Effect of high CO2 on the physiology and growth of the hermatypic coral Seriatopora hystrix in nano-sized chemostat

Growth of hermatypic coral Seriatopora hystrix was studied in a new original artificial chemostat. We succeed to maintain and growth small nubbins of 0.23±0.05g of the hermatypic coral S. hystrix in nano-sized chemostats (called 'nanocultures') of 400 mL each during 3 weeks. Main physico-chemical parameters are monitored and controlled using microcomputers. This includes temperature, salinity, pH, alkalinity, omega aragonite and calcium concentration. Artificial light of 250±30 µE.m-².s-1 on a 12h/12h light/dark cycle and a temperature of 27.0±0.1°C, salinity of 34±1, pH of 8.2±0.2, alkalinity of 2.9±0.3meq.kg-1 and [Ca++] of 410±10 mg.kg-1 give a growth rate of 1.1±0.5% per day for the nubbins, i.e., an increase in weight of more than 25% during the experiment.
The study of variation of the physico-chemical parameters, including true duplicates or triplicates, are possible with our system. In the near future, we propose to investigate the effect of increasing CO2 on growth and physiology of S. hystrix, his symbiotic zooxanthellae and his epibiontic bacterial colonies using these nanocultures. Relatively axenic conditions, measurement of the complete balance of inorganic/organic carbon in each chemostat, and concentration of the organic molecules released by the coral due to the extremely small volume potentially offer new insights on coral growth and physiology.