Figure 5. Microbial carbon demand and particulate carbon flux in the mesotrophic and oligotrophic North Atlantic.
a, Depth-dependent microbial biomass production, as measured by carbon uptake. b, Microbial carbon demand based on measured biomass production and applying an average open-ocean microbial growth efficiency of 20%. c, Microbial carbon demand based on measured biomass production and a measured microbial growth efficiency for the dark ocean of 2% according to ref. 60. Also shown is the depth-dependent particle flux calculated from a model (from ref. 52) using primary production values reflecting the mesotrophic and oligotrophic North Atlantic. In b and c, dissolved inorganic carbon fixation by microbes is added to the output of the flux model assuming that chemolithoautrophy represents a fresh source of non-sinking organic carbon in the dark ocean. Data from T. Reinthaler et al., unpublished.