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Today, we have four 1-2L prototypes of a new kind of chemostat. These original experimental devices, which are being patented (U.K. patent application number 1112269.4), allow us to maintain and study coral holobionts in both controlled and monitored environmental conditions. Hence, pH, temperature, partial pressure of oxygen or carbon dioxyde, alkalinity, nutrients concentration... are simultaneously measured and maintained at selected values for the experiment. Stability of these parameters in these chemostats is controlled by a computer and facilitated by predictive calculations using dynamic mathematical models.

A good understanding of the exchanges between the coral holobionts and their environment is thus obtained using a mathematical model. This model, once validated by data from the chemostats, allow us to understand how holobiont-environment interactions are modulated in the specific conditions of the experiment.

We use these chemostats to study the impact of physico-chemical changes in the environment on the coral holobiont. As many parameters are measured in real time, we can calculate photosynthesis, respiration, skelettogenesis and nutrients assimilation with time, with a temporal resolution close to one minute.

We try also to increase the time a holobiont can grow in such a small volume of seawater (currently, their growth is not affected in our chemostats before 4 to 10 days, depending on the kind of experiment). That way, we could measure other probable changes, like associated micro-organisms communities, the number and size of zooxanthellae, the tissues and cells of the coral, mucus or metabolites production, or other defensive or communication chemicals the coral could release in the water column (the small volume allows to concentrate released substances).

A couple of pictures

Here are a few pictures of the first prototypes (more "classical" versions than our currently patented system) that we have used in our lab in the past.

A rudimentary chemostat (end of 2009). Yellow devices (at the top) are peristaltic pumps that bring chemicals to stabilize the water composition in the chemostat.

A couple of constituents of our first, rudimentary chemostat before we design our original system: a pH/oxymeter (at the bottom), a carbon dioxyde analyzer (at the top right), a recording software (at the center). At the left, one can see how a coral frag is supended inside the chemostat.

There is long way since our first trials to grow coral frags in small water volumes (in beakers). The initial setup was simplissime: a thermostated bath, a magnetic stirrer, an artificial light, that's all!


"I am interested by this tool, I would like to read your publications on this subject, I would like to buy or commercialize such a chemostat..."
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Where our coral frags come from?

Our artificial mesocosms (click on the picture)...