Recent discoveries by GSO biogeochemists in samples from Deep Sea Drilling Program (DSDP) cores taken from the Pacific Ocean have significant implications for the nature and global distribution of life in the sediments of the subseafloor. For example, estimates of Earth’s total living biomass are now 10-45 percent lower than previously thought, and the depth to which the biosphere extends is now believed to be below the sediment/crust interface. Thus, up to 20 percent of the ocean bottom may exhibit an aerobic (free oxygen) ecosystem in the upper oceanic crust. Scientists found that subseafloor life (microbes) in sediment cores from the open ocean regions respired (used oxygen) at far lower rates than in regions with higher sedimentation rates (upwelling regions and regions near continents) due to the very low concentrations of total organic carbon (TOC) in the open ocean sediments. This, in turn, has implications for the oxidation state of material transferred into the mantle at subduction zones, which is important when materials erupt in explosive volcanoes of the Pacific Rim.