The surprising rich populations of life-forms that prosper around the hydro-thermal vents have been thought to be utterly dependent upon chemical energy for their survival. Such now seems to be a limited view. There is light at the bottom of the ocean!

Of particular interest is the potential for deep-sea vents and subsurface environments to support geothermally (rather than solar-) driven photosynthesis. Recent work on ambient light conditions at hydrothermal vents indicates that the photon flux generated by thermal radiation of 350° C water should be sufficient to sustain low-level photosynthesis, and there is at least one report of a faculative phototroph isolated from water samples taken near a deep-sea vent.

A particularly important implication of this undersea light source is that the evolution of photosynthesis need not have been dependent upon the existence of life on land. Also, hydrothermal vents could have served as refuges for photosynthesizing life forms down the geological eons when : (1) ocean surfaces were ice covered; (2) the terrestrial surface was exposed to deadly levels of radiation, as when the ozone layer was destroyed; and (3) when volcanism or dust from meteor impacts blackened the skies.

SCIENCE FRONTIERS
No. 124, JUL-AUG, 1999
SCIENCE FRONTIERS is a bimonthly collection of digests of scientific anomalies in the current literature. Published by the Sourcebook Project, P. O. Box 107, Glen Arm, MD 21057. Annual subscription: $7.00.
ISSN 1094-8325

http://www.knowledge.co.uk/frontiers/