Seawater carbonate chemistry and calcification during tropical reef studies at Younge reef (Great Barrier Reef), 1996

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 (Pg 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 Pg,R and Pg/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 (FCO2) 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. FCO2 decreased as a function of increasing daily irradiance.

本研究采用拉格朗日流动呼吸测定法（Lagrangian flow respirometry technique），对法属波利尼西亚莫雷阿岛的2处礁坪于南半球冬季、大堡礁永格礁于南半球夏季开展了群落代谢调查。所获数据被用于估算相关海-气二氧化碳失衡量。正弦函数无法较好拟合昼夜光响应曲线，且对代谢参数存在高估情况。群落总初级生产力（gross primary production，Pg）与呼吸速率（respiration，R）的区间为9~15 g C m⁻² d⁻¹，与此前针对礁坪的报道值相符；群落净钙化速率（net calcification，G）的区间为19~25 g CaCO₃ m⁻² d⁻¹，高于“标准”区间范围。两处研究位点的有机碳与无机碳吸收摩尔比均为6:1。与南半球夏季的既往测量结果相比，莫雷阿岛礁坪的有机生产速率更高，而钙化速率更低。本研究基于蒙特卡洛模拟（Monte Carlo simulation）流程，估算了每日代谢参数的近似不确定度。以均值百分比表示的Pg、R及Pg/R的标准误差均低于3%，但超额生产量E的标准误差相对更大，区间为6%~78%。野外实验全程的每日海-气二氧化碳通量（FCO₂）均为正值，表明莫雷阿岛与永格礁的礁坪在测量时段内向大气释放了二氧化碳。海-气二氧化碳通量随每日辐照度的升高而降低。