Reynaud-Vaganay S. 2000. Environmental control of the zooxanthellate scleractinian corals skeleton physiology and isotopic composition : an experimental approach. PhD these, Nice-Sophia Antipolis University, 215 p.

ABSTRACT

The skeleton of zooxanthellate scleractinian corals represents a potentially important database for environmental parameters. It is used more and more frequently for the reconstruction of paleoenvironments in tropical zones, for which only a few sources of information are presently available.
The use of corals cultured in aquaria leads to a precise control of environmental parameters and enables to change only one parameter at a time. An experimental technique of coral culture (Stylophora pistillata, Acropora sp. and Montipora verrucosa) under controlled conditions has been set up with success. This method allows the sampling of the newly formed skeleton and tissues with great accuracy.
This technique has been applied to determine relationships between environmental parameters and skeletal stable isotopes. The results showed that skeletal 18O is inversely correlated to temperature and salinity in all species. An inverse relationship between temperature and skeletal 13C was observed in Acropora sp. The skeletal 18O seemed to be affected by photosynthesis: skeletal 18O increased when photosynthesis was enhanced. Meanwhile, skeletal 13C seemed to be affected by calcification: a stimulation of calcification led to an increase of the skeletal 13C.
This new experimental approach opens many perspectives in the field of geochemical tracer validation (stable isotopes and trace elements). Efforts must presently concentrate on: the culturing of other genera, in particular Porites.

Key words : Scleractinian, culture, stable isotopes, temperature, salinity, nutrition, light, CO2 partial pressure.