Growth of transplants of the hermatypic Scleractinian Acopora muricata (Linnaeus, 1758) used as a bioindicator (Reunion Island, Indian Ocean)

Searching for bioindicators easy to use but integrating the influence of en vironmental factors, in order to help understanding the functioning of diff erent sites on a reef flat, we chose to study the growth of transplants of the hermatypic Scleractinian Acropora muricata. We asked if the growth of t ransplants of this sensitive coral could constitute an interesting bioindic ator. Are rapid and simple measures of the growth of the transplants, over a relatively short period (between 6 months and 1 year), able to express si gnificant differences among different biotopes? In our study, after one yea r, the growth of transplants results in a slender and open form on a dystro phic reef flat, in a balanced form in an oligotrophic reef flat non subject to a high level of predation, and in a stocky form showing numerous points of adaptative reiteration due to traumatisms on a reef flat subject to a s trong swell and a high level of predation. The easy observation of the tran splants allows to demonstrate the pressure of predation on living coral col onies, a phenomenon difficult to observe on large branching colonies. The b ioerosion which is fundamentally opposed to calcification appears to be, in the case of the external macroerosion by the fish Scaridae, a phenomenon t hat could secondarily stimulate the calcification. We estimate that the gro wth of transplants of Acropora muricata can constitute a good bioindicator of the effects of abiotic and biotic factors on sensitive Scleractininians.