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Phytoplankton photoacclimation and photoadaptation in response to environmental gradients in a shelf sea
Author(s) -
Moore C. Mark,
Suggett David J.,
Hickman Anna E.,
Kim Young-Nam,
Tweddle Jacqueline F.,
Sharples Jonathan,
Geider Richard J.,
Holligan Patrick M.
Publication year - 2006
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.2006.51.2.0936
Subject(s) - irradiance , photosynthesis , phytoplankton , chlorophyll fluorescence , carbon fixation , photosystem ii , chlorophyll a , deep chlorophyll maximum , photoinhibition , chlorophyll , biology , oceanography , environmental science , botany , ecology , photic zone , geology , physics , quantum mechanics , nutrient
Variability in the photosynthetic performance of natural phytoplankton communities, due to both taxonomic composition and the physiological acclimation of these taxa to environmental conditions, was assessed at contrasting sites within a temperate shelf sea region. Physiological parameters relating to the structure of the photosystem II (PSII) antenna and processes downstream from PSII were evaluated using a combination of fast repetition rate fluorescence, oxygen flash yields, spectral fluorescence, and 14 C photosynthesis versus irradiance measurements. Parameters relating to PSII antenna structure, specifically the functional absorption cross‐section (Σ PSII ) and the chlorophyll to PSII reaction center ratio, varied principally as a result of spatial (horizontal) taxonomic differences. Phenotypic plasticity in the size of the PSII light‐harvesting antenna appeared to be limited. In contrast, parameters related to electron transport rates (ETRs) downstream of PSII, including the maximum ETR (1/Τ PSII ), the chlorophyll‐specific maximum rate of carbon fixation ( P * max ), and the light‐saturation intensity ( E k ), all decreased from the surface to the subsurface chlorophyll maximum (SCM) in stratified waters. The primary photoacclimation response to the vertical light gradient thus resulted in decreasing light‐saturated carbon fixation per reaction center with increasing depth. Increases in the ratio of PSII reaction centers to carbon fixation capacity thus dominated the phenotypic response to decreased irradiance within the SCM. Perhaps counterintuitively, phytoplankton populations within fully mixed water columns, characterized by low mean irradiance, were acclimated or adapted to relatively high irradiance.