DEEP-SEA SMOKERS - WINDOWS TO A SUBSURFACE BIOSPHERE

Since the discovery of hyperthermophilic microbial activity in hydroth ermal fluids recovered from ''smoker'' vents on the East Pacific Rise, the widely accepted upper temperature limit for life (based on pure c ulture data) has risen from below the boiling point of water at atmosp heric pressure to approximately 115-degrees-C. Many microbiologists se em willing to speculate that the maximum may be closer to 150-degrees- C. We have postulated not only higher temperatures than these (under d eep-sea hydrostatic pressures), but also the existence of a biosphere subsurface to accessible seafloor vents. New geochemical information f rom the Endeavour Segment of the Juan de Fuca Ridge indicative of subs urface organic material caused us to re-examine both the literature on hyperthermophilic microorganisms cultured from deep-sea smoker enviro nments and recent results of microbial sampling efforts at actively di scharging smokers on the Endeavour Segment. Here we offer the case for a subsurface biosphere based on an interdisciplinary view of microbia l and geochemical analyses of Endeavour smoker fluids, a case in keepi ng with rapidly evolving geophysical understanding of organic stabilit y under deep-sea hydrothermal conditions.