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Projet MERTOX : PhD position in Mercury Biogeochemistry in Oxygen Minimum Zones

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Mediterranean Institute of Oceanography (MIO) & Geosciences Environment Toulouse (GET)

Fully-funded PhD Position

he Marseille Marine Mercury Laboratory at the Mediterranean Institute of Oceanography (MIO) and the Mercury Isotopes Group at Geosciences Environment Toulouse (GET) are seeking to recruit a scientist for a fully-funded 3-year PhD position to work at at the frontiers of trace metal oceanography, analytical sciences, stable isotopes biogeochemistry, and ecology. This PhD position is funded via the ANR (Agence Nationale de la Recherche) MERTOX project (2017-21) “Unraveling the origin of methylMERcury TOXin in marine ecosystems” (PI David Point, GET).
Mercury is global pollutant and a neurotoxin with a serious health risk for humans, mainly via the consumption of marine fish. Anthropogenic Hg emissions have largely altered natural Hg levels. Bacteria feeding on sinking marine organic matter in the mesopelagic zone are thought to produce the toxic methylmercury species (MMHg) that bioaccumulates along the marine trophic chain to harmful levels. This main goal of this PhD project to study mercury biogeochemistry in oxygen minimum zones (OMZ), and to develop new stable isotope tools for a better understanding of the marine biogeochemical Hg cycle. The MERTOX case study will be conducted in the Peruvian Humboldt OMZ, which is very productive, exhibits extreme redox gradients, and is known to enhance in situ MeHg production. This region accounts for 15% of worldwide commercial fisheries while representing 0.1% of the global ocean surface. Peruvian anchovy fisheries contribute to more than half of world landings used for fishmeal production and then fuels a critical portion of world aquaculture production. The MERTOX field campaigns are planned for April and August 2019, along several cruise transects covering the strong inshore/offshore organic matter gradients and steep shallow redox fronts. The cruises will be performed on board of IMARPE’s R/V Olaya and will be supported by bi-annual transect surveys. Complementary physical (salinity, temperature,..), chemical (macronutrients, Fe, Mn, CH4, HS-), microbiological (diversity, HgcAB methylating genes) and ecological (phytoplankton speciation, Chl-a,…) data will be gathered. The main field tasks of the PhD student is to sample and measure the full suite of Hg species (MMHg, DMHg, Hg°, Hg2+, pHg, pMMHg), perform isotopically labelled incubation experiments, and contribute to the isotopic measurement of both the Carbon (δ13C), and Hg (δ202Δ199Hg) atoms of the MeHg (CH3Hg) molecule, along the trophic chain (seawater, phyto-, zooplankton,…).
The PhD student will be based at the MIO (Lars-Eric Heimbürger, Sophie Bonnet, Marseille, France) and will closely collaborate with the GET laboratory (David Point, Jeroen Sonke, Toulouse, France) for stable isotopic analysis, the LMD/IPSL (Laurent Bopp, Paris, France) for biogeochemical modeling, the LEMAR (Anne Lorrain, Brest, France) for ecological/trophic web investigations, and the IMARPE (Michelle Graco, Lima, Peru) for the specifics of the biogeochemistry of the Humboldt OMZ and field work .
MIO is a joint research unit of AMU, CNRS, Institute of Research for Development (IRD) and University of Toulon (UTLN). MIO’s objectives are to better understand the ocean system and its response to global change, with expertise in chemical, physical and (micro-)biological oceanography. MIO has infrastructures at 5 sites : AMU Luminy, UTLN, the IFREMER marine base in La Seyne-sur-Mer and the IRD Centre in Nouméa, New Caledonia. MIO is structured in 5 disciplinary teams, with 6 cross-thematic research areas and 6 analytical platforms, a marine monitoring service supported by its own research vessel Antedon II, which will be used for method development.
The Marseille Marine Mercury Laboratory at MIO is fully equipped for basic and advanced Hg analysis : cold vapor atomic fluorescence spectrometry (3x CV-AFS Brook Rand), an automated total Hg analyzer purge & trap CV-AFS (Brooks Rand MERX-T), an automated methylHg analyzer purge & trap GC-CV-AFS (Brooks Rand MERX-M, an automated combustion atomic absorption spectrometry AAS (Leco AMA 254), and a brand-new gas chromatography (Thermo Trace 1300) coupled to the HR-ICPMS (Thermo Element XR) for Hg speciation by isotope dilution. One fulltime dedicated technician manages daily operations and maintenance of these facilities.
The PhD student will be trained in ultra-trace clean techniques, participate in several field campaigns, help with the validation and interpretation of all acquired data, help with the implementation of the data into numerical models and contribute to the publication of the findings. The PhD student will be lead author of at least 2 publications.
The PhD student will potentially be involved in another Pacific Ocean cruise in November-December 2019, as part of the submitted ANR proposal TONGA (PIs Sophie Bonnet, MIO, Cecile Guieu, LOV, Villefranche sur Mer) as part of the international GEOTRACES program. A qualification comparable to a Master’s degree or Diploma in chemistry, environmental chemistry, (chemical) oceanography or related field is required. Experience in analytical chemistry and / or marine biogeochemistry is desirable. An essential requirement for selection for the PhD projects is a top-quality MSc or equivalent 4–5 year degree. We also expect good English language skills, and that the candidate is willing and able to participate in sea-going expeditions. Most importantly, we are looking for a creative and curious mind. Applications including a letter of motivation, CV and contact details of 2 referees should be sent to as a single pdf file, using as email subject "PhD OMZ Hg".
PhD supervisors Dr. Lars-Eric Heimbürger, Dr. Sophie Bonnet (HDR) Mediterranean Institute of Oceanography, Aix Marseille University, CNRS/INSU, Université de Toulon, IRD, Marseille, France
Dr. David Point Geosciences Environment Toulouse, Observatoire Midi-Pyrénées, CNRS/IRD/Université Paul-Sabatier, Toulouse, France