The Distribution Characteristics and Influencing Factors of the CO2 Fluxes Across the Sea–Air Interface in the Artificial Reefs Area of Sanheng Island

In order to study the impact of artificial reef construction on marine carbon sinks, a one-year monitoring and analysis were carried out in the Sanheng artificial reef areas of Shengsi Island. The main parameters observed were sea surface temperature, salinity, pH, total alkalinity (TA), and dissolved inorganic carbon (DIC). The partial pressure of CO2 (pCO2w) in the surface water and the CO2 flux (FCO2) across the sea–air interface were calculated and analyzed. The results showed that the annual range of surface water pCO2w was 34.48~501.53 μatm, and the partial pressure of CO2 decreases in the following order: winter, spring, autumn, summer. The FCO2 was significantly negatively correlated with temperature and significantly positively correlated with salinity and TA. The FCO2 in the four seasons decreases in the following order: winter, spring, autumn, summer. The annual sea–air flux in the survey area ranged from −108.79 to 41.74 mmol m−2 d−1. In winter, both the reef area and the control area displayed positive FCO2 values, indicating a source of CO2, while in the other three seasons, CO2 flux values were negative, indicating an overall CO2 sink. Additionally, in autumn, the reef area exhibited a stronger CO2 sink than the control area. The results indicated that the construction of artificial reefs has a certain carbon sink effect, with no significant difference in effectiveness between different artificial reef construction models.