Archaea, Methane, and Oases of the Deep

The deep sea, fed by a slow trickling input of photosynthetically derived carbon, has historically been considered a low energy, oligotrophic environment. In localized areas, however, oases of elevated microbial biomass and activity within the deep sea do exist. Perhaps the most famous are hydrothermal vents, emerging along spreading centers and subduction zones, fueled by hot reduced fluids re-circulated within the Earth's crust. Equally rich, although less well known, areas of stimulated biomass production and activity also occur in the psychrophilic depths of the seafloor, fueled by large organic accumulations (i.e. food falls) and subsurface reservoirs of methane. The microbial ecology within these locally active deep-sea habitats is unique, supporting novel microbial associations and diverse pathways for carbon remineralization.