Photosynthetic parameters Marcel Babin measured variables Photosynthetic parameters
Photosynthetic parameters Marcel Babin
measured variables • Photosynthetic parameters derived from P vs. E (14 C) curves (10 depths, 1 L) • Parameters derived from measurements of variable fluorescence : – discrete samples : PAM (10 depth, 100 ml) – in situ measurements: FRRF
P vs E curve P (mg C m-3 h-1) Pmax P = Pmax tanh(PAR /Ek) Ek = Pmax /a a Ek PAR (mole Quanta m-2 s-1) Fc = P / 12 (PAR. a) mole C mole Quanta-1 a = absorption coefficient m-1 Fcmax = a / 12 a
PROSOPE Bruyant, 2002
Photo-physiological parameters might be dependant on phytoplankton community composition (POMME results) a* m 2 mg Chla-1 PBmax mg Chla-1 a. B FCmax h-1 mg Chla-1 h-1 mole Quanta m-2 s-1 mole C mole quanta micro 0. 020 ± 0. 002 7. 27 ± 0. 66 0. 105 ± 0. 660 0. 125 nano 0. 021 ± 0. 001 2. 33 ± 0. 24 0. 046 ± 0. 004 0. 051 pico 0. 037 ± 0. 001 0. 47 ± 0. 29 0. 017 ± 0. 005 0. 011 R 2 = 0. 91 R 2 = 0. 73 R 2 = 0. 72 n = 344
Main hypothesis to be tested on BIOSOPE : Is the efficiency of carbon fixation dependant on the taxonomic groups (size) which are present (large phytoplankton more efficient than small one)? • More easy to parameterise than a dependence on environmental variables (T°, Nutrient and light) • Potential applications for bio-optical models • Besides P vs E measurements : Absorption, HPLC pigments, and 14 C primary production (other approach to test the dependence of carbon fixation efficiency on taxonomic composition)
Parameters deduced from variable fluorescence measurements on discrete samples and in situ. f. PS 2 = (Fm – Fo ) / Fm s. PS 2 PSIIred Fm Fv PSIIox Fo 0
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