Articles | Volume 5, issue 6
Biogeosciences, 5, 1681–1691, 2008
Biogeosciences, 5, 1681–1691, 2008

  11 Dec 2008

11 Dec 2008

Influence of CH4 and H2S availability on symbiont distribution, carbon assimilation and transfer in the dual symbiotic vent mussel Bathymodiolus azoricus

V. Riou1,2, S. Halary3,4, S. Duperron3,4, S. Bouillon2,5,6, M. Elskens2, R. Bettencourt1, R. S. Santos1, F. Dehairs2, and A. Colaço1 V. Riou et al.
  • 1Department of Oceanography and Fisheries, IMAR-University of Azores, Horta, Portugal
  • 2Department of Analytical and Environmental Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
  • 3UPMC Université Paris 06, UMR 7138 SAE AMEX, Paris, France
  • 4CNRS UMR 7138 SAE AMEX, Paris, France
  • 5Netherlands Institute of Ecology, Centre for Estuarine and Marine Ecology, Yerseke, The Netherlands
  • 6Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Leuven, Belgium

Abstract. 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. A high level of symbiosis plasticity was observed, methane-oxidizers occupying between 4 and 39% of total bacterial area and both symbionts developing according to the presence or absence of their substrates. Using H13CO3 in the presence of sulphide, or 13CH4, we monitored carbon assimilation by the endosymbionts and its translocation to symbiont-free mussel tissues. Carbon was incorporated from methane and sulphide-oxidized inorganic carbon at rates 3 to 10 times slower in the host muscle tissue than in the symbiont-containing gill tissue. Both symbionts thus contribute actively to B. azoricus nutrition and adapt to the availability of their substrates. Further experiments with varying substrate concentrations using the same set-up should provide useful tools to study and even model the effects of changes in hydrothermal fluids on B. azoricus' chemosynthetic nutrition.

Final-revised paper