This paper documents community metabolism on four reef flats at La Reunion Island: (1) two undisturbed reef flats, (2) a reef flat damaged by the combined effects of nutrient loading and undergrazing (Planch’Alizés), and (3) a reef flat destroyed in 1989 by a hurricane (La Varangue). The undisturbed sites display similar excess productions (E), slightly positive in summer (56-59 μM O2 m-2 d-1, gross primary production to respiration ratio (Pg/R) = 1.11-1.13), and nil in winter. Whatever the season, E is positive at La Varangue (177-325 μM O2 m-2 d-1; Pg/R = 1.18-1.22); data suggest a tendency towards net heterotrophy at Planch’Alizés (E between -125 and -71 μM O2 m-2 d-1; Pg /R = 0.87-1); E is higher at La Varangue, and the Pg /R ratio lower at Planch’Alizés, than at the other sites. In winter, Planch’Alizés displays a lower daily net calcification than the other sites (18 and 110-182 μM CaCO3 m-2 d-1 respectively); in summer, a significant CaCO3 dissolution occurs at night at this site (respectively -16 and 3 to 5 μM CaCO3 m-2 h-1). Therefore, calcification and/or net productivity allow the characterization of the disturbed areas. At Saint-Leu, they reflect the shift in community structure, which occurred after the hurricane. The dominance of massive corals may affect the carbonate budget at Planch’Alizés. However, the negative E values and the night-time CaCO3 dissolution observed in summer at this site presumably result from an input of exogenous organic matter, and, therefore, mainly reflect anthropogenic disturbance.