The first C-DEBI theme, or avenue of investigation, is Microbial Activity in the Deep Subseafloor Biosphere. The deep subseafloor biosphere refers to all the life underneath the ocean; not deep in the ocean or living on the bottom of the ocean, like fish, but many feet and even miles below that. In the past decade, researchers have discovered that these distant subseafloor environments contain a substantial amount of biomass, as measured by carbon content. One of the big questions for scientists is how many of those cells are actually alive and active, as opposed to inert. It may sound as though this is veering off into the domain of philosophy, but there is great scientific significance to the answer to this question.