Microhabitat variation in the hydrothermal vent mussel, Bathymodiolus thermophilus, at the Rose Garden vent on the Galapagos Rift

C. R. Fisher, J. J. Childress, A. J. Arp, J. M. Brooks, D. Distel, J. A. Favuzzi, H. Felbeck, R. Hessler, K. S. Johnson, M. C. Kennicutt, S. A. Macko, A. Newton, M. A. Powell, G. N. Somero, T. Soto

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Abstract

Clumps of Bathymodiolus thermophilus were collected from three discrete areas at the 'Rose Garden' site on the Galapagos Rift using the deep submersible Alvin. Two mussel collections were made from the central Riftia mass, an area associated with very active venting, and three other collections were of two different peripheral mussel clumps. Before collection the clumps were extensively photographed and the water at two of the 'microhabitats' was analysed in situ for oxygen silica, sulfide and temperature. Sulfide levels of up to 300 μM were recorded at the central collection site, while the highest sulfide level recorded at the peripheral site assayed was 35 μM. Levels of RuBP carboxylase activity in the gills were significantly higher in mussels collected from the central 'Riftia site' than in either peripheral site. ATP sulfurylase was significantly higher in the gills of mussels from the central clump than in one of the peripheral clump collections. The chemical composition (% water, protein, carbohydrate, lipid and ash) and stable carbon isotope ratios (δ13C) of the mussels showed the same trends, with highest lipid and carbohydrate and the lowest water content and δ13C in the central site mussels. Similarly, the mussels from the central site were significantly depleted in stable nitrogen (δ15N) when compared with the peripheral site mussels. Variations between sites and tissues of the same animal may be indicative of differential utilization of inorganic or dissolved molecular nitrogen sources. The condition index (CI = soft tissue dry mass / internal shell volume) was similar for all animals collected at Rose Garden. The presence of a commensal polychaete, Branchipolynoe symmytilida, in the mantle cavity of the mussels was also correlated with the collection site, with the highest incidence of occurrence in the central clump. Levels of the enzyme RuBP carboxylase are quite variable in B. thermophilus and are on the average much lower (0.001 international units) than either Calyptogena magnifica (0.006 I.U.) or Riftia pachyptila (0.16 I.U.). We conclude that the mussels are able to thrive over a wider range of conditions than either C. magnifica or R. pachypila and that this is due to a lesser reliance on their symbiotic bacteria as a source of nutrition.

Original languageEnglish (US)
Pages (from-to)1769-1791
Number of pages23
JournalDeep Sea Research Part A, Oceanographic Research Papers
Volume35
Issue number10-11
DOIs
StatePublished - Jan 1 1988

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)

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