Thesis defended the 8th november 2013
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The chemosynthetic bivalves Bathymodiolus thermophilus and B. Azoricus are engineer species living in contrasted hydrothermal vents located on the East-Pacific and Mid-Atlantic Ridges. The response of these model species to the variability of their environment was investigated by using various aspects of marine ecogeochemistry. For this, the combined use of in situ chemical shell labeling with high-resolution sclerochronological analysis allowed to establish a temporal framework in the rhythmicity of B. Thermophilus and B. Azoricus growth rate. The presence of tidal cycles in their shell increment width formation compared to the in situ measurements of abiotic parameters reveal that both species are sensitive to changes in physico-chemical conditions, with higher growth rate when environment is unstable. This relationship is particularly relevant at the micro-habitat scale. Isotopic data highlight also an important variability at the spatial micro-scale in the use of energetic resources for B. Azoricus with a major δ13Cshell fractionation when sulfoxydation is dominant compared to methanotrophy. This interdisciplinary approach is particularly relevant in a context where the exploration of hydrothermal areas in the aim of exploitation is constantly expanding.
