[Spatial-Temporal Variations of CO2 and CH4 Flux Through a Water-air Interface Under the Effect of Primary Productivity in Wulixia Reservoir].

: In recent years, the effect of greenhouse gas has been a focus. In order to reveal the spatial-temporal variations of CO2 and CH4 flux through a water-air interface, Wulixia reservoir was selected as a typical case for measuring CO2and CH4 flux using a floating chamber during four study periods in 2016.The primary productivity of the water was also studied. The results indicate that surface-layer water in Wulixia reservoir is a CO2 sink in summer, varying between -30.14 and -3.47 mg·(m2·h)-1. However, it is the source of CO2 in autumn and winter, varying between 15.57 mg·(m2·h)-1 and 115.06 mg·(m2·h)-1. The variation of methane flux is obvious in summer, but it is stable in autumn and winter. The spatial distribution of CO2 and CH4 show that they are higher in the typical bay area and lower in the tailing dam as well as in the drawdown zone of the reservoir. In addition, the spatial and temporal variation of CO2 and CH4 are negatively and positively correlated with primary productivity (r -0.477 and 0.771), respectively. Due to the high activity of photosynthetic micro- organisms in summer, CO2 can be sequestered, allowing the surface-layer water in Wulixia reservoir to be a CO2 sink. In addition, methanogenic bacteria can oxidize organic carbon produced by photosynthetic micro-organisms. Therefore, CH4 has a negative correlation with primary productivity. The results provide important information for the study of microorganism functions in karst water systems.