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91 - Photosynthetic parameters - 14C P vs E -

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METHODES    ANALYSE / PRELEVEMENT / ACQUISITION

Babin, M., A. Morel, and R. Gagnon, An incubator designed for extensive and sensitive measurements of phytoplankton photosynthetic parameters, Limnology and Oceanography , 39 , 694-702, 1994.

Experiment Progress and Sample Analyses :

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. The incubation chambers are thermo-regulated with water circulation, and the light in each chamber is adjusted (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 and H. Claustre).

 

Determination of the Photosynthetical Parameters Values :

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 Platt et al. (1980) that allows us to obtain the values of the Photosynthetical Parameters.

Platt, T., C.L.Gallegos and W.G.Harrison, Photoinhibition of photosynthesis in natural assemblages of marine phytoplankton, Journal of Marine Research, 38, 687-701, 1980.

 

Stratégie d'échantillonage : Profils verticaux

Qualité du jeu de données : Validé

 

 

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