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

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±2.03μmol/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 towater.The mean CO_(2)fluxwasmuch 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.