ANOMALIES IN CORAL-REEF COMMUNITY METABOLISM AND THEIR POTENTIAL IMPORTANCE IN THE REEF CO2 SOURCE-SINK DEBATE

It is not certain whether coral reefs are sources of or sinks for atmo spheric CO2. Air-sea exchange of CO2 over reefs has been measured dire ctly and inferred from changes in the seawater carbonate equilibrium. Such measurements have provided conflicting results. We provide commun ity metabolic data that indicate that large changes in CO2 concentrati on can occur in coral reef waters via biogeochemical processes not dir ectly associated with photosynthesis, respiration, calcification, and CaCO3 dissolution. These processes can significantly distort estimates of reef calcification and net productivity and obscure the contributi on of coral reefs to global air-sea exchange of CO2, They may, nonethe less, explain apparent anomalies in the metabolic performance of reefs close to land and reconcile the differing experimental findings that have given rise to the CO2 debate.