Flavienne BRUYANT, Marcel BABIN.
Laboratoire de Physique et Chimie Marines
Quai de la Darse BP 08
06238 Villefranche sur Mer
France

Tel: +33 (0)4 93 76 37 21 //  Fax: +33 (0)4 93 76 37 39
Bruyant@obs-vlfr.fr

10 depth were sampled each day during the entire cruise on the noon 12 l bottles CTD between 1 and 150m :

· 1 10 depth profile at the UPWelling site.

· 5 10 depth profiles at the MIO site

· 5 10 depth profiles at the DYFamed site

· 1 10 depth profiles at each short station (9 profiles).

After inoculation with inorganic ¹⁴C, each sample is sub-divided in 12 sub-samples of 50ml and incubated at 12 different light levels in a radial photosynthetron as described in Babin et al. 1994. The incubation chambers are thermo-regulated with water circulation, and the light in each chamber is corrected (using neutral density filters LEE number 209,210 and 211) to simulate the in situ conditions. After 120 min incubation the samples are filtered and treated as described in Babin et al. 1994.

Back in the laboratory, the radioactivity in the samples was counted with a liquid scintillation counter (PACKARD Tricarb serie 4000). The radioactivity signal is then transformed in Carbon Fixation Rate using the calculation described in Parsons et al. 1984. The Carbon Fixation Rate (P) is then normalised by the TChl a concentration ( Allomers + Epimers + Chl a + Div- Chl a, data provided by J Ras, H. Claustre and J.C. Marty).

After the sample analyses, we obtain a relation for raw data between the Specific Chlorophyll Carbon Fixation Rate (P^B) and the Light Intensity (E). To these raw data, we fit the hyperbolic tangent model of Jassby and Platt (1976) that allows us to obtain the values of the Photosynthetical Parameters.

In the data file you will find 7 columns. The 3 first columns are related to the localisation of the sampling (Station Code, CTD number and Bottle number). The 4 next columns are related to the Photosynthetical Parameters themselves.

Column 4 : P^B_max :

· P^B_max is the Maximum Specific Chlorophyll Carbon Fixation Rate.

· Units : mgC (mgChl a)^-1 h^-1

· P^B_max is the asymptote of the P vs E curve

· P^B_max depends on the saturation of the enzymatic reaction of the dark phase of the Photosynthesis.

Column 5 : a^B :

· a^B is the Specific Chlorophyll Photosynthetical Efficiency.

· Units : mg C (mg Chl a)^-1 h^-1 (µmol Quanta m^-2 s^-1)^-1.

· a^B is the initial slope of the P vs E curve.

· a^B depends on the light phase of the Photosynthesis and on the pigment composition.

Column 6 : E_K :

· E_K is the saturation parameters.

· Units : µmol Quanta m^-2 s^-1 .

· E_K is calculated from the ratio between P^B_max and a^B.

· E_K represent the light level to which phytoplankton is adapted.

· E_K is the more robust of the Photosynthetical Parameters as it only depends on the light measurement in the incubator.

Column 7 : F_Cmax :

· F_Cmax is the Maximum Quantum Yield of Carbon Fixation.

· Units : mol C (mol Quanta)^-1 .

· F_Cmax is calculated from the ration between a^B and the Specific Absorption Coefficient a* (data provided by K. Oubelkheir).

· F_Cmax depends on the pigment composition, and on the state of the reaction centers.

· F_Cmax as a theoretical maximum value of 0.125 (1 C fixed for 8 photon absorbed).

Babin M., Morel A and Gagnon R., 1994. An incubator designed for extensive and sensitive measurements of phytoplankton photosynthetic parameters. Limnol. Oceanogr., 39(3), 694-702.

Jassby A.D. and Platt T., 1976. Mathematical formulation of the relationship between photosynthesis and light for phytoplankton. Limnol. Oceanogr. 21(4), 540-547.

Parsons T.R., Maita Y. and Lalli C.M., 1984. A Manual of Chemical and Biological Methods for Seawater Analysis. Pergamon Press, 173 pp.