversity hotspots for conservation priorities in the Amazon Basin
No full textConserving freshwater habitats and their biodiversity in the Amazon Basin is a growing challenge in the face of rapid anthropogenic changes. We used the most comprehensive fish-occurrence database available (2355 valid species; 21,248 sampling points) and 3 ecological criteria (irreplaceability, representativeness, and vulnerability) to identify biodiversity hotspots based on 6 conservation templates (3 proactive, 1 reactive, 1 representative, and 1 balanced) to provide a set of alternative planning solutions for freshwater fish protection in the Amazon Basin. We identified empirically for each template the 17% of sub-basins that should be conserved and performed a prioritization analysis by identifying current and future (2050) threats (i.e., degree of deforestation and habitat fragmentation by dams). Two of our 3 proactive templates had around 65% of their surface covered by protected areas; high levels of irreplaceability (60% of endemics) and representativeness (71% of the Amazonian fish fauna); and low current and future vulnerability. These 2 templates, then, seemed more robust for conservation prioritization. The future of the selected sub-basins in these 2 proactive templates is not immediately threatened by human activities, and these sub-basins host the largest part of Amazonian biodiversity. They could easily be conserved if no additional threats occur between now and 2050
TIP_finder : an HPC software to detect transposable element insertion polymorphisms in large genomic datasets
No full textTransposable elements (TEs) are non-static genomic units capable of moving indistinctly from one chromosomal location to another. Their insertion polymorphisms may cause beneficial mutations, such as the creation of new gene function, or deleterious in eukaryotes, e.g., different types of cancer in humans. A particular type of TE called LTR-retrotransposons comprises almost 8% of the human genome. Among LTR retrotransposons, human endogenous retroviruses (HERVs) bear structural and functional similarities to retroviruses. Several tools allow the detection of transposon insertion polymorphisms (TIPs) but fail to efficiently analyze large genomes or large datasets. Here, we developed a computational tool, named TIP_finder, able to detect mobile element insertions in very large genomes, through high-performance computing (HPC) and parallel programming, using the inference of discordant read pair analysis. TIP_finder inputs are (i) short pair reads such as those obtained by Illumina, (ii) a chromosome-level reference genome sequence, and (iii) a database of consensus TE sequences. The HPC strategy we propose adds scalability and provides a useful tool to analyze huge genomic datasets in a decent running time. TIP_finder accelerates the detection of transposon insertion polymorphisms (TIPs) by up to 55 times in breast cancer datasets and 46 times in cancer-free datasets compared to the fastest available algorithms. TIP_finder applies a validated strategy to find TIPs, accelerates the process through HPC, and addresses the issues of runtime for large-scale analyses in the post-genomic era
