Profil de David Point
Email : david.pointSPAMFILTER@ird.fr
Téléphone / phone: +33 5 61 33 26 29
Bureau / office : F003
Institution : IRD
Statut / status: Chercheur
2004 PhD, Université de Pau et des Pays de l’Adour/ Environmental Chemistry, Pau, France
Name of PhD Supervisor O.F.X Donard
2000 Master, Université de Pau et des Pays de l’Adour/ Environmental Chemistry, Pau, France
2008-2016 IRD, Chargé de Recherche (CR1), Laboratoire Geosciences Environnement Toulouse (GET), University of Toulouse, France
2005 – 2008 Postdoc, National Institute of Science and Technology (NIST), Analytical Chemistry Division, Charleson, South Carolina, USA
SUPERVISION OF PhD STUDENTS AND POSTDOCTORAL FELLOWS
2014 – 2016 Anabelle Baya, IRD Postdoc (France) “MeHg δ13C Compound Specific Isotopic Analysis, analytical developments and applications”
2014 - 2016 Andrea Pontes, CNPQ Postdoc (Brazil) MeHg sources and origin in estuaries from the Pernambuco Region, Recife, Brazil
2013 - 2016 Patrick Houssard, PhD Student, New Caledonia Government, MeHg levels and source origin in Tuna from the Southwestern Pacific Region
2010 – 2015 Lucia Alanoca PhD Student at IRD “Hg cycle in the extreme lake ecosystems of the Bolivian Altiplano region
2010 – 2014 Jeremy Masbou PhD Student at IRD “Investigation of the metabolic, ecological and biogeochemical processes controlling Hg stable isotopic fractionation in Arctic marine mammals”
Mercury (Hg) is a global contaminant of major concern to human and ecosystem health. Mercury has a tendency to be naturally converted into the organometallic compounds toxin namely methylmercury (CH3Hg, MeHg) which is characterized by elevated neurotoxicity, persistence, and natural biomagnification properties in food webs ( Choy et al., 2009; Jernel et al., 1971). Marine fish consumption represents the most important exposure pathways for humans to neurotoxic MeHg ( Sunderland, 2007).
The origin of MeHg in marine fish is heavily debated ( Driscoll et al., 2012; Mason et al., 2012). Methylmercury has long been thought to originate from marine sediments ( Fitzgerald and Lamborg, 2004). Recent mass balance considerations suggest that the stock of marine MeHg cannot be solely supplied by shelf/margin or deep sediment MeHg sources ( Mason et al., 2012). MeHg depth profiles in the open ocean consistently tend to show MeHg accumulation in the subthermocline oxygen minimum zone (OMZ) ( Cossa et al., 2009; Fitzgerald, 2007; Sunderland et al., 2009). Sulfate-reducing bacteria ( Benoit et al., 2001; Compeau and Bartha, 1985; Ranchou-Peyruse et al., 2009), and other anaerobic microorganisms hosting specific methylation genes have been identified as possible contributors ( Gilmour et al., 2013; Parks et al., 2013). Surprisingly, this genetic sequence is rarely found in pelagic marine water column metagenomes ( Podar et al., 2015). This hints at possible other unknown biotic pathways, possibly involving phytoplankton ( Heimburger et al., 2010), and/or the role of complementary abiotic processes ( Weber, 1993). These unknown mechanisms might also be at play in oxic surface waters where Hg methylation has also been observed recently ( Lehnherr et al., 2011; Monperrus et al., 2007; Whalin et al., 2007) Despite 25 years of important progress in Hg research, the origin of marine MeHg is still unexplained, and remains a question with acute bearing on the health and socioeconomics costs estimated to billions € per year ( Trasande et al., 2005).
Part of our lack of knowledge is related to the state of Hg analytical chemistry. Current Hg analytical tools offer only limited spatiotemporal, molecular, isotopic resolution and throughput to capture, and quantify complex in situ biogeochemical processes. The answer to these limitations requires the exploration of new biogeochemical concepts and dedicated tools capable of exploring the MeHg cycle at unprecedented resolutions, and at the frontiers of chemistry, ecology, physical oceanography and analytical disciplines.
Developing the tools that allow measuring for the very first time the variations in the stable isotopic signature of Mercury (Hg) and Carbon (C) atoms embedded in different Hg compounds are my most recent achievements, and provide new opportunities to trace and understand MeHgOrigin ( Masbou et al., 2015; Masbou et al., 2013). These recent analytical developments pave the way towards the new field of organometallic stable isotope research, and opens up new possibilities to explore trace metals–organic matter interactions, with MeHg being the most promising candidate to start with.
Dr. Paul R Becker, Arctic Hg isotope biomonitoring, National Institute of Standards and Technology, USA
Dr Dario Acha, Hg cycle in high altitude lakes of the Bolivian Alitplano, UMSA, La Paz, Bolivia
Ms Michelle Graco, Hg cycle in the Peruvian OMZ, IMARPE, Lima, Peru
Dr. Lars-Eric Heimbürger, Marine Hg biogeochemistry, CNRS-MIO, France
Dr David Amouroux, Hg speciation and biogeochemistry, CNRS-IPREM, France
Dr Mathilde Monperrus, Hg speciation and biogeochemistry, CNRS-IPREM, France
Dr Anne Lorrain, Marine top predators ecology, IRD-LEMAR, Brest, France
Dr Vincent Raimbault, Microfluidics, CNRS-LAAS, Toulouse France
2015 Head of the GC-C-IRMS Division, Observatoire Midi-Pyrenees, France
2009 Founder of the GC-ICP-MS Equipment at the Mass Spectrometry Division, Observatoire Midi-Pyrenees, France
Alanoca, L., Amouroux, D., Monperrus, M., Tessier, E., Goni, M., Guyoneaud, R., Acha, D., Gassie, C., Audry, S., Garcia, M.E., Quintanilla, J.,Point, D.,2015. Diurnal variability and biogeochemical reactivity of mercury species in an extreme high-altitude lake ecosystem of the Bolivian Altiplano.Environmental Science and Pollution Research, 1-15.(IF 2.8, - citations)
Masbou, J.,Point, D., Guillou, G., Sonke, J.E., Lebreton, B., Richard, P.,2015. Carbon Stable Isotope Analysis of Methylmercury Toxin in Biological Materials by Gas Chromatography Isotope Ratio Mass Spectrometry.Analytical Chemistry87, 11732-11738.(IF 5.6, -citations)
Masbou, J., Point, D., Sonke, J.E., Frappart, F., Perrot, V., Amouroux, D., Richard, P., Becker, P.R.,2015. Hg Stable Isotope Time Trend in Ringed Seals Registers Decreasing Sea Ice Cover in the Alaskan Arctic.Environmental Science & Technology49, 8977-8985. (IF 5.3, -citations)
Heimbürger, L.-E., Sonke, J.E., Cossa, D.,Point, D.,Lagane, C., Laffont, L., Galfond, B.T., Nicolaus, M., Rabe, B., van der Loeff, M.R.,2015. Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean. Scientific Reports 5, 10318(IF 5.6, 5 citations)
Pouilly, M.,Point, D., Sondag, F., Henry, M., Santos, R.V.,2014. Geographical Origin of Amazonian Freshwater Fishes Fingerprinted by 87Sr/86Sr Ratios on Fish Otoliths and Scales.Environmental Science & Technology48, 8980-8987.(IF 5.3, 6 citations)
Masbou, J.,Point, D., Sonke, J.E.,2013. Application of a selective extraction method for methylmercury compound specific stable isotope analysis (MeHg-CSIA) in biological materials.Journal of Analytical Atomic Spectrometry28, 1620-1628.(IF 3.5, 13 citations)
Point, D., Sonke, J.E., Day, R.D., Roseneau, D.G., Hobson, K.A., Vander Pol, S.S., Moors, A.J., Pugh, R.S., Donard, O.F.X., Becker, P.R.,2011♮. Methylmercury photodegradation influenced by sea-ice cover in Arctic marine ecosystems.Nature Geoscience4, 188-194.(IF 11.8, 68 citations).
Goix, S.,Point, D.,Oliva, P., Polve, M., Duprey, J.L., Mazurek, H., Guislain, L., Huayta, C., Barbieri, F.L., Gardon, J.,2011. Influence of source distribution and geochemical composition of aerosols on children exposure in the large polymetallic mining region of the Bolivian Altiplano.Science of The Total Environment412–413, 170-184.(IF 4.1, 17 citations)
Point, D., Monperrus, M., Tessier, E., Amouroux, D., Chauvaud, L., Thouzeau, G., Jean, F., Amice, E., Grall, J., Leynaert, A., Clavier, J., Donard, O.F.X.,2007♮. Biological control of trace metal and organometal benthic fluxes in a eutrophic lagoon (Thau Lagoon, Mediterranean Sea, France).Estuarine Coastal and Shelf Science72, 457-471.(IF 2.0, 67 citations)