Éditeur(s) : HAL CCSD Society of Exploration Geophysicists
Résumé : Read More: http://library.seg.org/doi/10.1190/geo2015-0411.1
International audience
Understanding the role of the unsaturated zone in aquifer recharge and contaminant attenuation processes is a major challenge for the protection and management of karstic water resources. We present the potential of the magnetic resonance soundings (MRS) geophysical method for characterizing the vadose zone of karst aquifers composed of epikarst and infiltration layers. To investigate the hydraulic functioning of the Durzon karst system located on the Larzac plateau (southern France), we used the MRS method at 16 sites. The MRS results have been compared with available geologic information and to core water content measurements. The remarkable spatial variability of the MRS response observed in the study area makes it possible to determine ranges of water storage properties in relation to the lithology of the investigated carbonate formations (dolomite, marly, and siliceous limestone). All soundings found either constant or increasing MRS water content with depth, which demonstrates that the infiltration zone might be the major water storage entity for permanent water storage, with important consequences for recharge quality and quantity. These results show the feasibility and potential of the MRS method for the characterization of the karst unsaturated zone and for understanding the vertical distribution of water content, which impacts the overall functioning of karst systems.Read More: http://library.seg.org/doi/10.1190/geo2015-0411.1
ISSN: 0016-8033

hal-01412654
https://hal.archives-ouvertes.fr/hal-01412654
https://hal.archives-ouvertes.fr/hal-01412654/document
https://hal.archives-ouvertes.fr/hal-01412654/file/mazilli2016.pdf
DOI : 10.1190/GEO2015-0411.1

Éditeur(s) : Blackwell science
Résumé : An experiment was conducted in six earthen ponds with 20 shrimps m(-2) Litopenaeus stylirostris (Stimpson) during the warm season in New Caledonia to study the dynamics of wastes in relation with water exchange rate (WER). The nitrogen budget was established, taking into account the different forms of nitrogen in the water, sediment, feed and shrimp. Data from a wide range of treatments applied in unreplicated ponds were treated using regression analysis to establish the relationship between WER and partial nitrogen budget, sediment characteristics and shrimp performance. To compare effluent quality between treatments during the season, data were analysed using the non-parametric sign test. The water outflow was characterized by a decrease in the concentrations of N-mineral forms (TAN, NO2--NO3-), an increase in the concentration of organic soluble and sestonic organic forms (expressed in terms of particulate nitrogen, particulate organic carbon, chlorophyll a) compared with the water inflow. Increasing WER increased the amount of exported wastes and mainly in the organic forms and TAN can be considered as negligible. The nitrogen budget showed that 19-46% of nitrogen input (feed+water) was exported into the coastal environment. The results showed that the quality of the sediment decreased as WER decreased. The potential negative impact of the developing industry in New Caledonia on the costal environment could be partially reduced in a first step by decreasing WER. However, if applied in the farms, this practice should be linked to a close survey of the evolution of sediment quality.
Aquaculture Research (1355-557X) (Blackwell science), 2006-06 , Vol. 37 , N. 9 , P. 938-948

Droits : 2006 Blackwell Publishing, Inc.
http://archimer.ifremer.fr/doc/2006/publication-1811.pdf
DOI:10.1111/j.1365-2109.2006.01515.x
http://archimer.ifremer.fr/doc/00000/1811/

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: Heterogeneous patterns of malaria transmission are thought to be driven by factors including host genetics, distance to mosquito breeding sites, housing construction, and socio-behavioural characteristics. Evaluation of local transmission epidemiology to characterize malaria risk is essential for planning malaria control and elimination programmes. The use of geographical information systems (GIS) techniques has been a major asset to this approach. To assess time and space distribution of malaria disease in Bandiagara, Mali, within a transmission season, data were used from an ongoing malaria incidence study that enrolled 300 participants aged under six years old ". Methods: Children's households were georeferenced using a handheld global position system. Clinical malaria was defined as a positive blood slide for Plasmodium falciparum asexual stages associated with at least one of the following signs: headache, body aches, fever, chills and weakness. Daily rainfall was measured at the local weather station. Landscape features of Bandiagara were obtained from satellite images and field survey. QGIS™ software was used to map malaria cases, affected and non-affected children, and the number of malaria episodes per child in each block of Bandiagara. Clusters of high or low risk were identified under SaTScan W software according to a Bernoulli model. Results: From June 2009 to May 2010, 296 clinical malaria cases were recorded. Though clearly temporally related to the rains, Plasmodium falciparum occurrence persisted late in the dry season. Two " hot spots " of malaria transmission also found, notably along the Yamé River, characterized by higher than expected numbers of malaria cases, and high numbers of clinical episodes per child. Conversely, the northeastern sector of the town had fewer cases despite its proximity to a large body of standing water which was mosquito habitat. Conclusion: These results confirm the existence of a marked spatial heterogeneity of malaria transmission in Bandiagara, providing support for implementation of targeted interventions. Background Malaria is one of the leading causes of morbidity and mortality in the world, with an estimated 3.3 billion people at risk of malaria [1]. The incidence of malaria worldwide is estimated to be 216 million cases per year, with 81% of these cases occurring in sub-Saharan Africa. Malaria kills approximately 655,000 people per year; 91% of deaths occur in sub-Saharan Africa [1], mostly in children under five years of age. In Mali, West Africa, malaria represents 36.5% of consultation motives in health center, it is a leading cause of morbidity and mortality children of less than five years of age and the first reason of anaemia in pregnant women [2]. Malaria transmission is seasonal. Malaria parasite transmission and clinical disease are characterized by important microgeographic variation, often between adjacent villages, households or families [3-8]. This local heterogeneity is driven by a variety of factors including human genetics [9,10], distance to potential breeding sites [11,12], housing construction
ISSN: 1475-2875

hal-01307672
https://hal-amu.archives-ouvertes.fr/hal-01307672
https://hal-amu.archives-ouvertes.fr/hal-01307672/document
https://hal-amu.archives-ouvertes.fr/hal-01307672/file/1475-2875-12-82.pdf
DOI : 10.1186/1476-072X-2-5

Éditeur(s) : HAL CCSD Springer-Verlag
Résumé : International audience
With hull-mounted multibeam echosounder data, wereport for the first time along the active Ecuadorian margin,acoustic signatures of water column fluid emissions and seep-relatedstructures on the seafloor. In total 17 flare-shaped acousticanomalies were detected from the upper slope (1250 m) to the shelfbreak (140 m). Nearly half of the flare-shaped acoustic anomaliesrise 200–500 m above the seafloor. The base of the flares is generallyassociated with high-reflectivity backscatter patchescontrasting with the neighboring seafloor. We interpret these flaresas caused by fluid escape in the water column, most likely gases.High-resolution seismic profiles show that most flares occur closeto the surface expression of active faults, deformed areas, slopeinstabilities or diapiric structures. In two areas tectonic deformationdisrupts a Bottom Simulating Reflector (BSR), suggesting thatburied frozen gas hydrates are destabilized, thus supplying free gasemissions and related flares. This discovery is important as it opensthe way to determine the nature and origin of the emitted fluids andtheir potential link with the hydrocarbon system of the forearcbasins along the Ecuadorian margin.
ISSN: 0033-4533

insu-01267238
https://hal-insu.archives-ouvertes.fr/insu-01267238
DOI : 10.1007/s00024-015-1230-7

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Growth hormone (GH) may stimulate water loss during exercise by activating sweating. This study investigated GH secretion and water loss during sequential cycling and running, taking postural changes into account. The two exercise segments had similar durations and were performed at the same relative intensity to determine their respective contributions to water loss and the plasma volume variation noted in such trials. Eight elite triathletes first performed an incremental cycle test to assess maximal oxygen consumption. Then, the triathletes performed one of two trials in randomized order: constant submaximal cycling followed by treadmill running (C 1 –R 2) or an inversed succession of running followed by cycling (R 1 –C 2). Each segment of both trials was performed for 20 minutes at ,75% of maximal oxygen consumption. The second trial, reversing the segment order of the first trial, took place two weeks later. During cycling, the triathletes used their own bicycles equipped with a profiled handlebar. Blood sampling (for GH concentrations, plasma viscosity and plasma volume variation) was conducted at rest and after each segment while water loss was estimated from the post-and pre-measures. GH increases were significantly lower in R 2 than C 2 (72.2650.1 vs. 164.06157 ng.ml 21 .min 21 , respectively; P,0.05). Water loss was significantly lower after C 1 –R 2 than R 1 –C 2 (11056163 and 12356153 ml, respectively; P,0.05). Plasma volume variation was significantly negative in C 1 and R 1 (26.1562.0 and 23.1665.0%, respectively; P,0.05), not significant in C 2 , and significantly positive for seven subjects in R 2 (4.0563.1%). We concluded that the lower GH increases in R 2 may have contributed to the smaller reduction in plasma volume by reducing sweating. Moreover, this lower GH response could be explained by the postural change during the transition from cycling to running. We recommend to pay particular attention to their hydration status during R 1 which could limit a potential dehydration during C 2 .
ISSN: 1932-6203

hal-01158212
https://hal.univ-antilles.fr/hal-01158212
DOI : 10.1371/journal.pone.0096145

Éditeur(s) : HAL CCSD
Résumé : We present high-resolution bulk sedimentary δ 15N data from the southern edge of the present-day oxygen minimum zone of the eastern South Pacific. The record is interpreted as representing changes in water column nitrogen removal during the last 70,000 years. We found significant fluctuations in the isotopic signal that suggest major reorganizations of the oxygen minimum zone at millennial timescales. These fluctuations were not related to other millennial-scale changes like the Northern Hemisphere's Dansgaard-Oeschger climate swings or local changes in primary productivity, so appear to be dictated by the Southern Hemisphere's climate rhythm. This is preliminarily corroborated by an overall agreement between our δ 15N data and the sedimentary proxy of ice sheet dynamics in Patagonia, which is in turn correlated with surface water properties at the midlatitude subduction region of the eastern South Pacific intermediate waters. Finally, potential implications on late Quaternary changes in atmospheric CO2 concentrations are discussed.
Paleoceanography / PALEOECEANOGRAPHY

hal-00407260
https://hal.archives-ouvertes.fr/hal-00407260
DOI : 10.1029/2006PA001308

Éditeur(s) : HAL CCSD Copernicus Publications
Résumé : This workshop report describes plans for scientific drilling in the Samail ophiolite in Oman in the context of past, current, and future research. Long-standing plans to study formation and evolution of the Samail crust and upper mantle, involving igneous and metamorphic processes at an oceanic spreading center, have been augmented by recent interest in ongoing, low temperature processes. These include alteration and weathering, and the associated sub-surface biosphere supported by chemical potential energy due to disequilibrium between mantle peridotite and water near the surface. This interest is motivated in part by the possibility of geological carbon capture and storage via engineered, accelerated mineral carbonation in Oman.
ISSN: 1816-8957

hal-00858243
https://hal.archives-ouvertes.fr/hal-00858243
DOI : 10.2204/iodp.sd.15.10.2013

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé :  
Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 × 1015 to 1.6 × 1015 grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.
ISSN: 0036-8075

hal-01032111
https://hal.archives-ouvertes.fr/hal-01032111
DOI : 10.1126/science.1164033

Éditeur(s) : HAL CCSD Royal Society of Chemistry
Résumé : International audience
Low-level water measurements of geological materials are fundamental in understanding the volatile inventories of the Earth from the mantle to crustal reservoirs. Here we describe the development of microanalytical techniques using the new SHRIMP SI ion microprobe to measure the abundances of OH− (as a proxy for water) in volcanic glass and nominally anhydrous minerals (NAMs). Samples were first analysed at the Carnegie Institute of Washington (CIW) on their Cameca ims-6f with calibrations based on previous FTIR and manometry analyses. SHRIMP SI is a large geometry ion microprobe and is currently mainly used for O and S isotope analyses. The analytical protocol used here incorporates multiple collection of 16O− and 16O1H− allowing rapid measurements. A single calibration line incorporating all glasses and NAMs for the SHRIMP SI allows calibration of 16O1H−/16O− to H2O over a wide range in concentration (50 to 15 000 ppm H2O). This calibration line has around a 10% uncertainty, which appears to be limited only by sample heterogeneity. The current background for SHRIMP analysis is between 20–40 ppm but this is expected to improve with improved pumping on the source chamber. A current limitation to water analysis of NAM samples, by any technique, is having a range of standard materials to enable OH− calibration to absolute H2O concentrations. Data are presented for 7 NAM samples (2 olivines, 2 orthopyroxenes and 3 clinopyroxenes) that appear to be promising as potential standards for international laboratory H2O measurements. These NAM samples have been analysed and characterised here by SHRIMP SI, FTIR, EMP and the Cameca ims-6f ion microprobe at CIW. Four of these samples have previously been measured by manometry to determine absolute H2O concentrations.
ISSN: 0267-9477

hal-01243514
https://hal.archives-ouvertes.fr/hal-01243514
DOI : 10.1039/c5ja00047e

Éditeur(s) : Elsevier Science Bv
Résumé : A Lagrangian approach based on a physical-biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the NorthWest African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates.
Science Of The Total Environment (0048-9697) (Elsevier Science Bv), 2015-02 , Vol. 505 , P. 870-888

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00252/36310/35200.pdf
DOI:10.1016/j.scitotenv.2014.10.045
http://archimer.ifremer.fr/doc/00252/36310/

Éditeur(s) : HAL CCSD INRA Editions
Résumé : International audience
The objective of this study was to examine the water relations and hydraulic architecture and vulnerability to cavitation in Virola surinamensis and V. michelii and to compare to similar measurements in Eperua falcata. In several previous reports Virola was seen to have a rather narrow range of xylem pressure potentials (Ψx) near zero in the course of a wet-season day while having water fluxes quite close to Eperua. We tested the hypothesis that the narrow range of Ψx might be consistent with very high hydraulic conductivities of stems, roots and shoots and high vulnerability to cavitation in Virola compared to Eperua. When this hypothesis proved false we concluded that the previous determinations of Ψx might be wrong in Virola due to latex. We re-examined the determination of Ψx in Virola by the pressure chamber technique and compared results to determination of Ψleaf by the thermocouple psychrometer technique and found that the likely range of Ψx are more negative than previously reported. Problems concerning the determination of Ψx in species with latex are discussed.
ISSN: 2268-4565

hal-01077475
https://hal.archives-ouvertes.fr/hal-01077475
https://hal.archives-ouvertes.fr/hal-01077475/document
https://hal.archives-ouvertes.fr/hal-01077475/file/JPH-1-e0002.pdf

Éditeur(s) : Mdpi Ag
Résumé : Marine pelagic diazotrophic cyanobacteria of the genus Trichodesmium (Oscillatoriales) are widespread throughout the tropics and subtropics, and are particularly common in the waters of New Caledonia. Blooms of Trichodesmium are suspected to be a potential source of toxins in the ciguatera food chain and were previously reported to contain several types of paralyzing toxins. The toxicity of water-soluble extracts of Trichodesmium spp. were analyzed by mouse bioassay and Neuroblastoma assay and their toxic compounds characterized using liquid chromatography coupled with tandem mass spectrometry techniques. Here, we report the first identification of palytoxin and one of its derivatives, 42-hydroxy-palytoxin, in field samples of Trichodesmium collected in the New Caledonian lagoon. The possible role played by Trichodesmium blooms in the development of clupeotoxism, this human intoxication following the ingestion of plankton-eating fish and classically associated with Ostreopsis blooms, is also discussed.
Marine Drugs (1660-3397) (Mdpi Ag), 2011-04 , Vol. 9 , N. 4 , P. 543-560

Droits : 2011 MDPI Publishing
http://archimer.ifremer.fr/doc/00040/15143/12576.pdf
DOI:10.3390/md9040543
http://archimer.ifremer.fr/doc/00040/15143/

Éditeur(s) : Elsevier
Résumé : Sediment cores were collected from April to August 2004 on tidal mudflats of the macrotidal Marennes-Oléron Bay (SW France), famous for the cultivation of Pacific oysters (Crassostrea gigas). The response of living (stained) benthic foraminifera to short-term biogeochemical disturbances in the sediment and overlying water, which may be involved in oyster summer mortality, was monitored. Short-term hypoxia occurred in early June, in conjunction with a sudden rise in temperature. In mid-June, the ammonia content of sediment porewater increased, leading to potentially maximal flux towards overlying waters. Foraminiferal assemblages, particularly in the topmost layer, were altered. Ammonia tepida was the most tolerant to temperature increase and hypoxic conditions whereas Brizalina variabilis and Haynesina germanica were sensitive to organic degradation and hypoxia. Cribroelphidium gunteri was the most opportunistic during recolonisation. Benthic foraminifera showed that short-term biochemical changes in the sediment are toxic and may be involved in the summer mortality of Pacific oysters.
Marine Environmental Research (0141-1136) (Elsevier), 2007-09 , Vol. 64 , N. 3 , P. 358-383

Droits : 2007 Elsevier Ltd All rights reserved
http://archimer.ifremer.fr/doc/2007/publication-2586.pdf
DOI:10.1016/j.marenvres.2007.02.007
http://archimer.ifremer.fr/doc/00000/2586/

Éditeur(s) : HAL CCSD American Geophysical Union
Résumé : The acquisition of reliable data sets representative of hydrological regimes and their variations is a critical concern for water resource assessment. For the subsurface, traditional approaches based on probe measurements, core analysis, and well data can be laborious, expensive, and highly intrusive, while only yielding sparse data sets. For this study, an innovative field survey, merging relative microgravimetry, magnetic resonance soundings, and hydrological measurements, was conducted to evaluate both surface and subsurface water storage variations in a semiarid Sahelian area. The instrumental setup was implemented in the lower part of a typical hillslope feeding to a temporary pond. Weekly measurements were carried out using relative spring gravimeters during 3 months of the rainy season in 2009 over a 350 × 500 m2 network of 12 microgravity stations. Gravity variations of small to medium amplitude (≤220 nm s−2) were measured with accuracies better than 50 nm s−2, revealing significant variations of the water storage at small time (from 1 week up to 3 months) and space (from a couple of meters up to a few hundred meters) scales. Consistent spatial organization of the water storage variations were detected, suggesting high infiltration at the outlet of a small gully. The comparison with hydrological measurements and magnetic resonance soundings involved that most of the microgravity variations came from the heterogeneity in the vadose zone. The results highlight the potential of time lapse microgravity surveys for detecting intraseasonal water storage variations and providing rich space-time data sets for process investigation or hydrological model calibration/evaluation
ISSN: 0043-1397

hal-00857351
https://hal.archives-ouvertes.fr/hal-00857351
DOI : 10.1002/wrcr.20235

Éditeur(s) : HAL CCSD
Résumé : 1 p.
For groundwater issues (potential leakages in waste repository, aquifer management ...), the development of modeling techniques is far ahead of the actual knowledge of aquifers. This raises two fundamental issues: 1) which and how much data are necessary to make predictions accurate enough for aquifer management issues; 2) which models remain relevant to describe the heterogeneity and complexity of geological systems. The French observatory H+ was created in 2002 with the twofold motivation of acquiring a large database for validating models of heterogeneous aquifers, and of surveying groundwater quality evolution in the context of environmental changes. H+ is a network of 4 sites (Ploemeur, Brittany, France; HES Poitiers, France; Cadarache, France; Campos, Mallorca, Spain) with different geological, climatic, and economic contexts. All of them are characterized by a highly heterogeneous structure (fractured crystalline basement for Ploemeur, karstified and fractured limestone for Poitiers, Cadarache and Mallorca), which is far to be taken into account by basic models. Ploemeur is exploited as a tap-water plant for a medium-size coastal city (15,000 inhabitants) for 20 years. Each site is developed for long term investigation and monitoring. They involves a dense network of boreholes, detailed geological and geophysical surveys, periodic campaigns and/or permanent measurements of groundwater flow, water chemistry, geophysical signals (including ground motions), climatic parameter, etc. Several large-scale flow experiments are scheduled per year to investigate the aquifer structure with combined geophysical, hydrogeological, and geochemical instruments. All this information is recorded in a database that has been developed to improve the sustainability and quality of data, and to be used as a collaborative tool for both site researchers and modelers. This project lasts now for 5 years. It is a short time to collect the amount of information necessary to apprehend the complexity of aquifers; but it is already enough to obtain a few important scientific results about the very nature of the flow heterogeneity, the origin and residence time of water elements, the kinetic of geochemical processes, etc. We have also developed new methods to investigate aquifers (in-situ flow measurements, flow experiment designs, groundwater dating, versatile in-situ probes, etc.). This experience aiming at building up long term knowledge appears extremely useful to address critical issues related to groundwater aquifers: the structure and occurrence of productive aquifer in crystalline basement, the assessment of aquifer protection area in the context of highly heterogeneous flow, the biochemical reactivity processes, the long term evolution of both water quantity and quality in the context of significant environmental changes, for instance.
AGU, Fall Meeting 2008
San Francisco, United States

insu-00375980
https://hal-insu.archives-ouvertes.fr/insu-00375980

Résumé : En 2013, Le Groupe d'experts Intergouvernemental sur l'Evolution du Climat (GIEC) publie son cinquième rapport concernant les changements climatiques. Il y est souligné que le réchauffement climatique est sans équivoque, et que de nouvelles émissions de gaz à effet de serre impliqueront une poursuite du réchauffement et des changements affectant toutes les composantes du système climatique. En région tropicale, une hausse de la température, ainsi qu'une intensification des événements de sécheresse et de pluviométrie extrêmes sont à prévoir. C'est dans ce contexte que s'inscrit ce travail, dont le but est d'étudier la réponse de la forêt tropicale à ces changements climatiques prédits en Guyane Française. Pour ce faire, j'ai utilisé les données du dispositif de suivi forestier de Paracou pour construire un modèle de dynamique individuel basé sur les traits fonctionnels des arbres. Un modèle de mortalité a d'abord été réalisé puis couplé à un modèle de croissance.Le modèle couplé ainsi construit permet de modéliser la croissance et la mortalité des arbres sur un pas de temps de 2 ans tout en tenant compte de leur ontogénie et de leurs traits fonctionnels. Ce modèle a d'abord été appliqué aux essences commerciales de Guyane Française en forêt naturelle et exploitée en y ajoutant un indice de stress hydrique. Ceci permet de montrer que le stress hydrique fait baisser la croissance et augmenter la mortalité, tandis que l'exploitation a l'effet inverse. Malgré le signal commun, différentes réponses sont observées selon les espèces. Le modèle a ensuite été appliqué à la communauté en forêt naturelle pour identifier les drivers climatiques et les processus impactés. Il ressort que la croissance est impactée par le stress hydrique et la température, et que la mortalité est impactée par le stress hydrique et la pluviométrie totale.Ces résultats ont enfin permis de construire un modèle complet de dynamique forestière climat dépendant, et de simuler l'évolution d'une communauté pendant un siècle selon différents scénarios correspondant aux prédictions du GIEC. Les simulations mettent en évidence une très forte diminution de la croissance, ainsi qu'une plus faible diminution de la mortalité. Ceci entraine une diminution notable de la surface terrière, du diamètre quadratique et de la biomasse fraiche. Une analyse de sensibilité montre que ces changements sont principalement dus à l'augmentation sévère des températures prédites pour le siècle à venir. Des pistes de réflexion sur les enjeux de modélisation et les échelles considérées sont proposées en discussion de ce travail.
In 2013 the intergovernmental panel on climate change (ipcc) publishes its fifth report. This report underlines that an increase of temperature and a strengthening of drought and extreme rainfall are expected in tropical regions. This work was made in this context of climate changes, and aimed to study the response of the rainforest to predicted climate changes. To do this, i used the data from the study site of Paracou French Guiana to build an individual based dynamics model based on the functional traits of trees. This model was first applied to species with a commercial interest in French Guiana, in natural and logged forest and adding a water stress index as predictor. Water stress decreases growth and increases mortality, while logging had the opposite effect. The model was then applied to the community in natural forest for identifying potential climate drivers and impacted processes. Growth is impacted by the water stress and temperature and mortality is imp acted by the water stress and the total rainfall. These results allowed us to build a climate dependent model of forest dynamics and to run simulations of the evolution of a community under different scenarios for the next century. Simulations showed a decrease of growth and a small decrease of mortality. This resulted in a substantial decrease of basal area, squared diameter and fresh biomass.

http://www.theses.fr/2014AGUY0802/document

Éditeur(s) : HAL CCSD
Résumé : Satellite and in situ chlorophyll concentration data collected as part of VALidation HYperspectral of a BIOgeochemical model (ValHyBio), a PNTS-sponsored project dedicated to satellite ocean-colour imaging of the Southwest Pacific, are analyzed to describe chlorophyll variability in the Coral Sea, a vast oligotrophic region characterized by a deep chlorophyll maximum and blue waters of high transparency. Average chlorophyll concentrations estimated from MODIS-Aqua are very low (<0.2 mg m-3) except in the vicinity of main islands and coral reefs, where enrichment may occur due to upwelling or internal waves that bring nutrients to the euphotic zone from the deep part of the water column. During the summer season, blooms of cyanobacteria (Trichodesmium) develop in the surface waters and may form large slicks. The nitrogen fixed by these slicks is a potential source of new nitrogen later assimilated by picoplankton and the marine food chain. Coastal areas exhibit higher chlorophyll concentrations because of nutrient input from the land, as observed in 2008 around New Caledonia. In lagoon areas, the sea colour is influenced by turbidity and bathymetry, and the MODIS OC3 algorithm is inadequate, with a systematic overestimation of chlorophyll concentration in the New Caledonia lagoon. Improved bio-optical algorithms are needed for those turbid and shallow waters, to allow not only a better description of chlorophyll variability, but also evaluation of chlorophyll simulations by recently developed biogeochemical models.
of the 12th International Coral Reef Symposium, 18E
CAIRNS, Australia

hal-00746470
https://hal.archives-ouvertes.fr/hal-00746470
https://hal.archives-ouvertes.fr/hal-00746470/document

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Despite the dramatic reductions in children's blood lead levels (BLLs), there is considerable evidence that low-level lead exposure is associated with intellectual deficits and behavioral problems, without apparent threshold. There are limited data, however, about the contribution of residential sources of lead to contemporary children's blood lead levels. The aim of this study is to calculate the contributions of residential sources of lead to assess the potential impact of setting new standards for lead levels in residential dust, soil and water. We enrolled 484 French children aged from 6 months to 6 years, and collected data on social, housing and individual characteristics. Lead concentrations in blood and environmental samples (water, soils, and dusts) were measured using inductively coupled plasma mass spectrometry. Data were analyzed using a multivariate generalized additive model accounting for the sampling design and the sampling weights. We found that exceedingly low concentrations of lead in dust, soil and water were significant predictors of children's BLLs, after adjustment for potential confounding variables. Lead-contaminated floor dust was the main source of lead in blood. BLLs (GM: 14μg/L) increased by 65%, 13%, 25%, and 5% when lead content in floor dust, loose soil, hard soil and water increased from their 25th percentile to their 95th percentile, respectively. We also observed that the steepest increase in BLLs occurred at the lowest levels of lead-contaminated floor dust, which indicates that lead contamination should be kept as low as possible. Impact of different possible standards on children's BLLs was also tabulated and indicated that unless standards are set low, they will only benefit a small proportion of children who have the highest exposures.
ISSN: 1438-4639

inserm-00821999
http://www.hal.inserm.fr/inserm-00821999
DOI : 10.1016/j.ijheh.2013.02.007
PUBMED : 23528234

Éditeur(s) : HAL CCSD Elsevier
Résumé : In this study, we assessed past and present influence of ancient mining activity on metal(loid) enrichment in sediments of a former mining watershed (Gardon River, SE France), that is now industrialized and urbanized. A sedimentary archive and current sediments were characterized combining geochemical analyses, zinc isotopic analyses and sequential extractions. The archive was used to establish local geochemical background and recorded (i) increasing enrichment factors (EFs) for Pb, Zn, Cd, Tl, Hg, As and Sb throughout the industrial era, (ii) a contamination peak in 1976 attributed to a tailings dam failure, and (iii) current levels in 2002 and 2011 similar to those of 1969, except for Sb and Hg, reflecting a persisting contamination pattern. Inter-element relationships and spatial distribution of EF values of current sediments throughout the watershed suggested that both ancient and current contamination had a common origin for Pb, Zn, Cd, Tl and As related to the exploitation of Pb/Zn mineralization while old Sb mines and coal extraction area were the main sources for Sb and Hg respectively. This prevailing mining origin was reflected for Zn by a relatively uniform isotopic composition at δ66Zn = 0.23 ± 0.03‰, although slight decrease from 0.23‰ to 0.18‰ was recorded from upstream to downstream sites along the river course in relation with the contribution of the lighter δ66Zn signature (~ 0.08‰) of acid mine drainage impacted tributaries. Results from sequential extractions revealed that the potential mobility of the studied metal(loid)s varied in the order Sb < Tl ≈ As < Zn < Pb < Cd, with an increase of the mobile pool for Cd, Pb, Zn and to a lesser extent for As and Tl associated to increased enrichment. Altogether, these results tend to demonstrate that ancient mining activity still contributes to metal enrichment in the sediments of the Gardon River and that some of these metals may be mobilized toward the water compartment.
ISSN: 0048-9697

hal-01054163
https://hal.archives-ouvertes.fr/hal-01054163
DOI : 10.1016/j.scitotenv.2014.02.078

Éditeur(s) : HAL CCSD Nature Publishing Group
Résumé : International audience
Lateralization, i.e. the preferential use of one side of the body, may convey fitness benefits for organisms within rapidly-changing environments, by optimizing separate and parallel processing of different information between the two brain hemispheres. In coral reef-fishes, the movement of larvae from planktonic to reef environments (recruitment) represents a major life-history transition. This transition requires larvae to rapidly identify and respond to sensory cues to select a suitable habitat that facilitates survival and growth. This ‘recruitment’ is critical for population persistence and resilience. In aquarium experiments, larval Acanthurus triostegus preferentially used their right-eye to investigate a variety of visual stimuli. Despite this, when held in in situ cages with predators, those larvae that previously favored their left-eye exhibited higher survival. These results support the “brain’s right-hemisphere” theory, which predicts that the right-eye (i.e. left-hemisphere) is used to categorize stimuli while the left-eye (i.e. right-hemisphere) is used to inspect novel items and initiate rapid behavioral-responses. While these experiments confirm that being highly lateralized is ecologically advantageous, exposure to chlorpyrifos, a pesticide often inadvertently added to coral-reef waters, impaired visual-lateralization. This suggests that chemical pollutants could impair the brain function of larval fishes during a critical life-history transition, potentially impacting recruitment success.
ISSN: 2045-2322

Droits : http://creativecommons.org/licenses/by/
hal-01585550
http://hal.upmc.fr/hal-01585550
http://hal.upmc.fr/hal-01585550/document
http://hal.upmc.fr/hal-01585550/file/s41598-017-09381-0.pdf
DOI : 10.1038/s41598-017-09381-0