Life at Ultra-High pH: Implications for Modern and Ancient Ecosystems on Earth (and Perhaps Elsewhere?)

Ken Nealson, University of Southern California

The Cedars is an environment in northern California in which a process called serpentinization predominates, leading to the emanation of water at pH~12, and Eh of -500 mV or less.  These springs represent some of the harshest environments known on Earth: environments that are nevertheless populated by microbes of several types.  How such ecosystems function is not entirely clear.  Such high pHs strongly impact the solubility of many elements usually needed for life, and such low Ehs severely restrict the range of feasible metabolic reactions. 

Such serpentinization sites are thought to be characteristic of the early Earth, where magmatic rocks were abundant, and interaction with anaerobic waters would have been a common occurrence.  Thus, understanding these systems provides a window not only on present-day subsurface environments, but on some of the earliest geobiology on the planet.  This presentation discusses the way in which physical, chemical, and biological components interact in this remarkable ecosystem, and in keeping with this symposium, why and how a systems approach may be the only way to begin understanding how life prospers under ultrabasic conditions.