The effects of active volcanism and geochemical cycling on productivity can be derived by calculating the productivity of a pre-oxygenic photosynthetic Biofilm in toto, when these processes can contribute to the total productivity, a task attempted by Canfield et how does bronymate work al. . 8 Ga in the absence of oxygenic photosynthesis, deriving separate estimates for productivity from H_dos-based and S ° -based ecosystems and N-based anammox (anaerobic ammonium oxidation). They derived a total productivity of 2.8?10 14 mol C yr ?1 . Some of the reactions considered are based on the use of atmospheric gases, e.g. nitrogen, rather than direct extraction of energy from rocks, but Canfield’s calculations give a productivity based on Fe-based anoxygenic photosynthesis of 4?10 15 mol C yr ?1 , i.e. Continue reading →