Terrestrial influences on the Shiraho fringing reef, Ishigaki Island, Japan: high carbon input relative to phosphate

Measurements of CO2 system parameters and nutrients showed the potential in fluence of terrestrial inputs on the carbon budget of a fringing coral reef on Ishigaki Island, Japan. Land-derived freshwaters. including river and g round water, make a relatively large contribution (0.5-1.2% by volume) to t he water circulation of the reef. These terrestrial waters exhibit extremel y high fugacity of CO2 (fCO(2) up to 6400 mu atm), reflecting enrichments i n total alkalinity and dissolved inorganic carbon. Since the dissolved inor ganic C:P ratio is anomalously high in terrestrial waters compared with the mean C:P ratios of primary production, excess carbon could be released int o the atmosphere. Terrestrial inputs deliver a large quantity of C relative to P. The study site was a source of CO2 at the time of measurement. Such a situation is likely to prevail all year round, and it may occur elsewhere .