Spatial variations in CO2 fluxes in a subtropical coastal reservoir of Southeast China were related to urbanization and land-use types.

• Subtropical coastal reservoirs are atmospheric CO 2 sources with strong spatiotemporal variations. • Much higher CO 2 concentrations and fluxes from waters adjacent to urban areas. • Exogenous carbon input from sewage is the important driver of CO 2 spatial variation. • Primary production, temperature and precipitation account for the seasonal variation in CO 2 fluxes. Carbon dioxide (CO 2) emissions from aquatic ecosystems are important components of the global carbon cycle, yet the CO 2 emissions from coastal reservoirs, especially in developing countries where urbanization and rapid land use change occur, are still poorly understood. In this study, the spatiotemporal variations in CO 2 concentrations and fluxes were investigated in Wenwusha Reservoir located in the southeast coast of China. Overall, the mean CO 2 concentration and flux across the whole reservoir were 41.85 ± 2.03 µmol/L and 2.87 ± 0.29 mmol/m2/h, respectively, and the reservoir was a consistent net CO 2 source over the entire year. The land use types and urbanization levels in the reservoir catchment significantly affected the input of exogenous carbon to water. The mean CO 2 flux was much higher from waters adjacent to the urban land (5.05 ± 0.87 mmol/m2/hr) than other land use types. Sites with larger input of exogenous substance via sewage discharge and upstream runoff were often the hotspots of CO 2 emission in the reservoir. Our results suggested that urbanization process, agricultural activities, and large input of exogenous carbon could result in large spatial heterogeneity of CO 2 emissions and alter the CO 2 biogeochemical cycling in coastal reservoirs. Further studies should characterize the diurnal variations, microbial mechanisms, and impact of meteorological conditions on reservoir CO 2 emissions to expand our understanding of the carbon cycle in aquatic ecosystems. [Display omitted] [ABSTRACT FROM AUTHOR]