No. 124: Jul-Aug 1999
The surprisingly rich populations of lifeforms that prosper around the hydrothermal 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 lowlevel 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.
(Van Dover, Cindy Lee; "Biology in Extreme Environments at Deep-Sea Hydrothermal Vents," Eos, 70:F54, 1998.)