TY - JOUR
T1 - Nitrogen- and irradiance-dependent variations of the maximum quantum yield of carbon fixation in eutrophic, mesotrophic and oligotrophic marine systems
AU - Babin, Marcel
AU - Morel, André
AU - Claustre, Hervé
AU - Bricaud, Annick
AU - Kolber, Zbigniew
AU - Falkowski, Paul G.
PY - 1996/8
Y1 - 1996/8
N2 - Natural variability of the maximum quantum yield of carbon fixation (φ(C max)), as determined from the initial slope of the photosynthesis-irradiance curve and from light absorption measurements, was studied at three sites in the northeast tropical Atlantic representing typical eutrophic, mesotrophic and oligotrophic regimes. At the eutrophic and mesotrophic sites, where the mixed layer extended deeper than the euphotic layer, all photosynthetic parameters were nearly constant with depth, and φ(C max) averaged between 0.05 and 0.03 mol C (mol quanta absorbed)-1, respectively. At the oligotrophic site, a deep chlorophyll maximum (DCM) existed and φ(C max) varied from ca 0.005 in the upper nutrient-depleted mixed layer to 0.063 below the DCM in stratified waters. Firstly, φ(C max) was found roughly to covary with nitrate concentration between sites and with depth at the oligotrophic site, and secondly, it was found to decrease with increasing relative concentrations of non-photosynthetic pigments. The extent of φ(C max) variations directly related to nitrate concentration was inferred from variations in the fraction of functional PS2 reaction centers (f), measured using fast repetition rate fluorometry. Covariations between f and nitrate concentration indicate that the latter factor may be responsible for a 2-fold variation in φ(C max). Moreover, partitioning light absorption between photosynthetic and non-photosynthetic pigments suggests that the variable contribution of the non-photosynthetic absorption may explain a 3-fold variation in φ(C max), as indicated by variations in the effective absorption cross-section of photosystem 2 (σ(PS2)). Results confirm the role of nitrate in φ(C max) variation, and emphasize those of light and vertical mixing.
AB - Natural variability of the maximum quantum yield of carbon fixation (φ(C max)), as determined from the initial slope of the photosynthesis-irradiance curve and from light absorption measurements, was studied at three sites in the northeast tropical Atlantic representing typical eutrophic, mesotrophic and oligotrophic regimes. At the eutrophic and mesotrophic sites, where the mixed layer extended deeper than the euphotic layer, all photosynthetic parameters were nearly constant with depth, and φ(C max) averaged between 0.05 and 0.03 mol C (mol quanta absorbed)-1, respectively. At the oligotrophic site, a deep chlorophyll maximum (DCM) existed and φ(C max) varied from ca 0.005 in the upper nutrient-depleted mixed layer to 0.063 below the DCM in stratified waters. Firstly, φ(C max) was found roughly to covary with nitrate concentration between sites and with depth at the oligotrophic site, and secondly, it was found to decrease with increasing relative concentrations of non-photosynthetic pigments. The extent of φ(C max) variations directly related to nitrate concentration was inferred from variations in the fraction of functional PS2 reaction centers (f), measured using fast repetition rate fluorometry. Covariations between f and nitrate concentration indicate that the latter factor may be responsible for a 2-fold variation in φ(C max). Moreover, partitioning light absorption between photosynthetic and non-photosynthetic pigments suggests that the variable contribution of the non-photosynthetic absorption may explain a 3-fold variation in φ(C max), as indicated by variations in the effective absorption cross-section of photosystem 2 (σ(PS2)). Results confirm the role of nitrate in φ(C max) variation, and emphasize those of light and vertical mixing.
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U2 - 10.1016/0967-0637(96)00058-1
DO - 10.1016/0967-0637(96)00058-1
M3 - Article
SN - 0967-0637
VL - 43
SP - 1241
EP - 1272
JO - Deep-Sea Research Part I: Oceanographic Research Papers
JF - Deep-Sea Research Part I: Oceanographic Research Papers
IS - 8
ER -