Coupled CH production and oxidation support CO supersaturation in a tropical flood pulse lake (Tonle Sap Lake, Cambodia).

Carbon dioxide (CO) supersaturation in lakes and rivers worldwide is commonly attributed to terrestrial-aquatic transfers of organic and inorganic carbon (C) and subsequent, in situ aerobic respiration. Methane (CH) production and oxidation also contribute CO to freshwaters, yet this remains largely unquantified. Flood pulse lakes and rivers in the tropics are hypothesized to receive large inputs of dissolved CO and CH from floodplains characterized by hypoxia and reducing conditions.