ABSTRACT: Community metabolism was investigated using a Lagrangian flow respirometry technique on 2 reef flats at 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.

KEY WORDS: Coral reefs · Primary production · Respiration · Calcification · Air-sea CO₂ flux · Light

Published in MEPS Vol. 145 (1996) on December 31
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1996