DIURNAL CHANGES IN THE PARTIAL-PRESSURE OF CARBON-DIOXIDE IN CORAL-REEF WATER

Coral reefs are considered to be a source of atmospheric carbon dioxid e because of their high calcium carbonate production and low net prima ry production. This was tested by direct measurement of diurnal change s in the partial pressure of carbon dioxide (P-CO2) in reef waters dur ing two 3-day periods; one in March 1993 and one in March 1994, on Shi raho reef of the Ryukyu Islands, Japan. Although the P-CO2 values in r eef waters exhibited large diurnal changes ranging from 160 to 520 mic roatmospheres, they indicate that the reef flat area is a net sink for atmospheric carbon dioxide. This suggests that the net organic produc tion rate of the reef community exceeded its calcium carbonate product ion rate during the observation periods.