Journal of Next-Generation Research 5.0
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Coral responses to a repeat bleaching event in Mayotte in 2010
No full textInternational audienceBackground. High sea surface temperatures resulted in widespread coral bleaching and mortality in Mayotte Island (northern Mozambique channel, Indian Ocean: 12.1 • S, 45.1 • E) in April-June 2010. Methods. Twenty three representative coral genera were sampled quantitatively for size class distributions during the peak of the bleaching event to measure its impact. Results. Fifty two percent of coral area was impacted, comprising 19.3% pale, 10.7% bleached, 4.8% partially dead and 17.5% recently dead. Acropora, the dominant genus, was the second most susceptible to bleaching (22%, pale and bleached) and mortality (32%, partially dead and dead), only exceeded by Pocillopora (32% and 47%, respectively). The majority of genera showed intermediate responses, and the least response was shown by Acanthastrea and Leptastrea (6% pale and bleached). A linear increase in bleaching susceptibility was found from small colonies (80 cm, 33% unaffected), across all genera surveyed. Maximum mortality in 2010 was estimated at 32% of coral area or biomass, compared to half that (16%), by colony abundance. Discussion. Mayotte reefs have displayed a high level of resilience to bleaching events in 1983, 1998 and the 2010 event reported here, and experienced a further bleaching event in 2016. However, prospects for continued resilience are uncertain as multiple threats are increasing: the rate of warming experienced (0.1 • C per decade) is some two to three times less than projected warming in coming decades, the interval between severe bleaching events has declined from 16 to 6 years, and evidence of chronic mortality from local human impacts is increasing. The study produced four recommendations for reducing bias when monitoring and assessing coral bleaching: coral colony size should be measured, unaffected colonies should be included in counts, quadrats or belt transects should be used and weighting coefficients in the calculation of indices should be used with caution
Avian cholera outbreaks threaten seabird species on Amsterdam Island
No full textInternational audienceInfectious diseases may be particularly critical for the conservation of endangered species. A striking example is the recurrent outbreaks that have been occurring in seabirds on Amsterdam Island for the past 30 years, threatening populations of three Endangered sea-bird species and of the endemic, Critically Endangered Amsterdam albatross Diomedea amsterdamensis. The bacteria Pasteurella multocida (avian cholera causative agent), and to a lesser extent Erysipelothrix rhusiopathiae (erysipelas causative agent), were both sus-pected to be responsible for these epidemics. Despite this critical situation, demographic trends were not available for these threatened populations, and the occurrence and charac-terization of potential causative agents of epizootics remain poorly known. The aims of the current study were to (i) provide an update of population trends for four threatened seabird species monitored on Amsterdam Island, (ii) assess the occurrence of P. multocida, and E. rhusiopathiae in live birds from five species, (iii) search for other infectious agents in these samples and, (iv) isolate and genotype the causative agent(s) of epizooties from dead birds. Our study shows that the demographic situation has worsened substantially in three seabird species during the past decade, with extremely low reproductive success and declining populations for Indian yellow-nosed albatrosses Thalassarche carteri, sootyalbatrosses Phoebetria fusca, and northern rockhopper penguins Eudyptes moseleyi. Pasteurella multocida or E. rhusiopathiae were detected by PCR in live birds of all five investi-gated species, while results were negative for eight additional infectious agents. A single strain of P. multocida was repeatedly cultured from dead birds, while no E. rhusiopathiae could be isolated. These results highlight the significance of P. multocida in this particular eco-epidemiological system as the main agent responsible for epizootics. The study stresses the urgent need to implement mitigation measures to alter the course of avian cholera outbreaks threatening the persistence of seabird populations on Amsterdam Island
Towards elimination of lymphatic filariasis in southeastern Madagascar: Successes and challenges for interrupting transmission
No full textInternational audienceIntroduction: A global strategy of mass drug administration (MDA) has greatly reduced the burden of lym- phatic filariasis (LF) in endemic countries. In Madagascar, the National Programme to elimi- nate LF has scaled-up annual MDA of albendazole and diethylcarbamazine across the country in the last decade, but its impact on LF transmission has never been reported. The objective of this study was to evaluate progress towards LF elimination in southeastern Madagascar.Methods: Three different surveys were carried out in parallel in four health districts of the Vatovavy Fitovinany region in 2016: i) a school-based transmission assessment survey (TAS) in the districts of Manakara Atsimo, Mananjary, and Vohipeno (following a successful pre-TAS in 2013); ii) a district-representative community prevalence survey in Ifanadiana district; and iii) a community prevalence survey in sentinel and spot-check sites of these four districts. LF infection was assessed using the Alere Filariasis Test Strips, which detect circulating filarial antigens (CFA) of adult worms. A brief knowledge, attitudes and practices questionnaire was included in the community surveys.Principal findings: None of the 1,825 children sampled in the TAS, and only one in 1,306 children from sentinel and spot-check sites, tested positive to CFA. However, CFA prevalence rate in individuals older than 15 years was still high in two of these three districts, at 3.5 and 9.7% in Mananjary and Vohipeno, respectively. Overall CFA prevalence in sentinel and spot-check sites of these three districts was 2.80% (N = 2,707), but only two individuals had detectable levels of microfilaraemia (0.06%). Prevalence rate estimates for Ifanadiana were substantially higher in the district-representative survey (15.8%; N = 545) than in sentinel and spot-check sites (0.8%; N = 618). Only 51.2% of individuals surveyed in these four districts reported taking MDA in the last year, and 42.2% reported knowing about LF.Conclusion: Although TAS results suggest that MDA can be stopped in three districts of southeastern Madagascar, the adult population still presents high CFA prevalence levels. This discor- dance raises important questions about the TAS procedures and the interpretation of their results
Les territoires agriurbains en Île-de-France : entre paysage ordinaire, paysage agricole et paysage alimentaire ?
No full textInternational audienceLes territoires agri-urbains (TAU), derniers nés des territoires de projet en région Île-de-France (1999), consacrent la prise en compte des espaces agricoles et de leurs paysages dans la construction de l'urbain. Cet article interroge les figures territoriales et paysagères promues par les acteurs parties prenantes, le paysage étant entendu dans ses deux dimensions matérielle et immatérielle. Construits au départ autour d'un projet d'agriurbanisme-qui a légitimé leur création-les TAU ont ainsi largement promu deux formes paysagères emblématiques que sont la lisière urbaine et le sentier d'interprétation agricole. La montée des préoccupations alimentaires dans les TAU modifie quelque peu ce projet désormais centré sur le paysage alimentaire. Les auteures questionnent les nouveaux motifs, notamment nourriciers, en voie d'apparition et leur éventuelle contribution à faire advenir au rang de paysage des territoires de franges ordinaires, longtemps (et encore aujourd'hui) perçus comme « sans qualités ». S'inscrivant à la croisée de la géographie et de la sociologie, le parti pris est d'essayer de mettre au jour certains des présupposés au fondement des actions et des discours à l'oeuvre sur ces territoires et présentés comme allant de soi. Les programmes agri-urbains, derniers nés (1999) des territoires de projet en région Île-de-France (RIF), consacrent la prise en compte des espaces agricoles et de leurs paysages dans la construction de l'urbain. Dispositifs éprouvés de manière informelle dès les années soixante-dix 1 , ils reçoivent une reconnaissance officielle en juillet 2001 quand le Comité interministériel d'aménagement et de développement du territoire décide d'un accompagnement financier pour sept d'entre eux, avant d'être institutionnalisés dans la loi rurale de février 2005. Devenus partie intégrante des systèmes métropolitains, les espaces « ouverts » agricoles sont désormais pensés comme nécessaires « à leur bonne santé » et comme ayant acquis une valeur pour les habitants (Poulot, 2013). Ils s'imposent au moins dans les débats et les discours comme un enjeu majeur de l'aménagement des territoires organisés par la ville et son développement, et plus encore de la notion de ville durable qui fonde aujourd'hui les pratiques de ceux qui construisent la ville. Devenus Territoires Agriurbains depuis les années 2010 (TAU), et soutenus financièrement depuis 2007 par la RIF, ces espaces, qui ourlent le front de l'avancée urbaine en ce début de XXI° siècle, épousent le contour de territoires sur lesquels des acteurs (agriculteurs, collectivités territoriales, habitants et associations) expriment une telle vision et s'emploient à incarner un développement et un aménagement durables à travers des dynamiques territoriales spécifiques visant à faire converger ville et agriculture dans un même projet de territoire. Les TAU ne correspondent nullement à des délimitations institutionnelles (communautés de communes et/ou d'agglomération) mais réunissent dans une même enveloppe spatiale des 1 Dans le cadre du SDRIF, en 1967 les ZNE, puis en 1983 la définition de la ceinture verte, à une échelle plus locale, au début des années 1980 la conception et la mise en oeuvre de lotissements agricoles à Périgny-sur-Yerres ou en regard de la ville nouvelle de Cergy, en 1976 le premier programme du Plateau de Saclay en 1976, pour ne citer que ces exemples, sont portés par une volonté forte de conserver des espaces agricoles et en cela préfigurent les programmes agri-urbains qui sont l'objet de cet article
Underwater ambient noise spatial and temporal coherence at basin scale
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Agglomerative hierarchical clustering of airborne electromagnetic data for multi-scale geological studies
No full textInternational audienceAirborne electromagnetic methods provide detailed subsurface resistivity imaging over extensive areas. The inversion of electromagnetic measurements can be conducted with a quasi-3D spatially constrained inversion scheme, which yields numerous vertical resistivity soundings. So as to conduct the interpretation, these soundings can be interpolated to obtain a 3D resistivity model. However, large surveys result in huge resistivity models, which can be challenging to interpret with 2D or even 3D views. We propose a complementary approach for the interpretation of airborne electromagnetic surveys based on agglomerative hierarchical clustering. With this statistical classification method, the numerous 1D vertical resistivity profiles distributed over the area of interest can be summarized in a 2D horizontal map. Inverted electromagnetic soundings are aggregated into clusters according to their vertical resistivity profiles. These clusters define areas with a consistent vertical resistivity response, i.e. to the first order, areas with comparable vertical (hydro)-geological structure. The clustering method is illustrated with an extensive airborne electromagnetic survey conducted over Reunion Island. After a description of the method, we show that the proposed classification facilitates the confrontation between airborne geophysical results and geological or hydrogeological observations/data. We highlight that hierarchical clustering is of high interest for multi-scale studies, from regional to local scales. This approach introduces a new way to use geophysical surveys to map areas with specific geological/hydrogeological behaviors
Evidence of a water δ<sup>18</sup>O negative shift driven by intensive deep CO<sub>2</sub> upflow at Shiwaga gas field (Rungwe, Tanzania)
No full textInternational audienceLocated on the flank of Ngozi volcanoes (Tanzania), the Shiwaga gas field is a spot of intense CO2(g) emanations. Physico-chemical measurements on different types of waters (rivers, puddles, and springs) as water and gas sampling were discontinuously performed over 10 years for equilibrated partial CO2 pressure calculations and stable isotopic analyses. The most striking result shows that meteoric H2O and deep originated CO2(g) exchanges are responsible for a negative 18O-shift of the studied waters in relation with waters electrical conductivity, pH, and pCO2eq changes. In spring waters, a maximum shift of − 11.2‰ in δ18O was observed and pCO2eq values up to 1196 mbar were computed. Although this trend has already been reported around the world, such extended shift is rarely measured and requires an important amount of CO2(g) with a CO2(g)/H2O ratio up more than 0.5 mol/mol. This approach is useful to better understand the hydro-geochemical processes involved in such environments. Moreover, this study evidences that an inventory as a monitoring of these gas fields are needed for the management of natural hazards and local resources
A newly designed analytical line to examine fluid inclusion isotopic compositions in a variety of carbonate samples
No full textInternational audienceδ18O and δD of fluid inclusions in carbonates provide insights into temperatures and fluid chemical compositions prevailing during the carbonate precipitation, however, various analytical restrictions limit a wider application of this proxy. This paper presents a new fluid inclusions isotopic analytical line coupled to an online cavity ring‐down spectrometer that increased the analytical productivity up to 10 carbonate samples per working day. This efficiency allowed for the first time to assess the reliability a large set of water samples with size ranging from 0.1 to 1 µL. Good reproducibility (±0.5‰ for δ18O and ± 2‰ δD; 1σ) is obtained for water quantity superior or equal to 0.3 μL and no evidence of memory effect is found. The line is further tested using two types of natural carbonates: (1) modern speleothems samples from caves for which δ18O and δD values of drip water were measured and (2) diagenetic carbonates for which the δ18O of the parent water were independently back‐calculated from carbonate clumped isotope Δ47 measurements. Speleothem fluid inclusion values despite falling close to the Global Meteoritic Water Line are not always representative of the isotopic composition of the parent drip water. Results on diagenetic cements show that the δ18Owater values measured in fluid inclusions agree, within 1%, with the δ18Owater independently derived from Δ47 measurements. Overall, this study confirms the reliability and accuracy of the developed analytical line for carbonate fluid inclusion analyses with a good reproducibility obtained for water quantity above 0.3 μL
Geology and Physical Properties Investigations by the InSight Lander
No full textInternational audienceAlthough not the prime focus of the InSight mission, the near-surface geology and physical properties investigations provide critical information for both placing the instruments (seismometer and heat flow probe with mole) on the surface and for understanding the nature of the shallow subsurface and its effect on recorded seismic waves. Two color cameras on the lander will obtain multiple stereo images of the surface and its interaction with the spacecraft. Images will be used to identify the geologic materials and features present, quantify their areal coverage, help determine the basic geologic evolution of the area, and provide ground truth for orbital remote sensing data. A radiometer will measure the hourly temperature of the surface in two spots, which will determine the thermal inertia of the surface materials present and their particle size and/or cohesion. Continuous measurements of wind speed and direction offer a unique opportunity to correlate dust devils and high winds with eolian changes imaged at the surface and to determine the threshold friction wind stress for grain motion on Mars. During the first two weeks after landing, these investigations will support the selection of instrument placement locations that are relatively smooth, flat, free of small rocks and load bearing. Soil mechanics parameters and elastic properties of near surface materials will be determined from mole penetration and thermal conductivity measurements from the surface to 3–5 m depth, the measurement of seismic waves during mole hammering, passive monitoring of seismic waves, and experiments with the arm and scoop of the lander (indentations, scraping and trenching). These investigations will determine and test the presence and mechanical properties of the expected 3–17 m thick fragmented regolith (and underlying fractured material) built up by impact and eolian processes on top of Hesperian lava flows and determine its seismic properties for the seismic investigation of Mars’ interior
Late Cretaceous–Palaeogene topography of the Chinese Tian Shan: New insights from geomorphology and sedimentology
No full textInternational audienceThe Cenozoic growth of the intra-continental Tian Shan Range initiated during the late Eocene–Oligocene, and led to a tectonic reactivation of the complex Palaeozoic and Mesozoic lithospheric structure. Due to the very low erosion rates linked to the semi-arid climate that characterised the Tian Shan region during most of the Cenozoic, the topography of the range is not at equilibrium with deformation. Fragments of pre-orogenic low relief surfaces are preserved among the Late Cenozoic Alpine-type topography. Using field observations and satellite image mapping of those fragments, as well as sedimentology and biostratigraphic analysis, we show that the pre-Oligocene topography of the Tian Shan region was indeed complex, combining hundreds of metres to one-and-a-half kilometre-high reliefs with a multi-phased Mesozoic planation surface incised by Late Mesozoic paleo-valleys. The occurrence of several metres-thick Late Cretaceous–Palaeogene calcareous paleosols, in the basins surrounding the range further implies a semi-arid climate, very low subsidence rates and no uplift at that time. Late Cretaceous and early Miocene fossil records in the northern Tian Shan suggest a possible connection, even if episodic, between the drainage system of the south Junggar foreland basin and the proto-Paratethys Sea to the west. A renewed late Eocene–early Oligocene sedimentation probably marks the onset of the Tian Shan uplift. We argue that in addition to the growth of the Pamir and Western Kunlun ranges, this incipient uplift was one of the driving mechanisms for the final retreat of the proto-Paratethys Sea from the Tarim Basin. This regression apparently did not change the climate in the studied area because semi-arid conditions seem to prevail at least since the Late Cretaceous. Finally, the Tian Shan uplift remained very limited up to the Miocene as revealed by the occurrence of Burdigalian lake deposits preserved in the paleo-valleys inside the present day range. In contrast, post-early Miocene deformation of the northern Tian Shan has produced 4000 to 5000 m of differential vertical movement between the uplifted range and the subsiding proximal foreland basin