Coupled CH 4 production and oxidation support CO 2 supersaturation in a tropical flood pulse lake (Tonle Sap Lake, Cambodia)

• DOI: 10.1073/pnas.2107667119
• Publication Date: 2022-02-14T21:25:59Z
• Authors: Benjamin Lloyd Mi...; Gordon William Ho...; Mauricio Eduardo ...; Sophorn Uy; Phen Chheng
• Keywords: Supersaturation

Carbon dioxide (CO2) supersaturation in lakes and rivers worldwide is commonly attributed to terrestrial-aquatic transfers of organic inorganic carbon (C) subsequent, situ aerobic respiration. Methane (CH4) production oxidation also contribute CO2 freshwaters, yet this remains largely unquantified. Flood pulse the tropics are hypothesized receive large inputs dissolved CH4 from floodplains characterized by hypoxia reducing conditions. We measured stable C isotopes CH4, respiration, during two flood stages Tonle Sap Lake (Cambodia) determine whether tropical ecosystem has a methanogenic origin. Mean 11,000 ± 9,000 μatm could not be explained respiration alone. 13C depletion relative other sources C, together with corresponding enrichment suggested extensive oxidation. A isotope-mixing model shows that depleted contributes between 47 67% Lake. was correlated independently rates within water column underlying lake sediments. However, mass balance indicates most occurs elsewhere, inundated soils floodplain habitats. Seasonal inundation common feature where high reported atmospheric emissions may part coupled