Carbon fluxes in coral reefs .1. Lagrangian measurement of community metabolism and resulting air-sea CO2 disequilibrium

Community metabolism was investigated using a Lagrangian flow respirometry technique on 2 reef flats al Moorea (French Polynesia) during austral winter and Yonge Reef (Great Barrier Reef) during austral summer. The data were used to estimate related air-sea CO2 disequilibrium. A sine function did not satisfactorily model the diel light curves and overestimated the metabolic parameters. The ranges of community gross primary production and respiration (P-g and R; 9 to 15 g C m(-2) d(-1)) were within the range previously reported for reef flats, and community net calcification (G; 19 to 25 g CaCO3 m(-2) d(-1)) was higher than the 'standard' range. The molar ratio of organic to inorganic carbon uptake was 6:1 for both sites. The reef flat at Moorea displayed a higher rate of organic production and a lower rate of calcification compared to previous measurements carried out during austral summer. The approximate uncertainty of the daily metabolic parameters was estimated using a procedure based on a Monte Carlo simulation. The standard errors of P-g, R and P-g/R expressed as a percentage of the mean are lower than 3 % but are comparatively larger for E, the excess production (6 to 78%). The daily air-sea CO2 flux (F-CO2) was positive throughout the field experiments, indicating that the reef flats at Moorea and Yonge Reef released CO2 to the atmosphere at the time of measurement. F-CO2 decreased as a function of increasing daily irradiance.