Effects of light, temperature and ground water level on the CO2 flux of the sediment in the high water temperature seasons at the artificial north salt marsh of Osaka Nanko bird sanctuary, Japan

Field investigations and indoor experiment were carried out to clarify the effect of temperature and chlorophyll a concentration of the sediment, photon flux density, and ground water level on the absorption and emission of CO2 from the surface sediment of the artificial salt marsh. The flux of CO2 absorption was closely related to sediment temperature, chlorophyll a and photon flux density. On the other hand, flux of CO2 emission changed depending on the sediment temperature and ground water level. The ground water level was thought to be indispensable for estimating CO2 emission from the sediment of the intertidal zone of the salt marsh. Using equations of CO2 flux with sediment temperature, chlorophyll a, photon flux density and ground water level, the total CO2 absorption and emission of the artificial north salt marsh of Osaka Nanko bird sanctuary was estimated as ca. 23 tons (4.3 g CO2 m−2 day−1) for absorption and ca.14 tons (2.6 g CO2 m−2 day−1) for emission in May to September 2014. These results suggest that a net of 9 tons of CO2 (1.7 g CO2 m−2 day−1) was absorbed, and that this salt marsh performs the function of a CO2 sink in high temperature seasons.