Successions of Microbioeroding Communities over a Year Period with a Monthly Resolution : Impact on Biogenic Dissolution in Dead Corals (New Caledonia)

Coral reefs maintenance results from the balance between constructive and destructive forces, those being mainly due to the agents of bioerosion. Microborers -cyanobacteria, microalgae and fungi- are the main agents of dissolution of dead tropical substrates. Such dissolution results essentially from the activity of the chlorophyte Ostreobium quekettii in substrates exposed more than 6 months to colonization. Very little is known on the early stages of community successions and the pattern of associated biogenic dissolution rates. To date, the expression of rates in kg of CaCO 3 /m 2 of reef per year poses a problem as it does not reflect the dynamic over time of the dissolution process. Here, an experiment was carried out at an inshore reef in New Caledonia with coral blocks of Porites sp. to study simultaneously successions of microboring communities and environmental factors such as temperature and nutrients, every month over a year period. This study highlights for the first time (a) when Ostreobium is recruited and dominates communities, (b) the pattern of the dissolution process with a fine resolution and (c) the influence of environmental factors.