Fig. 5
Dependencies of atmospheric oxygen level on various parameters. Response of atmospheric oxygen levels in the parameter space of A continental area vs. CO2 outgassing rate; B solar luminosity vs. CO2 outgassing rate; C the primary productivity of anaerobic photoautotrophs (Fred) vs. CO2 outgassing rate; D fraction of bioavailable phosphorus vs. primary productivity of anaerobic photoautotrophs; E burial efficiency of the exported organic carbon (α) vs. export production efficiency (fpo), and F C:P ratio of organic matter buried in sediment vs. CO2 outgassing rate. Parameters are varied from the condition of Fred of 7.50 × 1010 mol C year–1, bioavailable fraction of the riverine phosphorus (γbio = 1), solar luminosity of 83% of the present Earth, CO2 outgassing rate of present outgassing rate (6.7 × 1012 mol C year–1), seafloor spreading rate of 1.307 times the present rate, C:P ratio of organic matter buried in sediment (Rcp,bur) of 300, burial efficiency of the exported organic carbon (α) of 0.2, export production efficiency (fpo) of 0.1, and soil biological activity (fe) of 0.15. The areas filled with red and blue colors represent the conditions where high O2 levels (> ~ 10–2 PAL) and low O2 levels (< ~ 10–5 PAL) exist, respectively. Thin red/blue dashed line is the contour of the atmospheric oxygen level (PAL). Thick blue and red lines represent the conditions for the transition from the low pO2 state to high pO2 state and vice versa, respectively. Thick black line and grey-shaded areas represent the condition of haze formation (CH4/CO2 > 0.2)