An abundant deep-sea benthic community, dominated by the vestimentiferan
tube worm, Lamellibrachia barhami, a giant white clam, Calyptogena sp., and
a second clam, Solemya sp., was discovered along the northeast Pacific continental
margin during dives of DSRV Alvin off Oregon. The localities are tectonically controlled
and occur along submarine ridges that result from sediment deformation and
accretion at the leading edge of plate subduction. Ancient sea-water buried with the
sediment, dissolved methane and ammonia, and methane-derived carbonate are discharged
to the ocean floor along this tectonically active margin. We hypothesize that
the unusual benthic community is sustained by a chemosynthetic-energy metabolism
based on the oxidation of methane by free living and symbiotic microbial populations.
These organisms represent another significant adaptation of deep-sea biota to a site
where the abundanc of food (in this case not directly related to particulate input
from the sea surface but to tectonically generated methane), allows higher than normal
levels of productivity and metabolism, despite the high pressures and low temperature
of the deep-sea habitat. It is tempting to relate the global distribution of such faunas
to chemosynthetic food sources generated by tectonic forces.