Experimental shift in benthic community structure

Odile Naim (1) , Pascale Cuet (1) , Yves Letourneur (1)

1 ECOMAR - Laboratoire d'Ecologie Marine

In January 1989, hypersedimentation generated by hurricane Firinga was responsible for 99% mortality within the St-Leu reef flat coral community (Reunion Island, S.W. Indian Ocean). In September 1992, one homogeneous zone (400 m2) of dead Acropora pharaonis (60% coverage: cv) was selected on the inner ~eef flat: corals were almost totally covered by macroalgae and turfs (Stegastes nigricans territories). Macroalgae and turfs were removed from half of the zone (zone M, "modified") and the other half was left as control (zone C). In December 1994, despite similar salinity and nutrient concentrations in zones M and C (0.70 ~ 0.04 ~ DIN, 0.110 ~ 0.006 ~ DIP on average), rnacroalgae and turfs had not recovered in zone M (10% and 14% cv respectively) compared to zone C (42% and 35% cv), whereas crustose algal coverage and urchin densities were far higher in zone M than in C (M: 23% cv and 37 ind/m2; C: 2% cv and 8 ind/m2). Our experiment suggested that the removal of whole fleshy algae induced the formation of a new algal community controlled by herbivorous organisms, specially sea urchins. A longer monitoring is now necessary to determine whether or not this new state is stable and favourable to living coral recovery.

Domaines: Sciences du Vivant [q-bio]

Odile Naim, Pascale Cuet, Yves Letourneur. Experimental shift in benthic community structure. 8th International Coral Reef Symposium, Jun 1996, Panama City, Panama. pp.1873-1878. ⟨hal-00913761⟩