Fig. 1: Primitive methanogenic ecosystems.
From: Co-evolution of primitive methane-cycling ecosystems and early Earth’s atmosphere and climate
The ecosystem model resolves population abundance (total biomass, yellow arrows) of microbial H2-based methanogens (MG), CO-based acetogens (AG) and methanogenic acetotrophs (AT), along with CH4, CO, CO2, and H2 oceanic concentrations and atmospheric mixing ratios. Fluxes directly involved in the MG ecosystem function are indicated with black arrows. Fluxes additionally involved in the AG + AT ecosystem function are indicated in red. Key photochemical reactions are indicated with dotted arrows. The primary source of reducing power (H2) is volcanic outgassing. Fluxes across the ocean surface are governed by a stagnant boundary layer model. Rates of H2 escape to space and dead biomass burial in deep sediments are constant. Sulfate-based methanotrophs are not represented. See “Methods” for further details.
