To understand the factors controlling carbon dioxide (CO2) exchanges n
ear land-sea boundary diurnal observations have been made twice on CO2
in the air and water in a coastal region. The results suggest that CO
2 enrichment in intertidal water, relative to that in the nearshore wa
ter, is directly proportional to CO2 abundance in air and it provides
evidence for the supply of CO2 from intertidal zone to nearshore regio
n with tidal currents.