Carbon Cycle CO 2 Carbonate system: (H 2 CO 3 , HCO 3 - , CO 3 -2 ) Particulate Organic C CH 4 Respiration DOC (ethanol, lactic acid, acetate) Methanogens Denitrifiers, reducers (Mn, Fe, SO 4 2- ) Fermentation bacteria (Bacillus, Clostridium, etc.) Plants, algae Methanotrophs Next