Statistical modeling the effects of microclimate variables on carbon dioxide flux at the tropical coastal ocean in the southern South China Sea

The global ocean is a net carbon dioxide uptake and a major component of the biogeochemical carbon cycle. We measured carbon dioxide flux and other microclimate variables using the eddy covariance method to determine the effects of the latter on carbon dioxide (CO2) flux in the intertidal zone of the tropical coastal ocean in the southern South China Sea. The location is in the under-sampled “Eastern Boundary Current” province of the continental shelf in the South China Sea. Fluxes and microclimate variables were collected for more than one year, which encompassed all four Monsoons. Results show that the tropical coastal ocean uptakes CO2 with an annual average of -2.10 mol C m-2 yr-1. The Monsoon cycle decreased the role of the tropical coastal ocean as a CO2 sink by 60% during the Southwest Monsoon/Fall Transitional Monsoon phase due to increased precipitation. Cluster analysis of all the parameters measured showed two main clusters, the “dry” and “wet” season clusters while factor analysis reduced the number of variables to two main factors, the “weather” and the “CO2” factors. Thus, the Monsoonal CO2 flux at the tropical coastal ocean are significantly regulated by cumulative precipitation in comparison to other variables.