Hydrothermal Vent Clam and Tube Worm 13C/12C: Further Evidence of Nonphotosynthetic Food Sources.

The stable carbon isotope ratios in clam mantle tissues taken from both Galápagos and 21 degrees N hydrothermal vent sites were similar to the unusually low ratios of carbon-13 to carbon-12 previously reported for a Galápagos hydrothermal vent mussel. In marked contrast to these bivalves, vestimentiferan worm tissues from a Galápagos vent had isotope ratios that were higher than those of open ocean biota. These observations suggest that more than one nonpelagic and nonphotosynthetic carbon fixation pathway is of nutritional importance to vent animals, and that at least one of these pathways is common to two geographically separated vent sites.