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Relationship between the maximum quantum yield of carbon fixation and the minimum quantum yield of chlorophyll a in vivo fluorescence in the Gulf of St. Lawrence
Author(s) -
Babin Marcel,
Therriault Jean-Claude,
Legendre Louis,
Nieke Barbara,
Reuter Rainer,
Condal Alfonso
Publication year - 1995
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1995.40.5.0956
Subject(s) - diel vertical migration , phytoplankton , quantum yield , photosynthesis , estuary , chlorophyll a , carbon fixation , photosystem ii , biology , atmospheric sciences , botany , nutrient , fluorescence , physics , ecology , quantum mechanics
Intensive monitoring of the maximum quantum yield of carbon fixation ( ϕ max ) and of the minimum quantum yield of chlorophyll a in vivo fluorescence ( ϕ Fo ) was followed along the path of drifting buoys in the estuary and the Gulf of St. Lawrence, Canada. Samples were collected every third hour during two 24‐h periods. Over the 170 measurements, ϕ max varied by a factor of 20 [from 0.004 to 0.08 mol C (mol quanta) − 1 ]. As predicted by a model of primary processes in photosystem 2, a significant and positive linear relationship was observed between ϕ ma x and ϕ F o . In the estuary, the covariability of ϕ max and ϕ Fo seems to be driven by light, because it was observed only during daytime and was characterized by a parallel increase of ϕ max and ϕ Fo with depth. Examination of the spectral values of ϕ Fo suggests a contribution of photoprotectant carotenoids. In the gulf, because a parallel, although weaker, increase of ϕ max and ϕ Fo with depth also persisted during nighttime, nutrient deficiency is probably an additional cause of covariation between ϕ max and ϕ Fo . In both regions, an overall diel cycle was observed for ϕ max with a maximum at around noon; ϕ Fo did not show a clear diel periodicity. Despite the vertical covariability of ϕ max and ϕ F o , the diel cycle of ϕ max was uncoupled to ϕ F o and thus to photosystem 2 activity. These results suggest a significant diel variation in the photosynthetic quotient of natural phytoplankton.