Dublet G.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry |
Dublet G.,Aix - Marseille University |
Dublet G.,Ecole Polytechnique Federale de Lausanne |
Juillot F.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry |
And 11 more authors.
Geochimica et Cosmochimica Acta | Year: 2017
Because they can host significant amounts of Co, the Mn-oxides are commonly considered as the major Co-bearing mineral species in lateritic environments. However, little is known about the process leading to the formation and/or the weathering of these Co-rich Mn-oxides. This lack of knowledge is mainly due to the fact that Co concentrations are too low in primary silicates for classical speciation analysis. In this study, we investigated both Co and Mn speciation in a 64 m thick lateritic regolith developed upon peridotites in New Caledonia, by combining High Energy Resolution Fluorescence Detection X-ray absorption Near Edge Structure (HERFD-XANES) spectroscopy at the Co K-edge with classical XANES spectroscopy at the Mn K-edge, bulk chemistry (ICP) and mineralogy (XRD). The results obtained provide new insights into the evolution of Co and Mn speciation as a function of the weathering stages. Co and Mn primarily occur as Co(II) and Mn(II,III) in olivine and serpentine in the bedrock. During the first weathering stage, these forms of Co and Mn are progressively oxidized toward Co(III) and Mn(III,IV), which occur mainly as Co(III)-bearing Mn(III/IV)-oxides in the transition between the saprolite and the laterite. In the uppermost lateritic horizons, long-time weathering resulted in a strong leaching of Co and Mn, and the remaining of these elements occurs as Co(II) and Mn(III) substituting for Fe(III) in goethite. This latter scavenging process emphasizes the importance of Fe-oxides for the long-term stabilization of Co and Mn in such deeply weathered laterites. © 2017 Elsevier Ltd
Zarzoso-Lacoste D.,CNRS Mediterranean Institute for Biodiversity and Ecology Marine and Continental |
Zarzoso-Lacoste D.,British Petroleum |
Zarzoso-Lacoste D.,French National Center for Scientific Research |
Bonnaud E.,CNRS Ecology, Systematic and Evolution Laboratory |
And 11 more authors.
Biological Conservation | Year: 2016
On islands, invasive predators, particularly feral cats and rats, are key drivers of bird population decline and extinction. Diet studies can be used to assess predator impacts on prey populations. Here we first evaluated the resolution of morphological identification (Class to Species) of bird remains in cat and rat diet studies. We also analysed the effect of predator size/type (cat vs rat) and sample type (faecal vs stomach contents) on the taxonomic level of bird identification. We found that difficulty in identifying bird remains significantly increased with taxonomic resolution (from Class to Species) for both predators. Bird identification was more accurate in cat than in rat diets and no sample-type effect was detected in cat diets. Second, we developed a set of molecular resources (DNA sequence database and bird-specific primer pairs) to detect and identify bird DNA. We tested and validated primer pairs' taxonomic coverage and specificity using in silico and in vitro analyses. The performances of morphological and molecular methods were then compared in a case study of cat and rat diet samples collected on Niau Atoll (French Polynesia). Our results highlight the efficiency of the molecular method in both detection and high-resolution identification of birds in predator diet samples. As robust qualitative and quantitative diet analyses are required to accurately assess predator impacts on prey populations, we recommend combining morphological and molecular methods to maximise bird detection, identification and quantification, especially when rare or threatened birds are at stake. © 2015 Elsevier B.V..
Rochelle-Newall E.J.,Center Noumea |
Mari X.,Center Noumea |
Mari X.,Ecole Normale Superieure de Paris |
Pringault O.,Center Noumea |
Pringault O.,Montpellier University
Journal of Plankton Research | Year: 2010
Although many studies have addressed the role of bacteria in the degradation of organic matter, few have examined how bacteria alter the physicochemical properties of dissolved and colloidal organic matter in coastal systems. Here, we investigate how the sticking properties of transparent exopolymeric particles (TEP) varied with DOM age in batch cultures. We show that in two contrasted sites, despite different initial TEP sticking properties and bulk concentrations, after 48 h, the sticking properties were similar and increased (i.e. TEP became stickier) with increasing DOM age. We propose that TEP occurring after 48 h of incubation are mainly of heterotrophic origin, which is in contrast to the previously identified TEP of autotrophic origin. These results highlight the potential importance of bacterial DOM production, particularly in the aphotic zone, and further underline the potential of bacterial heterotrophs to produce biologically refractory dissolved organic matter that is physically reactive (i.e. sticky). © The Author 2010.
Merlot S.,French National Center for Scientific Research |
Merlot S.,Center Noumea |
Hannibal L.,Center Noumea |
Martins S.,French National Center for Scientific Research |
And 4 more authors.
Journal of Experimental Botany | Year: 2014
Nickel is an economically important metal and phytotechnologies are being developed to limit the impact of nickel mining on the environment. More than 300 plant species are known to hyperaccumulate nickel. However, our knowledge of the mechanisms involved in nickel accumulation in plants is very limited because it has not yet been possible to study these hyperaccumulators at the genomic level. Here, we used next-generation sequencing technologies to sequence the transcriptome of the nickel hyperaccumulator Psychotria gabriellae of the Rubiaceae family, and used yeast and Arabidopsis as heterologous systems to study the activity of identified metal transporters. We characterized the activity of three metal transporters from the NRAMP and IREG/FPN families. In particular, we showed that PgIREG1 is able to confer nickel tolerance when expressed in yeast and in transgenic plants, where it localizes in the tonoplast. In addition, PgIREG1 shows higher expression in P. gabriellae than in the related non-accumulator species Psychotria semperflorens. Our results designate PgIREG1 as a candidate gene for nickel tolerance and hyperaccumulation in P. gabriellae. These results also show how next-generation sequencing technologies can be used to access the transcriptome of non-model nickel hyperaccumulators to identify the underlying molecular mechanisms. © The Author 2014.