CRP El Niño member - Reynaud & Pagès
Ms. Stephanie Reynaud and Ms. Christine Ferrier-Pagès
Ferrier-Pagès Christine: team leader - PhD in 1992.
Reynaud Stéphanie: senior scientist - PhD in 2000.
The team is composed of three senior scientists, one post-doc, one to two PhD students and two technicians. We are working for at least 10 years on the ecophysiology of corals as well as on the calibration of isotopes and trace elements in coral skeletons. The team has published more than 40 peer-review papers on coral ecophysiology.
Current research topics
Since 1989, the CSM develops research focused on marine calcification with regard to global climatic changes. Marine biomineralization and symbiosis, the two major processes connected in corals, are studied, by two research teams with complementary expertise: a Physiology and Biochemistry team and an Ecophysiology team. The originality of our approach is the different study levels from molecule to reef (via cells, tissues, nubbins and colony).
Calcification, together with respiration and photosynthesis, is one of the main mechanisms controlling the concentration of carbon dioxide in atmosphere. Despite of the major importance of biomineralization, biological mechanisms are still largely unknown. Our work is mainly focused on corals. These are actually responsible, with the coccolithophores and the foraminifers, for 99.9% of the calcareous deposits on the surface of the globe. So, a better understanding of biomineralization processes in marine organisms should bring for a better understanding of the biogeochemistry of carbon and calcium.
In addition, these organisms all photosynthesize either directly (coccolithophores), or indirectly due to symbiosis with unicellular algae (foraminifera, corals). Light strongly stimulates calcification ("light-enhanced calcification"), However the relation between these two processes is still controversial.
On the other hand, coral skeletons provide recordings of physico-chemical conditions (temperature, light, CO2 concentration, nutriments), which prevailed at the time of their deposition, they are qualified as environmental archives. Interpretation of this information by paleoclimatologists should allow for a better prediction of climatic evolution. But how can the reading be done if the alphabet is not understood? No good interpretation can be made yet, because not enough is known about the biomineralization process.
In the laboratory, we have several rooms for coral culture, with small aquaria (20-40 l) were we can set up experiments in controlled conditions (temperature, light, nutrients, pH…). We have developed new techniques of coral culture to investigate the signature of trace elements and isotopes in the coral skeleton, or to monitor the uptake of radioactive elements by the corals. The first technique consists in making nubbins from one parent colony by cutting the apical end branches of the parent colony into small pieces. These pieces are suspended in seawater with a nylon mesh. After 3-4 weeks, tissue regenerates above the apparent skeleton, and the new colony can be used as an entire organism. The second technique consists in gluing small pieces of coral colony onto glass slides. After some time (2 months), a newly formed skeleton spreads above the glass slide. The building of this skeleton can be performed under entirely controlled conditions, and at the end of the experiment, the skeleton deposited on the slide can be removed with great accuracy (using a scalpel) and analyzed in order to calibrate isotopic ratio (or trace element ratio) in function of culture conditions. During the course of the experiment we can also measure biological parameters (such calcification, photosynthesis, respiration), and quantify the effect of physiology on isotopic signatures.