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Site du laboratoire d'Océanologie et de Géosciences UMR 8187 LOG:
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Armynot Du Châtelet Eric
Due to their geographical position, under the influence of the Southern Hemisphere westerly winds and under the influence of the Antarctic Circumpolar Current, Kerguelen archipelago, in the sub-Antarctic, is a perfect natural experimentation site for the record of recent environmental change.
The testate amoebae have been studied in Antarctica and the subantarctica islands through about a hundred studies. In the islands of Kerguelen, they are described in four rather extensive studies in 1904, 1908, 1912 and 1981. These studies reveal the presence of cosmopolitan species with a few rare of a more restricted distribution. The proportions of the different species and the composition of the communities depend on the hygrometric degree, the pH, the temperature and the biogeographical factors. On the other hand, the skeletons of these amoebae are preserved and are therefore witnesses of past environments. Thus, by characterizing the environmental constraints of testate amoeba communities within modern environment and by defining indicator species of all identifiable sub-environments, it is possible to reconstruct recent paleoenvironments and model the important changes operating in recent decades.
Thus, the long-term project consists of setting up a tool for characterizing the environmental changes recorded in the subantarctic islands based on observation of preserved testate amoeba. The objectives of the EnviKer program are:
1) To propose a denser and more exhaustive cartography of the amoeba communities in the different Kerguelen island landscape units following distincts gradients: a East-West precipitation gradient, a gradient of quality and quantity of the organic/inorganic substrate and a gradient of hydrolysis as revealed by clay minerals. The project will focus particularly on mineralogy and molecular geochemistry to precisely define the characteristics of the environment. The diversity of testate amoebae will be estimated by both genetic techniques and more classical observations. For each environmental unit, we will define the indicator species. The different interactions are summarized in the figure within the general objectives paragraph.2) To propose a reconstruction of paleo-environments based on the statistical analysis of testate amoebae indicator species, extracted from sediment cores. In lacustrine environments the studied cores are those recovered by the projects PROTEKER and PALAS managed by the EDYTEM Laboratory under the direction of Fabien Arnaud. Since these cores benefit from numerous analyzes from the point of view of organic, molecular and inorganic chemistry, we will benefit from an efficient database for the comparison of the paleoenvironments that we will reconstitute with the testate amoebae. We will complete the sampling with short cores in the peat bogs, soils and plants in pillows in which we will deploy all possible analyzes.