Water Temperature and Catchment Characteristics Drive Variation in Carbon Dioxide and Methane Emissions from Small Ponds in a Peatland-Rich, High-Altitude Tropical Ecosystem

Inland waters release significant amounts of carbon into the atmosphere, with small ponds acting as hot spots. High variability and limited research make emissions from small waterbodies a major source of uncertainty, especially in underrepresented tropical ecosystems where unique drivers remain poorly understood. We evaluated the magnitude and sources of variability in emissions from small waterbodies of the páramo, a tropical ecoregion in the Andes mountains, characterized by carbon-rich soils. We measured partial pressure of carbon dioxide (pCO2), methane (pCH4) and CO2 emissions from small (<5000 m^2) waterbodies, 11 ponds and 1 wetland, 3 times in the wet season and returned to 8 sites in the dry season. Sites were always supersaturated in pCH4 (1,096+/-1,482 μatm), but occasionally undersaturated in pCO2 (1,224+/-1,585 μatm). Variability between ponds was high and primarily driven by elevation and water temperature. Catchment soil-water connectivity was also predictive of pCO2. Mean wet-season emission rates were 0.34+/-0.54 g CO2-C m-2 d-1 and 0.012+/-0.018 g CH4-C m-2 d-1 and surface area fluctuations were a large source of seasonal variability in some ponds. Though an open-water transect of the wetland site was similar to ponds, we measured very high pCH4 (1678+/-2629 μatm) and pCO2 (5162+/-3207 μatm) along the wetland perimeter. Our findings provide essential insights for incorporating a significant yet understudied tropical ecosystem into global carbon budget by confirming previous observations that small ponds can emit a disproportionately large amount of carbon to the atmosphere, but also highlighting the importance of variables other than pond size in controlling emission hot-spots.