Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 6 2008 10.5194/bg-5-1681-2008 http://www.biogeosciences.net/5/1681/2008/ http://www.biogeosciences.net/5/1681/2008/bg-5-1681-2008.html http://www.biogeosciences.net/5/1681/2008/bg-5-1681-2008.pdf 1681 1691 2008-12-11 Influence of CH4 and H2S availability on symbiont distribution, carbon assimilation and transfer in the dual symbiotic vent mussel Bathymodiolus azoricus V. Riou virgriou@vub.ac.be S. Halary S. Duperron S. Bouillon M. Elskens R. Bettencourt R. S. Santos F. Dehairs A. Colaço Department of Oceanography and Fisheries, IMAR-University of Azores, Horta, Portugal Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Brussels, Belgium UPMC Université Paris 06, UMR 7138 SAE AMEX, Paris, France CNRS UMR 7138 SAE AMEX, Paris, France Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology, Yerseke, The Netherlands Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Leuven, Belgium High densities of mussels of the genus Bathymodiolus are present at hydrothermal vents of the Mid-Atlantic Ridge. It was previously proposed that the chemistry at vent sites would affect their sulphide- and methane-oxidizing endosymbionts' abundance. In this study, we confirmed the latter assumption using fluorescence in situ hybridization on Bathymodiolus azoricus specimens maintained in a controlled laboratory environment at atmospheric pressure with one, both or none of the chemical substrates. 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