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Living at the edge : increasing stress for plants 2-13 years after the retreat of a tropical glacier
No full textRapid warming is a major threat for the alpine biodiversity but, at the same time, accelerated glacial retreat constitutes an opportunity for taxa and communities to escape range contraction or extinction. We explored the first steps of plant primary succession after accelerated glacial retreat under the assumption that the first few years are critical for the success of plant establishment. To this end, we examined plant succession along a very short post-glacial chronosequence in the tropical Andes of Ecuador (2-13 years after glacial retreat). We recorded the location of all plant individuals within an area of 4,200 m2 divided into plots of 1 m2. This sampling made it possible to measure the responses of the microenvironment, plant diversity and plants traits to time since the glacial retreat. It also made it possible to produce species-area curves and to estimate positive interactions between species. Decreases in soil temperature, soil moisture, and soil macronutrients revealed increasing abiotic stress for plants between two and 13 years after glacial retreat. This increasing stress seemingly explained the lack of positive correlation between plant diversity and time since the glacial retreat. It might explain the decreasing performance of plants at both the population (lower plant height) and the community levels (lower species richness and lower accumulation of species per area). Meanwhile, infrequent spatial associations among plants indicated a facilitation deficit and animal-dispersed plants were almost absent. Although the presence of 21 species on such a small sampled area seven years after glacial retreat could look like a colonization success in the first place, the increasing abiotic stress may partly erase this success, reducing species richness to 13 species after 13 years and increasing the frequency of patches without vegetation. This fine-grain distribution study sheds new light on nature's responses to the effects of climate change in cold biomes, suggesting that faster glacial retreat would not necessarily result in accelerated plant colonization. Results are exploratory and require site replications for generalizatio
Forecasting the effectiveness of the DeWorm3 trial interrupting the transmission of soil-transmitted helminths in three study sites in Benin, India and Malawi
No full textBackground: The DeWorm3 project is an ongoing cluster-randomised trial assessing the feasibility of interrupting
the transmission of soil-transmitted helminths (STH) through mass drug administration (MDA) using study sites in
India, Malawi and Benin. In this article, we describe an approach which uses a combination of statistical and mathematical
methods to forecast the outcome of the trial with respect to its stated goal of reducing the prevalence of
infection to below 2%.
Methods: Our approach is first to define the local patterns of transmission within each study site, which is achieved
by statistical inference of key epidemiological parameters using the baseline epidemiological measures of age-related
prevalence and intensity of STH infection which have been collected by the DeWorm3 trials team. We use these
inferred parameters to calibrate an individual-based stochastic simulation of the trial at the cluster and study site level,
which is subsequently run to forecast the future prevalence of STH infections. The simulator takes into account both
the uncertainties in parameter estimation and the variability inherent in epidemiological and demographic processes
in the simulator. We interpret the forecast results from our simulation with reference to the stated goal of the
DeWorm3 trial, to achieve a target of 2% prevalence at a point 24 months post-cessation of MDA.
Results: Simulated output predicts that the two arms will be distinguishable from each other in all three country
sites at the study end point. In India and Malawi, measured prevalence in the intervention arm is below the threshold
with a high probability (90% and 95%, respectively), but in Benin the heterogeneity between clusters prevents
the arm prevalence from being reduced below the threshold value. At the level of individual study arms within each
site, heterogeneity among clusters leads to a very low probability of achieving complete elimination in an intervention
arm, yielding a post-study scenario with widespread elimination but a few ‘hot spot’ areas of persisting STH
transmission
Effects of livestock on nitrogen and carbon cycling in a savanna in Burkina Faso
No full textThe nitrogen and carbon cycles are fundamental ecosystem processes influenced by several factors including soil type and other abiotic factors, plant species, grazing and soil organisms. Herbivores profoundly influence the functioning of ecosystems and the recycling of nutrients in interaction with plants in natural ecosystems. This study focuses on the effects of livestock on carbon and nitrogen cycling in a grazed savanna in Burkina Faso. Dominant grass species (aerial and root parts) and soil samples were collected under grasses and bare soil patches in 48 plots (24 protected and 24 unprotected plots), 18 months after setting up herbivores exclosures. Soil and grass 13C and 15N were used as integrative indicators of carbon and nitrogen cycles. The results revealed no significant effect of livestock on soil total carbon and nitrogen and on soil delta13C and delta15N values. Moreover, grazing had no significant effect on grass carbon and delta13C, while it significantly increased grass total nitrogen and delta15N. Therefore, our hypothesis that grazing would increase soil 13C and 15N values and plant biomass was only verified for grass 15N. Grass delta15N results suggest that grazing improves the immediate availability of ni-trogen but could also increase nitrogen losse
Antibiotics in surface water of East and Southeast Asian countries : a focused review on contamination status, pollution sources, potential risks, and future perspectives
No full textThis review provides focused insights into the contamination status, sources, and ecological risks associated with multiple classes of antibiotics in surface water from the East and Southeast Asia based on publications over the period 2007 to 2020. Antibiotics are ubiquitous in surface water of these countries with concentrations ranging from <1 ng/L to hundreds mu g/L and median values from 10 to 100 ng/L. Wider ranges and higher maximum concentrations of certain antibiotics were found in surface water of the East Asian countries like China and South Korea than in the Southeast Asian nations. Environmental behavior and fate of antibiotics in surface water is discussed. The reviewed occurrence of antibiotics in their sources suggests that effluent from wastewater treatment plants, wastewater from aquaculture and livestock production activities, and untreated urban sewage are principal sources of antibiotics in surface water. Ecological risks associated with antibiotic residues were estimated for aquatic organisms and the prevalence of antibiotic resistance genes and antibiotic-resistant bacteria were reviewed. Such findings underline the need for synergistic efforts from scientists, engineers, policy makers, government managers, entrepreneurs, and communities to manage and reduce the burden of antibiotics and antibiotic resistance in water bodies of East and Southeast Asian countries
Protecting the downstream migration of salmon smolts from hydroelectric power plants with inclined racks and optimized bypass water discharge
No full textThe sustained development of hydropower energy in the last century has caused important ecological impacts, promoting recent advances in efficient mitigation measures to be implemented in existing and future hydropower plants. Although upstream fish migration has been largely addressed with the development of fish-pass infrastructures, downstream passage solutions are often missing or inefficient, strengthening the need for their improvement and efficiency assessment. The efficiency of horizontally inclined (26 degrees) low bar spacing racks associated to a bypass was assessed using salmon smolts radiotelemetry along three successive hydropower plants (HPP) in the Ariege River (southern France). In average, nearly 90% of the smolts were successfully protected by the racks and rapidly guided to the bypass, within few minutes in most cases. Furthermore, we detected a significant positive influence of the bypass discharge (Q(bp%) expressed as the proportion of concurrent HPP discharge) on the probability of successful bypass passage, reaching 85% of successful passage with a Q(bp%) of only 3%, and more than 92% when the Q(bp%) exceeded 5%. The probability of bypass passage without hesitation (e.g. passage within the first 5 min) also increased with Q(bp%), and reached 90% with 5% of Q(bp%). Passage without hesitation was especially detected on the site having larger bypass entrances and transversal currents, providing better guidance into the bypass. High-efficiency results of inclined racks yielded with reduced Q(bp%) confirmed their relevance to mitigate some of the HPP ecological impacts, re-establishing safe downstream salmon migration with lower impact on energy production than older less efficient solutions
Does the gap between health workers' expectations and the realities of implementing a performance-based financing project in Mali create frustration ?
No full textBackground Performance-Based Financing (PBF), an innovative health financing initiative, was recently implemented in Mali. PBF aims to improve quality of care by motivating health workers. The purpose of this research was to identify and understand how health workers' expectations related to their experiences of the first cycle of payment of PBF subsidies, and how this experience affected their motivation and sentiments towards the intervention. We pose the research question, "how does the process of PBF subsidies impact the motivation of health workers in Mali?" Methods We adopted a qualitative approach using multiple case studies. We chose three district hospitals (DH 1, 2 and 3) in three health districts (district 1, 2 and 3) among the ten in the Koulikoro region. Our cases correspond to the three DHs. We followed the principle of data source triangulation; we used 53 semi-directive interviews conducted with health workers (to follow the principle of saturuation), field notes, and documents relating to the distribution grids of subsidies for each DH. We analyzed data in a mixed deductive and inductive manner. Results The results show that the PBF subsidies led to health workers feeling more motivated to perform their tasks overall. Beyond financial motivation, this was primarily due to PBF allowing them to work more efficiently. However, respondents perceived a discrepancy between the efforts made and the subsidies received. The fact that their expectations were not met led to a sense of frustration and disappointment. Similarly, the way in which the subsidies were distributed and the lack of transparency in the distribution process led to feelings of unfairness among the vast majority of respondents. The results show that frustrations can build up in the early days of the intervention. Conclusion The PBF implementation in Mali left health workers frustrated. The short overall implementation period did not allow actors to adjust their initial expectations and motivational responses, neither positive nor negative. This underlines how short-term interventions might not just lack impact, but instil negative sentiments likely to carry on into the future
Early earthquake detection capabilities of different types of future-generation gravity gradiometers
No full textSince gravity changes propagate at the speed of light, gravity perturbations induced by earthquake deformation have the potential to enable faster alerts than the current earthquake early warning systems based on seismic waves. Additionally, for large earthquakes (M-w > 8), gravity signals may allow for a more reliable magnitude estimation than seismic-based methods. Prompt elastogravity signals induced by earthquakes of magnitude larger than 7.9 have been previously detected with seismic arrays and superconducting gravimeters. For smaller earthquakes, down to M-w similar or equal to 7, it has been proposed that detection should be based on measurements of the gradient of the gravitational field, in order to mitigate seismic vibration noise and to avoid the cancelling effect of the ground motions induced by gravity signals. Here we simulate the five independent components of the gravity gradient signals induced by earthquakes of different focal mechanisms. We study their spatial amplitude distribution to determine what kind of detectors is preferred (which components of the gravity gradient are more informative), how detectors should be arranged and how earthquake source parameters can be estimated. The results show that early earthquake detections, within 10 s of the rupture onset, using only the horizontal gravity strain components are achievable up to about 140 km distance from the epicentre. Depending on the earthquake focal mechanism and on the detector location, additional measurement of the vertical gravity strain components can enhance the detectable range by 10-20 km. These results are essential for the design of gravity-based earthquake early warning systems
Site-specific effects of organic amendments on parameters of tropical agricultural soil and yield: a field experiment in three countries in Southeast Asia
No full textOrganic amendments may improve the quality of acidic tropical agricultural soils with low organic carbon contents under conventional management (mineral fertilization and irrigation) in Southeast Asia. We investigated the effect of biochar, compost and their combination on maize growth and yield, soil physical, biological and chemical properties at harvesting time at four sites in three countries: Thailand, Vietnam and Laos. Treatments consisted of 10 t.ha(-1) cow manure compost and 7 t.ha(-1) of Bamboo biochar and their combination. Maize biomass production and cop yields were recorded for two seasons. Elemental content, pH and nutrient availability of soils were analyzed after the first growing season. We also characterized macrofauna abundance and water infiltration. Few changes were noted for maize biomass production and maize cop yield. Soil chemical parameters showed contrasting, site-specific results. Compost and biochar amendments increased soil organic carbon, pH, total K and N, P and K availability especially for sandy soils in Thailand. The combination of both amendments could reduce nutrient availability as compared to compost only treatments. Physical and biological parameters showed no treatment response. We conclude that the addition of compost, biochar and their mixture to tropical soils have site-specific short-term effects on chemical soil parameters. Their short-term effect on plants is thus mainly related to nutrient input. The site-dependent results despite similar crops, fertilization and irrigation practices suggest that inherent soil parameters and optimization of organic amendment application to specific pedoclimatic conditions need future attention
A hotspot of Toxoplasma gondii Africa 1 lineage in Benin : how new genotypes from West Africa contribute to understand the parasite genetic diversity worldwide
No full textAuthor summary The parasite Toxoplasma gondii is a worldwide-distributed pathogen, able to infect all warm-blooded animals. There are important differences in the clinical expression of the infection in direct relation with the parasite genetic profile. In some regions, the geographical structuration of its genetic diversity points towards a crucial role of human activities in some lineages introduction or sorting. Benin is a West African country with a history of extensive transcontinental exchanges. Our genetic study of Toxoplasma in Benin shows a surprisingly homogeneous and autochthonous diversity, which contrasts with previous studies from other West and Central African countries. In Benin, the absence of European Toxoplasma lineages may be explained by the extreme rarity of the house mouse (Mus musculus), a host species that was previously described as highly susceptible to the mouse-virulent African strains. Might Benin be the origin region for the Africa 1 lineage, our results suggest that Guinean Gulf coasts may be a starting point of this lineage towards South America, especially Brazil, during the slave trade. As a whole, the present study provides further insights into the recent evolutionary history of Toxoplasma gondii and its consequences on human and animal health. Through international trades, Europe, Africa and South America share a long history of exchanges, potentially of pathogens. We used the worldwide parasite Toxoplasma gondii to test the hypothesis of a historical influence on pathogen genetic diversity in Benin, a West African country with a longstanding sea trade history. In Africa, T. gondii spatial structure is still non-uniformly studied and very few articles have reported strain genetic diversity in fauna and clinical forms of human toxoplasmosis so far, even in African diaspora. Sera from 758 domestic animals (mainly poultry) in two coastal areas (Cotonou and Ouidah) and two inland areas (Parakou and Natitingou) were tested for T. gondii antibodies using a Modified Agglutination Test (MAT). The hearts and brains of 69 seropositive animals were collected for parasite isolation in a mouse bioassay. Forty-five strains were obtained and 39 genotypes could be described via 15-microsatellite genotyping, with a predominance of the autochthonous African lineage Africa 1 (36/39). The remaining genotypes were Africa 4 variant TUB2 (1/39) and two identical isolates (clone) of Type III (2/39). No difference in terms of genotype distribution between inland and coastal sampling sites was found. In particular, contrarily to what has been described in Senegal, no type II (mostly present in Europe) was isolated in poultry from coastal cities. This result seems to refute a possible role of European maritime trade in Benin despite it was one of the most important hubs during the slave trade period. However, the presence of the Africa 1 genotype in Brazil, predominant in Benin, and genetic analyses suggest that the triangular trade was a route for the intercontinental dissemination of genetic strains from Africa to South America. This supports the possibility of contamination in humans and animals with potentially imported virulent strains
The geography of metapopulation synchrony in dendritic river networks
No full textDendritic habitats, such as river ecosystems, promote the persistence of species by favouring spatial asynchronous dynamics among branches. Yet, our understanding of how network topology influences metapopulation synchrony in these ecosystems remains limited. Here, we introduce the concept of fluvial synchrogram to formulate and test expectations regarding the geography of metapopulation synchrony across watersheds. By combining theoretical simulations and an extensive fish population time-series dataset across Europe, we provide evidence that fish metapopulations can be buffered against synchronous dynamics as a direct consequence of network connectivity and branching complexity. Synchrony was higher between populations connected by direct water flow and decayed faster with distance over the Euclidean than the watercourse dimension. Likewise, synchrony decayed faster with distance in headwater than mainstem populations of the same basin. As network topology and flow directionality generate fundamental spatial patterns of synchrony in fish metapopulations, empirical synchrograms can aid knowledge advancement and inform conservation strategies in complex habitats