Interactions between chemistry and microbial population dynamics in snow: what are the consequences for mercury cycling in the Arctic?

• Main Author: Larose, Catherine
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Adaptation et pathogénie des micro-organismes Grenoble (LAPM), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université Joseph-Fourier - Grenoble I, Christophe Ferrari, Dominique Schneider
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2010
• Subjects: mercure; bactéries polaires; Arctique; métagénomique; neige; chimie; [SDU]Sciences of the Universe [physics]; Arctic; Arctique*; Ny Ålesund; Ny-Ålesund; Svalbard
• Online Access: https://theses.hal.science/tel-00452028; https://theses.hal.science/tel-00452028/document; https://theses.hal.science/tel-00452028/file/thesis.pdf

The main objective of this thesis is to characterize the interactions between seasonal snow chemistry and microbial community structure in an arctic snowpack. In order to do so, the biotic and abiotic compartments of the snowpack must be first characterized. From snow and meltwater samples obtained during a two-month field study held in Ny-Ålesund (Svalbard, Norway, 78°56'N, 11°52'E) in 2007, we showed that the sequence diversity in arctic snow and meltwater libraries is elevated. We also examined the fate of Hg in an arctic snowpack, from its deposition during atmospheric mercury depletion events up until its transfer during snow melt and reported an increase in methylmercury concentrations in the snowpack during late spring. The results from this campaign highlighted the need to improve our knowledge on mercury speciation and led to the development of a mer-lux biosensor to measure the bioavailable fraction of mercury. We deployed the biosensor during a second two-month field campaign in Ny-Ålesund in spring 2008 and the results obtained led to a novel model for mercury methylation in oxic environments. In parallel, we followed changes in microbial community structure in snow and meltwater samples using a 16S microarray. We modeled the interactions between snow chemistry and community structure and found a significant co-structure. We also explored functional community changes due to mercury contamination of snowpacks. Based on our results, methylmercury affects community structure and function at concentrations much lower than previously reported. Our results provide a basis for further studies on the interaction between chemistry and microbial community structure. L'objectif principal de cette thèse est de caractériser les interactions entre la composition chimique et la structure des communautés microbiennes dans un manteau neigeux arctique. Une attention toute particulière est portée au mercure, dont le cycle biogéochimique complexe est encore mal connu. Avant toute chose, les fractions biotiques et ...