Separating biological and physical changes in dissolved oxygen concentration in a coral reef

Abstract

Measured changes in dissolved oxygen (DO) concentrations in a coral reef at Miyako Island are markedly different from the diurnal sinusoidal pattern expected if biological processes are dominant. We were able to resolve this paradox by constructing a simple model that combines the influences of organic production and air-sea exchange with water flow and mixing through the reef system. The model successfully replicates the observed DO behavior, suggesting that the simple flow system we propose adequately accounts for these water advection effects. Our optimized estimates of gross production and respiration on the reef flat are 13 m and 5.2 g C m-2 d-1, giving a P : R ratio of 2.5. We obtained best fits to the data in the lagoon with a production rate of 4.9 g C m-2 d-1 and a respiration rate of 5.2 g C m-2 d-1 for a P : R ratio of 0.9.