The impact of coral reef ecosystems and upwelling events on the marine carbon dynamics of Southern Taiwan

Abstract

Abstract. The ocean is the largest carbon reservoir and plays a crucial role in regulating atmospheric CO2 levels, especially in the face of climate change. In coral reef ecosystems, the complexity and importance of the carbonate system must be better appreciated as atmospheric CO2 concentrations continue to rise. This study measured pCO2 over time and space in Nanwan Bay, a coral reef ecosystem in Southern Taiwan, to identify factors that influence its variation. The results showed that mean pCO2 values varied seasonally, with values of 394 µatm in spring, 406 µatm in summer, 399 µatm in fall, and 367 µatm in winter. These seasonal differences (ΔpCO2) were -2, 14, 7, and -29 µatm, respectively. These findings suggest that the Nanwan Bay coral reef ecosystem acts as a sink for atmospheric CO2 during the spring and winter, with an average sea-air gas flux of -1 gC m-2 year-1 and a net annual uptake of -29 t. The carbonaceous parameters of the surface water in this high-biodiversity sub-tropical marine ecosystem were influenced not only by seasonal temperature variation but also by vertical mixing, intermittent upwelling, and biological effects.