Coral reef metabolism and carbon chemistry dynamics of a coral reef flat

Global carbon emissions continue to acidify the oceans, motivating growing concern for the ability of coral reefs to maintain net positive calcification rates. Efforts to develop robust relationships between coral reef calcification and carbonate parameters such as aragonite saturation state (Ω arag ) aim to facilitate meaningful predictions of how reef calcification will change in the face of ocean acidification. Here we investigate natural trends in carbonate chemistry of a coral reef flat over diel cycles and relate these trends to benthic carbon fluxes by quantifying net community calcification and net community production. We find that, despite an apparent dependence of calcification on Ω arag seen in a simple pairwise relationship, if the dependence of net calcification on net photosynthesis is accounted for, knowing Ω arag does not add substantial explanatory value. This suggests that, over short time scales, the control of Ω arag on net calcification is weak relative to factors governing net photosynthesis.