Journal of Oceanography, Vol. 55 (No. 6), pp. 731-745, 1999
Atsushi Suzuki1 and Hodaka Kawahata1,2
1Marine Geology Department, Geological Survey of Japan, Tsukuba 305-8567, Japan
2Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
(Received 17 August 1998; in revised form 24 November 1998; accepted 26 November 1998)
Abstract: Factors controlling the CO2 system parameters, including the partial pressure of CO2(PCO2) in coral reef waters, were investigated in three mid-oceanic reefs of the Indo-Pacific region. Surface water PCO2 in the lagoons of Majuro Atoll and Palau barrier reef in the Pacific were 25 matm and 48 matm higher than those of the offshore waters, respectively, while South Male Atoll lagoon of the Maldives in the Indian Ocean exhibited relatively small difference in PCO2 compared to the offshore water. Observations from Majuro Atoll and Palau barrier reef are consistent with the view that calcium carbonate production predominates in coral reefs. On the other hand, results from South Male Atoll can be attributed to the thorough flushing of the lagoon, which is connected to the open ocean by numerous deep channels. The offshore-lagoon PCO2 difference depends on system-level net organic-to-inorganic carbon production ratio while reef topography, especially residence time of the lagoon, has a secondary effect on the magnitude of the offshore-lagoon difference. A potential for releasing CO2 might be more evident in an enclosed atoll where the reef water has a longer residence time. Oceanic atoll and barrier reef lagoons, which are in the terminal stage of evolutionary history of oceanic volcanic islands, have the potential to release CO2 to the atmosphere.