Abstract
Abstract: The sulfur isotope composition of soft tissues of Bathymodiolus septemdierum, B.aduloides, B.platifrons, and B.japonicus collected from deep-sea hydrothermal vent and cold seep communities in Japanese waters was measured. The.δ34S values(-0.4 to+5.5‰ relative to CDT)of B.septemdierum were similar to those of hydrogen sulfide in the associated hydrothermal fluids(δ34S=+3.1 to+5.6‰). The fairly low δ34S values of B.aduloides(-15.4 to-12.4‰)indicate assimilation of hydrogen sulfide derived from the dissimilatory reduction of seawater sulfate by sulfate-reducing bacteria. On the contrary, B.platifrons and B.japonicus had much higher values(δ34S=+12.7 to+19.8‰), which fall within the common isotopic range of marine plankton, algae, and benthic animals.These two species appears to assimilate seawater sulfate(δ34S= +21‰)with limited kinetic fractionation of sulfur isotopes(up to-6‰).The present sulfur isotopic analysis provides evidence for two kinds of sulfur source, i.e., isotopically light hydrogen sulfide vs. heavy seawater sulfates. The previously documented. δ34S values of Bathymodiolus from the Mid-Okinawa Trough, which were different from those obtained in the present analysis, are evaluated in terms of the species'physiological ecology on the basis of available data.
